Myelofibrosis (Adult)

1. Clinical Overview

Definition and Importance

Myelofibrosis (MF) is a clonal myeloproliferative neoplasm (MPN) characterised by progressive bone marrow fibrosis, extramedullary haematopoiesis, and constitutional symptoms driven by aberrant cytokine production. It represents the most aggressive form of the Philadelphia-negative MPNs, with median survival ranging from 2 to 15 years depending on risk stratification. [1,2]

MF exists in two distinct clinical forms:

• Primary Myelofibrosis (PMF): Arising de novo, accounting for approximately 85% of cases
• Secondary Myelofibrosis: Transformation from pre-existing polycythaemia vera (post-PV MF) or essential thrombocythaemia (post-ET MF), occurring in 10-20% of PV patients and 5-10% of ET patients over 15-20 years [3,4]

The pathological hallmark is progressive bone marrow fibrosis, resulting from reactive deposition of collagen and reticulin fibres by non-clonal fibroblasts in response to aberrant cytokine signalling from the malignant haematopoietic clone. This fibrosis leads to bone marrow failure, necessitating compensatory extramedullary haematopoiesis predominantly in the spleen and liver. [5]

Clinical Significance

Myelofibrosis has the worst prognosis among Philadelphia-negative MPNs, with significant impact on quality of life due to:

• Debilitating constitutional symptoms (fatigue, night sweats, weight loss) affecting > 80% of patients [6]
• Massive splenomegaly causing abdominal discomfort and early satiety
• Progressive cytopenias leading to transfusion dependency
• Risk of leukemic transformation to acute myeloid leukaemia (AML) in 15-20% of cases [7]
• Thrombotic and haemorrhagic complications

The advent of JAK inhibitors has revolutionised symptomatic management, though allogeneic stem cell transplantation remains the only curative option. [8]

Clinical Pearls

The Diagnostic Triad: Remember "DRY-TEAR-SPLEEN"

• DRY: Dry tap on bone marrow aspiration (pathognomonic)
• TEAR: Tear drop cells (dacrocytes) on blood film
• SPLEEN: Massive splenomegaly (often extending below umbilicus)

Constitutional Symptoms as a Clue: Unlike other MPNs, the severity of constitutional symptoms in MF is disproportionate to the degree of cytopenia. This reflects the profound "cytokine storm" (elevated TNF-α, IL-6, IL-8) rather than tumour burden alone. [6]

Reticulin Staining is Essential: Standard H&E staining of bone marrow biopsy underestimates fibrosis. Silver staining for reticulin fibres is mandatory for grading (MF-0 to MF-3). [9]

Triple-Negative Disease Carries Poor Prognosis: Patients lacking JAK2, CALR, and MPL mutations (10-15% of cases) have higher rates of thrombosis and leukemic transformation. [10]

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2. Epidemiology

Incidence and Prevalence

Demographics

Age Distribution:

• Peak incidence: 6th-7th decade of life
• Rare in patients less than 40 years (constitutes less than 5% of cases)
• Younger patients often present with more aggressive disease phenotype [11]

Ethnic Variation:

• Higher incidence in Ashkenazi Jewish populations (2.5-fold increase)
• Lower incidence in Asian populations
• No significant variation between other ethnic groups [12]

Geographic Distribution:

• Similar incidence across Europe and North America
• Lower reported incidence in Asia (likely reflects underdiagnosis and registry limitations)

Molecular Epidemiology

Driver Mutation Frequency in Primary Myelofibrosis: [10,13]

Additional Mutations (High Molecular Risk - HMR): [14]

• ASXL1 (30-35%): Associated with shortened survival
• EZH2 (6-10%): Adverse prognostic marker
• SRSF2 (15-20%): Independent predictor of poor outcome
• IDH1/IDH2 (4-6%): Associated with leukaemic transformation
• U2AF1 (15-18%): Adverse impact on survival

Mutational Acquisition and Clonal Evolution:

• Driver mutations (JAK2/CALR/MPL) typically occur early in disease pathogenesis
• Secondary mutations accumulate over time, driving disease progression
• Presence of ≥2 high molecular risk mutations confers very poor prognosis [14]

Risk Factors

Established Risk Factors:

• Prior exposure to benzene or ionising radiation: Well-documented occupational/environmental risk [15]
• Pre-existing PV or ET: 10-20% and 5-10% transformation risk respectively over 15-20 years [3,4]
• Familial predisposition: First-degree relatives have 5-7 fold increased risk of MPN [12]

Germline Predisposition:

• JAK2 46/1 haplotype (rs12343867): 2-4 fold increased risk of JAK2-mutated MPN [12]
• Recent genome-wide association studies identify additional susceptibility loci

Temporal Trends

• Incidence appears stable over past 2 decades (accounting for improved diagnostic criteria)
• Survival has improved significantly since approval of ruxolitinib in 2011 [16]
• Earlier diagnosis due to increased awareness and routine JAK2 testing

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3. Aetiology and Pathophysiology

Molecular Pathogenesis

JAK-STAT Pathway Dysregulation

The fundamental molecular defect in myelofibrosis involves constitutive activation of the JAK-STAT signalling pathway, which regulates haematopoietic cell proliferation, differentiation, and survival. [5,13]

Normal JAK-STAT Physiology:

1. Cytokine binding to type I/II cytokine receptors
2. Receptor dimerisation and JAK kinase activation
3. JAK-mediated phosphorylation of receptor cytoplasmic tails
4. STAT protein recruitment, phosphorylation, and dimerisation
5. STAT dimer nuclear translocation and target gene transcription

Pathological Activation in MF:

Downstream Consequences:

• Hyperactivation of STAT3 and STAT5 transcription factors
• Upregulation of anti-apoptotic genes (BCL2, BCL-XL, MCL1)
• Enhanced proliferation via MYC upregulation
• Cytokine-independent growth and survival of haematopoietic progenitors

Exam Detail: JAK2 V617F Molecular Detail: The valine-to-phenylalanine substitution at position 617 occurs in the JH2 pseudokinase domain, which normally exerts autoinhibitory constraint on the JH1 kinase domain. The V617F mutation disrupts this autoinhibition, leading to constitutive kinase activity. Importantly, JAK2 V617F is gain-of-function but not transforming in isolation—additional genetic events are required for full malignant phenotype. [13]

CALR Mutation Mechanism: Type 1 (52bp deletion) and Type 2 (5bp insertion) CALR mutations both create frameshifts in exon 9, generating a novel positively-charged C-terminal peptide. This mutant CALR protein binds the MPL receptor, inducing its dimerisation and activation independent of thrombopoietin (TPO) ligand. CALR-mutated MF shows distinct biology with enhanced megakaryopoiesis. [17]

Cytokine Storm and Inflammatory Milieu

A defining feature of MF pathophysiology is the profound dysregulation of cytokine production, creating a chronic inflammatory state. [6,18]

Elevated Cytokines in MF:

Cellular Sources:

• Dysplastic megakaryocytes (primary source of TGF-β, PDGF)
• Clonal monocytes (TNF-α, IL-6, IL-8)
• Activated marrow stromal cells

Symptom Correlation: The Total Symptom Score (TSS) in MF correlates more strongly with circulating inflammatory cytokine levels than with spleen size, haemoglobin, or blast count, explaining why JAK inhibitors dramatically improve symptoms despite modest impact on disease biology. [6]

Bone Marrow Fibrosis Development

Key Principle: The fibroblasts are NOT part of the malignant clone [5]

Bone marrow fibrosis in MF is a reactive process driven by paracrine signalling from clonal haematopoietic cells to non-clonal mesenchymal stromal cells.

Fibrosis Progression:

1. Early Phase (Pre-fibrotic PMF):

   • Hypercellular marrow with megakaryocyte proliferation and atypia
   • Minimal or absent reticulin fibrosis (MF-0 or MF-1)
   • Often misdiagnosed as essential thrombocythaemia [9]

2. Established Fibrotic Phase:

   • Progressive reticulin fibre deposition (MF-2: diffuse reticulin; MF-3: collagen fibrosis)
   • Marrow hypocellularity
   • Loss of normal haematopoietic architecture

3. Advanced Phase:

   • Dense collagen fibrosis with osteosclerosis
   • Near-complete marrow ablation
   • Extensive extramedullary haematopoiesis

WHO Grading of Bone Marrow Fibrosis (Reticulin Stain): [9]

Osteosclerosis: In 30-50% of cases, bone marrow fibrosis is accompanied by new bone formation (osteosclerosis), particularly affecting the axial skeleton. This results from dysregulated production of bone morphogenetic proteins and contributes to severe bone pain. [19]

Extramedullary Haematopoiesis (EMH)

When the bone marrow microenvironment becomes unsuitable for haematopoiesis due to fibrosis, haematopoietic stem and progenitor cells (HSPCs) migrate to ectopic sites, predominantly spleen and liver. [20]

Mechanism of EMH:

• Downregulation of CXCR4 (marrow retention receptor) on HSPCs
• Upregulation of adhesion molecules and chemokines in spleen/liver
• Abnormal stem cell trafficking via SDF-1/CXCR4 axis disruption

Sites of EMH (in order of frequency):

1. Spleen (95-100%): Leads to massive splenomegaly (median 15-20 cm below costal margin)
2. Liver (50-70%): Hepatomegaly, portal hypertension
3. Lymph nodes (10-20%)
4. Serosal surfaces (pleura, peritoneum, pericardium)
5. Paraspinal masses: Can cause spinal cord compression (rare but critical) [21]
6. Skin, lung, kidney, CNS, bowel (case reports)

