Haemophilia (Adult)

1. Clinical Overview

Summary

Haemophilia is a group of X-linked recessive bleeding disorders characterized by deficiency of specific clotting factors in the intrinsic coagulation pathway. It represents the archetypal "deep tissue bleeding disorder", manifesting with hemarthroses (joint bleeds), muscle hematomas, and delayed bleeding after trauma, in stark contrast to platelet disorders which cause immediate superficial mucocutaneous bleeding. [1,2]

The condition has profound historical significance as the "Royal Disease"

• Queen Victoria was a carrier, transmitting the mutated gene to royal families across Europe, including the Russian Tsarevich Alexei Romanov, whose haemophilia influenced political decisions during World War I. [3]

Modern management has revolutionized outcomes: whereas haemophilia was once uniformly fatal in childhood, contemporary prophylactic factor replacement, novel bispecific antibodies (emicizumab), and emerging gene therapies now offer near-normal life expectancy and quality of life. [4,5]

Classification

Haemophilia is classified by the specific clotting factor deficiency:

Clinical Note: Haemophilia A and B are clinically indistinguishable - specific factor assays are required for diagnosis. Haemophilia B historically termed "Christmas Disease" after Stephen Christmas, the first patient described with FIX deficiency in 1952. [6]

Severity Classification

Severity correlates directly with residual factor activity and determines bleeding phenotype:

Important: Approximately 70% of severe haemophilia patients have factor levels less than 1%, leading to devastating joint disease without prophylaxis. The remaining 30% of severe cases are de novo mutations with no prior family history. [7,8]

Key Facts

• Inheritance: X-linked recessive (males affected, females carriers with occasional symptoms)
• Hallmark Presentation: Hemarthrosis (spontaneous joint bleeding) - pathognomonic
• Laboratory Finding: Prolonged APTT with normal PT, platelet count, and bleeding time
• Gold Standard Treatment: Factor replacement (prophylactic > on-demand)
• Most Feared Complication: Inhibitor development (30% of severe haemophilia A)
• Life Expectancy: Near-normal with adequate prophylaxis (was less than 20 years pre-1960s)

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2. Epidemiology

Global Prevalence

• Haemophilia A: 1 in 5,000 live male births
• Haemophilia B: 1 in 25,000-30,000 live male births
• Combined prevalence: Approximately 400,000 people worldwide with haemophilia
• Geographic distribution: Uniform across all ethnic groups and geographic regions [9]

Demographics

Disease Burden

• Mortality: Historical ICH (intracranial haemorrhage) leading cause of death (25% of deaths)
• Morbidity: Chronic haemophilic arthropathy affects > 90% of adults with severe haemophilia without prophylaxis
• HIV/Hepatitis C legacy: 1980s contaminated factor concentrates infected > 90% of severe haemophilia patients in developed countries (now resolved with recombinant products) [10]

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3. Aetiology & Pathophysiology

Molecular Genetics

Haemophilia A (Factor VIII Deficiency)

• Gene: F8 gene located on chromosome Xq28
• Gene size: 186 kb spanning 26 exons
• Most common mutation (45% of severe cases): Intron 22 inversion - large chromosomal flip disrupting F8 gene
• Other mutations: Point mutations, deletions, insertions affecting FVIII synthesis or function
• Protein structure: FVIII is a cofactor (not an enzyme) that accelerates Factor IXa activity 200,000-fold [11]

Haemophilia B (Factor IX Deficiency)

• Gene: F9 gene located on chromosome Xq27
• Gene size: 34 kb spanning 8 exons
• Common mutations: Point mutations (> 1,000 different mutations identified), particularly in catalytic domain
• Leyden variant: Unique subtype where FIX levels increase at puberty (androgen-responsive promoter mutations) [12]

X-Linked Recessive Inheritance Pattern

Inheritance Scenarios:

1. Affected Father × Normal Mother
   - All sons: Normal (receive father's Y chromosome)
   - All daughters: Obligate carriers (receive father's X with mutation)

2. Carrier Mother × Normal Father
   - Sons: 50% affected, 50% normal
   - Daughters: 50% carriers, 50% normal

3. Carrier Mother × Affected Father (rare)
   - Sons: 50% affected, 50% normal
   - Daughters: 50% affected (homozygous), 50% carriers

Symptomatic Female Carriers: 10-20% of carriers have factor levels less than 40% and may experience bleeding symptoms (menorrhagia, post-partum haemorrhage, post-operative bleeding). Mechanisms include:

• Extreme lyonization (X-chromosome inactivation skewing)
• Turner syndrome (45,XO - only one X chromosome)
• Homozygous state (rare)
• Coincident Von Willebrand disease [13]

Coagulation Cascade Defect

Exam Detail: The Normal Cascade: Coagulation follows a two-stage model:

1. Initiation Phase (Extrinsic Pathway):

   • Tissue factor (TF) exposure after vascular injury
   • TF + Factor VIIa → activates small amounts of Factor X → small thrombin burst

2. Amplification Phase (Intrinsic Pathway):

   • Thrombin activates Factor VIII → Factor VIIIa (cofactor)
   • Thrombin activates Factor IX → Factor IXa (enzyme)
   • Tenase Complex forms: Factor VIIIa + Factor IXa + Ca²⁺ + phospholipid surface
   • Tenase complex activates Factor X at 200,000× efficiency
   • Massive thrombin generation → fibrin clot formation

The Haemophilia Defect:

In haemophilia A or B, the amplification phase fails:

• Initial platelet plug forms normally (primary hemostasis intact)
• Small thrombin burst occurs via extrinsic pathway
• Critical failure: Cannot form functional tenase complex
• Insufficient Factor X activation → inadequate thrombin → weak/absent fibrin mesh
• Clinical result: "Delayed bleeding"
• initial clot forms but disintegrates within hours as platelet plug alone cannot sustain hemostasis

Visual Mnemonic: "1-2-5-10 Pathway"

• Tissue Factor activates VII (extrinsic)
• VII activates X → small thrombin
• Thrombin activates VIII + IX (intrinsic amplification)
• VIII + IX activate X massively (100,000-fold amplification)
• Common pathway: V + X → prothrombinase → Thrombin burst → Fibrin

Haemophilia breaks the VIII or IX link, preventing amplification.

