Candidate gene analysis and genome-wide exome sequencing have identified somatic mutations and deletions implicated in the progression of DS-TMD to DS-AMKL, in genes including JAK1, JAK2, JAK3, FLT3, TP53, TRIB1, MPL, EZH2, APC, PARK-2, PACRG, EXT1, DLEC1 and SMC3, and further suggested that GATA-1 mutations alone in the context of HSA21 trisomy were sufficient for development of DS-TMD [4–12]. Here, EXT1 is linked to Dravet syndrome.