Polyarteritis nodosa: symptoms, diagnosis and treatment

Vasculitis means inflammation of blood vessels. Arthritis UK explains that in PAN the inflammation affects medium-sized arteries, particularly those that supply the gut and kidneys, and that it may affect only part of the artery wall, which becomes weak and may bulge to form an aneurysm, or involve the whole wall at one point, causing a blockage.

The NHS describes PAN as a rare type of vasculitis that particularly affects the arteries supplying the gut, kidneys and nerves. Great Ormond Street Hospital (GOSH), writing about children, says it affects medium and/or smaller sized arteries that become damaged and inflamed.

It is one of several kinds of vasculitis described by the NHS, alongside conditions such as giant cell arteritis, granulomatosis with polyangiitis and microscopic polyangiitis, which affect different vessels and organs and are treated somewhat differently.

Symptoms depend on which arteries are inflamed and which organs are therefore short of blood. The NHS lists muscle and joint pain, abdominal pain particularly after eating, a rash, pins and needles or numbness, and bleeding and ulcers in the gut. Arthritis UK, in its general vasculitis information, says vasculitis can cause fever, fatigue, weight loss and sweats.

GOSH, in its children's information, lists a persistent unexplained fever and feeling generally unwell, several types of skin rash or palpable lumps due to inflammation of the skin, tummy aches and weight loss, protein in the urine with sometimes high blood pressure, and possible involvement of the heart, lungs, brain, nerves and liver depending on which arteries are inflamed.

Because PAN can be very serious if not treated, as the NHS says, persistent unexplained fever, weight loss, new numbness or weakness, new severe tummy pain or a rash with unexplained illness should be assessed by a GP promptly, who can arrange blood and urine tests and refer to a specialist, usually rheumatology.

Call 999 or go to A&E for sudden severe tummy pain, vomiting blood or passing black or bloody stools, chest pain, sudden weakness or loss of speech, or collapse. Arthritis UK warns that an aneurysm which bursts can cause serious internal bleeding. The NHS page on vasculitis in general advises 111 for suspected giant cell arteritis because of risk of stroke and blindness, which is a separate condition that is important not to miss when someone has head or jaw symptoms.

GOSH explains that, as with most types of vasculitis, PAN is diagnosed from signs and symptoms that indicate inflammation after doctors have ruled out other diseases that can cause the same picture. A blood test is necessary and often a skin biopsy. Other biopsies may be needed to check the extent of damage to organs such as the liver or kidneys, and an arteriogram, an X-ray test of the arteries, can show changes in the arteries.

The NHS and Arthritis UK both note an association with hepatitis B in some cases. GOSH notes that protein in the urine can indicate kidney inflammation and that blood pressure may be raised, so urine tests and blood pressure checks are used to look for kidney involvement.

The NHS says the main treatment is steroid medicine, and sometimes other medicines that reduce the activity of the immune system. GOSH, for children, describes steroids to reduce inflammation together with a disease-modifying drug such as cyclophosphamide, azathioprine, mycophenolate mofetil or methotrexate, chosen by the doctor.

Steroids and immune-suppressing medicines carry side effects and increase the risk of infection, so treatment usually involves regular blood tests and clinic follow-up. If PAN is associated with hepatitis B, the infection also needs treatment, which a specialist will coordinate. You should not stop steroids suddenly without medical advice.

GOSH says there is a range of possible outcomes depending on the severity of disease and how much damage is already present in vital organs such as the kidneys. Early diagnosis and prompt treatment improve the outcome, but PAN can be a serious disease with a small risk of death, particularly if diagnosis is delayed. In children, it says many respond well to medicines and have no further relapses, others have a chronic relapsing course needing long-term medication, and overall most children need treatment for two to three years, after which treatment can usually be withdrawn without return of the disease. These figures relate to children and cannot be assumed for adults.

In the NHS, care is typically led by a rheumatologist, with kidney, gut or nerve specialists involved depending on organ involvement. Private specialist opinions can help with diagnosis, but long-term monitoring on immune-suppressing medicines is usually coordinated with an NHS rheumatology service. Vasculitis UK and Arthritis UK both provide patient information and support.