Two distinct cellular patterns in cutaneous necrotizing angiitis.

Two distinct cellular patterns of necrotizing angiitis involving venules in skin of patients with clinically identical cutaneous lesions were appreciated by the 1 -mum-thick section technique. In those individuals with serum hypocomplementemia, there was a perivenular inflitrate composed predominantly of neutrophils with fibrin deposition and nuclear debris. In patients with normal serum complement levels, in addition to an infiltrate of neutrophils and fibrin deposition, perivenular lymphocytes in various stages of activation were prominent. In both patterns the venules and not the arterioles were affected, mast cells exhibited various degrees of hypogranulation, and basophils and eosinophils were recognized only rarely. Lesions of different clinical age obtained from one hypocomplelmentemic patient and one normocomplementemic patient exhibited consistent cellular patterns, as did a single crop of lesions biopsied twice, 24 hr apart, in a patient with hypocomplementemia. No patient with hypocomplementemia became normocomplementemic or vice versa with persistence of lesions.