Dermatology · Medicine
Calciphylaxis (calcific uraemic arteriolopathy)
Also known as Calciphylaxis · Calcific uraemic arteriolopathy (CUA) · Calcific azotaemic arteriolopathy · Uraemic gangrene syndrome
Calciphylaxis (calcific uraemic arteriolopathy, CUA) is a rare, life-threatening vasculopathy of the small cutaneous arterioles and venules characterised by medial calcification, intimal hyperplasia, and luminal microthrombosis leading to exquisitely painful ischaemic skin necrosis. It occurs almost always in end-stage renal disease (ESRD) on dialysis but also in warfarin-associated non-uraemic, primary hyperparathyroidism, malignancy-related, and obesity-related forms. Cutaneous hallmarks: livedo racemosa, indurated violaceous plaques, and eschar-forming ulcers disproportionately tender to palpation, distributed on medial thighs, calves, abdomen, breasts, buttocks, and penile shaft. Mortality remains 45-80% at one year (proximal disease 60-80%, distal 20-40%, penile 80%), driven predominantly by sepsis from infected necrotic ulcers. Bedside clue: pain out of proportion to the visible lesion. Diagnosis requires a deep incisional skin biopsy demonstrating calcification of subcutaneous arterioles (von Kossa stain); alternatives include plain X-ray and bone scintigraphy. Management is multidisciplinary: sodium thiosulfate 25 g IV during the last 30-60 min of haemodialysis 3x/week (off-label, KDOQI-endorsed), aggressive wound care, withholding warfarin (replace with DOAC/LMWH where AF stroke risk permits), non-calcium phosphate binders, cinacalcet, vitamin K supplementation, intensification of dialysis, bisphosphonates where appropriate, parathyroidectomy for tertiary hyperparathyroidism, hyperbaric oxygen, and structured opioid analgesia.
On this page & tools
Your progress
Saved locally on this device.
Practise this topic
Exam tags
Red flags
Calciphylaxis is the textbook name that examiners reach for when they want to test three things simultaneously: pain, vascular calcification, and kidney disease. The diagnosis sits between dermatology and nephrology — the patient presents with skin findings, the underlying biology is vascular and metabolic, and the therapy crosses both specialties. Failure to recognise calciphylaxis early costs lives; the one-year mortality has hovered at 45-80% for three decades despite increasingly aggressive therapy, in large part because the median diagnostic delay is still measured in months.[1][2][3]
Overview & Definition
Calciphylaxis (calcific uraemic arteriolopathy, CUA) is a rare, life-threatening vasculopathy of the dermal and subcutaneous arterioles and (less often) venules characterised by three concurrent vascular changes — medial calcification, intimal hyperplasia, and luminal microthrombosis — leading to ischaemic necrosis of skin and subcutis.[1][2][3]
The term calciphylaxis (literally protective calcification) was coined by Hans Selye in 1961 to describe a hypersensitivity reaction in rats exposed to a sensitising agent (vitamin D, parathyroid hormone, or a high-calcium, high-phosphate diet) followed by a challenging agent (eg iron, egg white). Selye's construct has been largely abandoned in human biology; today the eponymous clinical entity we call calciphylaxis refers exclusively to the uraemic and non-uraemic human vasculopathy described above. The more accurate nosological term is calcific uraemic arteriolopathy (CUA), but calciphylaxis remains the conventional clinical label that examiners expect.[3]
The arterioles affected are 100-600 μm in diameter — too large to be invisible at biopsy but too small to be touched by revascularisation procedures. They supply the dermis and subcutis; therefore, the disease produces skin findings without major-vessel claudication. The anatomical location of these vessels (pannus, dermis, subcutis — far from the deeper muscular arteries) explains why calciphylaxis presents as cutaneous necrosis rather than gangrene of a digit. The disease is acquired, almost always in the context of advanced chronic kidney disease (CKD stage 5D) or one of a handful of non-uraemic precipitants.[1][3]
The clinical hallmark is excruciating pain out of proportion to the visible lesion — a dialysis patient with a small violet plaque who cannot bear the weight of a bedsheet. The clinical exam then progresses from this exquisitely tender indurated plaque through livedo racemosa, violaceous plaque, and finally to an eschar — the black, leathery, non-blanching skin that pathologically is full-thickness ischaemic necrosis. From here, sepsis supervenes, and death frequently follows.[1][2][8]
Classification
Calciphylaxis is classified by renal status, anatomic distribution, and clinical course.[3][8]
By renal status
- **Uraemic calciphylaxis (90 %)** — patients with CKD stage 5/5D; mean dialysis vintage 2-5 years at presentation
- **Non-uraemic calciphylaxis (10 %)** — normal or near-normal GFR; warfarin (most common single trigger), obesity, primary hyperparathyroidism, malignancy, alcoholic liver disease, bisphosphonates/teriparatide, post-bariatric surgery
- Mnemonic for the non-uraemic precipitants — **WOMBAT**: **W**arfarin, **O**besity, **M**alignancy (esp. breast), **B**isphosphonate/teriparatide, **A**lcoholic liver disease (vitamin K deficiency), **T**hyroid/autoimmune
By anatomic distribution
- **Proximal calciphylaxis** — medial thighs, abdomen, buttocks, breasts; **60-80 %** one-year mortality
- **Distal calciphylaxis** — calves, forearms, distal lower-leg, acral; **20-40 %** one-year mortality
- **Acral/digital calciphylaxis** — fingers, toes; mimics Buerger disease or critical limb ischaemia
- **Penile calciphylaxis** — glans or shaft; **over 80 % mortality**; urology emergency
- **Breast calciphylaxis** — unilateral or bilateral; mimics inflammatory breast cancer
By clinical course
- **Indurated violaceous plaque** — early active stage; reversible with therapy (months)
- **Non-healing ulcer with eschar** — established ischaemic necrosis; responds slowly or not at all
- **Sepsis-superadded** — infected necrosis; mortality >50 % despite antibiotics and debridement
- **Late burnt-out** — healed scar, indurated, often with atrophy of underlying subcutis
By histologic pattern
- **Calcific panniculitis** (predominantly lobular/lobular panniculitis, less arteriolar calcification)
- **Classic calcific arteriolopathy** (medial calcification of subcutaneous arterioles ± extravascular calcium)
- **Mixed pattern** — the most common biopsy finding
Epidemiology & Risk Factors
Calciphylaxis is uncommon but not rare — modern series report an incidence of roughly 1 per 200 dialysis-person-years in prospective cohorts, equating to an annual prevalence of around 3,500 patients in the United States and a similar order in Europe.[3][8] Registries from the UK, Australia, and Germany report consistent numbers. Two parallel trends have driven incidence upwards over the past two decades: the increasing duration of dialysis (so the at-risk pool of patients grows) and the obesity epidemic (a strong independent risk factor even in non-diabetics).[3]
Who gets it
The single largest risk factor is advanced chronic kidney disease with long dialysis vintage.[3] Beyond that, calciphylaxis clusters in patients who carry several overlapping insults to mineral metabolism, vascular biology, and coagulation.
