GATA1 is a transcription factor needed for erythroid and megakaryocyte development. Children with Down syndrome have a 10- to 20-fold increased risk of developing leukemia, particularly AMKL. As many as 10% of infants with Down syndrome present with transient myeloproliferative disorder (TMD), which may be a precursor to AMKL. Sanger sequencing is used to detect GATA1 mutations, which have been found in patients with Down syndrome with AMKL (Wechsler J et al. Nature Genet. 32: 148-152, 2002). Somatic mutations in exon 2 of GATA1 have subsequently been detected in essentially all cases of megakaryoblastic leukemia and transient myeloproliferative disorder (Gurbuxani S. et al. Blood 103: 399-406, 2004; Taub JW et al. Blood 104: 1588-1589, 2004).