Vasculitides & Systemic Granulomatous Disease

By completing this question set, you will be able to classify a systemic vasculitis by vessel size (large, medium, small, variable, single-organ) and apply that classification to direct the clinical workup; interpret ANCA serology in clinical context — c-ANCA/PR3 vs p-ANCA/MPO and the disease patterns each predicts (GPA, MPA, EGPA), the ~10% ANCA-negative classic-clinical-picture subset, and drug-induced ANCA forms (levamisole-cocaine, hydralazine, propylthiouracil); diagnose giant cell arteritis and apply the urgent treatment imperative that empiric high-dose corticosteroids must precede biopsy when GCA is suspected because vision loss is irreversible within hours; recognize the GCA-PMR overlap and distinguish PMR from RA by the absence of synovitis and the dramatic response to low-dose prednisone; diagnose Takayasu arteritis in young Asian women with arm claudication, asymmetric blood pressures, and bruits; recognize polyarteritis nodosa as a medium-vessel necrotizing vasculitis with renal and mesenteric microaneurysms that spares the lung and the glomerulus (distinguishing from MPA), and recognize the chronic HBV association; recognize Kawasaki disease in children <5 with fever ≥5 days plus 4 of 5 classic criteria, and apply the IVIG-within-10-days treatment imperative to prevent coronary artery aneurysms; recognize thromboangiitis obliterans (Buerger's) in young heavy smokers with distal extremity ischemia and "corkscrew collaterals," and apply the principle that complete smoking cessation is the only effective treatment; distinguish GPA from MPA from EGPA by clinical pattern, ANCA serology, and biopsy (granulomatous vs non-granulomatous vs eosinophilic); construct the pulmonary-renal syndrome differential using ANCA + anti-GBM + ANA + complement + biopsy IF pattern; recognize HSP/IgA vasculitis with its tetrad and the intussusception risk in children; recognize cryoglobulinemic vasculitis with its low-C4-disproportionate-to-C3 + RF-positive + HCV-positive serologic signature; recognize Behçet's disease in patients of Silk Road origin with the recurrent oral + genital ulcer + uveitis triad and HLA-B51 association; diagnose sarcoidosis as a systemic granulomatous disease including Löfgren and Heerfordt syndromes; explain the sarcoid hypercalcemia mechanism via macrophage 1α-hydroxylase-driven calcitriol production with appropriately suppressed PTH; and distinguish primary vasculitis from its mimics (APS, infective endocarditis, atrial myxoma, cholesterol embolization).