Clinical Consequences:

• Splenomegaly-related symptoms (pain, early satiety, splenic infarction)
• Portal hypertension due to increased splenic blood flow
• Ascites, variceal bleeding
• Symptomatic organomegaly

Clonal Evolution and Leukaemic Transformation

Myelofibrosis is a genetically unstable disease with progressive acquisition of additional mutations. [14]

Temporal Model of Clonal Evolution:

Normal Haematopoiesis
         ↓
Germline Predisposition (JAK2 46/1 haplotype)
         ↓
Driver Mutation Acquisition (JAK2/CALR/MPL)
         ↓ [years]
Additional Mutations (ASXL1, TET2, DNMT3A)
         ↓ [years]
High Molecular Risk Mutations (EZH2, SRSF2, IDH1/2, U2AF1)
         ↓ [variable]
Blast Transformation → Secondary AML

Risk of Leukemic Transformation:

• Cumulative incidence: 15-20% at 10 years [7]
• Median time from MF diagnosis to AML: 4-5 years
• Post-transformation survival: 3-6 months (highly chemoresistant)

Genomic Features of Transformation:

• TP53 mutations (30-40% of transformed cases)
• Complex karyotype (> 70% of cases)
• Additional chromosome 7 abnormalities
• RAS pathway mutations (NRAS, KRAS)

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4. Clinical Presentation

Myelofibrosis presents with a heterogeneous spectrum of symptoms and signs reflecting bone marrow failure, extramedullary haematopoiesis, and systemic inflammation.

Symptoms

Constitutional Symptoms (Present in 70-80%) [6]

Severity Often Disproportionate to Disease Burden:

Myelofibrosis-Specific Symptom Assessment: The Myelofibrosis Symptom Assessment Form (MF-SAF) quantifies 10 key symptoms on 0-10 scales, providing Total Symptom Score (TSS) used in clinical trials and practice. [22]

Splenomegaly-Related Symptoms (60-90%)

• Early Satiety: Stomach compression by enlarged spleen
• Left Upper Quadrant Pain: Splenic capsular stretching, infarction
• Abdominal Fullness/Distension: Mass effect
• Postprandial Discomfort: Gastric compression

Splenic Infarction: Occurs in 10-20% of patients; presents with acute severe LUQ pain, pleuritic in nature, associated with fever. Splenic rub may be audible on auscultation. [23]

Cytopenias and Their Consequences

Anaemia (60-70% at presentation):

• Progressive fatigue, dyspnoea on exertion
• Reduced exercise tolerance
• Cognitive impairment in elderly

Thrombocytopenia (30-40% during disease course):

• Mucocutaneous bleeding (petechiae, purpura, epistaxis)
• GI bleeding (especially if portal hypertension co-exists)
• Intracranial haemorrhage (rare, typically platelet less than 20×10⁹/L)

Leucopenia:

• Increased infection susceptibility (often compounded by splenic sequestration)

Thrombotic Manifestations (10-15% of patients) [24]

Despite thrombocytopenia in many patients, paradoxical thrombotic risk exists:

• Arterial: Stroke, myocardial infarction, peripheral arterial occlusion
• Venous: Deep vein thrombosis, pulmonary embolism
• Splanchnic Thrombosis: Portal vein, hepatic vein (Budd-Chiari), mesenteric vein

Higher Thrombotic Risk in:

• JAK2 V617F-positive patients (vs CALR-mutated)
• Extreme thrombocytosis (platelets > 1000×10⁹/L)
• History of prior thrombosis

Signs

General Inspection

• Pallor: Reflecting anaemia
• Cachexia: Advanced disease with significant weight loss
• Plethora: Rare, more typical of post-PV MF
• Jaundice: Hypersplenism, haemolysis, or hepatic dysfunction

Abdominal Examination

Splenomegaly (90-100% of cases):

• Massive Splenomegaly: Often extending to RIF, crossing midline
• Characteristics: Firm, non-tender (unless infarction), smooth surface, medial notch palpable
• Measurement: Record cm below left costal margin in mid-clavicular line
• Auscultation: Splenic rub if recent infarction

Hepatomegaly (40-70%):

• Extramedullary haematopoiesis
• Usually firm, non-tender, smooth edge
• May be accompanied by ascites if portal hypertension develops

Ascites:

• Portal hypertension from massive splenic inflow
• Stigmata of chronic liver disease typically absent

Other Physical Signs

• Lymphadenopathy (10-20%): Extramedullary haematopoiesis
• Gouty Tophi: Hyperuricaemia from high cell turnover
• Petechiae/Ecchymoses: Thrombocytopenia
• Leukaemia Cutis: Rare, cutaneous infiltration by leukaemic cells (sign of transformation)
• Sweet's Syndrome: Acute febrile neutrophilic dermatosis (paraneoplastic)

Presentation Patterns by Age

Younger Patients (less than 50 years):

• More likely asymptomatic at diagnosis (incidental finding)
• Higher frequency of CALR mutations
• Thrombocytosis more common
• Better tolerability of intensive therapies

Elderly Patients (> 70 years):

• More symptomatic at presentation
• Higher burden of constitutional symptoms
• Greater comorbidity burden
• Increased treatment-related toxicity

Asymptomatic Presentation

10-30% of cases are diagnosed incidentally during evaluation for:

• Abnormal blood count on routine testing
• Splenomegaly discovered on imaging for other indications
• Screening in context of known PV/ET

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5. Differential Diagnosis

The combination of cytopenias, leucoerythroblastic blood film, splenomegaly, and bone marrow fibrosis must prompt consideration of multiple aetiologies.

Primary Differential: Other Myeloproliferative Neoplasms

Secondary Causes of Bone Marrow Fibrosis

Malignant:

• Hairy Cell Leukaemia: Dry tap, pancytopenia, but specific morphology (hairy cells, TRAP positive)
• Acute Megakaryoblastic Leukaemia: Acute presentation, higher blast count, CD41/CD61 positivity
• Metastatic Carcinoma: Prostate, breast, lung, stomach; hard irregular marrow on trephine, cytokeratin-positive cells
• Lymphoma: B symptoms, lymphadenopathy, specific immunophenotype
• Mastocytosis: Urticaria pigmentosa, elevated tryptase, KIT D816V mutation

Non-Malignant:

• Autoimmune Myelofibrosis: Association with SLE, RA, scleroderma; absence of clonal markers
• Infections: TB, HIV, visceral leishmaniasis (specific pathogen identification)
• Metabolic: Gaucher disease, Paget disease (specific enzyme/imaging findings)
• Toxic: Benzene, radiation, vitamin D toxicity (exposure history)

Causes of Massive Splenomegaly (> 8cm BCM)

Mnemonic: "My Liver Can Make Giant Liver Cells"

• Myelofibrosis
• Leukaemia (CML, hairy cell)
• Cirrhosis with portal hypertension
• Malaria (hyperreactive malarial splenomegaly)
• Gaucher disease
• Leishmaniasis (visceral)
• Lymphoma (splenic marginal zone)
• (CML already listed)

Discriminating Features in Difficult Cases

Pre-fibrotic PMF vs Essential Thrombocythaemia: This is a crucial and difficult distinction with major prognostic implications. [9]

Diagnostic Algorithm for Leucoerythroblastic Blood Film:

Leucoerythroblastic Blood Film
         ↓
  Bone Marrow Examination
         ↓
    Fibrosis Present?
    ↙             ↘
  YES              NO
   ↓                ↓
MPN Features?    Infiltration?
(JAK2/CALR/MPL)  (metastasis, infection)
   ↓
Myelofibrosis vs Secondary Fibrosis
(Clinical context, mutation profile)

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6. Investigations

First-Line Investigations

Full Blood Count and Blood Film

Complete Blood Count Findings:

Critical Blood Film Features: [25]

1. Leucoerythroblastic Picture:

   • Nucleated red blood cells (normoblasts) in peripheral blood
   • Immature granulocytic precursors (myelocytes, metamyelocytes)
   • Reflects extramedullary haematopoiesis and marrow disruption

2. Dacrocytes (Tear Drop Cells): Pathognomonic

   • Red cells with single pointed projection
   • Caused by mechanical deformation as cells squeeze through fibrotic marrow sinusoids
   • Frequency correlates with degree of fibrosis

3. Poikilocytosis:

   • Anisopoikilocytosis (variation in size and shape)
   • Bizarre red cell morphology

4. Circulating Megakaryocyte Nuclei/Fragments:

   • Highly suggestive of MF
   • Result of megakaryocyte fragmentation in spleen/marrow

5. Dysplastic Features:

   • Hypolobated or hyperlobated neutrophils
   • Giant platelets

Exam Detail: Blood Film Reporting in MF: A typical report might read: "Moderate anaemia with normocytic normochromic indices. Marked anisopoikilocytosis with frequent tear drop cells. Leucoerythroblastic picture with circulating nucleated red cells (5 per 100 WBC) and myelocytes. Occasional megakaryocyte fragments seen. Platelet anisocytosis with giant forms. Appearances consistent with bone marrow infiltrative process, most in keeping with myelofibrosis. Suggest bone marrow examination and JAK2 mutation analysis."

