The abnormal proliferation of one or more terminal myeloid cell lines in the peripheral blood gives rise to a heterogeneous group of disorders called myeloproliferative neoplasms:
Chronic myeloid leukemia
Polycythaemia vera
Essential thrombocythaemia
Primary myelofibrosis
Definition
Polycythemia vera (PV) is a myeloproliferative neoplastic disorder involving uncontrolled red blood cell production resulting in elevated red blood cell (RBC) mass
Caused by aclonal malignancy of marrow stem cell!
Etiology
The etiology of the disease process appears to be neoplastic proliferation
There is a signaling defect leading to an abnormal response to growth factors, and the abnormal clonal line interferes with normal lineage proliferation.
The Janus kinase-2 (JAK2) gene involved with intracellular signaling is mutated in 90% of cases of polycythemia vera
Pathophysiology
The JAK2V617F mutation is a somatic mutation that occurs in hematopoietic stem cells in the bone marrow. This mutation leads to the constitutive activation of the JAK-STAT signaling pathway, which is responsible for regulating cell growth, differentiation, and survival
The mutated JAK2 enzyme leads to uncontrolled proliferation and reduced apoptosis (cell death) of erythroid progenitor cells, contributing to the elevated red blood cell count.
The JAK2 mutation also leads to the overproduction of other blood cells, including white blood cells (leukocytosis) and platelets (thrombocytosis).
The increased production of red blood cells, white blood cells, and platelets results in a higher concentration of these cells in the bloodstream. This can lead to hyperviscosity of the blood
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