Clinical meaning
Polyarteritis nodosa (PAN) is a systemic necrotizing vasculitis affecting medium-sized muscular arteries, causing segmental transmural inflammation with fibrinoid necrosis of the vessel wall, aneurysm formation, thrombosis, and downstream organ ischemia. Unlike ANCA-associated vasculitides, PAN is ANCA-negative and does NOT involve small vessels or glomerulonephritis (spares the lungs and glomeruli). The inflammation is immune complex-mediated, with approximately 30% of cases associated with hepatitis B virus (HBV) infection. Affected organs include kidneys (renal artery aneurysms causing renovascular hypertension, NOT glomerulonephritis), gastrointestinal tract (mesenteric artery involvement causing postprandial abdominal pain and bowel ischemia), peripheral nervous system (vasa nervorum inflammation causing mononeuritis multiplex), skin (livedo reticularis, subcutaneous nodules, ulcers), and musculoskeletal system (myalgias, arthralgias). Constitutional symptoms include fever, weight loss, and malaise.
Diagnosis & workup
Diagnostics & workup: - Conventional angiography (mesenteric or renal): shows characteristic microaneurysms and segmental stenosis of medium arteries — diagnostic gold standard - Hepatitis B surface antigen and HBV DNA — essential to identify HBV-associated PAN (different treatment approach) - ANCA testing — characteristically NEGATIVE (distinguishes PAN from ANCA-associated vasculitides like GPA) - ESR and CRP markedly elevated; leukocytosis and thrombocytosis common - Tissue biopsy (sural nerve, skin, or affected organ) showing transmural necrotizing inflammation of medium arteries - Serum creatinine, urinalysis (proteinuria but NO red blood cell casts — PAN does NOT cause glomerulonephritis) - Nerve conduction studies/EMG if mononeuritis multiplex suspected