Mumps associated with nephritis.

During an endemic of mumps in 1987, urinalysis was performed in 124 children with the symptoms of mumps during the acute phase of the disease, 36 children (29.0%) with microscopic hematuria and 8 children (6.4%) with proteinuria were studied. In the children with abnormal urinalysis, whose creatinine clearance was within the normal range, an urine culture for mumps virus was also performed. Nine specimens (20.4%) were positive, 8 (88.8%) of them during the first 5 days of illness. Renal biopsy, performed in a girl with persistent hematuria, revealed a mild mesangial proliferative glomerulonephritis with deposition of immunoglobulins A and M, C3, and mumps virus antigen in the glomerulus, suggesting an immune complex deposition. Electron microscopy demonstrated a moderate number of granular electron-dense deposits in the paramesangial regions. The relationship between the development of mumps and the onset of nephritis and the immunofluorescent demonstration of mumps antigen in the glomeruli suggested that the mesangial nephropathy may have developed after the mumps infection. Therefore, in our cases, the clinical course was benign.