Multicentric reticulohistiocytosis. Fine structural analysis of the synovium and synovial fluid cells

Abstract

Abstract A patient with progressive multicentric reticulohistiocytosis (MR) had foamy giant cells in the synovial fluid as well as in the synovial membrane and dermis. These cells did not stain for neutral fat, but stained faintly with Sudan Black B and periodic acid‐Schiff. Electron microscopy of these unusual macrophages showed they were filled with vacuoles and inclusions that contained a flocculent material. These inclusions bore a close relationship to the Golgi apparatus and, in some cells, appeared to be developing from smooth endoplasmic reticulum. A 3‐month trial on azathioprine did not improve the patient's arthritis nor reduce the size and number of skin nodules. This is the first patient described with this disorder in whom synovial fluid analysis revealed foamy appearing giant cells and in whom intracellular inclusions were related to the endoplasmic reticuium.