Glomerular basement membrane thickness in children. A morphometric study.
Measurements of glomerular basement membrane (GBM) thickness in children with minimal change nephrotic syndrome were made on electron micrographs of 43 biopsy specimens obtained from 35 children aged 1-13 years, of whom 13 were in remission at the time of biopsy. Measurements were also made in 2 children with non-glomerular disorders. A mean of 189 measurements per biopsy were made, using prints of x6,400-12,000 magnification. Quadratic curves were fitted by regression analysis to the mean GBM thickness for each of the 35 initial nephrotic biopsies, plotted against age for the whole group and separately for sex, race and the presence or absence of proteinuria at the time of biopsy. There were no significant differences in race or proteinuria, but there was a trend towards a thicker GBM in young males which disappeared by 9 years of age. From the mean +/- 2 SD of GBM thickness for each of the 35 initial nephrotic biopsies the calculated thickness ranged from 100-340 nm at 1 year of age to 190-440 nm at 9 years of age and older. The growth curve for GBM thickness increases steeply initially, reaching a plateau at 9 years of age. Because there was no significant difference between proteinuric patients and those in remission, while measurements in the nephrotic syndrome and non-glomerular disorders closely agreed, we believe that our results demonstrate the normal GBM thickness and growth pattern.