Case series of pediatric acute leukemia without a peripheral blood abnormality, detected by magnetic resonance imaging.

Although abnormal peripheral blood counts are a key diagnostic finding for acute leukemia in children, between 2003 and 2010 we observed seven pediatric cases without peripheral blood abnormalities and showing abnormal signals in the bone marrow by magnetic resonance imaging (MRI). The common chief complaint in these patients was bone pain and fever. Bone marrow tests revealed six out of the seven cases to be acute leukemia, whereas one patient was diagnosed with juvenile idiopathic arthritis (JIA). There was no evident difference in MRI findings between leukemia patients and JIA patient. In three cases of leukemia, initial bone marrow aspiration failed to show the presence of leukemic cells, and diagnosis was only made by repeated bone marrow examination. Our findings indicate that in some cases MRI detects leukemia at an earlier phase than does bone marrow aspiration, suggesting that MRI is useful for the diagnosis of acute leukemia.