Why Deep Tissue Bleeding?

The pattern of bleeding in haemophilia reflects the hemostatic demands of different tissues:

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4. Clinical Presentation

Cardinal Features

1. Hemarthrosis (Joint Bleeding) - The Hallmark

Hemarthrosis occurs in 75-90% of bleeding episodes in severe haemophilia and is pathognomonic. [14]

Acute Hemarthrosis Sequence:

1. Aura phase (minutes before bleeding): Tingling, warmth, "funny feeling" in joint (patients learn to recognize this)
2. Acute bleeding phase (0-6 hours): Progressive pain, swelling, heat, loss of range of motion
3. Resolution phase (days-weeks): Gradual resorption of blood; risk of recurrent bleeding in same joint

Target Joints (in order of frequency):

• Knee (45%) - most common due to weight-bearing stress
• Elbow (30%)
• Ankle (15%)
• Shoulder, Hip, Wrist (10% combined) - hinge joints affected preferentially

Physical Examination Findings:

• Joint held in flexed position (maximizes intra-articular volume, reduces pain)
• Tense effusion, warmth
• Severe pain on any movement
• Ballottement may be present (large effusions)

"Target Joint" Phenomenon: Repeated bleeding in the same joint (≥4 bleeds in 6 months) due to:

• Synovial hypertrophy from iron deposition
• Increased vascularity → more fragile vessels → more bleeding
• Vicious cycle leading to chronic haemophilic arthropathy [15]

Clinical Pearl: The "Tingling Aura": Experienced haemophilia patients can predict a joint bleed minutes to hours before objective signs appear. This represents subclinical bleeding and is the optimal window for factor replacement - treating at aura stage can abort a full hemarthrosis.

Many patients on home therapy self-administer factor immediately upon sensing this aura, preventing joint damage. Clinicians must respect patient self-reporting.

2. Muscle Hematomas

High-Risk Muscle Groups:

Iliopsoas Bleed - Key Emergency:

• Presents as hip/groin pain with positive psoas sign (pain on hip extension)
• Hip held in flexed + externally rotated position (maximizes iliopsoas space)
• CT abdomen shows retroperitoneal hematoma
• Femoral nerve compression → loss of knee extension, numbness over anteromedial thigh
• Requires high-dose factor replacement (100% levels) and ICU monitoring [16]

3. Mucosal Bleeding

Less common than joint/muscle bleeds but problematic:

• Epistaxis: Prolonged nosebleeds requiring packing/cautery
• Gingival bleeding: After tooth brushing, dental procedures (50% of mild haemophilia diagnosed after dental extraction)
• Gastrointestinal bleeding: Melena, hematemesis (often associated with NSAIDs/aspirin - absolutely contraindicated)
• Haematuria: Spontaneous or post-trauma; may cause ureteric obstruction from clots
• Oral bleeding: Tongue/lip bites can bleed for days

Menorrhagia in Carriers: 30-50% of female carriers experience heavy menstrual bleeding, especially if factor levels less than 40%. [13]

4. Life-Threatening Bleeds

Intracranial Haemorrhage (ICH)

• Occurs in 10% of severe haemophilia patients at some point in life
• Leading cause of death (25% mortality rate)
• ANY head trauma (even minor bumps) requires immediate factor replacement BEFORE imaging
• Spontaneous ICH can occur without trauma in severe haemophilia
• Neonates at risk during delivery (traumatic delivery should be avoided)

Emergency Protocol:

1. Immediate factor bolus to 100% (do NOT wait for CT)
2. Then CT head
3. Neurosurgical consultation
4. Maintain factor levels > 80% for ≥14 days [17]

Neck/Throat Bleeding

• Potential airway compromise
• Requires immediate factor replacement + airway assessment
• May need early intubation if swelling progresses

Post-Operative Bleeding

• Delayed bleeding 12-24 hours post-surgery (once platelet plug fails)
• Requires pre-operative factor loading + maintenance for 7-14 days depending on surgery type

Age-Related Presentations

Differential Diagnosis of Prolonged APTT

Exam Detail: When encountering isolated prolonged APTT, systematically consider:

Mixing Study:

• Mix patient plasma 1:1 with normal plasma
• If APTT corrects → factor deficiency (diluting in normal plasma provides missing factor)
• If APTT does NOT correct → inhibitor present (antibody neutralizes factor in normal plasma)

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5. Investigations & Diagnosis

Initial Coagulation Screen

The Classic Triad (diagnostic pattern):

Key Point: The APTT prolongation is proportional to severity - severe haemophilia (factor less than 1%) has massively prolonged APTT (> 100s), while mild haemophilia (factor 5-40%) may have only borderline APTT prolongation.

