The proposed WHO criteria for the diagnosis of primary myelofibrosis requires all three of the major criteria and at least two of the minor criteria listed below:
Major Criteria
- Presence of megakaryocyte proliferation and atypia, usually accompanied by either reticulin and/or collagen fibrosis; or, in the absence of significant reticulin fibrosis, the megakaryocyte changes must be accompanied by increased bone marrow cellularity characterized by granulocytic proliferation and often decreased erythropoiesis (so-called prefibrotic cellular-phase disease)
- Not meeting criteria for Polycythemia Vera (PV), CML, Myelodysplastic Syndrome, or other myeloid neoplasm
- Demonstration of JAK2(V617F) or another clonal marker; or, in the absence of a clonal marker, no evidence of bone marrow fibrosis caused by an underlying inflammatory disease or another neoplastic disease
- About 60% of patients with Primary Myelofibrosis carry a JAK2(V617F) mutation, and about 5% to 10% of the patients have activating mutations in the thrombopoietin receptor gene, MPL
- Almost 90% of the patients without JAK2(V617F) or MPL carry a somatic mutation of the calreticulin (CALR) gene, which is associated with a more indolent clinical course than is seen with JAK2(V617F) or MPL mutations
Minor Criteria- Leukoerythroblastosis
- Increased serum level of lactate dehydrogenase
- Anemia
- Palpable splenomegaly