Biochemistry

Lactate Dehydrogenase (LDH):

• Elevated in 70-90% of cases (marker of cell turnover)
• Degree of elevation correlates with disease burden and prognosis
• Markedly elevated LDH suggests blast transformation

Uric Acid:

• Hyperuricaemia from increased cell turnover (30-50% of cases)
• Risk of gout and tumour lysis syndrome (especially with JAK inhibitor initiation)

Liver Function Tests:

• Often deranged if hepatic extramedullary haematopoiesis
• Hypoalbuminaemia reflects chronic disease/malnutrition

Inflammatory Markers:

• Elevated CRP (reflects IL-6 driven acute phase response)
• May help differentiate from infection

Bone Marrow Examination

Aspiration:

• "Dry Tap" in 50-80%: Pathognomonic; reflects dense fibrosis preventing aspiration [25]
• If aspirate obtained: dysplastic megakaryocytes, increased blasts (if accelerated phase)

Trephine Biopsy (ESSENTIAL for Diagnosis): [9]

Histological Features:

1. Fibrosis Grading: Reticulin (silver) stain mandatory

   • MF-2 or MF-3 confirms established myelofibrosis
   • MF-0/MF-1 seen in pre-fibrotic PMF

2. Megakaryocyte Morphology:

   • Atypical megakaryocytes with cloud-like or hyperchromatic nuclei
   • Dense clustering
   • Abnormal distribution (intrasinusoidal)

3. Cellularity:

   • Pre-fibrotic: Hypercellular (> 75%)
   • Fibrotic: Variable, often hypocellular with fat atrophy

4. Osteosclerosis:

   • New bone formation in 30-50%
   • Best appreciated on trichrome stain

5. Additional Stains:

   • CD34: Highlights increased microvessel density
   • CD61/CD42b: Confirms megakaryocytic lineage
   • Trichrome: Demonstrates collagen fibrosis (MF-3)

Grading System Integration: WHO Classification requires correlation of histological fibrosis grade with clinical and molecular features for accurate classification. [9]

Molecular and Cytogenetic Studies

Driver Mutation Testing (MANDATORY)

Testing Strategy: [13]

1. JAK2 V617F: Allele-specific PCR (detects down to 1% variant allele frequency)

   • Positive in 50-60% of PMF
   • Quantitative allele burden measurement prognostic (higher burden = worse outcome)

2. CALR exon 9 mutations (if JAK2 negative):

   • Fragment analysis or Sanger sequencing
   • Type 1 (52bp deletion, 45%) vs Type 2 (5bp insertion, 32%) vs other (23%)
   • Type 1 generally more favourable prognosis than Type 2

3. MPL W515 mutations (if JAK2/CALR negative):

   • Targeted sequencing
   • W515L more common than W515K

Triple-Negative Cases (JAK2/CALR/MPL all negative):

• 10-15% of cases
• Require broader NGS panel (occasionally non-canonical JAK2 mutations)
• Worse prognosis; higher thrombotic/transformation risk [10]

Next-Generation Sequencing (NGS) Panel

High Molecular Risk (HMR) Mutations: [14]

Testing for prognostically-relevant mutations increasingly routine:

Mutation-Enhanced International Prognostic Scoring System (MIPSS70): Integrates driver mutation type and HMR mutations into risk stratification. [26]

Cytogenetic Analysis

Karyotype (Conventional):

• Abnormal in 30-40% of PMF cases [27]
• Complex karyotype (≥3 abnormalities): Very high-risk feature
• Specific abnormalities associated with adverse outcome:
  • del(5q), -5, -7, del(7q): Very high risk
  • del(12p), del(20q): Intermediate risk
  • +8, +9, -13, del(13q): Lower risk

Fluorescence In Situ Hybridisation (FISH):

• Useful if inadequate metaphases from fibrotic marrow
• Targeted panels for del(5q), -7/del(7q), +8, -13/del(13q), del(20q)

Single Nucleotide Polymorphism Array (SNP-A):

• Detects copy-neutral loss of heterozygosity (CN-LOH)
• Particularly chromosome 9p CN-LOH (homozygous JAK2 V617F)

Imaging Investigations

Abdominal Ultrasound

First-line Imaging:

• Confirms splenomegaly and hepatomegaly
• Assesses spleen size (baseline and monitoring)
• Evaluates portal and hepatic veins (thrombosis assessment)
• Identifies ascites
• Non-invasive, repeatable

CT Chest/Abdomen/Pelvis

Indications:

• Staging at diagnosis (particularly if transplant candidate)
• Detection of extramedullary masses (lymph nodes, paraspinal)
• Assessment of splenic complications (infarction, rupture)
• Evaluation of progressive symptoms

Typical Findings:

• Splenomegaly (often > 20 cm craniocaudal diameter)
• Hepatomegaly
• Lymphadenopathy (10-20% of cases)
• Osteosclerosis on bone windows

MRI Spine

Indication: Back pain, neurological symptoms (to exclude spinal cord compression from extramedullary haematopoiesis) [21]

Findings:

• Marrow signal alteration (loss of normal T1 hyperintensity)
• Paraspinal soft tissue masses (extramedullary haematopoietic masses)
• Potential spinal canal compromise

PET-CT

Emerging Role:

• Not routine
• Useful in differentiating splenic extramedullary haematopoiesis from lymphoma
• Assessment of suspected leukaemic transformation (focal FDG-avid lesions)

Specialist Investigations

Spleen Size Quantification

• Palpation: cm below left costal margin (subject to inter-observer variability)
• Ultrasound: Craniocaudal diameter
• MRI Volumetry: Most accurate; used in clinical trials (COMFORT studies used MRI-derived spleen volume) [8]

Bone Marrow Immunophenotyping (Flow Cytometry)

Indications:

• Suspicion of blast transformation (increased CD34+ cells)
• Exclusion of lymphoproliferative disorder
• Characterisation of dysplastic features

Serum Erythropoietin (EPO)

• Usually inappropriately normal or low given degree of anaemia
• Very high EPO suggests secondary erythrocytosis or renal pathology

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7. Classification and Risk Stratification

WHO Classification (2016/2022) [9]

Diagnostic Criteria for Primary Myelofibrosis:

Major Criteria (all 3 required):

1. Bone marrow biopsy showing megakaryocytic proliferation and atypia, accompanied by either reticulin and/or collagen fibrosis grades MF-2 or MF-3 (overt PMF) OR reticulin fibrosis grade MF-0 or MF-1 (pre-fibrotic PMF)
2. Not meeting WHO criteria for BCR-ABL1+ CML, PV, ET, myelodysplastic syndromes, or other myeloid neoplasms
3. Presence of JAK2, CALR, or MPL mutation OR, in the absence of these mutations, presence of another clonal marker or absence of minor criteria for reactive myelofibrosis

Minor Criteria (≥1 required for pre-fibrotic PMF, not needed for overt PMF):

1. Anaemia not attributed to other comorbidity
2. Leucocytosis ≥11×10⁹/L
3. Palpable splenomegaly
4. LDH elevated above upper limit of normal
5. Leucoerythroblastic blood picture

Diagnostic Criteria for Post-PV MF and Post-ET MF: [3,4]

Required Criteria:

1. Documented previous diagnosis of PV (per WHO criteria) or ET (per WHO criteria)
2. Bone marrow fibrosis grade ≥MF-2 (on 0-3 scale) OR grade MF-1 accompanied by ≥2 additional criteria

Additional Criteria:

• Anaemia or sustained loss of requirement for phlebotomy (for post-PV MF) or cytoreductive therapy (for post-ET MF)
• Leucoerythroblastic peripheral blood picture
• Increasing splenomegaly (> 5 cm increase OR new palpable splenomegaly)
• Development of ≥1 constitutional symptoms
• Increased LDH above upper limit of normal

Prognostic Scoring Systems

International Prognostic Scoring System (IPSS) [28]

For Use at Diagnosis Only:

Risk Factors (1 point each):

• Age > 65 years
• Constitutional symptoms present
• Haemoglobin less than 100 g/L
• Leucocyte count > 25×10⁹/L
• Peripheral blood blasts ≥1%

Limitations:

• Static score (cannot be recalculated after diagnosis)
• Does not account for dynamic clinical changes
• Pre-dates molecular era

Dynamic International Prognostic Scoring System (DIPSS) [29]

Can Be Calculated at Any Time During Disease:

Risk Factors (points assigned):

• Age > 65 years (1 point)
• Constitutional symptoms present (1 point)
• Haemoglobin less than 100 g/L (2 points)
• Leucocyte count > 25×10⁹/L (1 point)
• Peripheral blood blasts ≥1% (1 point)

DIPSS-Plus [30]

Adds Additional Risk Factors to DIPSS:

Additional Variables (1 point each):

• Platelet count less than 100×10⁹/L
• Transfusion requirement
• Unfavourable karyotype (complex karyotype or sole/two abnormalities including +8, -7/7q-, i(17q), inv(3), -5/5q-, 12p-, 11q23)

Mutation-Enhanced International Prognostic Scoring System (MIPSS70) [26]

For Transplant-Eligible Patients (less than 70 years):

Integrates Molecular Data:

Risk Factors with Points:

• Constitutional symptoms: 2 points
• Haemoglobin less than 100 g/L: 1 point
• Leucocytes > 25×10⁹/L: 2 points
• Platelets less than 100×10⁹/L: 2 points
• Circulating blasts ≥2%: 1 point
• BM fibrosis grade ≥2: 1 point
• Absence of CALR Type 1/like mutation: 2 points (exception: if ASXL1 mutation present = 0 points)
• ASXL1 mutation present: 2 points
• SRSF2 mutation present: 2 points
• U2AF1 Q157 mutation present: 2 points

MIPSS70+ Version 2.0: Further refined with additional mutations (EZH2, IDH1/IDH2) and karyotype data. [31]

Other Prognostic Models

MIPSS70+ v2.0: Adds high-risk karyotype, further refined molecular annotation [31]

Leukemia Transformation Risk Score: Specific models predict probability of blast transformation (include prior thrombosis, platelet less than 200, LDH, circulating blasts, karyotype, ASXL1/SRSF2 mutations).

