Nephrotic Syndrome in the First Year of Life: Two Thirds of Cases Are Caused by Mutations in 4 Genes (<i>NPHS1</i>, <i>NPHS2</i>, <i>WT1</i>, and <i>LAMB2</i>)

First, two thirds of nephrotic syndrome manifesting in the first year of life can be explained by mutations in 4 genes only (NPHS1, NPHS2, WT1, or LAMB2). Second, NPHS1 mutations occur in congenital nephrotic syndrome only. Third, infants with causative mutations in any of the 4 genes do not respond to steroid treatment; therefore, unnecessary treatment attempts can be avoided. Fourth, there are most likely additional unknown genes mutated in early-onset nephrotic syndrome.