Cause:Idiopathic autoimmune
Pathophys:Immune complex deposition leads to fibrinoid necrosis of vessel wall and thrombosis. An acute necrotizing vasculitis of small- and medium-sized vessels; focal lesions may lead to thrombosis or aneurysmal dilatation at site (Arth Rheum 1990;33:1065)
Sx:Fever, weight loss, arthralgias/arthritis, abdominal pain, headache, smokey urine, blindness
Si:Myalgias and myositis (39%), splenomegaly (34%), petechiae and purpura (20%), skin necrosis, urticaria, hypertension, mononeuritis multiplex, fever, fundal vessel damage, cutaneous and visceral nodular aneurysms, ulcers of corneal limbus
Renal involvement or failure (85%), infections, infarcts, and hypertension in 50% (Nejm 1997;337:1739); hepatic infarcts and cirrhosis (66%); cardiac (76%) infarcts and conduction abnormalities; pancreatic (35%) cysts and hemorrhage, blindness from retinal artery occlusion; gi tract (51%) ulcers, hemorrhage, and perforations; aneurysms of mesenteric vessels (25%); asthma (29%); Cogan’s syndrome (bilateral 8th cranial nerve palsies and eye keratitis)
Lab:
Hem:ESR elevated, sometimes eosinophilia (20%)
Path:Biopsies (pos if show involvement of nutrient vessels) of: kidney (also shows GN); sural nerve, esp if slowed nerve conduction velocities; liver; gastrocnemius or other muscle; testicular; skin
Serol:Complement levels depressed; rheumatoid titers elevated; antineutrophil cytoplasmic autoantibodies, r/o Wegener’s (Ann IM 1990;113:656)
Xray:Diagnostic microfusiform aneurysms on renal and hepatic angiography (Nejm 1970;282:1024)