Hypersensitivity angiitis.

Hypersensitivity angiitis is a disease in which patients present with palpable purpura dominant on the lower legs. As lesions evolve they become confluent, and sometimes hemorrhagic and ulcerate. Other organ systems may be involved, particularly the joints, gastrointestinal tract, and kidneys. Current evidence supports an immune complex pathogenesis in which a variety of antigens including bacteria, viruses, drugs, or chemicals are involved. Therapy consists of identifying the potential offending agent and administration of antiinflammatory drugs.