Polycythemia Vera

Key Features

Essentials of Diagnosis

• Autonomous overproduction of erythroid cells

• Elevated RBC mass

• Hematocrit > 49% in males or > 48% in females

• JAK2 V617F mutation

• Splenomegaly

• Normal arterial oxygen saturation

• Usually elevated white blood count and platelet count

General Considerations

• Although characterized by autonomous overproduction of erythroid cells, there is overproduction of all hematopoietic cell lines

Demographics

• 60% of patients are men

• Median age at presentation is 60 years

• Rarely occurs in persons under age 40 years

Clinical Findings

Symptoms and Signs

• Common complaints related to expanded blood volume and increased blood viscosity include

  • Headache

  • Dizziness

  • Tinnitus

  • Blurred vision

  • Fatigue

• Generalized pruritus is related to histamine release from basophils

• Epistaxis is probably related to engorgement of mucosal blood vessels in combination with abnormal hemostasis

• Thrombosis

  • Appears to be related both to increased blood viscosity and abnormal platelet function

  • Incidence of thrombotic complications of surgery is very high if polycythemia is uncontrolled; elective surgery should be deferred until the condition has been treated

• Increased bleeding can also occur

• Physical examination reveals plethora and engorged retinal veins

Differential Diagnosis

• Spurious polycythemia may be related to diuretic use or may occur without obvious cause

• Suspect secondary causes of polycythemia if

  • Splenomegaly is absent

  • Elevated hematocrit is not accompanied by increases in other cell lines

• Secondary causes of polycythemia include

  • Hypoxia: cardiac disease, pulmonary disease, high altitude

  • Carboxyhemoglobin: smoking

  • Kidney lesions

  • Erythropoietin-secreting tumors (rare)

  • Abnormal hemoglobins (rare)

• Polycythemia vera should be differentiated from other myeloproliferative disorders (Table 13–14)

Diagnosis

Laboratory Findings

• Hematocrit (at sea level) that exceeds 49% in males or 48% in females

• RBCs

  • RBC morphology is normal at presentation (Table 13–14)

    • However, microcytosis, hypochromia, and poikilocytosis may result from iron deficiency following treatment by phlebotomy

  • RBC mass is elevated

• White blood cells

  • Usually normal morphology, though basophilia and eosinophilia are frequently present

  • Count is usually elevated to 10,000–20,000/mcL

• Platelets

  • Morphology is usually normal

  • Count is variably increased, sometimes to counts exceeding 1,000,000/mcL

• Erythropoietin levels are suppressed

• Bone marrow

  • Hypercellular, with hyperplasia of all hematopoietic elements

  • Iron stores are usually absent

    ...