An Electron Microscope Study of Bone Marrow in Rheumatoid Disease

SUMMARY The marrow of patients with various haematological complications of rheumatoid disease has been studied with the electron microscope. Although there is evidence that reticulum cells may be reluctant to turn over body iron, yet there is no evidence of iron excess in the reticulum cells of the marrow nor of a morphological defect of normoblast maturation. Iron transfer is normal. Whereas in the early stages of red cell development iron can be seen to enter the normoblasts from the reticulum cells by the distinct process of ropheocytosis, in the late normoblast and reticulocyte aggregates of unused iron pass back to the reticulum cells. The reticulum cell is therefore important in regulating the distribution of iron within the marrow. The reticulo‐endothelial system in rheumatoid disease shows evidence of response to antigenic stimulation. In particular a case of Felty's syndrome showed reticulum cell hyperplasia, lymphoblasts and material resembling rheumatoid factor in the granulocytes. Hyperplasia of the marrow reticulum may lead to a maturation arrest constituting ‘hypersplenism’.