Cutaneous necrotizing venulitis in patients with cystic fibrosis.

Palpable purpura was noted to occur late in the course of some 
patients with cystic fibrosis. Skin biopsy specimens showed necrotizing venulitis characterized 
by a perivenular infiltrate composed of neutrophilic leukocytes, fibrin, hypogranulated mast 
cells, and endothelial cell necrosis. Circulating immune complexes were detected. Recurrent 
pulmonary infections and the chronic administration of therapeutic agents provide sources 
of potential antigens. 