Polyarteritis Nodosa

Overview

Polyarteritis nodosa (PAN) is a rare type of vasculitis, a group of disorders in which the walls of blood vessels become inflamed. In PAN, the inflammation targets small and medium-sized arteries. As the artery walls swell and weaken, blood flow to the tissues they supply is reduced, and small bulges called aneurysms can form along the vessels.

Because arteries throughout the body can be involved, PAN can affect many organs at once, most often the skin, peripheral nerves, joints, muscles, intestines, and kidneys. The lungs are usually spared, which helps distinguish PAN from some other forms of vasculitis. The cause is often unknown, but in a minority of people PAN is linked to chronic hepatitis B infection.

Symptoms

Symptoms depend on which arteries and organs are affected and often build up over weeks. General, whole-body symptoms are common early on.

• Fever, fatigue, and unintended weight loss
• Muscle and joint aches
• Numbness, tingling, or weakness from nerve damage (often in the hands or feet)
• Skin changes such as a lacy purple rash, tender lumps, or ulcers
• Abdominal pain after eating, sometimes with nausea or bleeding
• High blood pressure and signs of kidney involvement

Severe abdominal pain, blood in the stool, or sudden weakness on one side of the body can signal a serious complication and need urgent medical attention.

Causes

The exact cause of polyarteritis nodosa is usually not known. It is thought to result from the immune system mistakenly attacking the body's own artery walls.

• Idiopathic PAN: In most people, no clear trigger is found.
• Hepatitis B-associated PAN: In some cases the disease follows chronic hepatitis B infection, where immune complexes appear to drive the vessel damage.
• Other infections: Less commonly, other infections such as hepatitis C have been linked to the condition.

PAN is not contagious and is not directly inherited, although a rare genetic form caused by changes in a gene called ADA2 can appear in childhood.

Risk Factors

• Chronic hepatitis B (or, less often, hepatitis C) infection
• Middle age, though PAN can occur at any age
• A rare inherited deficiency of the enzyme ADA2 (in early-onset cases)

PAN affects men slightly more often than women, but anyone can develop it.

Diagnosis

There is no single test for PAN, so doctors combine the clinical picture with laboratory and imaging findings.

• Blood and urine tests: To look for inflammation, kidney involvement, and hepatitis B or C.
• Biopsy: A small sample of affected tissue, such as skin, muscle, or nerve, examined for the characteristic artery inflammation.
• Angiography: Imaging of the blood vessels that can reveal narrowing and small aneurysms typical of PAN.

Ruling out other forms of vasculitis is an important part of reaching the diagnosis.

Treatment

Treatment aims to control inflammation quickly, prevent organ damage, and keep the disease in remission. With modern therapy, most people improve substantially.

• Corticosteroids: High-dose steroids such as prednisone are usually the first treatment to bring inflammation under control.
• Immune-suppressing drugs: Medicines such as cyclophosphamide or azathioprine are added in more severe cases to allow steroid doses to be lowered.
• Antiviral therapy: When PAN is linked to hepatitis B, treating the virus is a key part of management.
• Supportive care: Blood pressure control, pain relief, and treatment of organ-specific problems.

Treatment is often needed for many months, and follow-up continues afterward because the disease can relapse.

Prevention

Because the cause is usually unknown, PAN itself cannot reliably be prevented. Some steps can lower related risks:

• Vaccination against hepatitis B reduces the chance of hepatitis B-associated PAN
• Taking medications exactly as prescribed helps maintain remission and prevent flares
• Regular follow-up allows early treatment of any relapse or medication side effects

When to See a Doctor

See a doctor if you have unexplained fever, weight loss, new numbness or weakness, or a persistent rash with tender lumps. Seek emergency care right away for:

• Sudden, severe abdominal pain or vomiting
• Blood in the stool or black, tarry stools
• Sudden weakness, numbness, or trouble speaking, which can signal a stroke
• Chest pain or fainting

Related Topics

Frequently Asked Questions

References

1. National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Vasculitis.
2. Mayo Clinic. Polyarteritis nodosa.
3. MedlinePlus, U.S. National Library of Medicine. Polyarteritis nodosa.
4. Vasculitis Foundation. Polyarteritis Nodosa.