Somatic mutations in the GATA1 transcription factor gene, encoded on the X chromosome, occur in most AMKL and almost every case of TMD in persons with DS, but not in other leukemias that occur in DS; further, GATA1 mutations have never been seen when AMKL occurs in euploid individuals except when the expanded blasts are trisomic for Hsa21 [45]. The gene discussed is GATA1; the disease is Dravet syndrome.