Definitive Diagnostic Tests

Factor Assays

Gold standard for diagnosis and classification:

• Factor VIII assay (for haemophilia A): Measures functional FVIII activity
• Factor IX assay (for haemophilia B): Measures functional FIX activity
• Reported as percentage of normal (normal = 50-150% or 0.50-1.50 IU/mL)

Interpretation:

• Severe: less than 1% (less than 0.01 IU/mL)
• Moderate: 1-5% (0.01-0.05 IU/mL)
• Mild: 5-40% (0.05-0.40 IU/mL)

Technical Note: Factor VIII is an acute phase reactant and can be elevated by:

• Pregnancy
• Stress, infection, inflammation
• ABO blood group (Group O has 25% lower FVIII than non-O) Therefore, repeat testing is essential for mild haemophilia diagnosis [18]

Inhibitor Screening (Bethesda Assay)

Indication: Any patient with haemophilia not responding to standard factor replacement

Bethesda Assay:

• Measures neutralizing antibodies (inhibitors) against FVIII or FIX
• Reported in Bethesda Units (BU) per mL
  • "Low titre: less than 5 BU/mL (may overcome with high-dose factor)"
  • "High titre: ≥5 BU/mL (requires bypassing agents or emicizumab)"

Prevalence: 30% of severe haemophilia A patients develop inhibitors (usually within first 50 exposure days to factor concentrate). Inhibitors far less common in haemophilia B (3-5%). [1,2]

Genetic Testing

Indications:

• Confirming diagnosis in patient
• Carrier detection in female relatives
• Prenatal diagnosis if requested
• Mutation identification for family counseling

Methods:

• Direct sequencing of F8 or F9 gene
• Inversion screening for intron 22/intron 1 inversions (haemophilia A)
• Linkage analysis if mutation unknown

Carrier Testing:

• Female relatives of affected males
• Genetic counseling prior to testing
• Factor levels PLUS genetic testing (levels alone unreliable due to lyonization)

Imaging for Complications

Joint Assessment

• Plain X-ray: Shows late-stage arthropathy (joint space narrowing, subchondral cysts, osteophytes) - insensitive for early disease
• MRI: Gold standard for detecting early synovial hypertrophy, cartilage damage, hemosiderin deposition
• Ultrasound: Point-of-care assessment of acute hemarthrosis (fluid + synovial thickening); increasingly used for monitoring

Pettersson Score (Radiographic joint score): 0-13 points per joint assessing:

• Osteoporosis
• Enlarged epiphysis
• Irregular subchondral surface
• Joint space narrowing
• Subchondral cyst formation
• Erosions
• Gross deformity

Score > 8 indicates severe arthropathy requiring surgical intervention consideration [15]

Bleed Localization

• CT head: Any head trauma (after factor given)
• CT abdomen/pelvis: Iliopsoas bleed, retroperitoneal hematoma
• MRI spine: Spinal canal hematoma (presents with acute back pain + neurology)
• Ultrasound: Muscle hematomas, joint effusions

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6. Management

Emergency Management of Acute Bleeds

GOLDEN RULE: "TREAT FIRST. SCAN LATER. DO NOT WAIT."

The cornerstone principle of haemophilia management is that clinical suspicion alone (or patient self-reporting of "aura") is sufficient indication for immediate factor replacement. Delays to obtain imaging, specialist review, or confirmatory tests can result in irreversible complications.

Immediate Treatment Protocol

Exam Detail: Step 1: Immediate Factor Replacement (within 2 hours of bleed onset)

Target factor levels depend on bleed severity:

Dosing Formulas:

Haemophilia A (Factor VIII):

Dose (IU) = Weight (kg) × Desired rise (%) × 0.5

Example: 70 kg patient, target 100% rise
Dose = 70 × 100 × 0.5 = 3,500 IU Factor VIII

Rationale: Each 1 IU/kg of FVIII raises plasma level by 2% (hence ×0.5 factor)

Haemophilia B (Factor IX):

Dose (IU) = Weight (kg) × Desired rise (%) × 1.0

Example: 70 kg patient, target 100% rise
Dose = 70 × 100 × 1.0 = 7,000 IU Factor IX

Rationale: Each 1 IU/kg of FIX raises plasma level by only 1% (FIX has larger volume of distribution - extravascular distribution)

Important: Factor IX requires double the weight-based dose compared to Factor VIII due to extravascular distribution.

Step 2: Adjunctive Measures

Tranexamic Acid (Antifibrinolytic)

• Dose: 1g PO/IV TDS or 10mg/kg TDS
• Mechanism: Prevents plasminogen activation → stabilizes formed clot
• Indications: Mucosal bleeds (oral, epistaxis, menorrhagia), post-dental procedures
• Contraindication: Haematuria (can cause clot obstruction in ureters → hydronephrosis)
• Duration: 5-7 days for dental procedures

Desmopressin (DDAVP)

• Indication: Mild haemophilia A ONLY (not effective in moderate/severe or haemophilia B)
• Mechanism: Releases stored FVIII from endothelial Weibel-Palade bodies (can increase FVIII levels 3-5 fold)
• Dose: 0.3 mcg/kg IV over 30 minutes OR 300 mcg intranasal
• Limitations:
  • Tachyphylaxis (repeated doses deplete stores - ineffective after 2-3 doses)
  • Hyponatraemia risk (ADH effect - fluid restriction required)
  • Test dose recommended before relying on DDAVP for procedures
• Response testing: Measure FVIII levels 1 hour post-dose (good response = > 3× baseline)

R.I.C.E. Protocol (Joint/Muscle Bleeds)

• Rest: Immobilize affected limb for 24-48 hours (splint/sling)
• Ice: Cold compresses for 15-20 minutes QID (vasoconstriction)
• Compression: Elastic bandage (not tight - monitor for compartment syndrome)
• Elevation: Reduce hydrostatic pressure

Analgesia

• Safe: Paracetamol, codeine, tramadol, morphine
• CONTRAINDICATED:
  • Aspirin (irreversible platelet inhibition)
  • NSAIDs (ibuprofen, diclofenac, naproxen) - reversible platelet inhibition + GI bleeding risk
  • Intramuscular injections (risk of hematoma formation - use IV/PO/SC routes only)

Step 3: Monitoring

• Monitor factor levels (trough levels should remain above target during treatment course)
• Assess clinical response (pain reduction, swelling stabilization, return of function)
• Monitor for compartment syndrome (muscle bleeds) - serial neurovascular exams

Long-Term Management: Prophylaxis vs On-Demand

The management paradigm has shifted from reactive on-demand treatment (treating bleeds as they occur) to proactive primary prophylaxis (preventing bleeds before they happen).

