Chronic idiopathic myelofibrosis is a clonal disorder of hematopoietic cells resulting in an increase of all three cell lines in the marrow and vigorous extramedullary hematopoiesis; however, circulating cell counts are variable. Anemia is usually present, but PMNs and platelets may be low, normal, or increased. Red cells are released early into the blood--nucleated red cells and dacryocytes (the product of splenic remodeling of a large cell) are seen on peripheral smears. Myeloid left shift to blasts and immature megakaryocytes are seen. Impressive fibrosis occurs in the marrow, as an epiphenomenon to the cell proliferation, but with predictably severe consequences. No bcr-abl translocation is present.
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