Polyarteritis nodosa !

A rare inflammation of medium-sized arteries that damages the gut, kidneys, nerves and skin. Some cases are linked to hepatitis B. The lungs are spared.

Updated 2026-11-01

Structures involved

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Why it happens

What it is

A systemic necrotising vasculitis of medium-sized muscular arteries that spares the lungs and does not involve glomeruli and is not associated with ANCA. Segmental inflammation produces aneurysms, thrombosis and infarcts in the kidneys, gut, peripheral nerves, skin and testes.

Who gets it

Rare in adults, most often diagnosed in middle age and slightly more in men. Hepatitis B–associated cases have fallen sharply where hepatitis B vaccination is widespread, as in Colombia's national immunisation programme. A cutaneous-only form and genetic forms (DADA2) occur in children and young adults.

Causes

Idiopathic in most cases today
Hepatitis B infection (immune-complex mediated); less often hepatitis C
Deficiency of adenosine deaminase 2 (DADA2), a genetic form in young people
Some cases associated with hairy cell leukaemia

Risk factors

Chronic hepatitis B infection
Injection drug use and other routes of hepatitis B exposure
Middle age

Pathophysiology

Transmural necrotising inflammation affects medium arteries segmentally, often at branch points, with lesions of different ages side by side. Weakening of the wall creates microaneurysms, and fibrosis or thrombosis narrows the lumen, causing ischaemia: renal infarcts and renin-mediated hypertension, mesenteric ischaemia, and nerve infarction (mononeuritis multiplex). Capillaries and the lungs are spared.

Classification

Systemic PAN (idiopathic)
Hepatitis B–associated PAN
Cutaneous PAN (skin-limited)
Genetic PAN-like disease (DADA2)

Symptoms and signs

Fever, weight loss, fatigue, muscle and joint pain
Mononeuritis multiplex: sudden foot drop or wrist drop, numbness in the territory of single nerves
Abdominal pain after meals, GI bleeding
New or severe hypertension
Skin nodules, livedo reticularis, ulcers or digital gangrene
Testicular pain

Diagnosis

Clinical: Suspected in a systemically unwell patient with mononeuritis multiplex, new hypertension, abdominal pain or skin nodules, especially with hepatitis B infection.
Tests: Raised ESR/CRP, anaemia; ANCA negative; creatinine and urinalysis (no active glomerular sediment); hepatitis B and C serology. Biopsy of an involved site (skin, sural nerve or muscle) showing necrotising arteritis confirms the diagnosis; nerve conduction studies document mononeuritis multiplex.
Imaging: Mesenteric or renal angiography (conventional or CT) shows multiple microaneurysms and segmental narrowing («string of beads» pattern) when no tissue is available.

Differential diagnosis

ANCA-associated vasculitides (microscopic polyangiitis involves capillaries, glomeruli and lungs)
Kawasaki disease, the medium-vessel vasculitis of young children
Cryoglobulinaemic vasculitis
Fibromuscular dysplasia and segmental arterial mediolysis
Infective endocarditis with emboli
Atherosclerotic mesenteric ischaemia

Goal of treatment

Suppress the inflammation quickly to prevent organ infarction and death, treat hepatitis B when present, and control blood pressure and ischaemic damage.

Treatment

Acute: Idiopathic PAN: glucocorticoids; cyclophosphamide is added for severe or organ-threatening disease (kidney, gut, heart or nerve), followed by a maintenance agent such as azathioprine or methotrexate.
Medical: Hepatitis B–associated PAN: antiviral therapy with a short course of glucocorticoids, often with plasma exchange, avoiding prolonged immunosuppression.
Medical: Blood-pressure control (ACE inhibitors are often used for renin-mediated hypertension), pain control and supportive care; surgery or endovascular treatment for bowel infarction or bleeding aneurysms.
Follow-up: Monitoring of blood pressure, kidney function, neurological status and abdominal signs; nursing care for foot drop (fall prevention, splints) and infection risk on treatment.

Complications

Bowel infarction, perforation or GI bleeding
Renal infarcts, hypertension and chronic kidney disease
Permanent foot drop or neuropathic pain
Myocardial infarction, heart failure or stroke
Aneurysm rupture
Infections from immunosuppression

Prognosis

Untreated it is often fatal; with treatment most patients reach remission and relapses are less common than in ANCA vasculitis. Gut, kidney, heart and nerve involvement at diagnosis worsens the outlook.

Prevention

Hepatitis B vaccination and safe injection and transfusion practices reduce hepatitis B–associated PAN

Test yourself

Think of the answer, then tap the question to see it.

Which organ is characteristically spared in polyarteritis nodosa?

The lungs (and glomeruli are not involved, so there is no glomerulonephritis).

Which infection is classically associated with PAN?

Hepatitis B.

What neurological pattern is typical of PAN?

Mononeuritis multiplex, for example a sudden foot drop from common fibular nerve infarction.

What does angiography show in PAN?

Multiple microaneurysms and segmental stenoses of medium arteries, especially renal and mesenteric («string of beads»).

Is PAN usually ANCA-positive?

No; ANCA is typically negative, which helps distinguish it from microscopic polyangiitis.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Polyarteritis nodosa (MedlinePlus (U.S. National Library of Medicine), 2026).

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Representative model, for educational purposes only.

Superior mesenteric artery highlighted on the Durgical 3D model