Differences in kidney prognosis between congenital and infantile nephrotic syndrome.

Background: More than half of patients with congenital nephrotic syndrome (CNS) or infantile nephrotic syndrome (infantile NS) have a monogenic aetiology. This study aimed to clarify differences in the clinical course, genetic background, and genotype-phenotype correlation between CNS and infantile NS.

Methods: We enrolled patients who were diagnosed with CNS or infantile NS and referred to our hospital for genetic analysis and investigated the clinical characteristics and genetic background of patients with identified causative genes.

Results: Among 74 patients enrolled, disease-causing genetic variants were detected in 50 patients. The median age for developing kidney failure in the genetic CNS (n = 33) and genetic infantile NS (n = 17) groups with monogenic variants was 13.2 and 19.0 months, respectively (P = 0.13). The age at developing kidney failure was significantly earlier in CNS patients with genes other than NPHS1 than in CNS patients with NPHS1 variants (1.0 vs. 31.0 months; P < 0.001). In patients with pathogenic variants other than NPHS1, there was a significant difference in the age at developing kidney failure between CNS and infantile NS patients (1.0 vs. 15.0 months; P < 0.001). Of patients with NPHS1 variants, no infants with NS had any truncating variants or developed kidney failure during follow-up.

Conclusions: The onset of CNS or infantile NS affects the kidney prognosis in patients with genetic nephrotic syndrome. Among patients with pathogenic variants in the same gene, patients with infantile NS may have a milder genotype and better prognosis than those with CNS.