Intro to Polycythemia

On my first day in Ambulatory GIM clinic, I met with a patient referred for polycythemia. Although he had a clear history of OSA, which may explain his BW findings of erythrocytosis, I reviewed the other causes of polycythemia for a comprehensive, thorough investigation of my patient's BW findings.  

Definition: an abnormal elevation of hemoglobin and/or hematocrit in peripheral blood.

a) Increased Hb: >10.3mmol/L (men) or >10.0mmol/L (women)

b) Increased hematocrit: >49% (men) or >48% (women)

Causes:

1) Primary Polycythemia
Caused by mutation in RBC progenitor cells that leads to increased RBC mass, most commonly polycythemia vera or another myeloproliferative neoplasm.

2) Secondary Polycythemia from elevated serum EPO

a) Hypoxia-associated:
- Cardiopulmonary disease such as chronic pulmonary disease, cyanotic heart disease, obstructive sleep apnea.
- High altitude
- Decreased release of oxygen to tissues from high oxygen affinity hemoglobin, such as CO toxicity.
- Smoking
- Diminished oxygen sensing by the kidneys can cause increased EPO production, including renal artery stenosis

b) Tumor-associated:
- Hepatocellular carcinoma
- Renal cell carcinoma
- Hemangioblastoma
- Pheochromocytoma
- Uterine myomata

History:

- Hyperviscosity symptoms: chest/abdominal pain, myalgia, weakness, fatigue, headache, blurred vision
- Thrombosis or bleeding
- Other symptoms: unexplained fever, sweats, weight loss, gout, erythromelalgia
- Social history: smoking, exposure to CO
- Family history

Investigations:
1. Pulse oximetry
2. Serum EPO
3. Electrolytes
4. Kidney and LFTs
5. Consider JAK2 genetic testing 
6. Consider CXR, abdominal U/S

-BH-

Resource: Diagnostic approach to the patient with polycythemia (uptodate)