Description: any MPN leading to bone marrow fibrosis, extramedullary hematopoiesis, and splenomegaly
Epidemiology
Peak incidence is between 50 and 74 years of age.
Etiology
Pathophysiology
Genetic mutations → hyperplasia of atypical megakaryocytes → ↑ TGF-β → ↑ fibroblast activity → bone marrow obliteration due to fibrosis → displacement of hematopoietic stem cells → extramedullary hematopoiesis
Clinical features
- Constitutional symptoms
- Anemia
- Symptomatic splenomegaly
- Thromboembolic events
- Due to thrombocytosis and leukocytosis in the prefibrotic proliferative phase
- Petechial bleeding
- Increased infections
Diagnostics
- CBC
- Classic presentation: anemia, thrombocytosis, and leukocytosis
- Patients may additionally present with:
- Thrombocytopenia (33%)
- Pancytopenia (10%)
- ↑ Leukocyte alkaline phosphatase, LDH
- Peripheral blood smear: dacrocytes (teardrop cells)
- JAK2 mutation
- Bone marrow studies
- Aspiration often fails (dry tap) because of severe marrow fibrosis.