Doctor's Notes on Polycythemia (High Red Blood Cell Count)
Polycythemia refers to an elevated number of red blood cells (termed erythrocytes) in the circulation. This can occur either as a primary condition in which the bone marrow produces too many red blood cells (called polycythemia vera) or it may occur as a reaction to other diseases and conditions (such as hypoxia or low oxygen levels due to any reason) that drive the body to produce an increased number of red blood cells.
Symptoms and signs of polycythemia can be non-specific and may include weakness, fatigue, easy bruising, headache, joint pain, and dizziness. Other associated signs and symptoms can include itching, problems with blood clotting, bleeding, cough, or poor exercise tolerance. The particular signs and symptoms depend on the reason for the elevated red blood cell count.
Polycythemia (High Red Blood Cell Count) Symptoms
Symptoms of polycythemia can vary widely. In some people with polycythemia, there may be no symptoms at all.
In secondary polycythemia, most of the symptoms are related to the underlying condition responsible for polycythemia.
Symptoms of polycythemia vera can be vague and quite general. Some of the important symptoms include:
- easy bruising;
- easy bleeding;
- blood clot formation (potentially leading to heart attacks, strokes, blood clots in the lungs [pulmonary embolism]);
- bone and joint pain (hip pain or rib pain);
- itching after taking a shower or bath (post-bath pruritus);
- dizziness; and
- abdominal pain.
Polycythemia (High Red Blood Cell Count) Causes
In primary polycythemia, inherent or acquired problems with red blood cell production lead to polycythemia. Two main conditions that belong to this category are polycythemia vera (PV or polycythemia rubra vera [PRV]) and primary familial and congenital polycythemia (PFCP).
- Polycythemia vera (PV) is related to a genetic mutation in the JAK2 gene, which is thought to increase the sensitivity of bone marrow cells to Epo, resulting in increased red blood cell production. Levels of other types of blood cells (white blood cells and platelets) are also often increased in this condition.
- Primary familial and congenital polycythemia (PFCP) is a condition related to a mutation in the EPOR gene and causes increased production of red blood cells in response to Epo.
Contrary to primary polycythemia in which overproduction of red blood cell results from increased sensitivity or responsiveness to Epo (often with lower than normal levels of Epo), in secondary polycythemia, more red cells are produced because of high levels of circulating Epo.
The main reasons for higher than normal Epo are chronic hypoxia (poor blood oxygen levels over the long-term), poor oxygen delivery due to abnormal red blood cell structure, and tumors releasing inappropriately high amounts of Epo.
Some of the common conditions that can result in elevated erythropoietin due to chronic hypoxia or poor oxygen supply include:
- chronic obstructive pulmonary disease (COPD, emphysema, chronic bronchitis),
- pulmonary hypertension,
- hypoventilation syndrome,
- congestive heart failure,
- obstructive sleep apnea,
- poor blood flow to the kidneys, and
- living in high altitudes.
2,3-BPG deficiency is a condition in which the hemoglobin molecule in the red blood cells has an abnormal structure. In this condition, hemoglobin has a higher affinity to hold on to oxygen and is less likely to release it to the tissues. This results in more red blood cells being produced in response to what the tissues in the body perceive as an inadequate oxygen level. The outcome is more circulating red blood cells.
Certain tumors have a tendency to secrete inappropriately high amounts of Epo, leading to polycythemia. The common Epo-releasing tumors are:
- liver cancer (hepatocellular carcinoma),
- kidney cancer (renal cell carcinoma),
- adrenal adenoma or adenocarcinoma, and
- uterine cancer.
There also are more benign conditions that may cause increase Epo secretion, such as kidney cysts and kidney obstruction.
Chronic carbon monoxide exposure can also lead to polycythemia. Hemoglobin naturally has a higher affinity for carbon monoxide than for oxygen. Therefore, when carbon monoxide molecules attach to hemoglobin, polycythemia (increased red cell and hemoglobin production) may occur in order to compensate for the poor oxygen delivery by the existing hemoglobin molecules. A similar scenario can also occur with carbon dioxide in long-termcigarette smoking.
Polycythemia in newborns (neonatal polycythemia) is often caused by transfer of maternal blood from the placenta or blood transfusions. Prolonged poor oxygen delivery to the fetus (intrauterine hypoxia) due to insufficiency of the placenta can also lead to neonatal polycythemia.
Anyone Can Have It
This illness means you have a lower than normal red blood cell (RBC) count. Normal values vary; blood tests like the complete blood count (CBC) can be explained by your doctor. Anemia may also result from low levels of hemoglobin, the protein that transports oxygen to the body. No matter what the cause, less oxygen is available and this produces weakness, dizziness, and shortness of breath. It is treatable once the underlying cause is identified. Long-standing or severe lack of oxygen can damage of the brain, heart, and other organs.
The three main causes of the illness are inadequate or faulty production of red blood cells, a high rate of destruction of red blood cells, and excessive bleeding. Megaloblastic is one type of faulty red cell production. The condition of anemia may be mild and easily treatable or severe and require immediate intervention.
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.