BACKGROUND: Dermatitis herpetiformis is an autoimmune disease typically characterized by pruritic vesicles located on the extensor surfaces. Classic disease consists of neutrophils in the dermal papillae. Additional histopathologic findings include fibrin deposition and edema within the dermal papillae. Subepidermal vesicles also may be present. Direct immunofluorescence demonstrates granular IgA in the dermal papillae. OBSERVATIONS: A 58-year-old man with tender and pruritic erythematous macules and papules ranging from 2 to 6 mm in diameter had bilateral knee, elbow, forearm, scalp, and neck involvement. Petechiae also were present on the hands, thigh, knee, and ankle. A biopsy specimen initially demonstrated leukocytoclastic vasculitis. The results of workup for systemic vasculitis were negative. Subsequent biopsy specimens and direct immunofluorescence showed histologic evidence of dermatitis herpetiformis and leukocytoclastic vasculitis in the setting of an elevated serum IgA antitissue transglutaminase level. Marked improvement of the lesions was observed with a reduction of gluten in the patient's diet. CONCLUSIONS: Physicians should consider the possibility of dermatitis herpetiformis in patients with petechiae and leukocytoclastic vasculitis because leukocytoclastic vasculitis may be a prominent feature of dermatitis herpetiformis.