According to recent studies using high-throughput sequencing technologies and covering the entire N/KRAS coding sequences (that is, exons 2, 3 and 4) [5, 12–17], MDS/MPN, notably CMML and JMML, harbor the highest incidence of N/KRAS mutations, ranging from 15% to 20% of cases for each gene. This evidence concerns the gene KRAS and myeloproliferative disorder.