Polycythaemia vera or polycythaemia rubra vera is a myelo -proliferative neoplasm (MPN) in which the total volume of red cells in the circulation is increased as a result of mutation of a multipotent haemopoietic stem cell. This is a disease mainly of middle and old age with an incidence of 1-3/100,000 per year. A familial predisposition occurs [1, 2].
Presentation may be with vascular complications such as cerebrovascular accident, myocardial infarction, splanchnic (mesenteric, hepatic or portal) vein thrombosis or peripheral ischaemia or gangrene. The incidence of venous thromboembolism is also increased. Patients may complain of itch, often exacerbated by a hot bath, and there is an increased incidence of peptic ulcer; both these disease features are related to histamine excess. Sometime the diagnosis is made incidentally when a blood count is performed for an unrelated reason.
On examination, there may be a plethoric complexion, conjunctival injection or palpable splenomegaly, in addition to physical signs as a result of vascular complications. The disease can progress to post-polycythaemic myelofibrosis. Acute transformation can also occur.
Haematological and pathological features
The blood count shows an increase in the red cell count (RBC), haemoglobin concentration (Hb) and haematocrit (Hct), except in those patients who have complicating iron deficiency. The white cell count (WBC) and the platelet count are sometimes also increased. The increased WBC is the result of neutrophilia; the absolute count of basophils is also often increased. The blood film appears 'packed' as a result of the increased viscosity of the blood (Figure 6.1). The bone marrow aspirate is hypercellular as a result of erythroid and granulocytic hyperplasia (Figures 6.2 and 6.3). Megakaryocyte numbers are often increased and megakaryocytes are pleomorphic with both large and small forms. Trephine biopsy confirms the features seen on the aspirate (Figures 6.4 and 6.5). The megakaryocytes may be clustered. Reticulin may be increased but characteristically this increase is slight (Figure 6.6).
Peripheral blood film of a patient with polycythaemia vera showing a 'packed' film and one basophil. MGG, high power.
Bone marrow aspirate film of a patient with polycythaemia vera showing a hypercellular fragment. MGG, low power.
Bone marrow aspirate film of a patient with polycythaemia vera showing erythroid hyperplasia. MGG, high power.
Bone marrow trephine biopsy section from a patient with polycythaemia vera showing increased erythropoiesis and a cluster of megakaryocytes. H&E, low power.