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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.

Ataxia-telangiectasia-like disorder (ATLD) is caused by mutations of the MRE11 gene and is characterized by cerebellar ataxia, increased frequency of chromosomal translocations and hypersensitivity to ionizing radiation. ATLD is a rare genetic disease and the associated pathological changes in the brain are unclear. Here, we report the neuropathological findings in the first cases of genetically confirmed ATLD in a pair of Japanese male siblings. Magnetic resonance imaging studies performed during infancy revealed that both subjects had cerebellar atrophy. They died of pulmonary cancer at 9 and 16 years. The siblings had the same compound heterozygous mutations of the MRE11 gene. Brain autopsy demonstrated mild and severe cerebellar atrophy in the vermis and medial part of the hemispheres, oral to the horizontal fissure, respectively. Nuclear immunoreactivity for MRE11 was absent in neurons of cerebellar cortex, cerebral cortex, basal ganglia and midbrain, whereas being widespread in normal control brains. Immunoreactivity for the DNA oxidative stress marker, 8-hydroxy-2'-deoxyguanosine, was identified in nuclei of granule cells and Bergmann glial cells. The combination of MRE11 deficiency and DNA oxidative injury might have led to selective cerebellar degeneration.

Chemotherapy seems to be the most effective therapy for steroid-resistant KMP cases.

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