Myeloproliferative Neoplasms (MPNs) Patient Registry

This is a patient registry — a database — for people with myeloproliferative neoplasms (MPNs), a group of rare bone marrow disorders where too many blood cells are produced, used to track disease patterns and outcomes over time. **You may be eligible if...** - You have been diagnosed with any of the following blood marrow disorders: essential thrombocythemia (too many platelets), polycythemia vera (too many red blood cells), primary myelofibrosis (bone marrow scarring), chronic myelomonocytic leukemia, chronic neutrophilic leukemia, chronic eosinophilic leukemia, juvenile myelomonocytic leukemia, mastocytosis, atypical CML, or related overlap syndromes **You may NOT be eligible if...** - There are no specific exclusion criteria — anyone with an MPN diagnosis may be eligible Talk to your doctor to see if this trial is right for you.