Polycythemia vera
Polycythemia vera (also known as primary polycythemia, erythremia, polycythemia rubra vera, splenomegalic polycythemia, or Vaquez-Osler disease) is a chronic myeloproliferative disorder characterized by increased red blood cell (RBC) mass, leukocytosis, thrombocytosis, and increased hemoglobin concentration, with normal or increased plasma volume. It rarely occurs before age 40 and affects more males than females.
The prognosis depends on age at diagnosis, the treatment used, and complications. Mortality is high if polycythemia is untreated or is associated with leukemia or myeloid metaplasia.
Causes
With polycythemia vera, uncontrolled and rapid cellular reproduction and maturation cause proliferation or hyperplasia of all bone marrow cells (panmyelosis). The cause of such uncontrolled cellular activity is unknown; however, it’s probably due to a stem cell defect.
Signs and symptoms
Increased RBC mass results in hyperviscosity and inhibits blood flow to microcirculation. Subsequently, increased viscosity, diminished velocity, and
thrombocytosis promote intravascular thrombosis.
thrombocytosis promote intravascular thrombosis.
Progressive features
In its early stages, polycythemia vera usually doesn’t produce symptoms. (Increased hematocrit may be an incidental finding.) However, as altered circulation (secondary to increased RBC mass) produces hypervolemia and hyperviscosity, the patient may complain of a feeling of fullness in the head, headache, dizziness, and other symptoms, depending on the body system affected. (See Clinical features of polycythemia vera.) Hyperviscosity may lead to thrombosis of smaller vessels with ruddy cyanosis of the nose and clubbing of the digits.
Complication
Paradoxically, hemorrhage is a complication of polycythemia vera. It may be due to defective platelet function or to hyperviscosity and the local effects from excess RBCs exerting pressure on distended venous and capillary walls.
Diagnosis
Laboratory studies confirm polycythemia vera by showing increased RBC mass and normal arterial oxygen saturation in association with splenomegaly or two of the following: thrombocytosis, leukocytosis, elevated leukocyte alkaline phosphatase level, or elevated serum vitamin B12 level or unbound vitamin B12–binding capacity.
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