NPHS2 p.V290M mutation in late-onset steroid-resistant nephrotic syndrome
The most frequently mutated gene of steroid-resistant nephrotic syndrome (SRNS) is NPHS2. Current guidelines propose the sequencing of all NPHS2 exons only in childhood-onset SRNS. A cohort of 38 Hungarian patients with childhood-onset nephrotic-range proteinuria was screened for NPHS2 mutations. The frequency of the p.V290M mutation in late-onset SRNS was examined in the French and PodoNet cohorts. Of the 38 Hungarian patients screened, seven carried NPHS2 mutations on both alleles, of whom two—diagnosed with proteinuria through school screening programs at the age of 9.7 and 14 years, respectively—did not develop nephrotic syndrome in childhood. The first, an 18-year-old boy, homozygous for p.V290M, has never developed edema. The second, a 31-year-old woman—compound heterozygous for p.V290M and p.R138Q—was first detected with hypoalbuminemia (<30 g/l) and edema at the age of 24.3 and 27.5 years, respectively. Both patients currently have a normal glomerular filtration rate. The mutation p.V290M was carried by three of the 38 patients in the Hungarian cohort, by two of the 95 patients with late-onset SRNS in the PodoNet cohort and by none of the 83 patients in the French cohort. We propose that not only the p.R229Q variant, but also the p.V290M mutation should be screened in Central and Eastern European patients with late-onset SRNS.