Bone marrow morphology in patients in long-term treatment with azathioprine.

The bone marrow was morphologically analysed in 25 patients receiving long-term azathioprine therapy for chronic renal diseases or after a renal transplantation. There were no significant changes within the granulopoietic or lymphopoietic part of bone marrow even after 10 years of treatment. However, there was a significant "shift to the left" within erythropoiesis as well as greater frequencies of megaloblasts and sideroblasts. A significant increase of "erythroblastic islands" may indicate an increased death rate of defective erythroblasts. The changes within erythropoiesis in some of the patients were so pronounced that the possibility of a preleukaemic condition cannot be excluded.