Exam Detail: #### Prophylaxis Regimens

Primary Prophylaxis: Started in early childhood (before second joint bleed and age 3 years) to prevent development of arthropathy

Standard Half-Life Factor Concentrates:

Extended Half-Life (EHL) Products: rFVIIIFc, rFIXFc, N9-GP

• Allow less frequent dosing (every 3-5 days for FVIII, weekly for FIX)
• Improved adherence, quality of life
• Fusion proteins (Fc-fusion) or pegylation extend half-life 1.5-5× [4]

Outcomes of Prophylaxis:

• Reduces annual bleeding rate by 80-90%
• Prevents/minimizes chronic arthropathy development
• Near-normal quality of life and physical activity participation
• Cost: £100,000-300,000/year per patient (standard factor) [5]

On-Demand Treatment (Episodic)

• Treatment only when bleeds occur
• Lower cost but higher morbidity (90% develop severe arthropathy by age 20)
• Reserved for mild haemophilia or resource-limited settings
• Not recommended for severe haemophilia due to inevitable joint damage

Novel Therapies

Emicizumab (Hemlibra) - The Game Changer

What is it?: Humanized bispecific monoclonal antibody mimicking FVIII cofactor function

Mechanism:

• One binding arm attaches to Factor IXa
• Other binding arm attaches to Factor X
• Physically bridges FIXa and FX → mimics tenase complex function
• Does NOT require Factor VIII → works in haemophilia A even with inhibitors

Administration:

• Subcutaneous injection (no IV access required - massive QOL improvement)
• Loading: 3 mg/kg weekly × 4 weeks
• Maintenance: 1.5 mg/kg weekly OR 3 mg/kg every 2 weeks OR 6 mg/kg every 4 weeks

Efficacy:

• Reduces bleeding rate by 87-99% in trials (HAVEN 1-4 studies)
• Many patients achieve zero bleeds for years
• Effective in patients with inhibitors (where factor replacement fails) [19]

Limitations:

• Haemophilia A ONLY (mimics FVIII function specifically)
• Does NOT fully correct factor levels → may still need factor for major surgery/trauma
• Thrombotic microangiopathy risk if combined with high-dose activated prothrombin complex concentrate (aPCC) - use rFVIIa instead for breakthrough bleeds
• Laboratory monitoring complex (APTT not useful - emicizumab corrects APTT)

Impact: Transformed haemophilia A management - particularly for children (no IV access), inhibitor patients, and those with poor venous access

Gene Therapy - The "One-Shot Cure"

Gene therapy delivers functional F8 or F9 gene to liver hepatocytes using adeno-associated virus (AAV) vectors, aiming for sustained endogenous factor production.

Approved Products:

Mechanism:

• Single IV infusion of AAV vector carrying functional F8/F9 gene
• AAV transduces liver hepatocytes (episomal - does not integrate into genome)
• Hepatocytes produce clotting factor → sustained expression

Eligibility Criteria:

• Severe haemophilia A or B
• Age > 18 years (most trials)
• No pre-existing AAV antibodies (prevent transduction)
• No active hepatitis, advanced liver disease
• No inhibitor history (relative contraindication)

Challenges:

• Declining factor levels: Expression peaks at 1-3 months then gradual decline over years (mechanism unclear - possibly immune-mediated hepatocyte loss)
• Immunosuppression: Many patients require corticosteroids to suppress anti-AAV capsid immune response
• Liver enzyme elevation: Transaminitis occurs in 30-50% (usually responsive to steroids)
• Durability unknown: Longest follow-up 8 years - unclear if expression sustained lifelong
• Cost: £2-3 million per patient (cost-effectiveness debated)
• Re-dosing not possible (anti-AAV immunity prevents second dose) [20]

Current Role: Considered for severe haemophilia patients with poor venous access, inhibitor history (selective), or preference to avoid lifelong factor injections. Long-term data still accumulating.

Management of Inhibitors (Alloantibodies)

Inhibitor development is the most serious complication of haemophilia treatment, rendering standard factor replacement ineffective.

Pathophysiology:

• IgG alloantibodies neutralize infused FVIII/FIX (recognized as foreign protein)
• Anamnestic response (antibody titre rises rapidly with repeat factor exposure)

Prevalence:

• Haemophilia A: 30% of severe patients (usually within first 50 exposure days)
• Haemophilia B: 3-5% (less common but more severe reactions, including anaphylaxis)

Detection:

• Suspect if bleeding persists despite adequate factor dosing
• Bethesda assay confirms (measures neutralizing antibody titre in BU/mL)

Classification:

• Low titre (less than 5 BU/mL): May overcome with high-dose factor (immune tolerance possible)
• High titre (≥5 BU/mL): Factor replacement ineffective - requires bypassing agents or emicizumab

Treatment Strategies:

Exam Detail: 1. Bypassing Agents (for acute bleeds in inhibitor patients):

2. Immune Tolerance Induction (ITI):

• Goal: Eradicate inhibitor through regular high-dose factor exposure
• Protocol: Factor VIII 100-200 IU/kg daily for 6-36 months
• Success rate: 60-80% (higher if low titre, less than 5 BU, short duration since inhibitor developed)
• Requires central venous catheter (infection risk)
• Very expensive (£200,000-500,000/year) [21]

3. Emicizumab:

• First-line for haemophilia A inhibitor patients
• Prevents bleeds without requiring FVIII (not neutralized by anti-FVIII antibodies)
• Subcutaneous administration
• Does NOT eradicate inhibitor (but makes it clinically irrelevant for bleed prevention)

Surgical Management

All surgery in haemophilia patients requires haematology consultation and meticulous peri-operative factor management.