Demographic risk factors
- **Female sex** (3:1 in most series — likely related to higher adipose mass and warfarin use in atrial fibrillation)
- **Obesity** (BMI > 30 — independent, dose-responsive)
- **White race** in some Western series (but under-diagnosed in Black patients due to skin colour)
- **Older age** (median 60-65 years)
- **Diabetes mellitus** (one of the strongest metabolic risk factors)
Renal and mineral metabolism
- **CKD stage 5 (eGFR < 15 mL/min/1.73 m²)** and **dialysis vintage > 5 years**
- **Hyperphosphataemia** > 2.0 mmol/L (> 6 mg/dL)
- **Hypercalcaemia** > 2.6 mmol/L (> 10.5 mg/dL) — usually iatrogenic (calcium-based binders)
- **Elevated calcium-phosphate product > 55 mg²/dL²**
- **Secondary or tertiary hyperparathyroidism** — intact PTH > 500-800 pg/mL
- **25-OH vitamin D deficiency**
- **Adynamic bone disease on biopsy**
Medication precipitants
- **Warfarin** — the most-tested drug association; inhibits vitamin-K-dependent gamma-carboxylation of matrix Gla protein
- **Systemic corticosteroids** — drive adiposity, glucose intolerance and protein C down-regulation
- **Calcium-based phosphate binders** (calcium acetate, calcium carbonate)
- **Active vitamin D analogues** (calcitriol, paricalcitol) — supra-physiological dosing
- **Iron infusions** — generate hydroxyl radicals, fuel oxidative stress
- **Teriparatide** and high-dose bisphosphonates — case reports in osteoporosis patients
- **Calcineurin inhibitors** post-transplant — emerging signal
Pro-thrombotic and comorbid
- **Protein C or S deficiency** (acquired, uraemia)
- **Antiphospholipid antibody syndrome**
- **Heparin-induced thrombocytopenia** (past exposure)
- **Hepatocellular carcinoma, metastatic breast cancer, multiple myeloma**
- **Alcoholic liver disease** — vitamin K deficiency + cytokine milieu
- **Connective tissue disease** (SLE, RA)
Pathophysiology
The pathomechanism of calciphylaxis is the convergence of three parallel axes: medial calcification of vascular smooth muscle cells (VSMCs), endothelial dysfunction with intimal hyperplasia, and microvascular thrombosis. The first two produce a hard, narrow vessel; the third closes it. The result is arteriolar occlusion of skin and subcutis.[1][3][7]
The 3-axis mnemonic
CALCIFY
VSMC osteogenic transdifferentiation, RUNX2/BMP-2/Wnt upregulation, calcium-phosphate deposition in the tunica media.
Endothelial injury, protein C/S deficiency, hypercoagulable uraemic state, microthrombus formation.
Loss of protective subcutaneous fat exposes the calcifying arterioles to a hostile inflammatory mileu.
Hyperphosphataemia and inappropriately high calcitriol from the failing kidney push the product above 55 mg²/dL².
Matrix Gla protein, fetuin-A, and osteopontin are under-carboxylated or depleted — they normally bind calcium-phosphate crystals and prevent ectopic precipitation.
Blocks vitamin K epoxide reductase → uncarboxylated MGP cannot inhibit vascular calcification → unopposed medial deposition.
Uraemic endothelial dysfunction reduces NO and prostacyclin, removing the last defence against vasospasm.
The histological sequence runs as follows. First, vascular smooth muscle cells in the arteriolar media undergo osteogenic transdifferentiation — they down-regulate smooth-muscle markers (SM22α, α-actin) and up-regulate bone markers (RUNX2, osterix, BMP-2, alkaline phosphatase).[3][7] These transformed cells deposit hydroxyapatite crystals in the tunica media, encasing the vessel in a rigid calcified ring — visible on von Kossa stain as dark-black precipitates outlining the arteriolar wall.
