Primary ultrastructural diagnosis of cryoglobulinemic glomerulonephritis

A 58-year-old woman suffering from epistasis was found to be hypertensive. Hypocomplementemia associated with normal serum creatinine level, erythrocytosis, microscopic hematuria, proteinuria, and normal serum immunoglobulin levels and immunoelectrophoresis results led to a renal biopsy. Light microscopy disclosed mesangial hypercellularity and accumulation of eosinophilic material in capillary loops and in the mesangium. Immunomicroscopy disclosed coarsely granular to globular deposition of IgG, IgM, and C3 in similar distribution. Electron microscopy demonstrated electron-dense mesangial and subendothelial deposits consisting of interlacing fibrillar bundles associated with infiltration of acute inflammatory cells characteristic of cryoglobulinemic glomerulonephritis. After the biopsy, the presence of circulating IgG-IgM cryoglobulins was documented. Substructure of the in vitro cryoprecipitate and the immune complexes in the kidney was very similar. These observations illustrate the importance of continued routine ultrastructural assessment in evaluation of renal biopsy material.