Idiopathic myelofibrosis--an update with particular reference to clinical aspects and prognosis

Idiopathic myelofibrosis (IMF) is characterized by excessive accumulation of connective tissue in the bone marrow as part of a clinical syndrome which in its classical form is featured by leukoerythroblastic anemia and huge splenomegaly at the time of diagnosis. An acute variant of the disease exists being featured by pancytopenia, nor or minimal splenomegaly and a rapidly fatal clinical course. This review describes the relationship of IMF to other chronic myeloproliferative disorders and highlights current concepts of the pathogenesis of bone marrow fibrosis, implicating the intramedullary release of various growth factors, including platelet-derived growth factor beta. In a subgroup of patients bone marrow fibrosis may develop consequent to autoimmune bone marrow damage. The clinical and laboratory findings in some of the larger series of patients are presented and the reasons for the highly variable clinical presentation and prognosis are critically discussed. It is proposed that studies on prognosis in IMF are based upon simple prognostic staging systems, which should include the Hb-concentration, platelet count, spleen size and the presence/absence of osteomyelosclerosis on X-ray. Using these parameters the patients are easily categorized into three prognostic groups with highly different survival times.