KMT2A and Increased total eosinophil count: In this report, we present a de novo heterozygous deletion mutation [c.74delG; p. (Gly26Alafs*2)] in the KMT2A gene, which was identified by trio-based whole exome sequencing from a 5.5-year-old boy with ID/DD, stereotypic hand movements and blood eosinophilia.