Myeloproliferative neoplasms (MPN) are a group of blood disorders related to leukaemia in which the body makes too many blood cells. MPN originates in the bone marrow - the soft tissue in the middle of our bones, where all our blood cells are made.

When people have MPN normal blood cell production breaks down. The bone marrow becomes over-active and makes far too many blood cells. This can cause the blood to become thick.

MPN can affect any of our blood cells. There are three essential types: red blood cells, which carry oxygen around the body; white blood cells, a vital part of our immune system needed to fight infection, and platelets, which clot the blood and stop us from bleeding and bruising easily.

Types of MPN