myeloproliferative disorders

introduction

myeloproliferative disorders are a heterogenous group of at least 4 chronic disorders characterized by cellular proliferation of 1 or more hematologic cell lines in the peripheral blood, distinct from acute leukaemia
these include:
- polycythaemia rubra vera
- myelofibrosis
- essential thrombocytosis
- CML
- WHO also includes:
  - chronic neutrophilic leukemia
  - chronic eosinophilic leukemia/hypereosinophilic syndrome
these are usually associated with acquired (rarely inherited) mutations of genes including:
- V617F of the Janus kinase 2 gene (JAK2)
- calreticulin gene (CALR)
  - only in patients with primary myelofibrosis or essential thrombocytosis who are negative for JAK2 and MPL mutations
  - not involved in polycythaemia rubra vera
- MPL
patients are at risk for:
- thrombotic events such as stroke (CVA)
- haemorrhagic events
- infection
- reactivation of herpes zoster
- gout
- hepatosplenomegaly
- anorexia, weight loss
- priapism, tinnitus, or stupor from leukostasis
- developing secondary acute leukemia from their underlying disorder, as well as from their treatment (radioactive phosphorus but not hydroxyurea increased risk of myelodysplastic syndrome and AML)
- development of myelofibrosis secondary to Rx by hydroxyurea of other myeloproliferative disorders