Polyarteritis nodosa is a segmental transmural necrotising vasculitis of medium-sized muscular arteries (it does not involve arterioles, capillaries or venules)

Aetiology

• Rare condition
• Most commonly occurs in men and usually presents in patients aged 40–60
• Association with hepatitis B
  • Where this association occurs, polyarteritis nodosa usually occurs within 6 months of the acquisition of hepatitis B

Clinical features

Polyarteritis nodosa is a multisystem condition with typical features including:

• Nerves - mononeuritis multiplex
• Kidney - renal infarction, renal failure
• Skin - livedo reticularis, nodules, ulcers, palpable purpura
• Musculoskeletal - arthralgias, arthritis, myalgias
• Gastrointestinal - abdominal pain, abnormal LFTs
• Cardiac - myocardial infarction, heart failure
• Central nervous system - stroke, seizures

Investigations

Diagnosis is based on:

• Clinical features
• Laboratory results:
  • Haematuria/proteinuria when renal involvement is present
  • Elevated CRP/ESR
  • Anaemia, thrombocytosis
  • Hypoalbuminaemia
  • Hepatitis B surface antigen (present in up to 50% depending on the case series)
  • In classical polyarteritis nodosa, ANCA, rheumatoid factor, antinuclear antibodies and cryoglobulins are negative
• Imaging:
  • Angiography (including MRA and CTA) can be used for diagnosis if biopsy is not feasible
    • Imaging findings including microaneurysms and wedge-shaped infarcts
• Biopsy:
  • If tissue is amenable to biopsy, this can confirm the diagnosis
  • Classically, histology shows a focal and segmental necrotising transmural vasculitis