JAK2V617F, a somatic gain-of-function mutation involving the JAK2 tyrosine kinase gene, occurs in nearly all patients with polycythemia vera (PV) but also in a variable proportion of patients with other myeloid disorders; mutational frequency is estimated at approximately 50% in both essential thrombocythemia (ET) and myelofibrosis (MF), up to 20% in certain subcategories of atypical myeloproliferative disorder (atypical MPD), less than 3% in de novo myelodysplastic syndrome (MDS) or acute myeloid leukemia, and 0% in chronic myeloid leukemia (CML).
Immunostaining with antibodies against tryptase, KIT, and CD25 and molecular analysis for detection of C-KIT point mutations were performed in approximately 550/4100 myelogenous malignancies including mastocytosis, almost all subtypes of myelodysplastic syndrome (MDS), myelodysplastic/myeloproliferative syndrome (MDS/MPD), MPD, and acute myeloid leukaemia (AML).
The other two children, one with ALL and one with ganglioneuroblastoma, developed fatal t-MPD and therapy-related acute myeloblastic leukemia (t-AML) preceded by myelodysplastic syndrome (t-MDS), respectively, 5 years after diagnosis, following administration of alkylating agents and irradiation.