Leukemic vasculitis: an unusual manifestation of leukemia cutis.

Leukemia cutis is frequently observed as papules, nodules, and plaques, but unusual clinical manifestations rarely occur. We report a 64-year-old woman with acute myeloid leukemia M1 who presented with erythematous papules and vesiculobullous lesions limited to the arms, hands, and neck in addition to purpuric papules on the legs. Because of the symmetric distal involvement and vesiculobullous nature of the skin lesions, the differential diagnosis included erythema multiforme and vasculitis. However, a skin biopsy specimen revealed infiltration with a striking predominance of blast cells in the dermis. These cells were also observed within the walls of the venules along with fibrin. Leukemia cutis associated with vasculitis was diagnosed. A few blast cells can be observed in many reactive dermatoses in patients with leukemia. However, in this patient a predominance of blast cells in the dermis and infiltration of vessel walls by these cells favored leukemic vasculitis.