Primary myelofibrosis (PMF), known in the past as agnogenic myeloid metaplasia or chronic idiopathic myelofibrosis, is one of the myeloproliferative neoplasms (figure 1). In addition to PMF, the group includes essential thrombocythemia (ET), and polycythemia vera (PV), both of which may undergo delayed disease transformation into a fibrotic state called post-ET myelofibrosis (post-ET MF) or post-PV MF, respectively. The conversion rates after 10 to 20 years of disease are less than 5 percent for ET and approximately 10 to 20 percent for PV. PMF, post-ET MF, and post-PV MF are all referred to as myelofibrosis (MF).
The prognosis and treatment of PMF will be reviewed here [1-4]. An overview of the myeloproliferative neoplasms, as well as discussions of pathogenetic mechanisms, clinical manifestations, and diagnosis of PMF, are presented separately. (See "Overview of the myeloproliferative neoplasms" and "Clinical manifestations and diagnosis of primary myelofibrosis" and "Pathogenetic mechanisms in primary myelofibrosis".)
Most patients with primary myelofibrosis (PMF) present with anemia, marked splenomegaly, early satiety, and hypercatabolic symptoms including severe fatigue, low grade fever, night sweats, and weight loss . During their clinical course, most patients experience massive hepatosplenomegaly along with progressive anemia requiring frequent red blood cell transfusions. Portal hypertension might accompany marked splenomegaly and could contribute to variceal bleeding or ascites. (See "Clinical manifestations and diagnosis of primary myelofibrosis".)
Hepatosplenomegaly in PMF results from extramedullary hematopoiesis (EMH), which might also involve other organ sites, including around the spinal column, causing cord compression, or in the pleural and peritoneal cavity, causing pleural effusion or ascites, respectively.
In an epidemiologic study of patients within Olmsted county, the three-year survival rate was 52 percent . Longer survival times have been reported in several non-population-based studies, including the series used for constructing the International Prognostic Scoring System (IPSS) for primary myelofibrosis (PMF), in which the median survival was reported to be 69 months .