Cause:Staphylococcus aureusnasal carriage associated w relapses possibly through induction of autoimmunity (Ann IM 1994;120:12)
Pathophys:ANCA-associated necrotizing granulomatous vasculitis of the small blood vessels of the upper and lower respiratory tract (90%) and kidney (80%, though <20% on presentation)
Rare but all forms of ANCA-associated small vessel vasculitis are the most common type of vasculitis in adults
Sx:Purulent rhinitis; sinusitis; insidious onset; fever; arthralgias, pneumonitis
Si:Pneumonitis, sinusitis, otitis media, rhinitis, peripheral neuropathies, purpura, arthritis
w/o rx, fatal in 80% at 1 yr, and 93% at 2 yr; 95% survival with rx (Ann IM 1983;98:76) vs 75% remission w rx, though resistance and recurrence predictable by pre-rx characteristics (Ann IM 2005;143:621)
Pulmonary insufficiency (20% of fatalities), massive pulmonary hemorrhage, tracheal sclerosis w stridor (15% adults, 50% children); renal failure (80% of fatalities); DVT/PE in 7% (Ann IM 2005;142:620)
r/o other ANCA-associated vasculitis (see below)
Lab:
Chem:Creatinine elevated, IgA increased in blood and secretions, normal IgG and IgM
Hem:ESR elevated, eosinophilia
Path:Bx of nose, throat, and lung show focal angiitis with granulomas; bx of kidney shows GN
Serol:IgG antineutrophil cytoplasmic antibodies (mostly antiprotease 3 ANCA) elevated, 66% sens, 98% specif (Ann IM 1995;123:925), can use to follow rx; but as many as 1/3 of the positives may be polyarteritis or idiopathic renal vasculitis? (Ann IM 1990;113:656); r/o other ANCA-associated small vessel vasculitis, usually anti-myeloperoxidase type ANCA; microscopic angiitis; Churg-Strauss syndrome (Ann IM 2005;143:632); and drug-induced types
Urine:Red cell casts
Xray:Cavitating pulmonary nodule
Rx:Rapid rx, crucial to survival, w iv cyclophosphamide until disease controlled, then po mtx or azothiaprine maintenance. Steroids po and/or iv pulse or maybe rituximab (Nejm 2010;363:211, 221, 265) for renal or respiratory failure; 93% complete remission, 30% cure? with good long-term survival. Azothiaprine maintenance? safer and as good as cyclophosphamide (Nejm 2003;349:36), perhaps for all ANCA-associated vascultis? (Nejm 2005;352:351)