Myeloproliferative disorders occur in families, thus giving rise to the theory that it is a genetic disease that may be caused by an abnormal gene in the DNA that can be passed from one generation of family members to another. DNA can be gathered from family members through blood samples and the investigators will investigate (through DNA testing) to see if there are abnormal genes that may be responsible for causing the MPDs. Understanding which genes are responsible for causing MPDs can help develop ways to identify people who may be at risk for developing an MPD, allow for the development of better treatments, possibly a cure, or even prevent the development of MPDs.

Inclusion Criteria:

• Families with 2 or more members diagnosed with polycythemia vera (PV), essential thrombocythemia (ET), PV and ET related myelofibrosis (PV-MF and ET-MF), idiopathic myelofibrosis (IM) or chronic myelogenous leukemia (CML).
• Healthy family members of subjects diagnosed with a myeloproliferative neoplasm (MPN).
• Participating subjects must be 7 years of age or older
• A written assent, parental permission or consent must be obtained prior to any study procedures being performed.

Exclusion Criteria:

• Subjects who have a known acquired cause of polycythemia (increased hemoglobin/hematocrit), such as people living in high altitudes (in excess of 14,000 feet), subjects with heart disease, left to right heart shunt, severe hypoxia, cyanotic congenital heart disease, or severe pulmonary disease, will be excluded from this study, secondary forms of thrombocytosis and secondary forms of myelofibrosis.

families with multiple member diagnosed with myeloproliferative disease