LAUSR

BACKGROUND Nephrotic syndrome (NS) is one of the most common kidney disorders seen by pediatric nephrologists and is defined by the presence of heavy proteinuria (>3.5 g/24 h), hypoalbuminemia (<3.5 g/dL), edema, and hyperlipidemia. Most children with NS are steroid-responsive and have a good prognosis following treatment with prednisolone. However, 10%-20% of them have steroid-resistant nephrotic syndrome (SRNS) and fail to respond to treatment. A significant proportion of these children progress to kidney failure. METHODS This retrospective study aimed to determine the underlying genetic causes of SRNS among Omani children below 13 years old, over a 15-year period and included 77 children from 50 different families. We used targeted Sanger sequencing combined with next-generation sequencing approaches to perform molecular diagnostics. RESULTS We found a high rate of underlying genetic causes of SRNS in 61 (79.2%) children with pathogenic variants in the associated genes. Most of these genetically solved SRNS patients were born to consanguineous parents and variants were in the homozygous state. Pathogenic variants in NPHS2 were the most common cause of SRNS in our study seen in 37 (48.05%) cases. Pathogenic variants in NPHS1 were also seen in 16 cases, especially in infants with congenital nephrotic syndrome (CNS). Other genetic causes identified included pathogenic variants in LAMB2, PLCE1, MYO1E, and NUP93. CONCLUSION NPHS2 and NPHS1 genetic variants were the most common inherited causes of SRNS in Omani children. However, patients with variants in several other SRNS causative genes were also identified. We recommend screening for all genes responsible for SRNS in all children who present with this phenotype, which will assist in clinical management decisions and genetic counseling for the affected families.