Polycythaemia Vera and Myelosclerosis: A Bone Marrow Study

Summary: Trephine bone biopsies have been performed on patients suffering from polycythaemia vera and other myeloproliferative disorders. These were assessed histologically with particular reference to cellularity and reticulin. It was found that marrow cellularity, when measured using Curtis's modification of a Chalkley array of points, is raised in polycythaemia vera and may become normal following radioactive phosphorus therapy. Marrow cellularity was also shown to be proportional to spleen size and a linear relationship between marrow cellularity and packed cell volume was demonstrated, providing major degrees of splenomegaly were excluded. Studies of the reticulin fibres in bone marrow showed that they increase in density with an increase in marrow cellularity, and that an increase is neither characteristic of any specific myeloproliferative disorder nor is it related to radioactive phosphorus therapy. It was concluded that the histological diagnosis of myelosclerosis should be confined to those bone marrows showing evidence of fibroblastic proliferation and disruption of marrow architecture by a process of fibrosis, and should not be made on the basis of reticulin density.