Table 1 Classification of erythrocytosis

a. Associated with reduced P50 (partial pressure of oxygen at which 50% of hemoglobin is saturated with oxygen)

   i. High-oxygen-affinity hemoglobinopathy

   ii. 2,3-bisphosphoglycerate

   iii. Methemoglobinemia

b. Associated with normal P50

   i. VHL gene mutations including Chuvash

   ii. Erythropoietin receptor mutations

2. Acquired erythrocytosis

a. Clonal (polycythemia vera)

b. Secondary

   i. Hypoxia driven

1. Chronic lung disease

2. Right-to-left cardiopulmonary shunts

3. High-altitude habitat

4. Tobacco use/carbon monoxide poisoning

5. Sleep apnea/hypoventilation syndrome

6. Renal artery stenosis

   ii. Hypoxia independent

1. Use of androgen preparations/erythropoietin injection

2. Post-renal transplant

3. Cerebellar hemangioblastoma/meningioma

4. Pheochromocytoma/uterine leiomyoma/renal cysts/parathyroid adenoma

5. Hepatocellular carcinoma/renal cell carcinoma