The precise distribution pattern of pediatric renal diseases has seldom been reported especially for young children. In order
to clarify the incidence and distribution of renal diseases in children, 599 renal biopsy specimens obtained from 547 pediatric
patients (≦15 years old) were analyzed by routine light, electron and immunofluorescence microscopy. Among the total biopsy
cases, the most common renal disease identified in childhood was IgA glomerulonephritis (IgAGN; 37%). More than 80%
of patients with IgAGN were discovered by urinary screening at the school, showing asymptomatic proteinuria and/or
hematuria. The other major renal diseases were minor glomerular abnormality (12.2%), Henoch-Schönlein purpura nephritis
(HSPN; 10.6%), and thin basement membrane disease (7.1%). One of the major causes of pediatric nephrotic syndrome were
minimal change nephrotic syndrome (58%), whereas the other causes were IgAGN (11.6%), HSPN (8.9%), membranous
glomerulonephritis (5.4%), membranoproliferative glomerulonephritis (3.6%). In conclusion, IgAGN was the most common
renal disease also in children as in adolescence. From the age of seven years, the incidence of IgA-GN was highest among
all the pediatric renal diseases during whole childhood period, and the incidence and number of the patients increased as they
grow. On the other hand, there are also many cases with non-progressive clinical courses, such as minor glomerular abnormality
and thin basement membrane disease in children. The renal biopsy following routine urinary screening at the school
may be important for the therapeutic and prognostic guidelines of pediatric group of patients with renal diseases
