Leukemia cutis exhibiting Darier's sign: a rare presentation of acute monoblastic leukemia.

Leukemia cutis is a rare cutaneous manifestation of acute myeloid leukemia, most frequently associated with monocytic differentiation. Darier's sign, a wheal-and-flare response classically linked to cutaneous mastocytosis, has only rarely been reported in leukemia cutis and may represent a diagnostic pitfall. We report a pediatric patient diagnosed with acute myeloid leukemia that developed multiple violaceous papules on the extremities and trunk. Mechanical stimulation induced erythema and edema consistent with a positive Darier's sign. Histopathological examination revealed dermal infiltration by myeloperoxidase (MPO)-positive leukemic blasts, confirming leukemia cutis. Bone marrow aspiration and flow cytometry were compatible with acute monoblastic leukemia (AML-M5). This case highlights that Darier's sign may rarely occur in leukemia cutis and should not be considered exclusive to mastocytosis.