What is polycythemia (excessive red blood cell count)?

From the Guidelines

Polycythemia is a blood disorder characterized by an abnormally high concentration of red blood cells in the bloodstream, which can lead to serious complications like blood clots, strokes, or heart attacks if left untreated. This condition can be classified as either primary (polycythemia vera), which stems from genetic mutations causing overproduction of blood cells in the bone marrow, or secondary, which occurs as a response to low oxygen levels or certain medical conditions 1. Symptoms typically include headaches, dizziness, fatigue, itchy skin, and a reddish or purplish appearance to the skin.

Key Characteristics of Polycythemia

• Elevated haematocrit (HCT) levels, which can be managed through phlebotomy to control HCT and low-dose aspirin to delay the need for cytoreductive therapy 1
• Increased risk of thrombosis, which can be reduced through risk stratification and selection of patients with low risk of vascular events 1
• Potential for evolution to myelofibrosis (MF), myelodysplastic syndrome (MDS), and/or acute myeloid leukaemia (AML) 1

Treatment and Management

• Phlebotomy to reduce blood volume and maintain hematocrit <45% 1
• Medications like hydroxyurea to slow bone marrow production, or aspirin to prevent clotting 1
• Regular monitoring of blood counts to manage the condition effectively and prevent potentially life-threatening complications 1 It is essential to address the underlying cause in cases of secondary polycythemia. Treatment depends on the type and severity of the condition, and maintaining proper blood viscosity through regular monitoring and management is crucial to prevent serious complications.

From the Research

Definition of Polycythemia

• Polycythemia vera (PV) is a myeloproliferative neoplasm characterized by an increased red blood cell mass and increased risk of thrombosis 2.
• It is typically characterized by erythrocytosis and often leukocytosis and thrombocytosis 3.
• PV is a haematological malignancy in the myeloproliferative neoplasm family, with clinical features including reduced life expectancy due to hazards of thrombosis, haemorrhage, and transformation to myelofibrosis and less frequently to a form of acute myeloid leukaemia called blast phase 3.

Diagnostic Criteria

• Erythrocytosis (hemoglobin >16.5 mg/dL in men or >16.0 mg/dL in women) is a required diagnostic criterion for PV 2.
• The presence of JAK2 mutation is expected in PV, with more than 95% of patients having a JAK2 gene variant 2, 3.
• Bone marrow morphology remains the cornerstone of diagnosis, and the presence of driver mutations (JAK2, CALR or MPL) can help distinguish PV from other myeloproliferative neoplasms 4.

Clinical Features and Complications

• Patients with PV may have pruritus, erythromelalgia, transient visual changes, and splenomegaly with abdominal discomfort 2.
• PV is associated with an increased risk of arterial and venous thrombosis, hemorrhage, myelofibrosis, and acute myeloid leukemia 2, 3.
• The median survival from diagnosis is 14.1 to 27.6 years, and the risk of thrombosis is higher in patients with a history of thrombosis or aged 60 years or older 2, 4.