The Full form of PV is Polycythemia Vera. PV is a slow-growing blood cancer in which the bone marrow makes too many RBCs (red blood cells). These excess cells thicken the blood, slowing its flow. They also cause complications, such as blood clots, which can lead to stroke or a heart attack. Polycythemia Vera isn’t common. It usually develops slowly, and a person might have it for years without knowing. Often the condition is found during a blood test done for another reason. Without treatment, PV can be life-threatening. But proper medical care can help ease signs, symptoms and complications of this disease. Over time, in some cases there’s a risk of progressing to more-serious blood cancers, such as acute leukemia or myelofibrosis. Many people with PV don’t have signs or symptoms. Others might have itchiness, especially following a warm bath or shower, headache, dizziness, bleeding or bruising, usually minor, weakness, fatigue, blurred vision, excessive sweating, painful swelling of one joint, often the big toe, shortness of breath, numbness, burning, tingling or weakness in hands, feet, arms or legs, a feeling of fullness or bloating in left upper abdomen due to an enlarged spleen, fevers, or unexplained weight loss.