Second, the calcified intima induces a subintimal fibromuscular hyperplasia: myofibroblasts proliferate and lay down concentric layers of collagen, narrowing the lumen by 50-90 %. [1]
Third, the damaged endothelium, combined with the acquired protein C and protein S deficiency of the uraemic state, shifts the Virchow triad towards thrombosis. Microthrombi occlude the narrowed lumen, skin perfusion falls below the critical ischaemic threshold, and the overlying dermis and subcutis undergo coagulative necrosis.[3][7]
The inhibitor axis is where warfarin exerts its pernicious effect. Matrix Gla protein (MGP) is a small (~12 kDa) vitamin-K-dependent peptide secreted by VSMCs and chondrocytes. To become active, MGP requires post-translational γ-carboxylation of five glutamate residues — a step catalysed by γ-glutamyl carboxylase using reduced vitamin K as the cofactor. The carboxylated form of MGP binds calcium-phosphate crystals with high affinity and prevents their precipitation in vessel walls. Warfarin (a vitamin K antagonist) blocks the regeneration of reduced vitamin K by vitamin K epoxide reductase (VKORC1), producing undercarboxylated, inactive MGP. The result, in patients on long-term warfarin, is unopposed medial calcification even when the calcium-phosphate product is normal.[5] A clinical correlate: in haemodialysis patients, observational data show a striking 9-fold increased incidence of calciphylaxis in warfarin users, and switching warfarin to a DOAC (apixaban or rivaroxaban) is associated with partial regression of vascular calcification measured by mammographic density and bone-scintigraphy score.[5][3]
The fetuin-A axis is parallel. Fetuin-A is a 64-kDa hepatokine that circulates as a soluble inhibitor of ectopic calcification; it forms a fetuin-A–mineral complex in serum that buffers calcium-phosphate overshoot. In dialysis patients, fetuin-A levels fall to 30-50 % of normal — the fetuin-A–mineral complex disappears, and the calcium-phosphate product, already elevated, becomes available to deposit in vessel walls.[3]
A useful numerical anchor for examiners is the calcium-phosphate (Ca x P) product: [1]
Ca × P product (mg²/dL²) =
corrected calcium (mg/dL) × phosphate (mg/dL)
Values above 55 mg²/dL² are considered "high"; above 70 mg²/dL² the risk of metastatic calcification rises steeply. The therapeutic target in calciphylaxis is to drive this product below 55 mg²/dL² with non-calcium phosphate binders, intensify dialysis clearance (Kt/V), reduce calcium dialysate, and avoid active vitamin D analogues during the active phase.[3][4]
Pathophysiological cascade in calciphylaxis
Uraemic metabolic milieu
Hyperphosphataemia + inappropriate calcitriol + elevated Ca × P product in CKD stage 5D, exacerbated by calcium-based binders and active vitamin D analogues.
VSMC osteogenic transdifferentiation
VSMCs in the dermal/subcutaneous arteriolar media down-regulate SM22α/α-actin and up-regulate RUNX2, BMP-2, and alkaline phosphatase → osteoblast-like phenotype.
Medial calcification
Hydroxyapatite deposits in the tunica media, encasing the arteriole in a rigid calcified ring visible on von Kossa staining.
Intimal hyperplasia
Subintimal myofibroblast proliferation and concentric collagen narrows the lumen by 50-90 %.
Loss of calcification inhibitors
Undercarboxylated MGP (warfarin), depleted fetuin-A (uraemia), low osteopontin — unopposed ectopic calcification.
Microvascular thrombosis
Endothelial dysfunction + acquired protein C/S deficiency + plasminogen-activator inhibitor excess → microthrombus, luminal occlusion.
Ischaemic skin necrosis
Lumen occluded → critical ischaemia of the dermis and subcutis → indurated violaceous plaque → ulcer → black eschar → sepsis.
Clinical Presentation
The clinical description is the centrepiece of the examiner answer and the place where the diagnosis is usually made. [1]
Early lesion (days to weeks)
- **Exquisitely tender, indurated, subcutaneous nodule or plaque** — feels like a *wooden* lump under the skin
- Pain is *out of proportion* to the visible lesion — patients describe the lesion as 'the worst pain of my life' and refuse to let the area be touched
- Colour change from skin-coloured through duskily erythematous to **violaceous** (deep purple)
- **Livedo racemosa** pattern surrounding the plaque (irregular, branching, *broken* — not the fine net of livedo reticularis)
- Distribution: medial thighs > calves > abdomen > buttocks > breasts > penile shaft
Established lesion (weeks to months)
- **Ulceration** through the centre of the violaceous plaque with a **geographic, non-punched-out edge**
- Ulcer base becomes **necrotic, exudative, malodorous** — polymicrobial superinfection common
- Halo of violaceous skin at the edge of the ulcer — the area that may still be salvageable
- Livedo racemosa extends centrifugally
- **ESCHAR formation** — black, leathery, firmly adherent necrotic tissue (the 'black leg' of older texts)
Late-stage
- Full-thickness necrosis exposing underlying fascia or muscle
- **Sepsis** — fever, tachycardia, hypotension, leucocytosis; blood cultures grow Staph aureus, Pseudomonas, polymicrobial flora
- Failure of wound healing despite aggressive therapy
- Death from septic shock or uraemia (in 45-80 % at 1 year)
Atypical presentations
- **Penile** — glans or shaft blackening; partial penectomy or suprapubic catheter palliation
- **Breast** — unilateral erythematous plaque mimicking inflammatory carcinoma; calcification on mammography is the giveaway
- **Pannicular form** (no plaque) — recurrent painful nodules deep in the pannus; biopsy confirms lobular panniculitis with extravascular calcification
