Polycythemia vera (PV) is a type of blood cancer that causes the bone marrow to make too many red blood cells. These cells carry oxygen throughout the body, but when too many of them, the blood becomes thicker and can cause circulation problems, such as blood clots. PV is a rare, slow-onset disease that usually affects people over 50.

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Children with PV can grow and develop normally, they should be able to carry out their normal activities, always following the advice of the MPN specialist doctor.