Pre-Operative:

• Check factor levels, inhibitor screen
• Load with factor to achieve 100% level immediately pre-operatively
• Consider central venous access if major surgery (for frequent factor dosing)

Intra-Operative:

• Maintain factor levels > 80-100% throughout procedure
• Use meticulous hemostatic technique (bipolar diathermy, topical hemostatic agents)
• Regional anaesthesia usually avoided (bleeding risk) - general anaesthesia preferred

Post-Operative:

• Maintain factor levels:
  • "Major surgery: > 80% for 7-10 days, then > 50% for day 11-14"
  • "Minor surgery: > 50% for 5-7 days"
• Monitor surgical site, drain outputs
• Tranexamic acid adjunct for oral/nasal procedures

Special Procedures:

Musculoskeletal Management (Chronic Arthropathy)

Physiotherapy:

• Acute phase: R.I.C.E., isometric exercises (maintain muscle without joint movement)
• Subacute: Gentle range-of-motion exercises
• Chronic: Strengthening exercises (quadriceps strength protects knee joint)
• Hydrotherapy ideal (low-impact, buoyancy reduces joint stress)

Orthopedic Interventions:

• Radiosynovectomy: Chemical/radioactive synovectomy for recurrent target joint (destroys hypertrophied synovium)
• Arthroscopic synovectomy: Surgical removal of diseased synovium (reduces bleeding frequency)
• Arthrodesis: Joint fusion for end-stage ankle/wrist (pain relief, stability)
• Arthroplasty: Total knee/hip/elbow replacement (salvage for severe arthropathy - requires lifelong factor prophylaxis)

Psychosocial Support

• Chronic disease with lifelong treatment burden
• Multidisciplinary team: haematologist, physiotherapist, nurse specialist, psychologist, genetic counselor
• Patient education: Home factor infusion training (empowerment, rapid treatment)
• Haemophilia centers/societies: Peer support, advocacy

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7. Complications

1. Haemophilic Arthropathy (Chronic Joint Disease)

The most common long-term complication, affecting > 90% of adults with severe haemophilia without adequate prophylaxis.

Pathophysiology:

Stage 1: Acute Hemarthrosis

• Blood in joint → inflammatory response
• Iron from hemoglobin degradation → synovial toxicity

Stage 2: Chronic Synovitis

• Hemosiderin deposition → synovial hypertrophy and hypervascularity
• Increased fragility → recurrent bleeding (target joint)

Stage 3: Cartilage Destruction

• Inflammatory cytokines (IL-1, TNF-α) from synovium → chondrocyte apoptosis
• Loss of articular cartilage

Stage 4: End-Stage Arthropathy

• Subchondral bone cysts, osteophytes, joint space loss
• Fixed flexion deformities, chronic pain, disability
• Requires arthroplasty [15]

Clinical Features:

• Pain (chronic, aching)
• Stiffness (morning stiffness, reduced range of motion)
• Swelling (effusion, synovial thickening)
• Muscle atrophy (quadriceps wasting in knee arthropathy)
• Fixed flexion deformity

Imaging:

• X-ray: Pettersson score (0-13 per joint) - late changes
• MRI: Early detection (cartilage loss, synovial hypertrophy, hemosiderin)

Management:

• Prevention is key: Primary prophylaxis prevents arthropathy development
• Physiotherapy, weight management
• Analgesia (paracetamol, opioids - not NSAIDs)
• Radiosynovectomy/arthroscopic synovectomy (for target joints)
• Arthroplasty (end-stage - outcomes inferior to osteoarthritis patients due to bleeding risk)

2. Inhibitor Development

Covered in detail in Management section - represents treatment failure and requires specialized bypassing agents or emicizumab.

Risk Factors:

• Severe haemophilia (vs mild/moderate)
• Null mutations (complete absence of protein → recognized as foreign)
• Intensive factor exposure early in life
• Family history of inhibitors (genetic susceptibility)
• Non-White ethnicity (higher risk in Black, Hispanic populations) [21]

3. Transfusion-Transmitted Infections (Historical)

The 1980s Tragedy:

• Plasma-derived factor concentrates pooled from thousands of donors
• No viral inactivation methods initially
• > 90% of severe haemophilia patients infected with HIV and/or Hepatitis C in US/UK
• Thousands died from AIDS
• Led to major compensation schemes (UK: £1.2 billion compensation fund) [10]

Current Safety:

• Recombinant factor concentrates (no human plasma) - zero viral transmission risk
• Viral inactivation for plasma-derived products (solvent-detergent, heat treatment)
• Donor screening, nucleic acid testing
• No documented HIV/HCV transmission since 1987 (with modern products)

Legacy:

• Older haemophilia patients may have HIV/HCV/HBV
• Require monitoring, antiretroviral therapy, hepatology follow-up
• Increased risk hepatocellular carcinoma (HCV cirrhosis)

4. Intracranial Haemorrhage

• Leading cause of death in severe haemophilia (25% of deaths)
• 10% lifetime risk
• Mortality 20-30%
• Can occur spontaneously or after minor trauma
• Prevention: Avoid contact sports, wear helmets (cycling, skiing), immediate factor for any head trauma

