Molecular Mechanisms in Myelodysplastic Syndromes and Implications for Evolution to Acute Leukemias

Myeloid dysplasia in familial 3-methylglutaconic aciduria

A kindred is reported with four members affected with neurodegenerative disorder and 3-methylglutaconic aciduria. Two siblings developed thrombocytopenia heralding a myelodysplastic syndrome; in one patient it evolved into acute myeloid leukemia with monosomy 7 in the marrow. The hematologic complications have hitherto not been previously reported in other cases of 3-methylglutaconic aciduria and are thus thought to represent a new disease entity. This family adds additional evidence to the genetic heterogeneity of Mendelian disorders in which the primary mutation may have a mutator effect that could give origin to myelodysplastic syndrome and acute myeloid leukemia through acquired chromosomal changes.

Comprehensive scanning of somatic mitochondrial DNA alterations in acute leukemia developing from myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are clonal myeloid disorders characterized by ineffective hematopoiesis resulting in refractory cytopenias. Transformation resulting in acute myeloblastic leukemia is the final stage in the multistep process of MDS evolution. Functional relevant mutations of mitochondrial DNA (mtDNA) have been related to sideroblastic anemia and MDS. To investigate the role of mtDNA in malignant transformation to acute leukemia, we used high-resolution techniques such as single-strand conformational polymorphism and fluorescence sequencing for investigation of the whole mitochondrial genome from blood cells of 10 patients with MDS. Functionally relevant point mutations in mitochondrial RNA and polypeptide-encoding genes were detected in 50% of patients with MDS. Their increasing mutation load connects MDS and the developing acute myeloid leukemias. Several point mutations of mtDNA, including secondary point mutations for Leber's hereditary optic neuropathy, occur in one bone marrow and may synergically affect bone marrow stem cells by an apoptotic pathway.