Significance of cytoplasmic microtubules in lupus nephritis.

Twenty-five renal and three skin biopsies from 14 cases of systemic lupus erythematosus with lupus nephritis were examined by electron microscope. Seventy-five renal biopsies from nonlupus cases consisting of 35 adults and 40 children were used for comparative study. Clusters of cytoplasmic microtubules, which have been referred to as virus-like particles, were observed in the endothelial cells of glomerular and peritubular capillaries in renal biopsies of all lupus cases. The clusters of microtubules were larger and more numerous in the initial biopsies with mild glomerular changes and in the second biopsies from two cases during a period of more severe relapse. Clusters of microtubules were fewer and smaller in renal biopsies with more advanced glomerular changes. Skin biopsies showed similar cytoplasmic inclusions in arterioles and capillaries. Cytoplasmic microtubules were also observed in 3 adults and 13 children of 75 patients who had no systemic lupus erythematosus. Although the formation of the cytoplasmic microtubules may be related to a virus infection, this suggestion cannot be confirmed from the morphologic findings of this study. Of additional interest is the evidence that these microtubules are not cytoplasmic changes secondary to corticosteroid therapy. It is concluded that the presence of many large clusters of cytoplasmic microtubules is specific for lupus nephritis, and it may be substantiated by similar findings in the skin.