IgA nephropathy in Japanese children and adults: a comparative study of clinicopathological features.

A comparative clinicopathological study was retrospectively performed in 61 children and 51 adults with IgA nephropathy. Hematuria and/or proteinuria as a chance finding was the most common initial clinical sign, being observed in 82.0% of the children and in 52.9% of the adults. At renal biopsy, hypertension and severe proteinuria were found in 9.8 and 33.3% of the adults and in 0 and 14.8% of the children (both p less than 0.05), respectively. Elevations of blood urea nitrogen and serum creatinine were found at this time of biopsy in 21.6 and 9.8% of the adults, but in none of the children (p less than 0.001 and p less than 0.05, respectively). Histologically, focal glomerulosclerosis and tubular atrophy were found in 52.9% of the adults and in 32.8% of the children (p less than 0.05). However, some features of the disease seen in both groups were similar, including the incidences of IgA nephropathy, sex ratio, the mode of onset, incidences of gross hematuria, and high IgA levels in the sera. Furthermore, the relationships between the severity of proteinuria and renal lesions were similar: mesangial proliferation, glomerulosclerosis, and tubular atrophy increased with the degree of the severity of proteinuria. These results suggest that IgA nephropathy is essentially identical in children and adults, although adult patients tend to be further advanced in their disease course at the time of diagnosis, and that focal glomerulosclerosis with tubular atrophy is correlated with deterioration of renal function.