[GATA1 analysis in myeloproliferative disorders associated to trisomy 21]. 
Neonatal transient myeloproliferative disorder and acute megakaryoblastic leukaemia of Down syndrome are considered different manifestations of the same disease.  In most cases, transient myeloproliferative disorders require no treatment, while acute megakaryoblastic leukaemia of Down's syndrome is characterised by an increased sensitivity to chemotherapy and its treatment should be adapted with a reduction in dose intensity.  Both entities share specific mutations at exón 2 of the transcription factor GATA1.  We analysed biological features and GATA1 mutations in 4 patients with transient abnormal myelopoiesis (2) and acute megakaryoblastic leukaemia (2) including one phenotypically normal trisomy 21 mosaicism.  We found abnormal GATA1 mutated clones in each case, and a specific point mutation at exón 2 was detected in three cases.  Given the heterogeneous phenotype of megakaryoblastic blasts and the low percentage of blasts at presentation, the recognition of GATA1 mutations was helpful for diagnosis.  In addition, molecular remission was established in 2 patients after subsequent normal mutational GATA1 analysis.  We conclude that GATA1 mutational study is a useful tool for the diagnosis and management of trisomy 21 associated myeloproliferative disorders.