a myeloproliferative disorder in which the proliferation of an abnormal type of bone marrow stem cell results in the replacement of the marrow with collagenous connective tissue fibers and thus fibrosis
mainly in those over 50 years age
associated with activation of the Janus kinase pathway resulting in increased signalling in some cytokines and growth factors involved in haematopoiesis and immune functions
overall survival from diagnosis without stem cell transplant is usually 2 - 11 years
survival of patients with primary myelofibrosis is dependent on the underlying mutually exclusive mutation1):
MPL exon 10 mutation ⇒ 60% 5yr survival, 30% 10 yr survival (median survival 8 yrs, 25% die in 1st 2 yrs )
appears to reduce spleen size or prevent it enlarging further
50% reduction in disease associated symptoms compared with 5% for placebo, but these return to baseline within 1 week of stopping Rx, and serious withdrawl symptoms make gradual dose reduction a recommendation.
BUT 82% developed anaemia, 67% thrombocytopenia and 15% neutropenia hence need to monitor FBE