Secondary polycythemia, also known as secondary erythrocytosis or secondary erythrocythemia, is a rare condition in which your body produces an excess amount of red blood cells.
This overproduction of red blood cells thickens your blood. This thickened blood can’t pass through your small blood vessels like capillaries easily. This increases your risk of having a stroke.
Causes of Secondary Polycythemia
Secondary polycythemia is caused by some other condition in your body, usually the excess production of the hormone erythropoietin, or EPO. However, secondary polycythemia can be genetic like primary polycythemia but is not caused by a mutation in your bone marrow cells.
The most common causes of secondary polycythemia are
- Obstructive sleep apnea
- Smoking or lung diseases
- Obesity hypoventilation syndrome
- Chronic obstructive pulmonary disease (COPD)
- Use of diuretics
- Use of performance-enhancement drugs, including EPO, testosterone, and anabolic steroids
Other common causes include:
- Chronic carbon monoxide poisoning
- Living at a high altitude
- Kidney disease or cysts
- Brain, liver, or uterine tumors
- Chronic heart disease
Differences Between Primary & Secondary Polycythemia
Primary polycythemia and secondary polycythemia are similar. However, the former starts inside the bone marrow (where our blood cells are formed), whereas the latter starts outside of the bone marrow. Still, in both conditions, the normal bone marrow is overstimulated to overproduce red blood cells.
The job of the red blood cells is to deliver oxygen to the body tissues. This is why something like smoking can cause secondary polycythemia because it interferes with the delivery of oxygen.
Since primary polycythemia is genetic, your doctor can use a genetic test that looks for the mutation in a gene that affects the bone marrow and blood cells, called JAK2. The test distinguishes primary and secondary polycythemia because in most primary polycythemia cases the test will come back positive for this gene.
Symptoms of Secondary Polycythemia
Patients with secondary polycythemia may have symptoms including:
- Blurred vision
- Reduced mental acuity
Secondary polycythemia symptoms occur because of the thickening of your blood after red blood cells are overproduced; in some cases, the overproduction is accompanied by a decrease in the volume of plasma (the fluid part of the blood that contains components except red blood cells). Some patients may have no symptoms at all.
Depending on the underlying cause (what caused secondary polycythemia), your symptoms may vary. For example, it could be a respiratory (breathing-related) or cardiac (heart-related) cause if the symptoms of sleep apnea, like cough, dyspnea, insomnia, snoring, and daytime somnolence are seen.
Diagnosing Secondary Polycythemia
Based on your symptoms, your doctor may recommend a routine medical exam where they would detail your medical history followed by a thorough physical exam.
The doctor will ask you about smoking, weight loss, cough, palpitations, dyspnea, snoring, and your family history. You will also be asked about whether you use any anabolic steroids for muscle mass and whether you have used any prescription medicine now or in the past.
Your doctor may also order diagnostic tests like an electrocardiogram, or ECG, to measure heart function as well as imaging tests like an X-ray, CT scan, or ultrasound to detect enlargement of the heart, liver, or spleen.
Treating Secondary Polycythemia
Correcting or eliminating the cause of secondary polycythemia is the most important aim of treating blood-related abnormalities. For this, doctors may use phlebotomy (blood-letting) or symptom relief.
Phlebotomy is used to reduce the number of red blood cells in plasma. In one sitting, as much as one pint of blood may be let out, depending on your condition. Symptom relief includes taking medication such as antihistamines to relieve itching or aspirin to soothe pain and burning associated with the disorder.
It’s frustrating when you are coping with one condition and learn that you have a second diagnosis as well, but once you treat the underlying cause, the symptoms will usually go away. Most underlying conditions for secondary polycythemia are well-known conditions and already have multiple treatment options available.
Smokers with this condition are usually asked to quit smoking and offered appropriate supportive, psychological, and pharmacological intervention.
Patients who have obesity hypoventilation syndrome are advised to lose weight through lifestyle changes, pharmacological therapy, and bariatric surgery.
Patients with chronic hypoxemia — typically caused by lung disease, right-to-left intracardiac shunts, renal transplantation, prolonged exposure to high altitudes, or hypoventilation syndromes — often develop secondary polycythemia. They can be treated with oxygen therapy and phlebotomy.
Tumor-associated erythrocytosis, a type of secondary polycythemia, occurs because of tumors or cysts in the kidneys, tumors in the liver, cerebellar hemangioblastoma (a type of brain tumor), or uterine leiomyoma (a tumor in the womb). This condition can be treated by removing the lesion.
Generally, secondary polycythemia on its own does not affect your lifespan, as long as the underlying condition is treated.