5. Chronic Pain Syndrome

• Multifactorial: arthropathy, neuropathic pain (nerve compression from hematomas), chronic opioid use
• Impairs quality of life significantly
• Requires multidisciplinary pain management (physiotherapy, psychology, pain clinic)

6. Pseudotumor (Haemophilic Pseudotumor)

• Rare (1-2% of severe haemophilia)
• Chronic, encapsulated hematoma that expands progressively
• Erodes adjacent bone → destructive, expansile mass
• Often in long bones (femur, pelvis), soft tissues
• Imaging: Lytic bone lesions, soft tissue mass (can mimic malignancy)
• Treatment: Surgical excision + factor coverage (high risk of recurrence) [22]

7. Compartment Syndrome

• Occurs with muscle hematomas (calf, forearm)
• Rising pressure within fascial compartment → vascular compromise → ischemia
• Clinical features: 5 P's - Pain (disproportionate), Pallor, Pulselessness (late), Paresthesia, Paralysis
• Diagnosis: Clinical + compartment pressure measurement (> 30 mmHg diagnostic)
• Treatment: SURGICAL EMERGENCY - immediate factor replacement to 100% + fasciotomy
• Delay → Volkmann's contracture (irreversible ischemic muscle fibrosis)

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8. Prognosis

Life Expectancy

Current Outcomes:

• With adequate prophylaxis: Near-normal life expectancy and quality of life
• Physical activity participation (sports, employment) comparable to general population
• Mortality now dominated by same causes as general population (cardiovascular disease, cancer) rather than bleeding

Predictors of Outcome

Good Prognosis:

• Primary prophylaxis started in early childhood
• No inhibitor development
• Good adherence to treatment
• Access to comprehensive haemophilia care
• Mild/moderate severity

Poor Prognosis:

• Late diagnosis, no prophylaxis (severe arthropathy inevitable)
• Inhibitor development (high titre, failed ITI)
• Poor venous access (non-adherence to prophylaxis)
• Co-morbidities (HIV, HCV, liver disease)

Quality of Life

Modern treatment goals extend beyond preventing death to optimizing quality of life:

Achievable with Optimal Management:

• Full-time employment
• Participation in low/moderate-impact sports (swimming, cycling - avoid contact sports)
• Independent living
• Minimal pain, no mobility limitations
• Normal psychological well-being

Emicizumab Era: Subcutaneous prophylaxis every 2-4 weeks (vs 3× weekly IV) has dramatically improved QOL, particularly for children and those with difficult venous access.

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9. Prevention & Screening

Genetic Counseling

Indications:

• Family history of haemophilia
• Known carrier status
• New diagnosis in proband (assess family cascade)

Carrier Testing:

• All female first-degree relatives of affected males
• Combination of:
  • Factor VIII/IX levels (unreliable alone due to lyonization)
  • Genetic testing (definitive if family mutation known)

Prenatal Diagnosis (if requested by family):

• Chorionic villus sampling (11-13 weeks) or amniocentesis (15-18 weeks)
• Genetic testing of fetal cells
• Ethical considerations discussed with family

Neonatal Management

Delivery:

• Avoid traumatic delivery (ventouse, forceps, fetal scalp electrodes)
• Caesarean section NOT routinely recommended (unless obstetric indications)
• Avoid intramuscular injections (vitamin K can be given orally)
• Defer circumcision until diagnosis confirmed and factor replacement available

Screening:

• Test cord blood factor levels if:
  • Known family history
  • Unexplained ICH/cephalohematoma
  • Prolonged bleeding after procedures

Preventing Complications

Joint Protection:

• Primary prophylaxis (prevents arthropathy)
• Physiotherapy (muscle strengthening → joint stability)
• Avoid high-impact contact sports (rugby, boxing, martial arts)
• Use protective equipment (helmets, knee pads)

Bleeding Prevention:

• Avoid aspirin, NSAIDs (platelet inhibition)
• Caution with anticoagulants (warfarin, DOACs - relatively contraindicated)
• Alert all healthcare providers to diagnosis (emergency card/bracelet)
• Home factor available for immediate self-treatment

Immunization:

• Hepatitis A and B vaccination (prevent liver disease)
• Routine childhood immunizations (subcutaneous route preferred over IM)

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10. Guidelines & Key Evidence

International Guidelines

1. World Federation of Hemophilia (WFH) Guidelines for the Management of Hemophilia (3rd Edition, 2020) [1]

   • Comprehensive global consensus
   • Evidence-based recommendations for diagnosis, treatment, complications
   • Adapted for resource-limited settings

2. UKHCDO (UK Haemophilia Centre Doctors' Organisation) Guidelines

   • UK-specific guidance on factor replacement, inhibitors, surgery
   • Regularly updated specialty-specific protocols

3. European Haemophilia Consortium (EHC) Best Practice Guidelines

Landmark Trials & Evidence

Evidence Levels

• Prophylaxis vs on-demand: Level I evidence (RCT) - prophylaxis superior [23]
• Emicizumab efficacy: Level I evidence (multicenter RCTs) [19]
• Gene therapy: Level II evidence (prospective cohorts, no RCT vs prophylaxis)
• ITI for inhibitors: Level II-III evidence (observational cohorts)
• Bypassing agents: Level III evidence (case series)

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11. Examination Focus (MRCP/Haematology)

History-Taking Checklist

Bleeding History:

• "Tell me about your bleeding episodes"
  • Spontaneous vs trauma-related?
  • Which joints affected? (knee > elbow > ankle - typical pattern)
  • Age at first bleed? (severe = infancy; mild = adulthood)
  • Any head injuries? (ICH risk assessment)

Treatment History:

• Current regimen: Prophylaxis (what product, frequency) or on-demand?
• Home therapy? (self-infusion indicates good disease understanding)
• Inhibitor history? (game-changer for management)
• Ever received emicizumab or gene therapy?

