Polyarteritis Nodosa (PAN)

What happens in polyarteritis nodosa

In PAN, immune-driven inflammation attacks the walls of medium-sized arteries, the vessels that feed organs such as the kidneys, intestines, nerves and skin. Segments of the wall die (necrosis) and may balloon into small aneurysms or narrow and clot. Blood flow to the tissue beyond is reduced, causing infarcts (tissue death) and organ damage.

Unlike several other vasculitides, PAN:

• usually spares the lungs
• does not affect the smallest vessels (capillaries), so it does not cause glomerulonephritis
• is not associated with ANCA antibodies

Causes

• Idiopathic: most cases have no known trigger.
• Hepatitis B: once a major cause; now less common due to vaccination.
• Hepatitis C, HIV and some other infections, less often.
• DADA2 (deficiency of adenosine deaminase 2): a genetic condition causing PAN-like disease and early strokes in children and young adults.
• Hairy cell leukemia and some other blood disorders.

PAN typically affects adults aged 40 to 60 and is slightly more common in men.

Types

• Systemic PAN: affects multiple organs.
• Cutaneous PAN: limited mainly to the skin, with painful nodules, livedo and ulcers on the legs, sometimes with joint pain and nerve symptoms; generally milder.

Symptoms

General

• fever, night sweats, fatigue
• weight loss
• muscle aches and joint pain

Nerves

• mononeuritis multiplex: sudden numbness, tingling or weakness in the area of one nerve and then another, such as foot drop or wrist drop
• symmetrical peripheral neuropathy

Skin

• tender red or purple nodules, usually on the legs
• livedo reticularis: a lacy purple pattern
• ulcers and dark, dying fingertips or toes

Kidneys

• new or severe high blood pressure from narrowed kidney arteries
• kidney damage, blood in urine, sudden flank or side pain from kidney infarcts

Gut

• abdominal pain, often after meals
• nausea, bleeding, and in severe cases bowel perforation

Other

• testicular pain or swelling
• heart attack, heart failure
• strokes (especially in DADA2)
• eye problems

Diagnosis

1. Blood tests: raised ESR and CRP, anemia, kidney function, hepatitis B and C tests, ANCA (negative in PAN, which helps distinguish it from granulomatosis with polyangiitis and microscopic polyangiitis).
2. Biopsy: of skin, nerve or muscle showing necrotizing inflammation of medium-sized arteries.
3. Angiography (CT, MR or catheter): shows microaneurysms and narrowing in kidney, liver and gut arteries.
4. Genetic testing for DADA2 in young patients or those with strokes.
5. Nerve conduction studies for nerve involvement.

Treatment

Idiopathic PAN

• Glucocorticoids (such as prednisone) are the foundation.
• For severe disease (kidney, gut, heart or nerve involvement), cyclophosphamide or other immunosuppressants are added.
• Maintenance: azathioprine or methotrexate to keep disease in remission while steroids are tapered.
• Milder disease may be treated with steroids alone or with methotrexate or azathioprine.

Hepatitis B-associated PAN

Antiviral therapy for hepatitis B, often with a short course of steroids and sometimes plasma exchange. Long-term immunosuppression is avoided because it can worsen the infection.

DADA2

TNF inhibitors are very effective at preventing strokes and controlling inflammation.

Supportive care

• blood pressure control
• treatment of nerve pain and physical therapy
• wound care for ulcers
• bone protection during long-term steroid use

Outlook

Untreated systemic PAN has a high mortality. With treatment, most people achieve remission, and 5-year survival is around 80% or higher. Relapses occur less often than in some other vasculitides. Long-term effects can include nerve damage, kidney impairment and high blood pressure.

Frequently asked questions

What is polyarteritis nodosa?

Polyarteritis nodosa is a rare disease in which the immune system inflames and damages medium-sized arteries. This reduces blood flow to organs such as the nerves, skin, kidneys and gut, causing symptoms like fever, weight loss, nerve damage, skin nodules and abdominal pain.

What causes polyarteritis nodosa?

In most people the cause is unknown. Some cases are linked to hepatitis B infection, and less often to hepatitis C or HIV. A genetic condition called DADA2 causes PAN-like disease in children and young adults.

What are the first symptoms of polyarteritis nodosa?

Early symptoms are often general: fever, tiredness, weight loss, and muscle and joint pain. These may be followed by numbness or weakness in a hand or foot, painful skin lumps or a lacy purple rash, abdominal pain or high blood pressure.

How is polyarteritis nodosa treated?

Treatment usually starts with steroids, with cyclophosphamide or other immunosuppressants for severe disease. Hepatitis B-related PAN is treated mainly with antivirals. DADA2 responds to TNF-inhibitor medicines. Most people achieve remission with treatment.

Is polyarteritis nodosa curable?

Many people achieve long-term remission and can eventually stop treatment, especially when the disease is caught early. Some have relapses or lasting effects such as nerve damage or kidney impairment that need ongoing care.