Atlas of pathophysiology, 2 Edition

Part II - Disorders

Hematologic Disorders

Polycythemia vera

Polycythemia vera is a chronic disorder characterized by increased red blood cell (RBC) mass, erythrocytosis, leukocytosis, thrombocytosis, elevated hemoglobin level, and low or normal plasma volume. This disease is also known as primary polycythemia, erythremia, or polycythemia rubra vera. It occurs most commonly among Jewish males of European descent.

Age Alert

Polycythemia vera usually occurs between ages 40 and 60; it seldom affects children.

Prognosis depends on age at diagnosis, treatment, and complications. In untreated polycythemia, mortality is high and associated with thrombosis, hyperviscosity, or expanded blood volume. Additionally, myeloid metaplasia (ectopic hematopoiesis in the liver and spleen) with myelofibrosis (fibrous tissue in bone marrow) and acute leukemia may develop.

Causes

Unknown, but probably related to a clonal stem cell defect

Pathophysiology

In polycythemia vera, uncontrolled and rapid cellular reproduction and maturation cause proliferation or hyperplasia of all bone marrow cells (panmyelosis). Increased RBC mass makes the blood abnormally viscous and inhibits blood flow through the microcirculation. Diminished blood flow and thrombocytosis set the stage for intravascular thrombosis.

Clinical Tip

Secondary polycythemia is excessive production of circulating RBCs due to hypoxia, tumor, or disease. It occurs in approximately 2 of every 100,000 people living at or near sea level; the incidence increases among those living at high altitudes.

Spurious polycythemia is characterized by an increased hematocrit but decreased plasma volume. It usually affects the middle-aged population and is more common in men than in women. Causes include dehydration, hypertension, thromboembolic disease, or elevated serum cholesterol or uric acid.

Signs and symptoms

·   Feeling of fullness in the head, dizziness, headache

·   Ruddy cyanosis (plethora) of nose

·   Clubbing of digits

·   Painful pruritus

·   Ecchymosis

·   Hepatosplenomegaly

·   Alterations in vision

·   Abdominal fullness

Diagnostic test results

·   Laboratory studies reveal:

§  increased RBC mass

§  normal arterial oxygen saturation

§  increased uric acid level

§  increased blood histamine levels

§  decreased serum iron concentration

§  decreased or absent urinary erythropoietin.

·   Bone marrow biopsy shows excess production of myeloid stem cells.

Treatment

·   Phlebotomy to reduce RBC mass

·   Myelosuppressive therapy with hydroxyurea or radioactive phosphorous

·   Interferon-alfa

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PERIPHERAL BLOOD SMEAR IN POLYCYTHEMIA

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