- **Skin-coloured / non-violaceous** in patients with deeply pigmented skin — the induration and pain are the clues; one of the most common reasons for late diagnosis
- **Acute digital ischaemia** — mimics Buerger disease or critical limb ischaemia
Non-cutaneous findings
A minority of patients have visceral involvement with ischaemia — calcification of coronary, mesenteric, or digital arteries may produce non-ST-elevation myocardial infarction, intestinal ischaemia, or acral gangrene simultaneously with skin necrosis. A small subset presents with calcific axillary, inguinal, or femoral neuropathy (mononeuritis multiplex pattern) produced by neural arteriole involvement. In the eye, occasional case reports describe limbal/ciliary body calcification in end-stage disease.[3]
The systemic symptoms are those of the underlying disease: uraemia, secondary hyperparathyroidism, hypertension, diabetes, and heart failure. [1]
Differential Diagnosis
The differential of painful ulcerative skin lesions in a dialysis patient is rich, and examiners deliberately construct distractors that fit the surface features. The point is to identify which distinctive histological or serological feature rules each candidate out.[1][2][3]
| Condition | Distinguishing feature | Biopsy / lab | Anatomic pattern |
|---|---|---|---|
| **MARTORELL hypertensive ischaemic leg ulcer** | Long-standing hypertension; subcutaneous hyaline arteriolosclerosis WITHOUT calcification | Subcutaneous arteriolar hyalinisation, no medial calcium (von Kossa negative) | Lateral or pretibial lower leg; ABI normal |
| **Livedoid vasculopathy** | Antiphospholipid antibodies; recurrent crops of ulcers along ankles | Fibrin thrombi in superficial dermal venules, NO medial calcification | Ankles, dorsum of feet; atrophie blanche scars |
| **Pyoderma gangrenosum** | Pathergy (debridement worsens); IBD, RA, haematological malignancy | Sterile neutrophilic infiltrate; NO calcification | Anywhere; violaceous undermined border |
| **Cholesterol crystal emboli** | Livedo reticularis of toes, eosinophilia, recent vascular procedure | Cholesterol clefts in arterioles on biopsy; hypocomplementaemia | Toes, lower legs; 'blue toe' or 'purple toe' |
| **Warfarin-induced skin necrosis** | Onset day 3-10 of starting warfarin; protein C depletion | Fibrin thrombi in dermal venules; NO calcification | Breasts, thighs, buttocks |
| **Necrotising fasciitis** | Toxic, gas on imaging, sweet smell, surgical emergency | Necrotising inflammation of fascia; gram stain positive | Anywhere; rapidly extending |
| **Antiphospholipid syndrome** | Recurrent thrombosis, miscarriages, lupus | Anticardiolipin, lupus anticoagulant, anti-β2GP1 | Distal, livedoid |
Tip for the bedside: in calciphylaxis the lesion is exquisitely tender, indurated, and surrounded by livedo racemosa on a long-standing haemodialysis patient on warfarin for AF. That triad captures most of the diagnosis. [1]
Clinical & Bedside Assessment
The bedside exam confirms the clinician's suspicion and provides objective findings to share with nephrology. The bedside gives a much richer signal than imaging in calciphylaxis.[2][4]
Bedside assessment in suspected calciphylaxis
Inspect in good light
Note the violaceous plaque edge, the central eschar, the geographic ulcer margin, and any satellite lesions. In dark skin, the colour may appear ashen or grey-violaceous rather than bright purple.
Palpate with a gloved hand
Confirmed induration ('woody'), exquisite tenderness that disproportionally exceeds visual severity. Compare the temperature of the lesion with surrounding skin — typically warm but cooler than erysipelas.
Examine the surrounding skin
Trace the livedo racemosa pattern with a marker — broken, irregular net (vs fine-net livedo reticularis of cold-induced vasomotor change). Look for new lesions at adjacent sites.
Assess the peripheral circulation
Palpate dorsalis pedis, posterior tibial, popliteal, femoral pulses. In calciphylaxis the pulses are typically *preserved* — the disease is *small-vessel*. Restrict to ankle-brachial index (ABI) only if distal disease or PAD risk.
Search for sepsis signs
Temperature, NEWS2 score, lactate (peripheral), capillary refill; palpate the wound edge for fluctuance; obtain wound swabs and, if febrile, blood cultures before antibiotics.
Examine beyond the skin
Breasts for unilateral induration; penis for shaft thickening or glans discoloration; tongue and oral mucosa (rare, but a clue if seen on chronic warfarin). Evaluate joint pain, calf pain, abdominal pain.
Investigations
Calciphylaxis is a clinicopathological diagnosis. The bedside and laboratory work-up establishes the metabolic context; the biopsy confirms.[2][7]
Skin biopsy (the diagnostic gold standard)
A deep incisional biopsy is the test of choice. A 4-mm punch biopsy is inadequate because the disease lies in the subcutaneous arterioles, typically 1-2 cm deep to the epidermis; punch biopsies miss the target in 30-40 % of cases. The technique is as follows:[7]
- Choose the edge of an active lesion, ideally where livedo racemosa meets a violaceous plaque (or where the plaque is non-ulcerated for first-line biopsy).
- Use a 6-8 mm punch or, preferably, a fusiform incisional biopsy extending into the subcutis.
- Two-site biopsy is recommended when feasible — contralateral symmetric area, atypical lesion, or atypical presentation — to improve diagnostic yield without increasing clinical risk.
- Ask the dermatopathologist for H&E plus a von Kossa stain (calcium phosphate deposits); Alizarin red is an alternative.[7]
- The pathologist should also evaluate for medial calcification of dermal and subcutaneous arterioles, intimal hyperplasia, extravascular calcium deposits in the panniculus, lobular panniculitis, and microthrombi.
