Adult T-cell acute lymphoblastic leukemia presenting as concurrent viral exanthem-like reaction and palpable purpura.

Leukemia cutis is an extramedullary manifestation of leukemia resulting from direct invasion of leukemic cells into the skin. It most commonly develops in patients with acute myeloid leukemia (AML) and rarely occurs in patients with acute lymphoblastic leukemia (ALL). 1 Here we report a case of an adult case of T-cell ALL (T-ALL) who initially presented with an unusual form of leukemia cutis. A 66-year-old woman without major systemic disease presented with a 1-month history of generalized asymptomatic skin eruptions. The rash initially presented on the lower extremities, and gradually progressed to the trunk. She reported no constitutional symptoms. Physical examination revealed palpable purpuras on the lower extremities (Figure 1A) and blanchable erythematous maculopapules and confluent patches on the trunk (Figure 1B). No lymphadenopathy was detected. A tentative diagnosis of leukocytoclastic vasculitis with concurrent viral exanthem-like eruption was made. Complete blood count and peripheral blood smear showed anemia (hemoglobin 9.9 g/ dl) and leukopenia (total leukocyte count 3.08*106/L) with 28% of blast cells. A bone marrow biopsy was performed, which showed diffuse interstitial infiltrate of blasts (>20%). These cells showed negative staining for myeloperoxidase, CD4, CD8, CD20, and positive staining for terminal deoxynucleotidyl transferase(TdT), CD3, CD5, CD7, CD34, suggesting an infiltrate of precursor T-cells. A skin biopsy of the palpable purpura on the right lower extremity revealed dense der-mal infiltrate of histiocytes and lymphocytes, with some medium-sized atypical mononuclear cells exhibiting high nuclear to cytoplasmic ratio and prominent nucleoli. Nuclear dusts and extravasation