Calciphylaxis
Reviewed by Andrew Schox, BSc(Hons) PGradDipPod MPod, November 2026
Calciphylaxis is a rare but serious condition. Calcium builds up in the small blood vessels of the skin and fat, and clots can form too. This cuts off the blood supply and causes painful skin ulcers that heal slowly and can become infected. It mostly affects people with advanced kidney disease, especially those on dialysis, where 1 to 4 per cent are reported to be affected. Pain is the main symptom. Outcomes are often poor, no treatment is approved, and care focuses on wound care, pain control and managing risk factors.
What is it?
Calciphylaxis is a rare condition in which the tiny blood vessels in the skin and the fat beneath it become blocked. Calcium builds up in the walls of these vessels (small arteries and arterioles), and clots can form inside them. With less blood getting through, the skin is starved of oxygen and starts to break down.
The result is painful skin lesions that often turn into ulcers. They heal slowly, and they can become infected. The condition can also damage other organs.
It is also called calcific uraemic arteriolopathy, or CUA. Calciphylaxis is serious and often life-threatening. It is also rare, and doctors don't yet know exactly why it happens.
Who does it affect?
Calciphylaxis mostly affects people with advanced chronic kidney disease, most commonly stage 4 or 5, and especially people on dialysis. About 1 to 4 per cent of people on dialysis are reported to be affected. Reported rates are higher in people on peritoneal dialysis (4.1 to 9.0 cases per 1000 patient-years) than in people on haemodialysis (0.4 to 3.5 cases per 1000 patient-years).
It can also happen in people whose kidneys work normally, but this is less common. Only about 15 to 20 per cent of cases are in people without kidney failure.
Signs and symptoms
Pain is the hallmark. It is often severe, and it can start before any skin changes appear. It can also be much worse than the skin looks.
The skin changes often begin as tender, dusky purple-pink lumps or hardened patches under the skin. Some people have a net-like mottled pattern, purple patches or firm nodules. These can blister and break down into ulcers, often with black, hard dead tissue (called eschar) on top. The ulcers mostly appear on fatty areas such as the belly, thighs and buttocks, and sometimes on the lower limbs.
Some signs are more serious. They include:
- Ulcers with black, dead tissue, or tissue that is dying (gangrene). This can lead to tissue loss, and sometimes amputation.
- A wound that is red, warm, leaking pus, or comes with a fever. These can mean an infection. Infection can spread through the body as sepsis, the most common cause of death in calciphylaxis.
- Pain that gets worse, skin that keeps breaking down, or new or growing nodules.
A painful skin rash in someone taking the blood thinner warfarin can also be a sign of calciphylaxis.
Early on, calciphylaxis can look like other problems, such as cellulitis (a skin infection), nodules or purple spots (purpura). This is one reason it is often missed.
What causes it?
The exact cause isn't known. Calcium building up in small vessels and clots forming inside them are thought to be the main processes. Because the cause is unclear, treatment is difficult and often based on trial and error.
Several things are linked to a higher risk: diabetes, higher body weight, low albumin (a protein in the blood), abnormal calcium and phosphate levels, taking warfarin, and being female. These are links, not proven causes. Anaemia, ongoing inflammation, smoking, high blood pressure and less effective dialysis have also been named, though the links are less consistent.
Warfarin has been described as a risk factor in its own right. Reports on it have been mixed, though, and it isn't yet clear whether stopping it improves outcomes. Doctors usually weigh up the risks and benefits rather than simply stopping it.
How is it diagnosed?
There is no single agreed way to diagnose calciphylaxis. Some doctors diagnose it mainly from the story, the look of the skin and the person's risk factors. Others rely on a skin biopsy (a small sample of skin examined under a microscope).
Often the diagnosis comes after other causes of painful ulcers have been ruled out. A biopsy can help when the picture is unusual or looks like other skin conditions. It also carries risks: it can cause new lesions, make existing ones worse, or lead to infection, bleeding or tissue death.
Blood tests can add clues. A marker of inflammation called C-reactive protein can be raised in calciphylaxis, but it is also raised by infection, so it can't tell the two apart.
Treatment
No treatment is approved for calciphylaxis, and none has been proven to work. Care usually combines several parts: treating the calcium build-up, caring for wounds, and controlling pain. Lesions can keep appearing despite treatment, and management may take many months.
Looking after it at home
Where there are lesions, it is advised to protect the skin from knocks, pressure and injury. Injection sites (for example for insulin) are usually rotated. It isn't yet clear whether avoiding triggers such as injury from injections, warfarin or iron improves outcomes.
Pain is often severe and under-treated. Many painkillers are cleared by the kidneys, so choosing and adjusting them needs extra care, and several medicines are often needed together.
Treatment from your kidney team
Your kidney team usually leads care. It looks after the calcium build-up and your medicines, including a review of warfarin where relevant. It also works with wound and pain specialists. Wound care aims to protect the skin and prevent infection, though people often describe wound care as varied.
Other options
When usual care isn't enough, it isn't yet clear which other treatments work best. Ongoing wound care, careful pain control and protecting lesions from injury remain the main supports.
Recovery
The outlook is often poor. Reported death rates in the first year range from 30 to 80 per cent, and in some reports more than half of people die within a year of diagnosis. Sepsis is the most common cause, and deaths are largely driven by wound infections and heart and blood vessel events.
Further skin lesions can appear despite treatment, and health can worsen. Managing calciphylaxis can take many months. People also describe delays in diagnosis, pain that isn't well controlled, and little emotional support, so support for how you are feeling matters as well as the wounds.
Preventing it
No way of preventing calciphylaxis has been proven. Some measures have been suggested for doctors to consider in people at risk:
- Making dialysis as effective as possible.
- Keeping blood pressure, anaemia and diabetes under control.
- Losing weight cautiously if overweight.
- Quitting smoking.
- Avoiding substances that are toxic to the liver.
- Switching from warfarin-type blood thinners to other types where possible.
- Fine-tuning calcium and phosphate levels.
These are ideas to explore, not proven steps. Changing medicines such as warfarin carries its own risks, which is why it needs a careful review of risks and benefits.
Frequently asked questions
Is calciphylaxis the same as calcific uraemic arteriolopathy?
Yes. Calcific uraemic arteriolopathy, or CUA, is the longer medical name for calciphylaxis in people with kidney disease. You may see either name, and both describe painful skin ulcers caused by blocked small blood vessels.
Why is calciphylaxis so painful?
The pain is thought to come from two things: skin and tissue starved of blood, and nerve involvement. It is often severe and hard to control, and can start before the skin changes show.
Can calciphylaxis be cured?
No treatment is approved or proven to cure it. Care aims to protect the skin, treat wounds, control pain and manage risk factors. Outcomes vary, and some people have new lesions despite treatment.
Can calciphylaxis come back after it heals?
It isn't yet clear how often it returns after healing. What is known is that new lesions can develop while a person is being treated, which is why care can go on for many months.
Further reading
This is general information, not medical advice. For advice about your own situation, see your health professional. For urgent advice, call your local health advice line or emergency number, or go to an emergency department.