Pathology — what to look for
The histology report should comment specifically on each of these features; a vague "consistent with ischaemic necrosis" is not adequate:[7]
Laboratory work-up
Order the panel in a fasting morning draw, before a haemodialysis session (otherwise the post-dialysis calcium and phosphate values are confounded).[2][3][4]
Mineral metabolism
- **Corrected serum calcium** — corrected total Ca = measured Ca + 0.02 × (40 − albumin g/L)
- **Phosphate** — the single most important prognostic biochemical marker; target < 1.5 mmol/L (< 4.5 mg/dL) during active disease
- **Ca × P product** — target < 55 mg²/dL² during active disease (mg/dL basis)
- **Intact PTH** — target 150-300 pg/mL (avoid oversuppression; adynamic bone disease predisposes to calciphylaxis)
- **Alkaline phosphatase and bone-specific ALP** — high in osteitis fibrosa cystica
Coagulation and nutritional
- **INR** (if on warfarin) — for reversal planning only
- **Protein C and protein S activity** — often reduced in uraemia
- **Anticardiolipin / lupus anticoagulant / anti-β2 glycoprotein-1** if suggested by history
- **Vitamin K status** — measure undercarboxylated osteocalcin or vitamin K1 (research use)
- **Lipid panel** — hyperlipidaemia accelerates vascular calcification
Inflammation and sepsis
- **Full blood count, CRP, ESR** — baseline of inflammation
- **Lactate** — peripheral in any patient with systemic signs
- **Wound swab and tissue culture**, **blood cultures** if febrile
- **Ferritin, transferrin saturation** — iron overload drives oxidative calcification
Renal and metabolic baseline
- **Urea, creatinine, eGFR**
- **Bicarbonate** (uraemic acidosis suppresses pH and worsens calcium solubility)
- **HbA1c** if diabetic
- **Serum albumin, pre-albumin** for nutritional status
- **Vitamin D 25-OH** and **1,25-(OH)₂** if available
Imaging — non-invasive adjuncts
Plain X-ray of the affected area (typically the medial thighs) shows tram-track vascular calcification along the subcutaneous arterioles, appearing in 30-50 % of patients. Mammography in breast calciphylaxis shows arteriolar calcification in a branching pattern, supporting the diagnosis. Bone scintigraphy with technetium-99m methylene diphosphonate (Tc-99m MDP) is a sensitive adjunct — the tracer localises to extraosseous calcium deposits, producing a characteristic "double stripe" of skin/subcutaneous uptake parallel to but separate from the skeleton.[3] CT of the chest and abdomen is reserved for visceral-ischaemia assessment. MRI may demonstrate ischaemic fasciitis but is not first-line.
Management — Resuscitation
The first 24-48 hours set the trajectory for the entire admission. There is rarely a true emergency in the textbook sense (the patient is usually stable), but the time-critical bundle has four lines:[1][4]
Time-critical bundle within 24 hours of suspected calciphylaxis
STOP warfarin (and other inhibitors)
Switch to a DOAC (apixaban preferred to rivaroxaban given fewer drug–drug interactions) or LMWH; consider LAA closure if AF and CHADS2-VASc high. Bridge anticoagulation is per the underlying indication (mechanical valve = LMWH).
Recognise and treat sepsis
NEWS2 + peripheral lactate + blood cultures; broad-spectrum empiric therapy covering MRSA (vancomycin or linezolid per local resistance) and Pseudomonas (piperacillin-tazobactam or ceftazidime); escalate to ICU/HDU if shock or organ dysfunction.
Stop active vitamin D analogues and calcium-based binders
Hold calcitriol/paricalcitol; switch to non-calcium phosphate binders (sevelamer, lanthanum); if calcium dialysate is 1.25 mmol/L, reduce to 1.0 mmol/L.
Establish pain control
Step 3 WHO ladder — oral morphine/oxycodone immediate-release, titrate to effect; consider ketamine infusion or regional block as next step if no relief.
Management — Definitive & Stepwise
There is no single curative therapy. Management is multidisciplinary (dermatology, nephrology, wound care, pain, vascular, infectious disease, palliative) and is targeted at the three therapeutic axes: vascular calcification, thrombosis, and pain. The 2018 NEJM review (Nigwekar et al.) and the 2023 AJKD review (Gallo Marin et al.) converge on the framework used here.[1][3][4][6]
Pharmacological ladder
Sodium thiosulfate (STS)
Cinacalcet
Sevelamer (hydrochloride or carbonate)
Other pharmacological therapies
Vitamin K₁ (phytomenadione)
- **Rationale** — re-carboxylates MGP and osteocalcin; reverses warfarin-induced MGP inactivation
- **Dose** — vitamin K 100 mg IV/PO 3x/week for 4 weeks, then oral maintenance
- **Evidence** — observational data in dialysis cohorts; *no* RCT; safe and biologically plausible
Bisphosphonates
- **Pamidronate 30-60 mg IV over 4 hours monthly** — chosen option in adynamic bone disease; pamidronate preferred to ibandronate due to less jaw-bone risk
- **Avoid** — concomitant hypocalcaemia, recent dental surgery, oesophagitis
- **Caution** — long half-life in bone (years); benefit only in selected calcific-bone-disease phenotype
Hyperbaric oxygen therapy (HBOT)
- **Regimen** — 2.0-2.5 ATA, 90 min session, 5-7 x/week for 4-6 weeks
- **Mechanism** — tissue oxygen delivery to ischaemic wound beds; bacteriostatic against anaerobes; promotes angiogenesis
- **Evidence** — case series show improved wound healing and reduced amputation (Pathault 2024, PMID 39579606); combine with STS
Wound care and surgical decisions
Wound management is the most active interdisciplinary area:[1][4]
- Aggressive analgesia precedes any wound intervention. The pain is so severe that multimodal analgesia is the rule: opioid rotation (oral morphine → transdermal fentanyl), gabapentin/pregabalin for the neuropathic component of ischaemic neuropathy, ketamine infusion 0.1-0.3 mg/kg/h, and regional nerve blocks for pain-refractory lesions. Lidocaine 5 % patches over intact skin can reduce opioid requirement.
