Loss ofrasOncogene Mutation in a Myelodysplastic Syndrome after Low-Dose Cytarabine Therapy

Abstract
To the Editor: The myelodysplastic syndromes are a group of hematopoietic stem-cell disorders characterized by cytopenia due to defective erythroid, myeloid, and megakaryocytic maturation.1 Transformation to acute nonlymphocytic leukemia occurs in 30 percent of all cases. Mutational activation of ras oncogenes occurs frequently in acute nonlymphocytic leukemia.2 Recently, mutations of N-ras and Ki-ras have been identified in myelodysplastic syndromes.3 , 4 Genes of the human ras family are believed to play a part in the transduction of receptor-mediated signals across the cell membrane.5 Their activation in human tumors by single nucleotide alterations at codons 12, 13, and 61 with corresponding . . .