Synovial fluid cells in systemic lupus erythematosus: light and electron microscopic studies

Joint fluid findings in systemic lupus erythematosus (SLE) have been described in only a few series and systematic electron microscopic study of the synovial fluid (SF) cells has not been reported. We describe the evaluation of 17 SF in patients with SLE with routine analysis and electron microscopy. Joint effusions had a wider range of leukocyte counts than often appreciated, with counts varying from 875 to 39,250 cells per mm3. LE inclusions were seen in eight fluids and have been shown to contain chromatin-like filaments by electron microscopy. There was little associated electron dense immunoglobulin-like material. Tubuloreticular structures (TRS) found in seven SF were mostly in mononuclear cells including some LE cells. The known association of TRS with alpha interferon and viral infections may have important implications for pathogenesis.