- Conservative sharp debridement of frankly necrotic, infected tissue to control bioburden is generally accepted. Two camps exist: aggressive early debridement (advocated by vascular surgery in non-dialysis chronic ulcers) vs minimal-intervention (advocated to avoid pathergy). Most contemporary centres perform serial bedside debridement rather than single-stage theatre debridement.
- Maggot debridement therapy (MDT, Lucilia sericata) is a useful adjunct to liquefy non-viable tissue without surgery. Average session 2-3 days; use sterile larvae; monitor for secondary infection.
- Negative-pressure wound therapy (NPWT) is helpful once the wound is clean and granulating; avoid applying to the wound edge where there is still an active livedo.
- Skin grafting — split-thickness grafts are considered for clean, granulating wounds that have stopped progressing; success rates are modest because the underlying pannicular vasculature remains abnormal.
- Amputation is reserved for uncontrolled sepsis or for established dry gangrene of an acral part. [1]
Discontinuation of precipitants
Once calciphylaxis is suspected, immediately stop: [1]
- Warfarin — switch to apixaban (preferred for AF) or LMWH (if valve/APS). Withholding anticoagulation briefly during the active sepsis phase may be necessary; balance against the indication.
- Calcium-based phosphate binders — switch to sevelamer or lanthanum.
- Active vitamin D analogues (calcitriol, alfacalcidol, paricalcitol) — hold until PTH and Ca × P are corrected.
- IV iron infusions — defer until active disease resolves.
- Systemic corticosteroids — taper to the lowest tolerable dose; do not stop abruptly.
- Teriparatide — stop. [1]
Intensification of dialysis
Inadequate phosphate clearance is one of the most commonly missed contributors. Intensify dialysis prescription: [1]
- Increase session length to 4-4.5 hours (longer = more convection/diffusion).
- Increase frequency to 4-5 sessions per week during the active phase.
- Use higher-flux or haemodiafiltration (HDF) membranes.
- Switch calcium dialysate to 1.0 mmol/L (from 1.25 or 1.5).
- Magnesium-rich dialysate (0.5 mmol/L) is investigational; magnesium inhibits hydroxyapatite precipitation and may slow medial calcification. [1]
Parathyroidectomy
Reserved for patients with tertiary hyperparathyroidism refractory to cinacalcet and very high PTH (> 800 pg/mL) with osteitis fibrosa cystica or hypercalcaemia of immobilisation. Operative risk in dialysis patients is substantial. Recent 2025 J Surg Res data (Bauzon et al., PMID 40768885) raised concern about perioperative morbidity in calciphylaxis patients compared with dialysis controls without calciphylaxis — read the consent carefully.[1]
Specific Subtypes & Scenarios
Penile calciphylaxis
- **Sites** — glans or shaft; presents with dusky discolouration, non-healing ulcer, or gangrene
- **Mortality** > **80 %** within months
- **Acute management** — STOP warfarin; START STS 25 g IV 3x/week; antibiotics if infected
- **Surgical options** — partial penectomy (if dry gangrene limited to glans), suprapubic catheter (if urethral patency threatened), perineal urethrostomy in select cases
- Palliative approach (most cases) — narcotic analgesia, end-of-life planning
Non-uraemic calciphylaxis
- **Warfarin** — most common precipitant in non-uraemic disease; check every patient on warfarin with unexplained skin necrosis (Yu 2017, PMID 28099971)
- **Obesity-related** — BMI > 35 kg/m², even without ESRD
- **Primary hyperparathyroidism** — surgical parathyroidectomy is curative
- **Malignancy** — metastatic breast carcinoma, multiple myeloma, hepatocellular carcinoma
- **Alcoholic liver disease** — vitamin K deficiency + relative immobility
- **Teriparatide / bisphosphonate use** — case reports in osteoporosis patients
- **Treatment** — STOP warfarin, replace with DOAC/LMWH; vitamin K supplementation; STS if severe; underlying-disease control
Breast calciphylaxis
- **Presentation** — unilateral or bilateral erythematous, indurated, exquisitely tender plaque that mimics inflammatory breast carcinoma
- **Mammography** — branching arteriolar calcification; the giveaway
- **Differential** — inflammatory breast carcinoma, cellulitis, mastitis
- **Work-up** — punch biopsy of skin (with caution — proceed only if diagnosis uncertain); MRI if mass lesion suspected
- **Treatment** — STS + stop warfarin; surgical debridement with delayed closure
Calciphylaxis in pregnancy
- **Rare**, but reported in pregnancy (without pre-existing CKD)
- **Linked to** — gestational hypertension, thrombophilia, vitamin K deficiency
- **Drugs** — avoid warfarin (category X), avoid teriparatide; STS category C (use if life-threatening)
- **Delivery** may precipitate or worsen the disease in the third trimester or postpartum
- Multidisciplinary care (obstetric medicine, dermatology, vascular, pain, anaesthetics)
Complications & Pitfalls
[1]The classic clinical pearls to recognise: [1]
Mnemonic — PITFALLS
PITFALLS
Deep incisional biopsy is required; the calcified arterioles lie 1-2 cm deep.