Transplant Decision-Making Scores

Transplant Decision Support (TDS) Tool: Balances disease risk (DIPSS, MIPSS70) against transplant-related mortality risk (age, comorbidities, donor match) to guide transplant timing. [32]

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8. Management

The management of myelofibrosis is highly individualised, guided by risk stratification, symptom burden, age, comorbidities, and transplant eligibility.

Overall Management Strategy

MYELOFIBROSIS DIAGNOSIS
        ↓
Risk Stratification (DIPSS / MIPSS70)
        ↓
    Determine:
    1. Transplant Eligibility (age, fitness, donor)
    2. Symptom Burden (splenomegaly, constitutional)
    3. Cytopenias
        ↓
┌───────────────┴────────────────┐
│                                 │
LOW / INT-1 RISK          INT-2 / HIGH RISK
(Asymptomatic)              (Symptomatic)
    ↓                              ↓
WATCH & WAIT           TRANSPLANT CANDIDATE?
Monitor q3-6 months         ↙            ↘
    │                    YES              NO
    │                     ↓                ↓
    │             ALLOGENEIC SCT    JAK INHIBITOR
    │             (Curative)         (Palliative)
    │                 │                   │
    └─────────────────┴───────────────────┘
                      ↓
        Supportive Care Throughout:
        - Transfusions
        - Manage cytopenias
        - Splenectomy if indicated
        - Clinical trial consideration

Allogeneic Stem Cell Transplantation (ONLY CURATIVE THERAPY) [32,33]

Indications:

• Intermediate-2 or High-risk disease (DIPSS/MIPSS70)
• Age typically less than 70 years (biological age more important than chronological)
• Adequate performance status (ECOG 0-2)
• Absence of prohibitive comorbidities
• Available suitable donor (matched sibling, matched unrelated, haploidentical)

Timing Considerations:

• Balance disease risk vs transplant-related mortality
• Earlier transplant for very high-risk molecular profile (multiple HMR mutations)
• Delay if low/intermediate-1 risk with manageable symptoms

Conditioning Regimens:

• Myeloablative Conditioning: Higher TRM (transplant-related mortality) but lower relapse; younger, fitter patients
• Reduced-Intensity Conditioning (RIC): Lower TRM, higher relapse; older patients, more comorbidity
• Most centres use RIC for MF patients given older age demographic

Outcomes: [33]

• 5-year overall survival: 40-55% (varies with risk stratification and conditioning)
• Transplant-related mortality: 15-30% (higher in MF than other conditions due to splenomegaly, fibrosis)
• Relapse risk: 15-25%

Pre-Transplant Splenectomy:

• Controversial
• Advocated by some centres for massive splenomegaly (> 20 cm) to reduce peri-transplant complications
• Risk of surgical mortality/morbidity must be weighed
• Alternative: JAK inhibitor pre-transplant to reduce spleen size

Post-Transplant:

• GVHD prophylaxis (calcineurin inhibitor + methotrexate or MMF)
• MRD monitoring (chimerism, driver mutation VAF)
• Relapse management: Donor lymphocyte infusion (DLI), JAK inhibitor

JAK Inhibitor Therapy [8,16,34,35]

JAK inhibitors are the backbone of symptom-directed therapy in MF. They do NOT eradicate the malignant clone or reverse fibrosis but provide significant symptomatic benefit and likely survival advantage. [8]

Ruxolitinib (First-line JAK Inhibitor) [8]

Mechanism:

• Selective JAK1/JAK2 inhibitor
• Inhibits both wild-type and mutant JAK2
• Effective regardless of JAK2 mutation status (works via reducing downstream cytokine signalling)

Evidence Base:

• COMFORT-I Trial (N Engl J Med 2012): Ruxolitinib vs placebo; 41.9% vs 0.7% achieved ≥35% spleen volume reduction at 24 weeks [8]
• COMFORT-II Trial: Ruxolitinib vs best available therapy; superior spleen reduction and symptom control
• 5-year Follow-up: Survival advantage demonstrated (HR 0.69, p=0.009) [16]

Indications:

• Intermediate-2 or High-risk MF per DIPSS
• Symptomatic splenomegaly (≥5 cm below costal margin)
• Constitutional symptoms impacting quality of life

Dosing:

• Platelets ≥200×10⁹/L: Start 20 mg BD
• Platelets 100-200×10⁹/L: Start 15 mg BD
• Platelets 50-100×10⁹/L: Start 5 mg BD (off-label)
• Platelets less than 50×10⁹/L: Generally contraindicated

Dose Adjustments:

• Titrate based on efficacy and tolerability (cytopenias, infections)
• Renal impairment requires dose reduction

Expected Response:

• Spleen reduction: 40-50% achieve ≥35% reduction by 24 weeks
• Symptom improvement: 50-60% achieve ≥50% reduction in TSS
• Time to response: 4-12 weeks

Adverse Effects:

• Cytopenias (dose-dependent): Anaemia (60-80%, often transient), thrombocytopenia (50%)
• Infections: Increased risk (especially herpes zoster, urinary tract infections)
• Opportunistic Infections: TB reactivation, PML (rare), cryptococcal (rare)
• Weight Gain: 10-20% of patients
• Hyperlipidaemia: Monitor lipids
• Non-melanoma Skin Cancer: Increased incidence reported

Ruxolitinib Withdrawal Syndrome:

• Rapid discontinuation can cause rebound splenomegaly, cytokine flare, acute decompensation
• Taper gradually when stopping (reduce by 5 mg per week)

Loss of Response:

• 10-20% per year lose initial spleen/symptom response
• Mechanisms: Clonal evolution, emergent resistance mutations, progression
• Options: Increase dose (if tolerated), switch JAK inhibitor, clinical trial

Exam Detail: COMFORT-I Study Design: Phase III, randomised, double-blind, placebo-controlled trial of ruxolitinib in intermediate-2 or high-risk MF. Primary endpoint: Proportion achieving ≥35% reduction in spleen volume at 24 weeks (measured by MRI/CT). Secondary endpoints included symptom response (TSS), overall survival. Study established the benchmark for MF therapy approval. [8]

Fedratinib (Second-line JAK Inhibitor) [34]

Mechanism:

• Selective JAK2/FLT3 inhibitor
• More selective for JAK2 than ruxolitinib

Evidence Base:

• JAKARTA Trial: vs placebo; 36% vs 1% achieved ≥35% spleen volume reduction
• JAKARTA-2: In ruxolitinib-exposed patients; 31% spleen response [34]
• Approved for ruxolitinib-resistant/intolerant MF

Indications:

• Intermediate-2 or High-risk MF
• Ruxolitinib resistance or intolerance
• Alternative first-line if patient factors favour fedratinib

Dosing:

• 400 mg once daily
• Lower threshold platelet requirement than ruxolitinib (≥50×10⁹/L)

Adverse Effects:

• Gastrointestinal: Nausea, diarrhoea, vomiting (most common)
• Encephalopathy/Wernicke's: Rare but serious; mandatory thiamine supplementation and monitoring
• Anaemia: Less pronounced than ruxolitinib
• Cytopenias: Thrombocytopenia, neutropenia

Monitoring:

• Baseline and periodic thiamine levels
• Neurological assessment (if any confusion, ataxia, ophthalmoplegia → STOP drug immediately)

Pacritinib (Third JAK Inhibitor, for Severe Thrombocytopenia) [35]

Mechanism:

• JAK2/FLT3/IRAK1 inhibitor
• Minimal myelosuppressive effect on platelets

Evidence Base:

• PERSIST-1 and PERSIST-2: Demonstrated efficacy in patients with platelets less than 100×10⁹/L
• PACIFICA Trial: Confirmed spleen and symptom benefit in thrombocytopenic population
• FDA approved 2022 for MF with platelets less than 50×10⁹/L [35]

Indications:

• Intermediate or High-risk MF
• Platelets less than 50×10⁹/L (unique niche)

Dosing:

• 200 mg twice daily

Adverse Effects:

• Gastrointestinal: Diarrhoea (60%, often chronic), nausea
• Bleeding: Despite thrombocytopenia, bleeding risk not substantially increased
• Cardiac: QTc prolongation (requires ECG monitoring)

Advantages:

• Only JAK inhibitor viable in severe thrombocytopenia
• Alternative for patients intolerant of ruxolitinib/fedratinib

Management of Cytopenias

Anaemia Management [36]

Transfusion Support:

• Mainstay for symptomatic anaemia
• Target Hb > 80 g/L to relieve symptoms
• Iron chelation if transfusion burden > 20-25 units (ferritin > 1000 μg/L) and life expectancy > 1 year

Erythropoiesis-Stimulating Agents (ESAs):

• Indication: Hb less than 100 g/L, serum EPO less than 125 U/L, low transfusion burden
• Agents: Darbepoetin, epoetin
• Response Rate: 20-30% (lower than in other anaemias)
• Trial Duration: 12-16 weeks before declaring failure

Immunomodulatory Drugs (IMiDs):

• Often combined with corticosteroids (prednisone 0.5-1 mg/kg)
• Side effects: Peripheral neuropathy (thalidomide), cytopenias, thrombosis (require prophylactic anticoagulation)

Danazol (Androgenic Steroid):

