Leukemia cutis represents a skin infiltration by leukemic cells. Clinically it can mimic a wide variety of dermatoses. We describe the case of a 64-year-old man with psoriasis who presented with a 4-day history of erythematous, slightly scaly, asymptomatic plaques distributed on the trunk and upper-extremities, and associated asthenia, myalgias, and anorexia. A skin biopsy revealed a leukemic infiltrate. Studies of peripheral blood and bone marrow provided a diagnosis of acute monocytic leukemia. This case report shows the importance of the clinical suspicion for the diagnosis of leukemia.