[Studies on urinary protein components in renal diseases in children. I--Characteristics of urinary protein components in renal diseases in children, with a focus on the relationship between IgA nephropathy and urinary IgA excretion].

Urinary protein components in children with renal disease were analyzed by the Reversed-Single Radial Immunodiffusion (R-SRID) method. The results were as follows: (1) In idiopathic nephrotic syndrome, the percentage of urinary albumin excretion was very high (79.5%). Urinary IgA excretion was 0.1% and IgG excretion was 1.6%, hence the excretion of these high-molecular-weight proteins amounted to 1.7% of the total urinary protein. (2) In membranous glomerulonephritis, urinary IgA was not detected, whereas the percentage of urinary IgG excretion was high (5.4%). (3) The percentage of urinary IgA excretion was higher in IgA nephropathy (IgAN) and Henoch-Schönlein purpura nephritis (HSPN) (2.4%, 1.6% respectively) than in other diverse renal diseases. (4) The percentage of urinary IgA excretion was correlated significantly with the serum IgA concentration in IgAN and HSPN (P < 0.001), but there was no such correlation in other diverse renal diseases. (5) In IgAN, the percentage of urinary IgA excretion was significantly higher in the subgroup with a duration of less than one year from the onset (3.6%) than in the subgroup with a duration longer than one year (1.5%) (p < 0.01).