Family History:

• Maternal grandfather/uncles with bleeding? (X-linked pattern)
• Any females in family with heavy periods? (carrier status)
• Consanguinity? (rare but raises autosomal recessive differentials)

Social History:

• Occupation (physically demanding jobs may not be feasible)
• Sports participation (contact sports contraindicated)
• Impact on daily life (QOL assessment)

Physical Examination Pearls

Inspection:

• Gait: Antalgic gait (painful joints - arthropathy)
• Joint deformities: Fixed flexion at knees/elbows (chronic hemarthroses)
• Muscle wasting: Quadriceps atrophy (chronic knee arthropathy)
• Venous access scars: Antecubital fossae scarring (repeated IV access)
• Port-a-cath: Central venous access device (difficult peripheral access or frequent treatment)

Joint Examination:

• Swelling: Effusion (acute bleed) vs synovial thickening (chronic)
• Range of motion: Restricted (arthropathy)
• Crepitus: Cartilage loss
• "Boggy" synovium: Synovial hypertrophy on palpation

Specific Signs:

• Psoas sign (pain on hip extension): Iliopsoas hematoma
• Compartment tightness: Muscle hematoma - check neurovascular status

Viva Voce Questions & Model Answers

Exam Detail: Q1: A 5-year-old boy presents with a swollen, painful right knee after a minor fall. APTT is prolonged, PT normal, platelets normal. Factor VIII is less than 1%. What is your diagnosis and immediate management?

Model Answer: "This is severe haemophilia A presenting with acute hemarthrosis. The APTT prolongation with normal PT and platelets localizes the defect to the intrinsic pathway, and factor VIII less than 1% confirms severe haemophilia A.

My immediate management priorities are:

1. Immediate factor VIII replacement - I would give recombinant factor VIII aiming for 50% level, using the formula: Dose (IU) = weight (kg) × 50 × 0.5. For a 20kg child, this would be 500 IU.
2. R.I.C.E. - Rest, ice, compression, elevation to support hemostasis
3. Analgesia - paracetamol or codeine, avoiding NSAIDs and aspirin (platelet inhibition)
4. Avoid aspiration unless very tense (introduces infection risk)

For longer-term management:

• Refer to haemophilia center for primary prophylaxis (factor VIII 3× weekly or emicizumab subcutaneously)
• Genetic counseling for family
• Education on early bleed recognition and home therapy
• Physiotherapy to prevent joint damage

The goal is to prevent this becoming a 'target joint' with recurrent bleeds leading to chronic arthropathy."

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Q2: What is the mechanism of action of emicizumab, and why can it only be used in haemophilia A?

Model Answer: "Emicizumab is a bispecific monoclonal antibody that mimics the cofactor function of factor VIII.

Mechanism: It has two binding sites:

• One arm binds to activated factor IX (FIXa)
• The other arm binds to factor X (FX)
• By bringing FIXa and FX into close proximity, it replicates the function of the tenase complex (FVIIIa + FIXa), enabling FIXa to activate FX efficiently

Why only haemophilia A? It specifically replaces the missing cofactor function of factor VIII. In haemophilia B, the defect is in factor IX itself (the enzyme, not the cofactor), so emicizumab cannot compensate - there's no FIX for emicizumab to bring together with FX.

Clinical advantages:

• Subcutaneous administration (every 2-4 weeks) vs IV factor (3× weekly)
• Effective even in patients with inhibitors (doesn't require FVIII)
• Dramatically improves quality of life and adherence
• Bleeding reduction of 87-99% in trials"

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Q3: A 30-year-old with severe haemophilia A presents to A&E after bumping his head on a cupboard door. He feels well, GCS 15, no neurological deficit. What is your management?

Model Answer: "This is a potential intracranial haemorrhage - a haematological emergency in haemophilia.

Critical principle: TREAT FIRST, SCAN LATER.

Immediate management:

1. Immediate factor VIII bolus to achieve 100% level - I would give a weight-based dose: For 70kg patient = 70 × 100 × 0.5 = 3,500 IU factor VIII IV stat
2. Then urgent CT head (do not delay factor waiting for imaging)
3. Full neurological examination including GCS monitoring
4. Neurosurgical consultation if any hemorrhage detected

If CT shows ICH:

• Admit to ICU/neurosurgery
• Maintain factor VIII levels > 80-100% for at least 14 days (half-life ~12h, so needs BID dosing)
• Serial CT imaging to assess progression
• Surgical intervention if mass effect/deterioration

If CT normal:

• Still admit for 24h observation
• Repeat factor VIII dose at 12h (ensure sustained > 50% levels)
• Safety-net advice for deterioration

Rationale: Even minor head trauma can cause delayed ICH in severe haemophilia. Early factor replacement prevents expansion of small bleeds. Mortality from ICH is 20-30%, so aggressive prophylactic approach is justified."

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Q4: How do you differentiate haemophilia A from von Willebrand disease?

Model Answer:

Clinical Clues:

Laboratory Differentiation:

Pathophysiology difference:

• Haemophilia A: Direct deficiency of factor VIII (intrinsic pathway defect)
• VWD: Deficiency of von Willebrand factor, which normally:
  • Carries and protects FVIII in circulation (so FVIII may be secondarily low)
  • Mediates platelet adhesion (so platelet function impaired despite normal count)

Treatment difference:

• Haemophilia A: Recombinant factor VIII or emicizumab
• VWD: Desmopressin (releases vWF from endothelial stores) or vWF/FVIII concentrates"

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Q5: What are the indications for immune tolerance induction (ITI) in haemophilia, and what does it involve?