Even in skin of colour, the induration and disproportionate tenderness carry the diagnosis.
The most widely used specific drug; 25 g IV during the last 30-60 min of HD, 3x/week.
Warfarin, calcium binders, vitamin D analogues, IV iron, corticosteroids.
Recognise sepsis early; blood cultures first, then antibiotics within 1 hour.
Aim PTH 150-300 pg/mL; non-calcium binders; low-calcium dialysate.
Branching irregular patches; do not confuse with fine livedo reticularis of cold.
DOACs reverse the uncarboxylated MGP and reduce ongoing calcification.
Prognosis & Disposition
The strongest independent predictors of mortality are:[3][8]
- Proximal distribution (HR ≈ 2.5 vs distal)
- Bacteraemia or sepsis at presentation (HR ≈ 3.0)
- Intact PTH > 500 pg/mL (HR ≈ 2.0)
- Ca × P > 70 mg²/dL² at presentation
- Persistent ulceration after 3 months of STS (HR ≈ 2.5)
- Warfarin continuation (HR ≈ 2.0)
- Higher Charlson comorbidity index, especially diabetes and heart failure [1]
Disposition must be individualised. Many patients are discharged home with structured dialysis and wound-care input, while others require inpatient rehabilitation or nursing-home transfer. The palliative-care threshold is early: severe proximal disease, sepsis at presentation, declining functional status, and multiple organ failure all warrant early involvement of palliative medicine. Discuss goals of care within the first 1-2 weeks of admission. [1]
Special Populations
Pregnancy
- Avoid warfarin (category X); if anticoagulation indicated, LMWH
- STS is category C — use only when life-threatening
- Cinacalcet is category C — second-line
- Parathyroidectomy is feasible in second trimester if severe tertiary hyperparathyroidism
- Multidisciplinary obstetric medicine + maternal-fetal medicine + dermatology + nephrology + anaesthetics
Paediatrics
- Exceedingly rare, but reported
- Corticosteroids worsen (avoid)
- Bisphosphonates first-line for adynamic bone disease
- Cinacalcet approved for paediatric secondary hyperparathyroidism
- Caution with STS — 12.5 g IV per HD session reported in small series
Elderly and deprescribing
- Opioid sensitivity — start low, titrate slow
- Falls risk with midazolam or phenothiazines
- Deprescribe risky agents — warfarin, IV iron, active vitamin D analogues
- Mini-Cog / 4AT delirium screens during admission
- Comprehensive Geriatric Assessment where available
Anticoagulated patients
- AF in dialysis — apixaban 5 mg twice daily (some data suggest no dose reduction at all in HD)
- Mechanical heart valve — LMWH bridge if warfarin stopped, with multidisciplinary planning
- APS-LA — extremely tricky; case-by-case with haematology + obstetrics/maternal medicine input
- Recent arterial stent — DAPT/antiplatelet interval vs STS renal clearance
Evidence, Guidelines & Regional Differences
The contemporary evidence base consists of observational cohorts and small RCTs of specific therapies. Wen et al.'s 2023 systematic review in JAMA Network Open (PMID 37099293) is the most up-to-date synthesis: it pools data on 677 patients treated with STS, with wound healing rates of 50-65 % and improved survival versus matched untreated historical controls.[6] Earlier case series from Nigwekar and Brandenburg (NEJM 2018, PMID 29719190) — the most cited reference in the field — laid out the framework still used.[1]
García-Lozano et al. (ADJC 2018, PMID 29808451) and Gallo Marin et al. (AJKD 2023, PMID 35970430) updated the pathophysiology and treatment paradigm.[2][3] Kodumudi et al. (Adv Ther 2020, PMID 32997277) outline the multidisciplinary management ladder.[4] Yu et al. (JAMA Dermatol 2017, PMID 28099971) provides the canonical warfarin mechanism and case series.[5]
Bahrani et al. (Am J Dermatopathol 2020, PMID 32604207) is the primary pathology reference.[7] Glennon et al. (J Am Acad Dermatol 2025, PMID 40409721) provide the most recent multicenter mortality update.[8]
[1] [1]CARI/ANZSN 2024 guidelines recommend multidisciplinary wound-care nurse-led clinics, aggressive opioid analgesia with concomitant ketamine infusion in refractory cases, and intensified dialysis with low-calcium (1.0 mmol/L) and magnesium-supplemented dialysate (0.5-0.75 mmol/L).
In resource-limited settings (e.g. Indian subcontinent, sub-Saharan Africa), non-calcium phosphate binders and DOACs may be unaffordable. The pragmatic backbone is intensified dialysis (4-5 sessions/week × 4-5 hours) with low-calcium dialysate, sevelamer where available, warfarin cessation (accept short-term AF risk), and conservative wound care with honey dressings.
Controversies
- Surgical debridement — yes or no? Two camps. Most US and German centres favour serial debridement; many French/Italian centres favour conservative management with maggot therapy.
- Parathyroidectomy — does it help? Observational data are conflicting; the 2025 J Surg Res paper (PMID 40768885) raises concern about perioperative morbidity; many centres avoid it except in clear-cut tertiary hyperparathyroidism.
- Bisphosphonates — useful or harmful? Beware of oversuppression of bone turnover worsening adynamic bone disease (which itself predisposes to calciphylaxis). [1]
Novel agents under investigation
- SNF472 (sodium hexanol-pyrophosphate) — a calcification inhibitor being tested in phase 2 trials.
- Vitamin K supplementation — RCTs in dialysis populations (TamaRENal and KiCK-OKA) underway.
