Somatic mutations of the two genes coding for the histone acetyltransferase genes, CREEBP and EP300 have been identified as a pathogenetic mechanism shared by common forms of B-cell non-Hodgkinós lymphomas. A screening for somatic mutations in CREEBP and EP300 genes in patients with myeloproliferative neoplasms (MPNs) has not previously been performed. DNA was purified from diagnostic samples of 56 MPN patients. We designed a mutation screening assay based on denaturing gradient gel electrophoresis and direct sequencing. Our results suggest that CREBBP and EP300 mutations are not major pathogenetic mechanisms of MPNs. The rationale for using HDACi in these patients seems reasonable.