Cutaneous presentation of aleukemic monoblastic leukemia cutis - a case report and review of literature with focus on immunohistochemistry.

Aleukemic monoblastic leukemia cutis is a rare cutaneous manifestation of a systemic hematological disorder associated with dermal infiltration of monoblasts preceding bone marrow or peripheral blood involvement. We report a case of a 75-year-old woman who presented with an erythematous maculopapular rash, which was clinically diagnosed as viral exanthema. Microscopy of the skin biopsy showed features of monoblastic leukemia. Her general physical condition rapidly deteriorated and she died 4 weeks later. We present this case to alert dermatologists of innocuous erythematous skin lesions clinically resembling a viral exanthema, which, in rare instances, may be a presenting feature of an aleukemic monoblastic leukemia cutis. This entity poses problems for dermatopathologists even on immunohistochemistry as monoblasts are negative for hemopoietic precursor cell antigens like CD34, Terminal deoxynncleotidy1 transferase (TdT) and CD117.