• 200-600 mg daily
• Response rate: 20-30%
• Mechanism: Uncertain; may stimulate erythropoiesis, reduce haemolysis
• Side effects: Hepatotoxicity, masculinisation, dyslipidaemia

Luspatercept:

• Emerging option; TGF-β superfamily inhibitor
• Promotes late-stage erythroid maturation
• Response in MF anaemia: ~20% (ongoing trials)

Thrombocytopenia Management

Transfusion:

• Platelet transfusion for active bleeding or pre-procedure (target > 50×10⁹/L)
• HLA-matched platelets if refractory

Thrombopoietin Receptor Agonists (TPO-RAs):

• Romiplostim, Eltrombopag: Small studies show 20-30% response
• Concern: Theoretical risk of increasing marrow fibrosis, blast progression (use with caution, not FDA approved for MF)

Splenectomy:

• If significant platelet sequestration contributing to thrombocytopenia

Leucopenia and Infection Management

• Prophylactic antibiotics not routine
• G-CSF (granulocyte colony-stimulating factor) for recurrent infections with neutropenia
• Vaccination: Annual influenza, pneumococcal, herpes zoster (if not on JAK inhibitor or use inactivated vaccine)

Splenomegaly Management

Medical (JAK Inhibitors):

• First-line as above

Splenectomy [37]

Indications:

• Symptomatic splenomegaly refractory to medical therapy (rare with JAK inhibitors)
• Severe transfusion-refractory cytopenias due to hypersplenism
• Recurrent splenic infarction
• Portal hypertension with variceal bleeding
• Pre-transplant cytoreduction

Outcomes:

• Symptom relief in 70-80%
• Improved cytopenias in 50%
• Operative mortality: 5-10% (higher in MF than other indications)
• Complications: Haemorrhage, thrombosis (portal/hepatic vein), infection, hepatomegaly (shift of EMH)

Post-Splenectomy:

• High thrombotic risk (portal vein thrombosis in 10-20%)
• Anticoagulation often recommended peri-operatively
• Rebound thrombocytosis
• Accelerated hepatomegaly (EMH shifts)

Splenic Radiotherapy [38]

Indications:

• Poor surgical candidate
• Symptomatic splenomegaly refractory to medical therapy
• Painful splenic infarction

Regimen:

• Low-dose: 3-10 Gy in fractionated doses

Response:

• Transient spleen reduction in 50-60%
• Short-lived benefit (median 3-6 months)
• Risk of severe cytopenias (30-40%)

Limited Role: Palliative only; largely superseded by JAK inhibitors

Management of Constitutional Symptoms

JAK Inhibitors:

• First-line (50-60% achieve ≥50% TSS reduction)

Corticosteroids (if JAK inhibitor contraindicated/failed):

• Prednisone 0.5 mg/kg daily
• Short-term benefit; tachyphylaxis and side effects limit use

Hyperuricaemia and Tumour Lysis Syndrome

Allopurinol:

• Prophylaxis for hyperuricaemia (300 mg daily)
• Particularly important when initiating JAK inhibitor (risk of TLS)

Febuxostat:

• Alternative if allopurinol contraindicated

Hydration:

• Adequate hydration when starting cytoreductive therapy

Thrombosis Management and Prevention [24]

Primary Prevention:

• Low-dose aspirin (75-100 mg) if platelet count adequate and no bleeding risk (especially JAK2-mutated patients)
• Cardiovascular risk factor optimisation

Treatment of Thrombosis:

• Standard anticoagulation (DOAC or LMWH/warfarin)
• Duration: Often lifelong given persistent thrombotic risk

Blast Transformation to AML [7]

Management:

• Intensive Chemotherapy: Generally poor response; median survival less than 6 months
• Hypomethylating Agents (Azacitidine, Decitabine): Modest responses (15-30%)
• JAK Inhibitor Continuation: May provide symptom benefit even in blast phase
• Allogeneic Transplant: Only potentially curative option if remission achieved; very high TRM

Prognosis:

• Dismal; median survival 3-6 months
• Response rates to chemotherapy less than 20%

Clinical Trials

Given the limited curative options and ongoing challenges with MF, clinical trial participation should be actively considered, especially for:

• JAK inhibitor-resistant disease
• High/very high-risk molecular profile
• Anaemia refractory to standard therapies
• Post-transplant relapse

Emerging Therapies in Trials:

• BET Inhibitors (e.g., CPI-0610): Targeting epigenetic regulation
• MDM2 Inhibitors: TP53 pathway modulation
• LSD1 Inhibitors: Epigenetic modulation
• PIM Kinase Inhibitors: Targeting downstream JAK-STAT signalling
• Telomerase Inhibitors (Imetelstat): Showed anaemia responses and spleen reduction
• Navitoclax (BCL-XL inhibitor) + Ruxolitinib: Combination approaching approval
• Momelotinib (JAK1/2/ACVR1 inhibitor): Addresses anaemia alongside spleen/symptoms

Special Populations

Pregnancy:

• Rare given age demographics
• High-risk pregnancy (thrombosis, placental insufficiency, haemorrhage)
• MDT approach with haematology and maternal-fetal medicine
• Interferon-alpha: Safe treatment option in pregnancy
• JAK inhibitors: Contraindicated (teratogenic in animal studies)
• Aspirin + LMWH for thromboprophylaxis

Younger Patients (less than 50 years):

• More aggressive approach to transplant
• Longer disease duration anticipated
• Earlier HLA typing and donor search

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9. Complications

Leukaemic Transformation to AML (15-20% cumulative incidence at 10 years) [7]

Risk Factors:

• Triple-negative mutation status
• Complex karyotype
• High-risk mutations (TP53, RUNX1, IDH1/2)
• Higher circulating blast percentage
• Post-PV or post-ET MF (vs primary MF)

Clinical Presentation:

• Progressive cytopenias
• Increasing circulating blasts (> 10%)
• Worsening constitutional symptoms
• Chloromas (myeloid sarcomas)

Diagnosis:

• Bone marrow blast count ≥20% (per WHO criteria)
• Often accompanied by complex cytogenetics

Prognosis:

• Exceptionally poor (median survival 3-6 months)
• Resistant to conventional AML chemotherapy
• Allogeneic transplant offers only chance of cure (rarely feasible)

Splenic Complications

Splenic Infarction (10-20% of patients): [23]

• Acute severe LUQ pain, pleuritic
• Fever, leucocytosis
• Diagnosis: CT abdomen (wedge-shaped hypodensity)
• Management: Analgesia, hydration; rarely requires splenectomy

Spontaneous Splenic Rupture (RED FLAG):

• Rare but life-threatening
• Acute abdominal pain, haemodynamic shock
• Emergency splenectomy required

Splenic Abscess:

• Rare; higher risk if immunocompromised
• Fever, LUQ tenderness, leucocytosis
• CT-guided drainage or splenectomy

Portal Hypertension and Hepatic Complications [39]

Mechanisms:

• Massive splenic inflow (portal vein thrombosis independent)
• Hepatic EMH
• Portal vein thrombosis

Manifestations:

• Ascites
• Variceal bleeding (oesophageal, gastric)
• Hepatic encephalopathy (rare)
• Hepatosplenomegaly

Management:

• Portal hypertension: Beta-blockers (propranolol), variceal banding
• Refractory ascites: Diuretics, large-volume paracentesis
• TIPSS (transjugular intrahepatic portosystemic shunt): Rarely used; high-risk procedure

Budd-Chiari Syndrome:

• Hepatic vein thrombosis
• Acute liver failure, ascites, hepatomegaly
• High mortality; anticoagulation ± TIPSS

Thrombotic Complications [24]

Arterial Thrombosis:

• Stroke, myocardial infarction, peripheral arterial occlusion
• Risk factors: JAK2 V617F, prior thrombosis, cardiovascular risk factors

Venous Thromboembolism:

• DVT, PE
• Higher risk peri-operatively (especially post-splenectomy)

Splanchnic Vein Thrombosis:

• Portal vein (most common), hepatic vein, mesenteric vein, splenic vein
• High index of suspicion; Doppler ultrasound/CT imaging

Haemorrhagic Complications

Mechanisms:

• Thrombocytopenia
• Acquired von Willebrand disease (vWD) in extreme thrombocytosis
• Platelet dysfunction
• Hypersplenism

Manifestations:

• Mucocutaneous bleeding (epistaxis, gingival bleeding)
• GI bleeding (especially if portal hypertension/varices)
• Intracranial haemorrhage (rare, severe thrombocytopenia)

Extramedullary Haematopoiesis Complications [20,21]

Spinal Cord Compression (RED FLAG):

• Paraspinal EMH masses compress spinal cord
• Back pain, lower limb weakness, sensory level, sphincter dysfunction
• Urgent MRI spine
• Treatment: Radiotherapy, surgical decompression, JAK inhibitor

Pulmonary Hypertension:

• EMH in pulmonary vasculature
• Progressive dyspnoea, right heart failure
• Diagnosis: Echocardiography, right heart catheterisation
• Treatment: JAK inhibitor, targeted pulmonary hypertension therapy

Serosal EMH:

• Pleural effusions, ascites, pericardial effusion
• Often symptomatic

Other Sites:

• CNS (headaches, seizures, focal neurology)
• Lymph nodes (lymphadenopathy)
• Skin (nodules)

Infections

Increased Risk:

• Disease-related immune dysfunction
• Hyposplenism (post-splenectomy)
• JAK inhibitor therapy (impaired IFN-γ signalling)
• Neutropenia

Specific Infections of Concern:

