MPLW515L mutation in acute megakaryoblastic leukaemia.

The thrombopoietin receptor gene (MPL) is expressed in megakaryocytes and exhibits the gain of function point mutation W515K/L in approximately 5% of patients with primary myelofibrosis/idiopathic myelofibrosis (PMF) representing one subtype of the chronic myeloproliferative disorders (myeloproliferative neoplasm). A series of primary and secondary acute myeloid leukaemias (AML) with megakaryoblastic phenotype and myelofibrosis unrelated to PMF (n=12) was analysed for the MPL(W515K/L) mutation by pyrosequencing. In three cases (25%), MPL(W515L) was found and in two of these a combination with trisomy 21 or the Philadelphia chromosome occurred. None of the secondary AML cases evolving from pre-existing PMF showed MPL(W515K/L) (n=4). We conclude that MPL(W515L) occurs in a considerable proportion of acute megakaryoblastic leukaemias with myelofibrosis unrelated to PMF.