Is erythrocytosis (elevated Hemoglobin (HgB)) normal in a 17-year-old girl?

Elevated Hemoglobin in a 17-Year-Old Girl: Assessment and Considerations

Elevated hemoglobin (erythrocytosis) is not normal in a 17-year-old girl and requires thorough investigation to determine the underlying cause, as it could indicate a serious medical condition affecting morbidity and mortality. 1

Normal Hemoglobin Values for Adolescent Females

According to reference data from the National Health and Nutrition Examination Survey (NHANES):

• Normal hemoglobin range for 15-19 year old females: 121.6-144.2 g/L (12.16-14.42 g/dL)
• 95th percentile value: 146.0 g/L (14.6 g/dL) 1

Values above this range should be considered elevated and warrant investigation.

Classification of Erythrocytosis

Erythrocytosis can be categorized as:

1. True polycythemia (increased red cell mass >125% of predicted)

   • Primary: Autonomous erythroid proliferation

     • Polycythemia vera (PV)
     • Primary familial and congenital polycythemia (PFCP)

   • Secondary: Driven by extrinsic factors (usually erythropoietin)

     • Hypoxia-driven (lung disease, high altitude, congenital heart disease)
     • Non-hypoxic causes (tumors, renal disorders, genetic disorders) 1, 2

2. Apparent polycythemia (normal red cell mass with reduced plasma volume)

   • Dehydration
   • Stress-induced
   • Diuretic use 1

Diagnostic Approach for a 17-Year-Old Female with Erythrocytosis

Initial Evaluation:

1. Confirm true erythrocytosis by checking:

   • Complete blood count with indices
   • Repeat hemoglobin/hematocrit to confirm persistence
   • Assess for microcytosis (MCV <80 fL) which may indicate iron deficiency 1

2. Measure serum erythropoietin (EPO) level:

   • Low EPO: Suggests primary erythrocytosis
   • Normal/high EPO: Suggests secondary erythrocytosis 3

Key Considerations in Adolescents:

1. Congenital heart disease - Particularly important in adolescents

   • Cyanotic heart defects can cause secondary erythrocytosis
   • Right-to-left shunting leads to hypoxemia and compensatory erythrocytosis 1

2. Genetic causes - More common in younger patients

   • Mutations in EPO receptor gene
   • High oxygen-affinity hemoglobinopathies
   • Mutations in oxygen-sensing pathway genes 4

3. Renal disorders

   • Hydronephrosis has been reported to cause polycythemia even with low EPO levels in adolescents 5
   • Renal tumors or cysts can produce EPO 1

4. Endocrine disorders

   • Androgen excess states
   • Pheochromocytoma 1

5. Polycythemia vera - Though rare in adolescents, should be considered

   • JAK2 mutation testing is recommended if suspected 1

Warning Signs and Complications

Elevated hemoglobin in adolescents can lead to serious complications:

• Thrombotic events - Including stroke, deep vein thrombosis
• Hyperviscosity symptoms - Headache, dizziness, visual disturbances, fatigue
• Bleeding complications - Due to acquired platelet dysfunction 1

Management Considerations

Management depends on the underlying cause:

1. For secondary erythrocytosis:

   • Treat the underlying condition (e.g., congenital heart disease, renal disorder)
   • Avoid dehydration
   • Consider phlebotomy only for symptomatic hyperviscosity with hematocrit >65% 1

2. For primary erythrocytosis:

   • Referral to hematology
   • Consideration of phlebotomy and low-dose aspirin 4

3. For all patients:

   • Avoid iron deficiency (microcytosis increases stroke risk)
   • Maintain adequate hydration 1

Key Pitfalls to Avoid

1. Inappropriate phlebotomy - Can cause iron deficiency, which paradoxically increases thrombotic risk due to microcytosis 1

2. Misdiagnosis as stress polycythemia - True erythrocytosis requires thorough investigation, especially in young patients 1

3. Missing congenital causes - Particularly important in adolescents with family history of erythrocytosis 4

4. Overlooking renal pathology - Renal disorders can cause erythrocytosis even with normal or low EPO levels 5

In conclusion, elevated hemoglobin in a 17-year-old girl is abnormal and requires comprehensive evaluation to identify the underlying cause, which will guide appropriate management and prevent serious complications.