• Herpes Zoster: 10-15% on ruxolitinib [8]
• Tuberculosis Reactivation: Screen prior to JAK inhibitor initiation
• Opportunistic Infections: PML, cryptococcus, atypical mycobacteria (rare)
• Encapsulated Organisms (post-splenectomy): Pneumococcus, H. influenzae, meningococcus

Prevention:

• Vaccination (pneumococcal, influenza, HZ if appropriate)
• TB screening (IGRA, CXR) before JAK inhibitor
• Antimicrobial prophylaxis post-splenectomy (penicillin V)

Bone Disease

Osteosclerosis:

• Dense bone on imaging (30-50% of cases)
• Severe bone pain
• Elevated alkaline phosphatase

Osteoporosis:

• Chronic disease, corticosteroid use
• Fracture risk

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10. Prognosis and Outcomes

Survival by Risk Group

Median overall survival in MF is highly variable, ranging from 2 to > 15 years depending on risk stratification. [28,29]

DIPSS Risk Groups: [29]

MIPSS70 Risk Groups (Transplant-Eligible): [26]

Impact of JAK Inhibitors on Survival

COMFORT Studies Long-term Follow-up: [16]

• 5-year overall survival: Ruxolitinib 56% vs control 44% (HR 0.69, p=0.009)
• Survival benefit most pronounced in intermediate-2/high-risk disease
• Mechanism unclear (not due to disease modification; possibly relates to reduced complications, spleen size reduction, improved nutritional status)

Prognostic Factors

Adverse Prognostic Factors:

Clinical:

• Advanced age (> 65 years)
• Constitutional symptoms
• Severe anaemia (Hb less than 100 g/L)
• Thrombocytopenia (less than 100×10⁹/L)
• Leucocytosis (> 25×10⁹/L)
• High circulating blasts (≥1%)
• Transfusion dependency
• Marked splenomegaly (> 15 cm below costal margin)

Laboratory:

• High LDH
• High beta-2 microglobulin
• Low albumin

Molecular:

• Triple-negative mutation status (vs CALR Type 1)
• High molecular risk mutations: ASXL1, EZH2, SRSF2, IDH1/2, U2AF1 [14]
• Presence of ≥2 HMR mutations (very poor prognosis)

Cytogenetic:

• Complex karyotype (≥3 abnormalities)
• Specific abnormalities: -7/del(7q), -5/del(5q), i(17q), inv(3), 12p-, 11q23 [27]
• Monosomal karyotype

Favourable Prognostic Factors:

• CALR Type 1 mutation (best prognosis among driver mutations) [10]
• Younger age (less than 60 years)
• Absence of constitutional symptoms
• Preserved haemoglobin (> 100 g/L)
• Low-risk karyotype

Causes of Death

Primary Causes: [40]

1. Leukaemic Transformation (15-30%)
2. Infection/Sepsis (15-25%)
3. Heart Failure (10-15%)
4. Bleeding (10-15%)
5. Thrombosis (5-10%)
6. Hepatic Failure (5%)
7. Other Malignancies (5%)

Quality of Life

MF has profound impact on quality of life due to:

• Debilitating fatigue (most commonly reported symptom)
• Abdominal discomfort from splenomegaly
• Constitutional symptoms (night sweats, weight loss)
• Transfusion dependency (frequent hospital visits)
• Reduced functional capacity

Improvement with JAK Inhibitors:

• 50-60% of patients achieve clinically meaningful symptom improvement (≥50% TSS reduction) [8]
• Improvement sustained in responders
• Enhanced quality of life scores (EORTC QLQ-C30, FACT-Lym)

Post-Transplant Outcomes [33]

Survival:

• 5-year overall survival: 40-55%
• Disease-free survival: 35-50%

Relapse:

• Cumulative incidence: 15-25% at 5 years
• Molecular relapse often precedes clinical relapse (monitor chimerism, driver mutation VAF)

Non-Relapse Mortality:

• 15-30% (higher in MF than other transplant indications)
• Primary causes: GVHD, infections, organ failure

Prognostic Factors for Transplant Outcome:

• Favourable: Younger age, low comorbidity index, matched sibling donor, RIC
• Adverse: High-risk cytogenetics, uncontrolled splenomegaly, poor performance status, HLA-mismatched donor

---

11. Evidence and Guidelines

Key Clinical Practice Guidelines

Landmark Clinical Trials

COMFORT-I (2012) [8]

Design:

• Phase III, randomised, double-blind, placebo-controlled
• 309 patients with intermediate-2/high-risk MF
• Ruxolitinib vs placebo

Primary Endpoint:

• ≥35% reduction in spleen volume at 24 weeks: 41.9% vs 0.7% (pless than 0.001)

Secondary Endpoints:

• ≥50% improvement in TSS: 45.9% vs 5.3%
• Overall survival benefit at 5 years (HR 0.69) [16]

Impact:

• Led to FDA approval of ruxolitinib (2011)
• Established spleen volume reduction as regulatory endpoint

COMFORT-II (2012)

Design:

• Phase III, open-label, ruxolitinib vs best available therapy (BAT)
• 219 patients

Primary Endpoint:

• ≥35% reduction in spleen volume at 48 weeks: 28% vs 0% (pless than 0.001)

Impact:

• Confirmed COMFORT-I findings in open-label setting

JAKARTA Trial (2015) [34]

Design:

• Phase III, randomised, placebo-controlled
• Fedratinib vs placebo

Primary Endpoint:

• ≥35% spleen volume reduction at 24 weeks: 36% vs 1%

Impact:

• Led to FDA approval of fedratinib (2019, after temporary hold for encephalopathy concerns)

PERSIST-2 / PACIFICA Trials (2018-2021) [35]

Design:

• Pacritinib in thrombocytopenic MF patients (platelets less than 100×10⁹/L)

Key Findings:

• Spleen and symptom benefit even in severe thrombocytopenia
• Minimal impact on platelet counts

Impact:

• FDA approval 2022 for MF with platelets less than 50×10⁹/L

Emerging Evidence

Navitoclax + Ruxolitinib (TRANSFORM-1 Trial):

• Combination showed superior spleen and symptom responses vs ruxolitinib alone
• Anaemia improvement with navitoclax (BCL-XL inhibitor reduces aberrant megakaryocytes)
• Approaching regulatory approval

Momelotinib (MOMENTUM Trial):

• JAK1/2/ACVR1 inhibitor (ACVR1 inhibition reduces hepcidin, improves anaemia)
• Non-inferior spleen response vs ruxolitinib; superior anaemia response
• FDA approved 2023

Imetelstat:

• Telomerase inhibitor
• Phase II data showed anaemia responses and spleen reduction
• Ongoing phase III trials

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12. Patient and Layperson Explanation

What is Myelofibrosis?

Myelofibrosis is a rare blood cancer where the bone marrow (the spongy tissue inside your bones that makes blood cells) becomes severely scarred. "Myelo" means marrow, and "fibrosis" means scarring. This scarring stops the bone marrow from making blood cells properly.

Why Does the Spleen Become So Large?

Because the bone marrow can't do its job, your body tries to compensate by making blood cells in other places—mainly the spleen and liver. This is called "extramedullary haematopoiesis" (blood cell production outside the marrow). The spleen swells up massively because it's working overtime. This can make your abdomen feel full, cause pain, and make it hard to eat normal-sized meals.

What Causes the Symptoms?

Fatigue and Weakness: Your bone marrow isn't making enough red blood cells (anaemia), which carry oxygen around your body. Low oxygen means you feel exhausted, short of breath, and weak.

Night Sweats and Weight Loss: The abnormal cells in myelofibrosis release chemicals called "cytokines" that cause inflammation throughout your body. These cytokines trigger drenching night sweats (often so severe you need to change your sheets), fevers, and weight loss. It's like having a constant low-level infection.

Bone Pain: The scar tissue in your marrow and sometimes new bone formation (osteosclerosis) can cause deep, aching bone pain.

Is Myelofibrosis Cancer?

Yes, myelofibrosis is a type of chronic blood cancer called a "myeloproliferative neoplasm." Unlike acute leukaemias that progress rapidly, myelofibrosis usually develops slowly over years. However, it can significantly affect your quality of life and, in some cases (15-20%), can transform into acute leukaemia.

Can It Be Cured?

Stem Cell Transplant (Bone Marrow Transplant): The only cure for myelofibrosis is an allogeneic stem cell transplant, where you receive healthy bone marrow from a donor. This is a major procedure with significant risks, so it's usually reserved for younger, fitter patients with high-risk disease.

JAK Inhibitor Tablets: For most people, treatment focuses on controlling symptoms and slowing disease progression. JAK inhibitor drugs (like ruxolitinib, fedratinib, pacritinib) are tablets that block the faulty signals causing the scarring and inflammation. They can dramatically shrink the spleen, stop the night sweats, and help you feel much better, though they don't cure the disease.

What Are the Side Effects of Treatment?

JAK Inhibitors:

• Can lower your blood counts (anaemia, low platelets), making you more tired or prone to bruising
• Slightly increased risk of infections (especially shingles)
• Weight gain in some people

Stem Cell Transplant:

• Major procedure with risks of infection, graft-versus-host disease (where the donor cells attack your body), and organ damage
• Long recovery period
• Only offered if potential benefits outweigh risks

How Long Can I Live with Myelofibrosis?

This varies greatly depending on:

• Your age and overall health
• How severe your symptoms are
• Your blood test results
• Genetic mutations in the disease

Some people live for many years (10-15+) with good quality of life, especially if they have low-risk disease and respond well to treatment. Others with high-risk features may have a shorter prognosis (2-5 years). Your haematologist will give you a personalised estimate based on scoring systems that factor in all these variables.

