Polycythemia Vera (PV) is a condition characterized by the overproduction of red blood cells relative to the other components of the blood. These excess cells have the ability to thicken blood, which in turn slows its flow. PV has the tendency to cause complications such as blood clots which can lead to a potential heart attack or stroke. Like the other myeloproliferative neoplasms (MPNs), PV is also thought to be caused by mutations in blood forming stem cells (aka hematopoietic stem cell, HSC). Everyone is born with a few tens of thousands of HSCs that are the source for all of the blood cells people make during their life. In PV, mutations in the JAK2 gene are found in the blood cells of virtually all patients. These JAK2 mutations cause the HSCs to yield too many red blood cells (RBCs) and typically, also lead to increased numbers of white blood cells and platelets. JAK2 protein is part of a signaling system that helps regulate blood cells production. The mutated JAK2 signals more than it should and this signaling increases the number of blood cells produced.
PV is not a common disorder, affecting approximately 2 people per 100,000 in the general population, and it typically develops slowly. It can occur at any age, but is more common in adults older than 60. It is possible that someone could have the disease for many years without knowing it. Sometimes the first indication that someone has PV is the development of an abnormal blood clot. Clots can develop anywhere in the body, either in veins or arteries. Routine blood testing conducted for another reason is sometimes the first indication of PV. If left untreated, PV could be life-threatening, however, with proper medication, the signs, symptoms and complications of the disease can be managed. Sometimes, PV can progress to more serious blood cancers such as myelofibrosis or acute leukemia.
PV cannot be cured, however there are treatments available that focus on managing the symptoms of PV and reducing thrombotic complications. Phlebotomy is one form of treatment, which is often combined with other therapies. Phlebotomy refers to the removal of blood from the body, reducing number of excess red blood cells and thereby reducing the risk of blood clots. Other treatments include aspirin, as a blood thinner, to further reduce the risk for various thrombotic complications. Cytoreductive agents (for example, hydroxyurea and interferon) are often used to reduce the number of excess blood cells in PV. Targeted drugs that block the abnormal signals from the JAK2 are sometimes used to treat PV. FDA has approved one JAK2-inhibitor, called ruxolitinib or Jakafi, for treatment of PV. In certain cases, bone marrow transplant is considered to be a possible way to treat the disease. NewYork-Presbyterian Hospital/Weill Cornell Medicine offers one of the best Bone Marrow and Stem Cell Transplant (BMT) programs in the United States and around the world.