Acute neutrophilic dermatosis with myeloblastic infiltrate in a leukemia patient receiving all-trans-retinoic acid therapy.

We report a case of leukemia-associated acute febrile neutrophilic dermatosis (Sweet's syndrome) that is unique because its initial histologic findings mimicked leukemia cutis. Otherwise, the clinical manifestations and response to corticosteroid therapy were typical of Sweet's syndrome. The onset of the dermatosis coincided with the onset of neutrophilic differentiation induced by single-agent leukemia therapy with all-trans-retinoic acid (ATRA). Subsequent exacerbation of the manifestations of Sweet's syndrome and the ultimate conversion of the histologic picture to the expected mature neutrophilic dermal infiltrate coincided with the completion of neutrophilic differentiation in the peripheral blood and bone marrow. The ability of immature neutrophil precursors to induce cutaneous lesions of Sweet's syndrome may indicate an ATRA-induced functional maturation that slightly precedes its effect on morphologic maturation. We conclude that a cutaneous infiltrate of early neutrophil precursors does not preclude a diagnosis of Sweet's syndrome in patients with acute leukemia who respond to ATRA therapy.