Infant Leukemia Suggestive of Natural Killer Cell Precursor Origin Followed an Unusual Clinical Course

We report a patient with infant leukemia showing the rare phenotypes of CD2+, CD4+, CD7+, CD56+, CD3–, CD5– who followed an unusual clinical course. The patient was a 3-month-old girl who was admitted because of unusual purpura looking like a black ring. On admission WBC count was 85.8 × 10 9 /l and bone marrow aspiration revealed a nucleated cell count of 112.0 × 10 9 /l with 70.8% atypical lymphocytes. On the 3rd hospital day, the WBC count decreased by about 1/5 without chemotherapy and partial remission was obtained. But about 3 weeks later, the WBC count increased again and she died. Based on surface marker analysis, genotypic analysis and autopsy, we diagnosed infant leukemia suggestive of natural killer (NK) cell precursor origin.