Polycythemia vera (older term: polycythemia rubra vera) is a myeloproliferative neoplasm that results in an excess of red blood cells in the bloodstream.
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Terminology
The standalone word polycythemia, a.k.a. erythrocytosis, is the medical term for the presence of an excessive number of red blood cells in the circulation 6.
Epidemiology
The estimated prevalence is around 2-3 per 10,000 people. It typically presents in older individuals. There may be a slightly greater male predilection.
Diagnosis
Major WHO criteria are as follows:
hemoglobin >16.5 g/dL in men and >16 g/dL in women, or hematocrit >49% in men and >48% in women, or red cell mass >25% above mean normal predicted value
bone marrow biopsy showing hypercellularity for age with trilineage growth (panmyelosis) including prominent erythroid, granulocytic, and megakaryocytic proliferation with pleomorphic, mature megakaryocytes (differences in size)
presence of JAK2V617F or JAK2 exon 12 mutation
The minor WHO criterion is:
serum erythropoietin level below the reference range for normal
Clinical presentation
Polycythemia vera has a varied presentation, with the most serious features being those of venous and arterial thrombosis, as well as transformation into acute myeloid leukemia.
Features include:
hypertension
unbearable pruritus, classically after taking a warm bath/shower
venous thrombosis: e.g. acute superior mesenteric venous thrombosis, dural venous sinus thrombosis, Budd-Chiari syndrome
arterial thrombosis: e.g. splenic infarction, ischemic stroke, myocardial infarction
conjunctival injection
facial plethora
erythromelalgia
Pathology
Genetics
JAK2 mutations (particularly the V617F mutation) can be found in more than 95% of people with polycythemia vera.
Radiographic features
Radiographic manifestations are varied and non-specific and can affect a number of systems, including:
organ infarcts: e.g. splenic infarcts
features of extramedullary hematopoiesis
increased radiographic attenuation of cerebral arteries, veins and dural sinuses: may mimic cerebral vein thrombosis
Treatment and prognosis
The overall prognosis can be variable with a wide natural course among individuals. Treatment options include venesection, aspirin, or cytoreductive therapy. If refractory, advanced therapy (e.g. ruxolitinib, anagrelide, etc.) can be used. Oral radiophosphorus (32-P) is now avoided in "benign" myeloproliferative diseases due to the risk of inducing acute myeloid leukemia 5.
Differential diagnosis
Other causes of polycythemia (i.e. secondary polycythemia) such as chronic obstructive pulmonary disease may have a similar biochemical presentation but will generally have a very different clinical presentation.
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