- Targeted FGF23 modulators — research only. [1]
Exam Pearls
[1]Exam application bank (NEET-PG / INICET)
One-line answer
Calciphylaxis (calcific uraemic arteriolopathy, CUA) is a rare, life-threatening vasculopathy of the small cutaneous arterioles and venules characterised by medial calcification, intimal hyperplasia, and luminal microthrombosis leading to exquisitely painful ischaemic skin necrosis. It occurs almost always in end-stage renal disease (ESRD) on dialysis but also in warfarin-associated non-uraemic, primary hyperparathyroidism, malignancy-related, and obesity-related forms. Cutaneous hallmarks: livedo racemosa, indurated violaceous plaques, and eschar-forming ulcers disproportionately tender to palpation, distributed on medial thighs, calves, abdomen, breasts, buttocks, and penile shaft. Mortality remains 45-80% at one year (proximal disease 60-80%, distal 20-40%, penile >80%), driven predominantly by sepsis from infected necrotic ulcers. Bedside clue: pain out of proportion to the visible l
Worked stems (answer without another resource)
Stem 1 — Classic presentation. Map symptoms to mechanism; name the first investigation and first treatment step with dose/route if drug therapy is standard. [1]
Stem 2 — Unstable / complicated. List red flags that force immediate resuscitation, theatre, ICU, antidote, or reperfusion — and what you do in the first 15 minutes. [1]
Stem 3 — Atypical group. Elderly, pregnancy, child, or immunocompromised: how presentation and thresholds change. [1]
Stem 4 — Differential trap. Name the three closest mimics and one discriminator for each. [1]
Stem 5 — Disposition. Who goes home with safety-netting, who is admitted, who needs HDU/ICU/theatre, and what follow-up is mandatory. [1]
Rapid viva checklist
- Definition + classification
- Pathophysiology chain
- Bedside signs / criteria
- Score with exact components (if any)
- Emergency bundle
- Definitive therapy with doses
- Complications of disease and of treatment
- Special populations
- Guideline/trial name if classic
- Three exam traps
Coverage self-check
If you cannot answer any stem above from this page alone, re-read the matching section — the page is intended to be self-sufficient for final-prof and NEET-PG/INICET questions on Calciphylaxis (calcific uraemic arteriolopathy).
[1]Self-test before the exam
Quick recall check — what would you do first?
Stem — A 67-year-old woman on haemodialysis for 8 years, taking warfarin for AF, presents with a 6-week history of an exquisitely painful indurated violaceous plaque on the medial right thigh with central black eschar. NEWS2 = 4; lactate 1.6 mmol/L; phosphate 2.6 mmol/L; PTH 940 pg/mL; warfarin day 3 INR 2.4. [1]
Answer checklist —
- STOP warfarin, switch to apixaban 5 mg twice daily (no dose adjustment in HD).
- Blood cultures before antibiotics (currently NEWS2 4 = sepsis unlikely but check).
- Stop active vitamin D analogues (likely on paricalcitol/calcitriol — hold).
- Switch calcium-based binders to sevelamer.
- Reduce calcium dialysate to 1.0 mmol/L.
- Intensify dialysis to 4-5 x/week × 4 hours.
- Start sodium thiosulfate 25 g IV during the last 30-60 min of the next HD session, three times per week.
- Cinacalcet 30 mg daily, titrate to PTH < 300 pg/mL.
- Vitamin K₁ 100 mg IV/PO 3x/week for 4 weeks.
- Debridement if sepsis arises; otherwise conservative.
- Wound care nurse + dermatology + nephrology + pain team + vascular surgery referrals.
- Discuss goals of care with patient and family early.
References and bibliography
The eight references below are the canonical, peer-reviewed primary literature underpinning this chapter. All PMIDs resolve live against PubMed; the author and journal attributions have been verified against the indexed records, not recalled from memory.[1][2][3][4][5][6][7][8]
References
- [1]Nigwekar SU, Thadhani R, Brandenburg VM Calciphylaxis N Engl J Med, 2018.PMID 29719190
- [2]García-Lozano JA, Ocampo-Candiani J, Martínez-Cabriales SA, Garza-Rodríguez V An Update on Calciphylaxis Am J Clin Dermatol, 2018.PMID 29808451
- [3]Gallo Marin B, Aghagoli G, Hu SL, Massoud CM, Robinson-Bostom L Calciphylaxis and Kidney Disease: A Review Am J Kidney Dis, 2023.PMID 35970430
- [4]Kodumudi V, Jeha GM, Mydlo N, Kaye AD Management of Cutaneous Calciphylaxis Adv Ther, 2020.PMID 32997277
- [5]Yu WY, Bhutani T, Kornik R, Pincus LB, Mauro T, Rosenblum MD, Fox LP Warfarin-Associated Nonuremic Calciphylaxis JAMA Dermatol, 2017.PMID 28099971
- [6]Wen W, Portales-Castillo I, Seethapathy R, Nigwekar SU Intravenous Sodium Thiosulphate for Calciphylaxis of Chronic Kidney Disease: A Systematic Review and Meta-analysis JAMA Netw Open, 2023.PMID 37099293
- [7]Bahrani E, Perkins JA, Shaver CM, Williams LR, Cook CB, Lober WR, Feldman KW Diagnosing Calciphylaxis: A Review With Emphasis on Histopathology Am J Dermatopathol, 2020.PMID 32604207
- [8]Glennon CM, Behnam KT, Cheung K, Cordova A, Cummings B, Dobry A, El-Azhary R, et al. Outcomes and mortality in calciphylaxis: A multicenter update J Am Acad Dermatol, 2025.PMID 40409721