Polycythaemia vera

What it is

Polycythemia vera is a myeloproliferative neoplasm: the marrow makes red cells autonomously, so the RBC rises independent of EPO. It is often associated with a JAK2 mutation, and it can raise the WBCs and the platelets as well, not the red cells alone. The symptoms come from hyperviscosity and from cell turnover.

Causes and risk

Polycythemia vera is the primary cause of erythrocytosis, and the whole point of the tests is to set it against the rest.

Secondary and physiologic, from poor tissue oxygenation or hypoxia:

• Carbon monoxide poisoning, heavy smoking, high altitude
• Pulmonary disease: COPD, sleep apnea, pulmonary hypertension
• Cardiovascular disease: R to L shunt, that is Eisenmenger syndrome
• RBC defects: Hb with increased O2 affinity, methemoglobinemia

Inappropriate production of erythropoietin:

• Tumours: hepatocellular carcinoma, renal cell carcinoma, cerebellar hemangioblastoma, pheochromocytoma, uterine leiomyoma, ovarian tumour
• Other: polycystic kidney disease, post-kidney transplant, hydronephrosis, androgens, exogenous erythropoietin

Relative polycythemia, where the plasma volume falls while the RBC mass does not rise, comes from dehydration and burns.