Myelofibrosis is a type of myeloproliferative neoplasms which is rare chronic blood cancers because of increased fibrosis or scarring in the bone marrow resulting in subnormal blood counts and an enlarged spleen. Myelofibrosis can happen on its own (primary myelofibrosis) or as a sequalae from another myeloproliferative neoplasm like polycythemia vera or essential thrombocythemia (secondary myelofibrosis.
