Interferon-alpha-induced morphological changes of megakaryocytes: a histomorphometrical study on bone marrow biopsies in chronic myeloproliferative disorders with excessive thrombocytosis.

Interferon(rIFN)-alpha, a successful therapeutic agent in the control of thrombocytosis, has been shown to suppress human megakaryopoiesis. We investigated bone marrow biopsies from 12 patients with thrombocytosis due to chronic myeloproliferative disorders. Prior to treatment as well as during rIFN-alpha-2c therapy, several morphometric parameters of megakaryopoiesis were evaluated. Megakaryocyte density decreased significantly in all patients, megakaryocyte size decreased in polycythaemia vera, agnogenic myeloid metaplasia, and essential thrombocythaemia, but increased in chronic myeloid leukaemia. The various changes observed during therapy indicate an inhibitory effect of rIFN-alpha-2c on megakaryopoiesis and suggest a selective influence on megakaryocytes at various stages of maturation. Increased numbers of pyknotic (bare) nuclei may reflect a shortening of megakaryocyte life-span. No remarkable changes were found in the fibre content of the bone marrow.