Calciphylaxis
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Direct answer
Calciphylaxis is calcific uraemic arteriolopathy, a rare disorder of small arteries that causes painful necrotic skin lesions, most often in patients with end-stage kidney disease on dialysis. Calcification of the arteriolar media narrows the vessels, causing thrombosis and tissue necrosis. Treatment reduces calcium and phosphate loading, controls parathyroid hormone and uses intravenous sodium thiosulfate, and mortality remains high.
What you must remember
- Histology: medial calcification of small arterioles, with intimal thickening and thrombosis, is the defining lesion.
- Clinical picture: severely painful livedo-like or purple plaques that progress to necrotic ulcers and eschars, often over fatty areas of the thighs, buttocks and abdomen.
- Risk factors: end-stage kidney disease, female sex, obesity, hyperphosphataemia, a high calcium-phosphate product and hyperparathyroidism.
- Drugs to limit: calcium-based phosphate binders, active vitamin D analogues and warfarin, all of which promote arterial calcification.
- Sodium thiosulfate: given intravenously, usually after dialysis, it is the main specific treatment and works partly through calcium chelation.
- Parathyroid control: cinacalcet or parathyroidectomy is considered for refractory hyperparathyroidism.
- Wound care: analgesia, debridement and antibiotics for infection are essential, because sepsis is the usual cause of death.
- Normal values: serum calcium and phosphate can be near normal, so the diagnosis is clinical and histological.
Recognising and treating calciphylaxis
A dialysis patient with painful skin lesions should be assessed for calciphylaxis early, because delay allows necrosis to spread. The steps below set out the usual sequence.
- Recognise the pain. Pain out of proportion to the skin findings, with livedo reticularis or purple plaques, points to the disease.
- Confirm with biopsy. A skin biopsy shows calcified small arterioles with intimal thickening and thrombosis, which confirms the diagnosis.
- Measure the mineral profile. Calcium, phosphate and parathyroid hormone are checked, although normal values do not exclude the disease.
- Stop the triggers. Calcium-based binders, active vitamin D and warfarin are withdrawn, and non-calcium binders such as sevelamer replace them.
- Start sodium thiosulfate. It is given intravenously, usually after each dialysis session, and it is the mainstay of specific therapy.
- Care for the wounds. Debridement, analgesia and antibiotics for infection are started, since infected necrosis carries the highest risk to life.
Where the exam tries to catch you
Examiners test whether you recognise the disease as an arteriolopathy rather than a vasculitis, and whether you avoid the drugs that worsen it.
- Trap: using calcium-based binders to control phosphate in calciphylaxis Correct: they add calcium load, so non-calcium binders such as sevelamer are preferred.
- Trap: assuming normal calcium excludes the disease Correct: calciphylaxis can occur with normal serum calcium and phosphate, so biopsy and clinical features decide the diagnosis.
- Trap: calling it a primary vasculitis Correct: the key histology is medial calcification of small vessels, not primary inflammatory vasculitis.
Frequently asked questions
What is the typical skin presentation of calciphylaxis?
Calciphylaxis presents with severely painful livedo reticularis or purple plaques that progress to necrotic ulcers and eschars, often over fatty areas such as the thighs, buttocks and abdomen. The pain is typically out of proportion to the visible skin findings.
Which histological finding confirms calciphylaxis?
A skin biopsy confirms calciphylaxis by showing calcification of the media of small arterioles, often with intimal hyperplasia and thrombosis. This arteriolar calcification helps distinguish calciphylaxis from primary vasculitis.
What is the specific treatment for calciphylaxis?
Intravenous sodium thiosulfate, usually given after each dialysis session, is the main specific treatment for calciphylaxis. It is combined with stopping calcium-based binders and vitamin D analogues, control of phosphate and parathyroid hormone, and careful wound care.
Which drugs increase the risk of calciphylaxis in dialysis patients?
Calcium-based phosphate binders, active vitamin D analogues and warfarin increase the risk of calciphylaxis in dialysis patients by promoting arterial calcification. Corticosteroids and obesity are also recognised risk factors for the disease.
What is the usual cause of death in calciphylaxis?
Sepsis from infected necrotic wounds is the usual cause of death in calciphylaxis, and overall mortality is high. Early wound care and prompt treatment of infection can improve the outlook, but the disease carries a poor prognosis.