Polycythemia vera is a rare, chronic blood disorder where the bone marrow produces too many red blood cells, and sometimes white blood cells and platelets. This overproduction thickens the blood, hindering its flow and increasing the risk of complications. While there is no cure, early understanding is important for managing symptoms and preventing serious health issues.
What Polycythemia Vera Is
Polycythemia vera is a myeloproliferative neoplasm, a type of blood cancer originating in the bone marrow. The bone marrow produces an excessive number of red blood cells, and sometimes white blood cells and platelets. This overproduction results in a higher concentration of blood cells, particularly red blood cells, in the bloodstream.
This excess cell production increases blood thickness, or viscosity. Thicker blood flows less efficiently through blood vessels, slowing circulation and reducing oxygen delivery to the body’s tissues and organs. This sluggish flow contributes to various symptoms and complications.
How Polycythemia Vera Develops
Polycythemia vera develops due to a genetic alteration occurring during a person’s lifetime, rather than being inherited. The most common cause is the JAK2 V617F mutation, found in most individuals with polycythemia vera.
The JAK2 gene normally produces a protein that regulates blood cell production in the bone marrow. When this gene mutates, it causes the bone marrow to produce blood cells uncontrollably, independent of normal body signals like erythropoietin. This unregulated growth leads to the characteristic overproduction of blood cells.
Identifying Symptoms
Symptoms of polycythemia vera can vary and often start subtly, sometimes not appearing for many years. Some symptoms relate to increased blood viscosity, such as headaches, dizziness, and blurred or double vision. Individuals may also experience fatigue, weakness, and itchy skin, which often worsens after a warm bath or shower.
Other indicators include redness of the face or skin, or a burning pain in the hands or feet. An enlarged spleen, a common finding, can cause abdominal discomfort or a feeling of fullness after eating. Less common symptoms include bleeding issues like nosebleeds or bleeding gums, and conditions like gout.
Diagnosis and Treatment Approaches
Diagnosis typically begins with a medical history, physical examination, and specific blood tests. A complete blood count shows elevated red blood cell mass, hemoglobin, and hematocrit levels. Genetic testing for the JAK2 mutation, especially the JAK2 V617F variant, is a standard diagnostic step. Erythropoietin levels may also be checked, as they are often low due to unregulated red blood cell production. A bone marrow biopsy may also be performed.
Treatment aims to reduce blood cell numbers and prevent complications. Phlebotomy, a procedure that removes blood from the body, is a common treatment to decrease red blood cell count and blood thickness. Low-dose aspirin is frequently prescribed to help prevent blood clots. For higher-risk individuals or those not responding to phlebotomy, medications like hydroxyurea, interferon alpha, or ruxolitinib may suppress blood cell production, especially if hydroxyurea is ineffective or causes severe side effects. Staying well-hydrated also helps manage blood viscosity.
Potential Complications
Unmanaged polycythemia vera can lead to several serious complications. The primary risk is blood clot formation (thrombosis) in various parts of the body. These clots can lead to life-threatening events like stroke or heart attack, as well as deep vein thrombosis or pulmonary embolism.
Over time, some individuals may progress to myelofibrosis, a condition where bone marrow scar tissue impairs healthy blood cell production. In rare instances, polycythemia vera can transform into acute myeloid leukemia (AML). These outcomes underscore the importance of ongoing medical management.