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Q1: Definition and recognition (2 min)
Examiner: Define polyarteritis nodosa. How would you recognise it clinically, and what two findings distinguish it from the ANCA-associated vasculitides?
Expected answer:
- Polyarteritis nodosa (PAN) is a necrotising vasculitis of MEDIUM-sized muscular arteries producing transmural inflammation, fibrinoid necrosis and microaneurysms (the 'nodosa').
- Recognise it from mononeuritis multiplex (sequential wrist/foot drop from nerve infarction) with constitutional symptoms (fever, weight loss), livedo reticularis, tender subcutaneous nodules, ulcers, abdominal angina (mesenteric ischaemia), new hypertension and testicular pain.
- The two distinguishing negatives: the urinalysis is BLAND (no glomerulonephritis) and ANCA is NEGATIVE — because PAN involves the kidney at the artery level (renovascular), not the glomerulus, and it is not an ANCA-associated vasculitis.
- Peak age 40-60; male predominance ~2:1; classically associated with hepatitis B.
Q2: Investigations (3 min)
Examiner: How do you confirm PAN?
Expected answer:
- Bloods: raised ESR/CRP; U&E/creatinine for renal impairment; ANCA negative; bland urinalysis (no proteinuria, haematuria or casts); LFTs; HBV serology (HBsAg, anti-HBc) is mandatory, plus HCV/HIV; complement often low and cryoglobulins present in HBV-associated PAN.
- Angiography (CT, MR or conventional mesenteric/renal) — the radiological hallmark: microaneurysms and a 'beaded' irregular outline of the renal, mesenteric and hepatic arteries.
- Tissue biopsy of an involved organ (sural nerve + muscle, skin nodule, testis, gut) — transmural medium-vessel vasculitis with fibrinoid necrosis and disruption of the internal elastic lamina.
- Nerve conduction studies localise mononeuritis multiplex. A standard renal biopsy targets the glomerulus and is often unhelpful because PAN spares it.
- The absence of glomerulonephritis and a negative ANCA are diagnostic — if the urine is active or ANCA positive, reconsider MPA.
Q3: Management (3 min)
Examiner: Walk me through the treatment. Why does HBV status matter?
Expected answer:
- Idiopathic PAN: high-dose corticosteroids — prednisolone 1 mg/kg/day (IV methylprednisolone pulses for severe/organ-threatening disease); add cyclophosphamide for severe disease (neuropathy, gut, cardiac, renal), then azathioprine or methotrexate maintenance.
- HBV-associated PAN: antiviral therapy (entecavir or tenofovir) plus plasma exchange plus a SHORT course of corticosteroids. The goal is HBV clearance, NOT long-term immunosuppression — the vasculitis is driven by circulating HBV-antigen immune complexes.
- Cutaneous-limited PAN: steroids alone, or colchicine/dapsone for skin-limited disease.
- Supportive: antihypertensives (renovascular hypertension), neuropathy rehabilitation, PJP prophylaxis and bone protection with steroids/cyclophosphamide, vaccination.
- Monitor with the BVAS, inflammatory markers, renal function and angiography.
Q4: Complications and prognosis (2 min)
Examiner: What are the complications and the outlook?
Expected answer:
- Mononeuritis multiplex with residual disability (foot/wrist drop); mesenteric ischaemia, gut perforation, ischaemic pancreatitis; renovascular hypertension and chronic kidney disease (not GN); coronary arteritis, cardiac failure, ischaemic heart disease; stroke or cerebral vasculitis; microaneurysm rupture and haemorrhage.
- Treatment-related: infection, osteoporosis, cyclophosphamide toxicity (haemorrhagic cystitis, infertility, malignancy).
- Prognosis: five-year survival ~80% with modern treatment; worse with severe gut, cardiac, renal or CNS disease (stratified by the five-factor score / FFS — age over 65, cardiac, GI, renal insufficiency, no ENT involvement).
- HBV-PAN is usually monophasic and rarely relapses once HBV is cleared; idiopathic PAN can relapse and needs maintenance immunosuppression and long-term cardiovascular/renal surveillance.