What is the diagnosis and management for a patient with erythrocytosis?

Management of Erythrocytosis

Therapeutic phlebotomy is only indicated for this patient if they develop symptoms of hyperviscosity, as the current hemoglobin (163 g/L) and hematocrit (0.50 L/L) levels do not meet criteria for intervention. 1

Diagnosis Assessment

The patient presents with laboratory findings consistent with erythrocytosis:

• Hemoglobin: 163 g/L (elevated above normal range of 115-155 g/L)
• Hematocrit: 0.50 L/L (elevated above normal range of 0.35-0.46 L/L)
• RBC: 5.63 x 10^12/L (slightly elevated above normal range of 3.60-5.60 x 10^12/L)
• Normal iron studies

This represents a mild erythrocytosis with normal iron studies, which requires further evaluation to determine the underlying cause.

Classification of Erythrocytosis

Erythrocytosis can be classified as:

1. Primary erythrocytosis:

   • Polycythemia vera (PV) - characterized by JAK2 mutations
   • Congenital primary erythrocytosis - rare genetic disorders

2. Secondary erythrocytosis:

   • Physiological response to hypoxemia (most common)
   • Pathological erythropoietin production
   • Congenital causes (rare genetic disorders)

Diagnostic Algorithm

1. Confirm true erythrocytosis:

   • Elevated hemoglobin and hematocrit (confirmed)
   • Rule out relative erythrocytosis due to dehydration

2. Measure serum erythropoietin (EPO) level:

   • Low EPO suggests primary erythrocytosis
   • Normal/high EPO suggests secondary erythrocytosis

3. If low EPO: Test for JAK2 mutations (V617F, exon 12)

   • Positive: Diagnose polycythemia vera
   • Negative: Consider rare congenital primary erythrocytosis

4. If normal/high EPO: Evaluate for causes of secondary erythrocytosis:

   • Cardiopulmonary evaluation (cyanotic heart disease, COPD, sleep apnea)
   • Renal imaging (renal cysts, tumors)
   • High altitude exposure
   • Smoking history
   • Medication review (androgens, erythropoietin)

Management Approach

1. Treat underlying cause if identified (e.g., CPAP for sleep apnea, smoking cessation)

2. Phlebotomy indications:

   • Only indicated when hemoglobin >20 g/dL (200 g/L) AND hematocrit >65% WITH symptoms of hyperviscosity 1
   • Current values (Hgb 163 g/L, Hct 0.50 L/L) do NOT meet criteria for phlebotomy

3. Avoid routine phlebotomies:

   • Repeated phlebotomies can cause iron deficiency
   • Iron deficiency reduces oxygen-carrying capacity
   • Increases risk of stroke and thrombosis 1

4. Monitor for complications:

   • Thrombotic events
   • Bleeding diathesis
   • Hyperviscosity symptoms (headache, dizziness, visual disturbances)

5. Maintain hydration:

   • Dehydration increases blood viscosity and thrombotic risk

Special Considerations

If Secondary to Cyanotic Heart Disease

• Erythrocytosis is a compensatory mechanism to improve oxygen transport 1
• Avoid phlebotomy unless clear symptoms of hyperviscosity are present
• Maintain iron repletion as iron deficiency can worsen symptoms 1

If Polycythemia Vera

• Refer to hematology for cytoreductive therapy consideration
• Low-dose aspirin may be indicated

Common Pitfalls to Avoid

1. Unnecessary phlebotomy:

   • Routine phlebotomy without meeting criteria (Hgb >20 g/dL, Hct >65%, symptoms) can lead to iron deficiency and paradoxically increase thrombotic risk 1

2. Failure to evaluate underlying cause:

   • Secondary erythrocytosis requires identification and treatment of the primary condition

3. Confusing relative and absolute erythrocytosis:

   • Dehydration can cause relative erythrocytosis that resolves with hydration

4. Ignoring iron status:

   • Iron deficiency in erythrocytosis can lead to microcytosis and increased blood viscosity despite lower hemoglobin 1

This patient's erythrocytosis is mild and does not currently require therapeutic phlebotomy, but warrants investigation for underlying causes and monitoring for progression or development of symptoms.