Polyarteritis nodosa

Systemic necrotizing vasculitis of medium-sized muscular arteries causing ischemia and infarction in multiple organs. Characteristically spares the lungs and glomeruli. Often associated with hepatitis B infection.

• Life-threatening if untreated (5-year survival <15% without therapy). Early recognition allows aggressive immunosuppressive treatment to prevent organ infarctions (e.g., bowel, kidney, nerve). Also, PAN is a classic vasculitis on exams, highlighting key concepts like HBV association, ANCA-negativity, and the importance of distinguishing medium-vessel vs small-vessel vasculitides.

• Insidious onset with constitutional symptoms (fever, weight loss, malaise, myalgias) followed by signs of medium-vessel ischemia in various organs. Adults (typically ages 40–60, male > female) often present with a combination of: skin lesions (painful subcutaneous nodules, livedo reticularis, ulcers); mononeuritis multiplex (asymmetric peripheral neuropathy leading to foot drop or hand weakness); hypertension (renal artery involvement); and abdominal pain (especially postprandial "intestinal angina") with gastrointestinal bleeding. Kidney involvement is typically via renal artery microaneurysms/infarcts rather than glomerulonephritis.
• Pediatric cases are rare, but childhood PAN can occur. Children may present with recurrent fever, skin nodules, and strokes (if a genetic cause like ADA2 enzyme deficiency is present). Unlike Kawasaki disease (another medium-vessel vasculitis in kids), PAN usually lacks mucocutaneous symptoms. A limited form, cutaneous PAN, causes chronic skin ulcers/nodules and is often less severe but can precede systemic disease.

1. Consider PAN in patients with unexplained systemic illness involving multiple organs (skin, nerves, kidney, GI) without lung involvement. Differentiate from ANCA-associated vasculitides: order ANCA testing (PAN is usually ANCA-negative) and note that presence of lung or glomerular involvement suggests alternate diagnoses (MPA/GPA).
2. Always test for hepatitis B (HBsAg) in suspected PAN, since ~30% of cases are HBV-related and management includes antiviral therapy.
3. Confirm diagnosis with tissue biopsy of an affected site (e.g., skin nodule, sural nerve, testis) showing transmural necrotizing arteritis with fibrinoid necrosis. If biopsy is not feasible, perform an angiography (usually mesenteric or renal): look for multiple small aneurysms and irregular constrictions ("beads-on-a-string" appearance, also called the rosary sign).
4. Assess extent of organ involvement: monitor renal function (creatinine, urinalysis) and blood pressure (for renal ischemia); evaluate gastrointestinal symptoms with imaging (mesenteric ischemia can cause bowel perforation); and do a thorough neurologic exam (peripheral nerve deficits occur in ~70% of PAN cases).

1. Corticosteroids (high-dose prednisone ~1 mg/kg/day) are first-line and can induce remission. For severe disease (organ-threatening), add cyclophosphamide to improve survival (cyclophosphamide + steroids for induction).
2. For HBV-associated PAN, prioritize treating the infection: start antivirals (e.g., entecavir) and use a shorter course of steroids ± plasmapheresis instead of prolonged cyclophosphamide (to avoid immunosuppression while virus is active).
3. Manage complications and supportive care: aggressive blood pressure control (renin-driven hypertension is common, often requiring ACE inhibitors); monitor renal artery aneurysms (intervene if risk of rupture); and perform surgery if needed for bowel perforation or organ infarction.

• PAN = Pulmonary Artery Not involved (no lung findings) and P-ANCA Negative (unlike ANCA-associated vasculitides).
• Angiography often shows multiple aneurysms strung like beads ("rosary sign").
• About 30% of cases are associated with hepatitis B infection—always check viral serologies.

• Acute abdominal pain and GI bleeding in PAN → suspect mesenteric ischemia leading to bowel infarction (surgical emergency).
• Peripheral nerve pain/weakness (e.g., foot drop) in a PAN patient → mononeuritis multiplex from nerve infarction; indicates active severe vasculitis requiring urgent treatment.
• New-onset severe hypertension in PAN → renal artery involvement causing renovascular HTN; high risk for renal infarction (requires prompt therapy).

1. Systemic symptoms + multi-organ signs (skin, neuro, renal, GI) → suspect PAN (especially if no lung involvement).
2. Order labs: inflammatory markers (↑ESR/CRP), comprehensive metabolic panel (for renal function, LFTs), and HBV serologies; ANCA testing helps exclude ANCA vasculitis (PAN is typically ANCA-negative).
3. Confirm diagnosis: biopsy of involved tissue (e.g., skin, nerve) or angiography of mesenteric/renal arteries to demonstrate aneurysms.
4. Start high-dose corticosteroids promptly. Add cyclophosphamide for moderate-to-severe disease (e.g., significant organ ischemia). If hepatitis B positive, initiate antiviral therapy (with limited steroid use and possible plasmapheresis).
5. Follow closely: monitor blood pressure, renal function, and symptoms of organ ischemia. Address complications (e.g., dialysis for renal failure, surgery for GI perforation) as needed.

• Middle-aged man with months of fever, weight loss, tender subcutaneous nodules on the legs, and new-onset testicular pain; lab tests show high ESR and positive HBsAg → think polyarteritis nodosa.
• Patient with foot drop (peroneal neuropathy) and post-prandial abdominal pain with melena; angiogram reveals multiple small aneurysms in mesenteric arteries ("string of pearls") → classic PAN (medium-vessel vasculitis involving nerves and GI, sparing the lungs).