Myeloproliferatie Neoplasms, or MPN, are a group of bone marrow disorders that can lead to overproduction of different bone marrow elements. The "classical" MPN usually includes essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF). These diseases usually affect older individuals, and are very rare in the pediatric population. ET is a disorder characterized by elevated platelets (blood cells important for stopping bleeding). PV is a disorder of red blood cells characterized by an elevated hemoglobin, and it can also have elevated white blood cells or platelets. Primary myelofibrosis is a disorder of overgrowth of bone marrow scar tissue. ET can transform into PV, while ET and PV both can transform into a secondary form of myelofibrosis. All three of the classical MPN can transform into AML. Bleeding and blood clots, as well as a variety of clinical symptoms, can develop from an MPN. A majority of MPN are due to mutations in one of three genes: the most common is JAK2 (which can cause all 3), the second most common is CALR (which can cause ET or PMF), and the least common is MPL (which can cause ET or PMF). Treatments for MPN can include phlebotomy (where blood is removed to lower the hemoglobin), aspirin, or a more specialized medication such as interferon or hydroxyurea.
Due to the rare nature of these diseases, less is known about MPN in children than in adults. Children can get any of the forms of classical MPN, although ET and PV are more common (and less severe) than PMF. Symptoms in children can include headaches, abdominal pain, itching, bleeding, and blood clots. Children being evaluated for an MPN should expect to have a number of blood tests taken (including genetic tests) and also a bone marrow study. Treatments in children can vary and your child's doctor will discuss appropriate options with you. Research is being done in children to better understand why these diseases happen in children, how they affect children, what are the long term issues when a child has an MPN, and what are the best and safest treatment options for children with an MPN.