Occasionally, patients meet the general criteria to classify their conditions as myeloproliferative neoplasms (MPNs), but do not meet all the criteria for any one specific disorder, or they may exhibit characteristics from more than one category. These patients may be diagnosed with myeloproliferative neoplasm, unclassifiable (MPN-u). MPN-u may actually be very early stages or very late transformational stages of a specific MPN, such as PV, ET, or PMF.
Symptoms are similar to those previously described for the MPNs and include hepatosplenomegaly. White cell counts and platelet counts are typically increased. Red cell counts are variable. Bone marrow findings include increased megakaryocyte proliferation with variable hypercellularity in granulocytic or erythrocytic cell lines. Increasing bone marrow fibrosis can occur with the progression of the disease. There are no defined cytogenetic or molecular abnormalities associated with this MPN category.
By examining follow-up peripheral blood and bone marrow samples, it is possible to more accurately classify the patient's MPN, which allows for better treatment regimens.