Definition of Myelofibrosis

Myelofibrosis: Fibrosis (spontaneous scarring) of the bone marrow. This can be associated with a variety of diseases, primarily myeloproliferative (pre-leukemic) disorders. Sometimes used interchangeably with agnogenic myeloid metaplasia. Myelofibrosis is characterized by significant anemia and an enlarged spleen. Acute myelofibrosis is a distinct disorder characterized by acute inadequate blood cell production (pancytopenia), marrow fibrosis, but no enlargement of the spleen or liver.