Model Answer: "ITI is used to eradicate inhibitors (neutralizing anti-FVIII antibodies) in haemophilia A patients.

Indications:

• High-titre inhibitors (≥5 BU) making factor replacement ineffective
• Persistent low-titre inhibitors despite attempts to overcome with high-dose factor
• Goal: Restore ability to use standard factor VIII prophylaxis

Protocol:

• High-dose factor VIII (100-200 IU/kg) administered daily for 12-36 months
• Rationale: Regular exposure induces immune tolerance (desensitization)
• Requires central venous access (port-a-cath) due to daily IV administration

Success factors:

• Good prognosis: Low peak inhibitor (less than 200 BU), short time since inhibitor detected (less than 5 years), age less than 6 years
• Poor prognosis: Very high peak inhibitors, long delay, older age

Success rate: 60-80% overall (inhibitor eradicated, can resume standard factor VIII)

Complications:

• Line infections (central line sepsis)
• Extremely expensive (£200,000-500,000/year)
• Requires prolonged commitment (1-3 years)

Alternatives if ITI fails:

• Emicizumab (now first-line for inhibitor patients - avoids need for ITI in many cases)
• Bypassing agents for breakthrough bleeds (rFVIIa, aPCC)
• Consider rituximab (anti-CD20 antibody to deplete B-cells producing inhibitor)"

Common OSCE/PACES Scenarios

Station 1: Explain haemophilia to a parent whose son has just been diagnosed

Station 2: Explain genetic risks to a female carrier considering pregnancy

Station 3: Joint examination - chronic haemophilic arthropathy (fixed flexion deformities, muscle wasting)

Station 4: Breaking bad news - inhibitor development

Station 5: History - adult with mild haemophilia presenting with first bleed after dental extraction

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12. Patient/Layperson Explanation

"What is Haemophilia?"

Haemophilia is a genetic bleeding disorder where your blood doesn't clot properly. Think of blood clotting like building a wall to plug a hole - you need bricks (platelets) and cement (clotting factors). In haemophilia, you have normal bricks but the cement is missing or weak (factor VIII or IX deficiency).

What happens: When you cut yourself, the bleeding stops initially (the platelet "bricks" form a plug), but then starts again hours later because the plug isn't strong enough without the "cement" to hold it together.

"Why did my child get haemophilia?"

Haemophilia is inherited - it's passed down through families on the X chromosome.

How it works:

• Boys have XY chromosomes (one X from mum, Y from dad)
• Girls have XX chromosomes (one X from mum, one X from dad)
• The haemophilia gene is on the X chromosome

If mum is a carrier:

• Each son has a 50% chance of having haemophilia
• Each daughter has a 50% chance of being a carrier

If dad has haemophilia:

• All daughters will be carriers (they get dad's affected X)
• All sons will be unaffected (they get dad's Y, not his X)

New mutations: In 1 in 3 cases, haemophilia happens for the first time (no family history) - this is a new mutation.

"What are the symptoms?"

The main symptom is bleeding that won't stop:

In babies/toddlers:

• Large bruises from minor bumps
• Bleeding from mouth/tongue when teething
• Swollen, painful joints when starting to walk

In children/adults:

• Joint bleeds (especially knees, elbows) - the joint becomes hot, swollen, painful, and hard to move
• Muscle bleeds - swelling, pain, bruising
• Bleeding after injuries/surgery that goes on for hours or days
• Nosebleeds that are hard to stop

Severity depends on factor level:

• Severe (less than 1%): Bleeds happen without injury, 1-2 times per week
• Moderate (1-5%): Bleeds after minor injuries
• Mild (5-40%): Bleeds only after surgery or major injuries

"How is it treated?"

The main treatment is replacing the missing clotting factor:

1. Factor injections (into a vein):

   • Provides the missing "cement" to stop bleeding
   • Can be given when bleeding happens (on-demand)
   • Better: Regular injections 2-3 times a week (prophylaxis) to prevent bleeds

2. Emicizumab (Hemlibra) - newer treatment:

   • Injection under the skin (like insulin) every 2-4 weeks
   • Acts like a substitute for factor VIII
   • Prevents most bleeds

3. Gene therapy (newest option):

   • One-time treatment - a virus carries a working gene into your liver
   • Your liver then makes factor VIII/IX naturally
   • Still experimental but very promising

Home treatment: Many patients learn to inject factor at home - this means they can treat bleeds immediately (within minutes) before serious damage occurs.

"Can my child live a normal life?"

Yes - with modern treatment, people with haemophilia can live near-normal lives:

What you CAN do:

• Go to school/work normally
• Play low-contact sports (swimming, cycling, tennis)
• Travel (take factor with you)
• Have relationships, children (with genetic counseling)

What to AVOID:

• Contact sports (rugby, boxing, martial arts) - high risk of injury
• Aspirin/ibuprofen (makes bleeding worse) - use paracetamol instead
• Injections into muscle (causes bleeding) - ask for skin/vein injections

Important:

• Always tell doctors/dentists you have haemophilia
• Wear a medical alert bracelet
• Treat bleeds early (don't "wait and see")
• If you hit your head, even slightly, get factor immediately - don't wait for symptoms

"What about the future?"

The outlook has improved dramatically:

• 50 years ago, life expectancy was 30-40 years
• Today: With good treatment, near-normal life expectancy (70+ years)
• New treatments (emicizumab, gene therapy) mean fewer injections and better quality of life
• Research is ongoing - a cure may be possible in the future

The key is good treatment from early childhood - regular prophylaxis prevents joint damage and allows normal development.

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