We and others previously reported that the progression of MF to more overt phases of the disease and to MPN-BP is associated with abnormalities in the TP53 pathway including deletion of TP53, acquisition of inactivating mutations, and up-regulation of negative regulators of p53 including MDM2/MDM4 and PPM1D [23]. The gene discussed is PPM1D; the disease is myeloproliferative neoplasm.