Polycythemia vera is a rare blood cancer where the bone marrow produces too many red blood cells. It is caused by a mutation in the JAK2 gene. Symptoms include headache, dizziness, itchiness, and fatigue. Diagnosis involves blood tests showing elevated red blood cells and the JAK2 mutation. Treatment focuses on reducing blood cell counts through phlebotomy and medications to control symptoms and prevent complications like blood clots. While incurable, polycythemia vera can be managed long-term.