Mesangial deposits of IgM in patients with the nephrotic syndrome.

Kidney biopsies from fourteen patients with the nephrotic syndrome were studied by light, immunofluorescence and electron microscopy. Morphologically, all cases showed moderate diffuse mesangial cell proliferation. In all cases, immunofluorescent microscopy demonstrated diffuse and generalized deposits of IgM as the sole or predominant immunoglobulin. Electron microscopic examination showed electron dense deposits localized in the mesangium in seven cases. One nephrotic patient experienced spontaneous remission and eight others were steroid responsive. Only one of the five steroid resistant patients treated with chlorambucil showed clinical remission. Five steroid responsive patients relapsed. At present, four patients are healthy, having not relapsed for the past two years. Although deposits of IgM may be related to the renal pathology in cases of the nephrotic syndrome, immunofluorescence findings do not seem to be sufficiently consistent or characteristic to justify a possible subclassification of the idiopathic nephrotic syndrome.