PV belongs to the myeloproliferative neoplasms (see MPN) and is characterized by an overproduction of red blood cells. The incidence increases with age and varies between 0.7–2.6:100,000/year in Europe and North America. In approx. 20% of all patients, cytogenetic abnormalities can be detected already upon diagnosis (especially trisomy 8 and 9, deletions in the long arm of chromosome 20 and 13 or in the short arm of chromosome 9). The abnormalities are progressive and have been observed in post PV myelofibrosis in 80-90% of all cases.
Other moleculargenetic diagnostic criteria are the JAK2-V617F mutation or JAK Exon 12 mutations. The JAK2-V617F mutation is found in more than 95% of all patients with PV; one of 8 known JAK2 exon 12 mutations can usually be detected in the remaining cases. Another marker is the overexpression of the PRV1 gene, which can be detected in nearly 100% of all PV patients. Both markers correlate with elevated erythropoietin independent, erythroid colonies (EEC). It is assumed that JAK2 and PRV1 use the same signaling pathway; however, they are most likely not the initial cause of the disease. Medication is currently being developed which specifically impact this signaling pathway.