In simple terms, polycythaemia (or erythrocytosis) means an increase in red cell count, haemoglobin and packed cell volume (PCV) above the normally accepted levels. Polycythaemia due to an absolute increase in red cell mass may occur as a myeloproliferative neoplasm (polycythaemia vera (PV) ) or secondary to hypoxia or an abnormal focus of erythropoietin secretion. In ‘apparent polycythaemia’ the raised haemoglobin and PCV are not accompanied by a significantly raised red cell mass; usually the plasma volume is relatively reduced (Fig 32.1).

Clinical syndromes

Polycythaemia vera (PV)

PV is a myeloproliferative neoplasm; other diseases in this category are essential thrombocythaemia and myelofibrosis (see p. 66). In PV a pluripotential stem cell is mutated. Almost all patients with the disease (and some with essential thrombocythaemia and myelofibrosis) have an identical acquired point mutation in the Janus kinase 2 (JAK2) gene.

Clinical features. The raised red cell mass and total blood volume with associated hyperviscosity causes the symptoms and signs of the disease. Common complaints include headaches, dizziness, lethargy, sweating and pruritus (the latter particularly after a hot bath). Most importantly, there is an increased risk of arterial and venous thrombosis, particularly strokes. Paradoxically, a combination of hyperviscosity and platelet dysfunction may cause a bleeding tendency. The increased cell turnover can lead to gout (Fig 32.3). Patients are characteristically plethoric and may have rosacea (Fig 32.4). Palpable splenomegaly may be present.

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Jun 12, 2016 | Posted by in HEMATOLOGY | Comments Off on Polycythaemia

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