Long-term follow up of renal function in IgA nephropathy.

Fifty one children with IgA nephropathy verified at biopsy have been followed up clinically and functionally for 0.4-16.8 years from the onset of symptoms. Renal function was evaluated by determining the glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) from the clearances of inulin and para-aminohippuric acid. Fifteen (29%) of the children had raised serum creatinine concentrations at the onset. Mean GFR was significantly lower than that of controls at the first investigation. During the follow up GFR and ERPF decreased and were significantly lower than in the controls after eight years of disease. The significant fall in renal function was found in children with proteinuria and especially in boys, in whom GFR and ERPF decreased from a mean (SEM) of 117 (5) and 616 (31) at 2.8 years to 97 (6) and 509 (36) ml/min/1.73 m2 at 7.5 years. Patients with raised serum creatinine concentrations at the onset had significantly lower GFRs, and patients with macroscopic haematuria at this time did not show decreased renal function at follow up. In conclusion, children with IgA nephropathy do not seem to have a benign clinical course. Boys with proteinuria show a significant decrease in renal function during follow up.