Polycythemia vera
A slow-growing blood cancer in which the bone marrow makes too many red cells, thickening the blood and raising the risk of clots. Usually driven by a JAK2 gene mutation, it is picked up from a persistently high haematocrit and haemoglobin.
What it is
Polycythemia vera (PV) is a myeloproliferative neoplasm — a chronic blood cancer in which the bone marrow over-produces red blood cells, and often platelets and white cells too. The excess red cells make the blood thicker, which slows flow and raises the risk of clots (stroke, heart attack, deep-vein thrombosis) as well as, paradoxically, some bleeding. Over 95% of cases carry a mutation in the JAK2 gene, which is the confirmatory test. It usually appears after age 60 and is found when a routine blood count shows a persistently high haematocrit and haemoglobin that isn't explained by dehydration or low oxygen. It must be distinguished from secondary polycythaemia, where the marrow is responding normally to low oxygen (lung disease, sleep apnoea, altitude, smoking) or excess erythropoietin. Managed well, many people live for decades.
Key lab markers
- Haematocrit and haemoglobin — persistently high; the trigger finding.
- Red cell count — raised.
- White cells and platelets — often also high (points toward PV over secondary causes).
- JAK2 V617F mutation — positive in >95%; the confirmatory test.
- Erythropoietin (EPO) — low in PV (the marrow drives itself), high in secondary polycythaemia.
- Ferritin — often low, as red-cell production consumes iron.
Symptoms
- Often none early — found on a routine blood count
- Headache, dizziness, blurred vision
- Itching, classically after a warm shower or bath
- Ruddy, reddened complexion
- Fatigue, night sweats
- Burning pain and redness in hands or feet (erythromelalgia)
- An enlarged spleen (fullness in the upper-left abdomen)
- Clots — stroke, heart attack, leg or abdominal-vein thrombosis (a serious first presentation)
Related lab panels
When to discuss with a doctor
A persistently high haematocrit and haemoglobin that isn't explained by dehydration deserves a proper work-up rather than watchful waiting, because thickened blood carries a real clot risk that treatment reduces. A confirmed PV (usually JAK2-positive with a low EPO) is managed by haematology, typically with regular venesection (removing blood to lower the haematocrit), low-dose aspirin, and sometimes marrow-suppressing medication, aiming to keep the haematocrit below a target. New clot symptoms — chest pain, one-sided weakness, a swollen painful leg, sudden severe abdominal pain — are emergencies. Mediora.AI flags a high haematocrit/haemoglobin pattern and the accompanying counts; the diagnosis and treatment belong with haematology.