The most common chronic myeloproliferative disorder characterized by neutrophilic leukocytosis. It is associated with the Philadelphia (Ph) chromosome and/or the BCR/ABL fusion gene. Most patients are middle-aged or elderly. Common findings at presentation include fatigue, weight loss, anemia, night sweats, and splenomegaly. The disease is bi- or triphasic: an initial indolent chronic phase is followed by accelerated or blast phase. Allogeneic bone marrow transplantation is currently the only curative therapy (adapted from WHO 2001). — 2003