What Should I Watch Out For? (RED FLAGS)

Contact your doctor urgently if you develop:

• Rapidly worsening fatigue or breathlessness: Could indicate severe anaemia or disease progression
• Severe abdominal pain: Could be splenic infarction or rupture
• Fever and confusion: Could be infection (especially if on JAK inhibitors)
• Back pain with leg weakness or numbness: Could be spinal cord compression from extramedullary masses
• Easy bruising or bleeding that won't stop: Could indicate very low platelets

Living with Myelofibrosis

Regular Monitoring: You'll need regular blood tests and clinic visits (every 3-6 months, or more often if on treatment) to monitor your disease and manage complications.

Supportive Care:

• Blood transfusions if anaemia is severe
• Medications to manage symptoms (itching, bone pain, gout)
• Nutritional support if weight loss is significant

Stay Connected: Join patient support groups (e.g., MPN Voice, Leukaemia Care) to connect with others living with myelofibrosis. Many patients find this invaluable for practical advice and emotional support.

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13. References

Primary Sources

1. Tefferi A, Guglielmelli P, Larson DR, et al. Long-term survival and blast transformation in molecularly annotated essential thrombocythemia, polycythemia vera, and myelofibrosis. Blood. 2014;124(16):2507-2513. doi:10.1182/blood-2014-05-579136

2. Mehta J, Wang H, Iqbal SU, Mesa R. Epidemiology of myeloproliferative neoplasms in the United States. Leuk Lymphoma. 2014;55(3):595-600. doi:10.3109/10428194.2013.813500

3. Cervantes F, Dupriez B, Pereira A, et al. New prognostic scoring system for primary myelofibrosis based on a study of the International Working Group for Myelofibrosis Research and Treatment. Blood. 2009;113(13):2895-2901. doi:10.1182/blood-2008-07-170449

4. Barosi G, Mesa RA, Thiele J, et al. Proposed criteria for the diagnosis of post-polycythemia vera and post-essential thrombocythemia myelofibrosis: a consensus statement from the International Working Group for Myelofibrosis Research and Treatment. Leukemia. 2008;22(2):437-438. doi:10.1038/sj.leu.2404914

5. Verstovsek S. Therapeutic potential of JAK2 inhibitors. Hematology Am Soc Hematol Educ Program. 2009;2009:636-642. doi:10.1182/asheducation-2009.1.636

6. Mesa RA, Schwager S, Radia D, et al. The Myelofibrosis Symptom Assessment Form (MFSAF): an evidence-based brief inventory to measure quality of life and symptomatic response to treatment in myelofibrosis. Leuk Res. 2009;33(9):1199-1203. doi:10.1016/j.leukres.2009.01.035

7. Tefferi A, Lasho TL, Jimma T, et al. One thousand patients with primary myelofibrosis: the mayo clinic experience. Mayo Clin Proc. 2012;87(1):25-33. doi:10.1016/j.mayocp.2011.11.001

8. Verstovsek S, Mesa RA, Gotlib J, et al. A double-blind, placebo-controlled trial of ruxolitinib for myelofibrosis. N Engl J Med. 2012;366(9):799-807. doi:10.1056/NEJMoa1110557

9. Arber DA, Orazi A, Hasserjian R, et al. The 2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia. Blood. 2016;127(20):2391-2405. doi:10.1182/blood-2016-03-643544

10. Tefferi A, Lasho TL, Finke CM, et al. CALR vs JAK2 vs MPL-mutated or triple-negative myelofibrosis: clinical, cytogenetic and molecular comparisons. Leukemia. 2014;28(7):1472-1477. doi:10.1038/leu.2014.3

11. Passamonti F, Rumi E, Pungolino E, et al. Life expectancy and prognostic factors for survival in patients with polycythemia vera and essential thrombocythemia. Am J Med. 2004;117(10):755-761. doi:10.1016/j.amjmed.2004.06.032

12. Hinds DA, Barnholt KE, Mesa RA, et al. Germ line variants predispose to both JAK2 V617F clonal hematopoiesis and myeloproliferative neoplasms. Blood. 2016;128(8):1121-1128. doi:10.1182/blood-2015-06-652941

13. Vainchenker W, Kralovics R. Genetic basis and molecular pathophysiology of classical myeloproliferative neoplasms. Blood. 2017;129(6):667-679. doi:10.1182/blood-2016-10-695940

14. Vannucchi AM, Lasho TL, Guglielmelli P, et al. Mutations and prognosis in primary myelofibrosis. Leukemia. 2013;27(9):1861-1869. doi:10.1038/leu.2013.119

15. Björk J, Albin M, Mauritzson N, et al. Smoking and myelodysplastic syndromes. Epidemiology. 2000;11(3):285-291. doi:10.1097/00001648-200005000-00010

16. Verstovsek S, Mesa RA, Gotlib J, et al. Long-term treatment with ruxolitinib for patients with myelofibrosis: 5-year update from the randomized, double-blind, placebo-controlled, phase 3 COMFORT-I trial. J Hematol Oncol. 2017;10(1):55. doi:10.1186/s13045-017-0417-z

17. Klampfl T, Gisslinger H, Harutyunyan AS, et al. Somatic mutations of calreticulin in myeloproliferative neoplasms. N Engl J Med. 2013;369(25):2379-2390. doi:10.1056/NEJMoa1311347

18. Tefferi A, Vaidya R, Caramazza D, et al. Circulating interleukin (IL)-8, IL-2R, IL-12, and IL-15 levels are independently prognostic in primary myelofibrosis: a comprehensive cytokine profiling study. J Clin Oncol. 2011;29(10):1356-1363. doi:10.1200/JCO.2010.32.9490

19. Thiele J, Kvasnicka HM, Facchetti F, et al. European consensus on grading bone marrow fibrosis and assessment of cellularity. Haematologica. 2005;90(8):1128-1132.

20. Koch CA, Li CY, Mesa RA, Tefferi A. Nonhepatosplenic extramedullary hematopoiesis: associated diseases, pathology, clinical course, and treatment. Mayo Clin Proc. 2003;78(10):1223-1233. doi:10.4065/78.10.1223

21. Shallis RM, Wang R, Davidoff A, Ma X, Zeidan AM. Epidemiology of acute myeloid leukemia: recent progress and enduring challenges. Blood Rev. 2019;36:70-87. doi:10.1016/j.blre.2019.04.005

22. Emanuel RM, Dueck AC, Geyer HL, et al. Myeloproliferative neoplasm (MPN) symptom assessment form total symptom score: prospective international assessment of an abbreviated symptom burden scoring system among patients with MPNs. J Clin Oncol. 2012;30(33):4098-4103. doi:10.1200/JCO.2012.42.3863

23. O'Reilly RA. Splenomegaly in 2,505 patients at a large university medical center from 1913 to 1995. West J Med. 1998;169(2):88-97.

24. Barbui T, Finazzi G, Carobbio A, et al. Development and validation of an International Prognostic Score of thrombosis in World Health Organization-essential thrombocythemia (IPSET-thrombosis). Blood. 2012;120(26):5128-5133. doi:10.1182/blood-2012-07-444067

25. Wilkins BS, Erber WN, Bareford D, et al. Bone marrow pathology in essential thrombocythemia: interobserver reliability and utility for identifying disease subtypes. Blood. 2008;111(1):60-70. doi:10.1182/blood-2007-05-091850

26. Guglielmelli P, Lasho TL, Rotunno G, et al. MIPSS70: Mutation-Enhanced International Prognostic Score System for transplantation-age patients with primary myelofibrosis. J Clin Oncol. 2018;36(4):310-318. doi:10.1200/JCO.2017.76.4886

27. Tefferi A, Jimma T, Sulai NH, et al. IDH mutations in primary myelofibrosis predict leukemic transformation and shortened survival: clinical evidence for leukemogenic collaboration with JAK2V617F. Leukemia. 2012;26(3):475-480. doi:10.1038/leu.2011.253

28. Cervantes F, Dupriez B, Pereira A, et al. New prognostic scoring system for primary myelofibrosis based on a study of the International Working Group for Myelofibrosis Research and Treatment. Blood. 2009;113(13):2895-2901. doi:10.1182/blood-2008-07-170449

29. Passamonti F, Cervantes F, Vannucchi AM, et al. A dynamic prognostic model to predict survival in primary myelofibrosis: a study by the IWG-MRT (International Working Group for Myeloproliferative Neoplasms Research and Treatment). Blood. 2010;115(9):1703-1708. doi:10.1182/blood-2009-09-245837

30. Gangat N, Caramazza D, Vaidya R, et al. DIPSS plus: a refined Dynamic International Prognostic Scoring System for primary myelofibrosis that incorporates prognostic information from karyotype, platelet count, and transfusion status. J Clin Oncol. 2011;29(4):392-397. doi:10.1200/JCO.2010.32.2446

31. Tefferi A, Guglielmelli P, Nicolosi M, et al. MIPSS70+ Version 2.0: Mutation and Karyotype-Enhanced International Prognostic Scoring System for primary myelofibrosis. J Clin Oncol. 2018;36(17):1769-1770. doi:10.1200/JCO.2018.78.9867

32. Kröger N, Giorgino T, Scott BL, et al. Impact of allogeneic stem cell transplantation on survival of patients less than 65 years of age with primary myelofibrosis. Blood. 2015;125(21):3347-3350. doi:10.1182/blood-2014-10-608315

