Glomerulonephritis in the acute phase of Ross River virus disease (epidemic polyarthritis).

Hematuria and proteinuria were detected at the peak of symptoms in a case of Ross River virus (RRV) disease. No other infective cause was identified. A renal biopsy 28 days after the onset of nephritis showed mild mesangial proliferative changes and one segmental sclerotic lesion. Immunofluorescence showed widespread linear deposition of IgG in glomerular capillary walls with similar but weak staining for IgM, complement (C3) and fibrinogen; granular deposits of IgM and C3 in several arterioles; and IgM in a few mesangial cells. No electron-dense deposits were detected, nor was RRV antigen found in the renal tissue. Anti-glomerular basement membrane antibodies were not detected in the serum. Recovery from the renal disturbance was complete within three months although rheumatic symptoms persisted for 30 months.