Reversal of bone marrow fibrosis and subsequent development of polycythemia in patients with myeloproliferative disorders.

Bone marrow fibrosis is a characteristic finding in agnogenic myeloid metaplasia and in the spent phase of polycythemia vera. It is commonly believed that the reticulin deposition is irreversible. However, we report four patients who demonstrated clinical and laboratory evidence of transition from myelofibrosis to polycythemia. The transition was documented by improvement in the hemoglobin concentration and by determination of the Cr51 red blood cell mass, accompanied by a resolution of the fibrosis on serial bone marrow biopsies. Two of the patients had been treated with alkylating agents and splenectomy, one with myelosuppressive therapy without splenectomy, and one with splenectomy alone. These findings indicate that bone marrow fibrosis in the chronic myeloproliferative disorders is not always an irreversible phenomenon. Pathogenetic implications will be discussed.