33. Gupta V, Malone AK, Hari PN, et al. Reduced-intensity hematopoietic cell transplantation for patients with primary myelofibrosis: a cohort analysis from the center for international blood and marrow transplant research. Biol Blood Marrow Transplant. 2014;20(1):89-97. doi:10.1016/j.bbmt.2013.10.018

34. Pardanani A, Harrison C, Cortes JE, et al. Safety and efficacy of fedratinib in patients with primary or secondary myelofibrosis: a randomized clinical trial. JAMA Oncol. 2015;1(5):643-651. doi:10.1001/jamaoncol.2015.1590

35. Mascarenhas J, Hoffman R, Talpaz M, et al. Pacritinib vs best available therapy, including ruxolitinib, in patients with myelofibrosis: a randomized clinical trial. JAMA Oncol. 2018;4(5):652-659. doi:10.1001/jamaoncol.2017.5818

36. Cervantes F, Pereira A. Does ruxolitinib prolong the survival of patients with myelofibrosis? Blood. 2017;129(7):832-837. doi:10.1182/blood-2016-11-731604

37. Mesa RA, Nagorney DS, Schwager S, et al. Palliative goals, patient selection, and perioperative platelet management: outcomes and lessons from 3 decades of splenectomy for myelofibrosis with myeloid metaplasia at the Mayo Clinic. Cancer. 2006;107(2):361-370. doi:10.1002/cncr.22021

38. Elliott MA, Chen MG, Silverstein MN, Tefferi A. Splenic irradiation for symptomatic splenomegaly associated with myelofibrosis with myeloid metaplasia. Br J Haematol. 1998;103(2):505-511. doi:10.1046/j.1365-2141.1998.01997.x

39. Belhadj K, Reyes F, Farcet JP, et al. Hepatosplenic γδ T-cell lymphoma is a rare clinicopathologic entity with poor outcome: report on a series of 21 patients. Blood. 2003;102(13):4261-4269. doi:10.1182/blood-2003-05-1675

40. Tefferi A, Guglielmelli P, Larson DR, et al. Long-term survival and blast transformation in molecularly annotated essential thrombocythemia, polycythemia vera, and myelofibrosis. Blood. 2014;124(16):2507-2513. doi:10.1182/blood-2014-05-579136

41. Reilly JT, McMullin MF, Beer PA, et al. Guideline for the diagnosis and management of myelofibrosis. Br J Haematol. 2012;158(4):453-471. doi:10.1111/j.1365-2141.2012.09179.x

42. Tefferi A, Pardanani A. Myeloproliferative neoplasms: a contemporary review. JAMA Oncol. 2015;1(1):97-105. doi:10.1001/jamaoncol.2015.89

43. Barbui T, Tefferi A, Vannucchi AM, et al. Philadelphia chromosome-negative classical myeloproliferative neoplasms: revised management recommendations from European LeukemiaNet. Leukemia. 2018;32(5):1057-1069. doi:10.1038/s41375-018-0077-1

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14. Examination Focus

Common Exam Questions (MRCP, FRACP, Haematology)

Question 1: Diagnostic Triad Q: A 68-year-old man presents with fatigue and massive splenomegaly. Blood film shows tear drop cells and a leucoerythroblastic picture. Bone marrow aspirate is "dry". What is the most likely diagnosis?

• A: Primary Myelofibrosis
• Classic triad: Dry tap + Dacrocytes + Splenomegaly

Question 2: Mutation Prognostic Significance Q: Which driver mutation in primary myelofibrosis confers the most favourable prognosis?

• A: CALR Type 1 mutation
• Better prognosis than JAK2 V617F, MPL, or triple-negative

Question 3: Risk Stratification Q: A 70-year-old woman with newly diagnosed primary myelofibrosis has Hb 95 g/L, WCC 28×10⁹/L, platelets 120×10⁹/L, 2% circulating blasts, and constitutional symptoms. What is her DIPSS risk category?

• A: High risk (score 5)
• Hb less than 100 (2 points) + constitutional symptoms (1) + WCC > 25 (1) + blasts ≥1% (1) = 5 points

Question 4: Curative Treatment Q: What is the only curative treatment for myelofibrosis?

• A: Allogeneic stem cell transplantation

Question 5: JAK Inhibitor Mechanism Q: Ruxolitinib is effective in myelofibrosis regardless of JAK2 mutation status. Why?

• A: It inhibits both wild-type and mutant JAK2, reducing downstream cytokine signalling (JAK-STAT pathway activation) which drives symptoms in all MF subtypes

Question 6: Histological Stain Q: Which stain is essential for grading bone marrow fibrosis in myelofibrosis?

• A: Reticulin (Silver stain)
• Grades MF-0 to MF-3

Question 7: Red Flag Complication Q: A patient with myelofibrosis presents with acute back pain and lower limb weakness. What urgent investigation is required?

• A: MRI spine to exclude spinal cord compression from extramedullary haematopoietic mass

Question 8: Blast Transformation Q: What is the approximate cumulative incidence of leukaemic transformation in primary myelofibrosis at 10 years?

• A: 15-20%

Question 9: Post-Splenectomy Complication Q: What is the most concerning thrombotic complication following splenectomy in myelofibrosis?

• A: Portal vein thrombosis (occurs in 10-20% of cases)

Question 10: Anaemia Management Q: Which androgenic steroid is used to manage anaemia in myelofibrosis?

• A: Danazol (200-600 mg daily); response rate ~20-30%

Viva Points (Oral Examination)

Viva Point: Opening Statement: "Myelofibrosis is a clonal myeloproliferative neoplasm characterised by progressive bone marrow fibrosis, extramedullary haematopoiesis predominantly in the spleen and liver, and a profound inflammatory cytokine-driven syndrome. It has the worst prognosis among Philadelphia-negative MPNs with median survival ranging from 2 to 15 years depending on risk stratification."

Key Facts to Mention:

1. Incidence: 0.5-1.5 per 100,000; median age 67 years

2. Driver Mutations: JAK2 V617F (50-60%), CALR (25-30%), MPL (5-10%), triple-negative (10-15%)

3. Pathognomonic Features:

   • Dry tap on bone marrow aspiration
   • Tear drop cells (dacrocytes) on blood film
   • Leucoerythroblastic picture
   • Massive splenomegaly

4. Risk Stratification: DIPSS (Dynamic International Prognostic Scoring System) and MIPSS70 (integrates molecular data)

5. Management:

   • Allogeneic SCT: Only curative option (for Int-2/High risk, age less than 70, fit)
   • JAK Inhibitors: Ruxolitinib (first-line), Fedratinib (second-line), Pacritinib (thrombocytopenic)
   • Supportive care: Transfusions, ESAs, IMiDs, androgens

6. Evidence: COMFORT-I/II trials demonstrated ruxolitinib superiority for spleen reduction (41.9% vs 0.7%) and survival benefit (HR 0.69 at 5 years)

7. Complications: Blast transformation (15-20%), portal hypertension, splenic infarction, spinal cord compression

Common Mistakes in Examinations

❌ Mistake 1: Confusing Pre-fibrotic PMF with Essential Thrombocythaemia

• Pre-fibrotic PMF has hypercellular marrow with dysplastic megakaryocytes and proliferative granulopoiesis
• ET has normocellular marrow with large hyperlobulated megakaryocytes
• Consequence: Incorrect prognostication (pre-fibrotic PMF has worse prognosis)

❌ Mistake 2: Assuming JAK Inhibitors Cure or Modify Disease

• JAK inhibitors provide symptom control and spleen reduction
• They do NOT reverse fibrosis or eradicate the clone
• Only transplant is curative

❌ Mistake 3: Forgetting to Screen for TB Before JAK Inhibitor

• JAK inhibitors impair IFN-γ signalling → increased infection risk
• Mandatory TB screening (IGRA, CXR) before initiation

❌ Mistake 4: Missing Spinal Cord Compression from Extramedullary Masses

• Back pain + neurological symptoms = urgent MRI spine
• Delay leads to irreversible paralysis

❌ Mistake 5: Using IPSS Instead of DIPSS for Monitoring

• IPSS is for diagnosis only (static)
• DIPSS can be calculated at any time (dynamic)

Model Answers for Common Viva Scenarios

Q: A 65-year-old presents with massive splenomegaly and pancytopenia. Describe your diagnostic approach.

A: "I would approach this systematically. First, I would take a detailed history including constitutional symptoms (night sweats, weight loss, fevers), bone pain, and symptoms of cytopenias (fatigue, bleeding, infections). I would examine for splenomegaly size and hepatomegaly.

My initial investigations would include:

1. FBC and Blood Film: Looking for leucoerythroblastic picture with tear drop cells (dacrocytes), which would suggest marrow infiltration, most likely myelofibrosis
2. LDH and Urate: Elevated in high cell turnover
3. Bone Marrow Examination: Aspirate (likely dry tap) and trephine biopsy (essential) with reticulin stain to grade fibrosis
4. Molecular Testing: JAK2 V617F, CALR, MPL mutations; NGS panel for high-risk mutations (ASXL1, EZH2, SRSF2)
5. Cytogenetics: Karyotype for prognostic stratification
6. Imaging: Abdominal ultrasound/CT to quantify splenomegaly

If myelofibrosis confirmed, I would:

• Apply DIPSS or MIPSS70 risk stratification
• Assess transplant eligibility (age, fitness, donor availability)
• Discuss treatment options (watch and wait if low-risk asymptomatic; JAK inhibitor if symptomatic; transplant if high-risk and eligible)
• Provide supportive care (transfusions, symptom management)"

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Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances and be made in consultation with appropriate specialists. Always refer to current local and national guidelines.