A sequential histological study of bone marrow fibrosis in idiopathic myelofibrosis.

A sequential histological study of bone marrow biopsies from 36 patients with idiopathic myelofibrosis was performed to investigate the accumulation of connective tissue in the bone marrow during the course of the disease and the influence of therapy on this process. The degree of bone marrow fibrosis was graded semiquantitatively from 0 (normal) to +5 (extensive collagen fibrosis and ostemyelosclerosis). The median interval between the first and final biopsy was 25 months (range 3 to 103) in patients with chronic idiopathic myelofibrosis and 2 months (range 1 to 14) in patients with a syndrome of acute myelofibrosis. In most patients with chronic IMF the bone marrow fibrosis remained unchanged. Regression of bone marrow fibrosis in 9 patients with chronic IMF was associated with immunosuppressive/-cytotoxic treatment or splenectomy. Severe bone marrow fibrosis completely resolved during intensive chemotherapy of a patient with acute myelofibrosis. No relationship existed between spleen size and the degree of bone marrow fibrosis.