Clinical Presentation, Genetic Testing, and Outcome of Congenital Nephrotic Syndrome in KwaZulu-Natal, South Africa

Introduction: The aetiology of congenital nephrotic syndrome (CNS) is heterogenous with genetic and more rarely infectious or maternal allo-immune disease causes. In resource-replete settings, 60-80% of CNS is attributable to monogenic causes, with other causes much more rarely diagnosed. The relative prevalence of these aetiologies and differences in clinical presentation are understudied in southern Africans. We describe the aetiology, clinical presentation, outcomes, and results of genetic testing in black African infants with CNS. Methods: We enrolled 36 children with CNS from a tertiary referral center in KwaZulu-Natal, South Africa. Chart reviews were performed to identify aetiology, clinical features, and outcomes. Genetic testing for variants in NPHS1, NPHS2, WT1, LAMB2, and PLCE1 was performed for a subset of 9 children with CNS without infection. Results: Of the 36 CNS cases, 15 (41.7%) children were diagnosed with infection-associated CNS: 11 (30.6%) with cytomegalovirus (CMV) and 4 (11.1%) with human immunodeficiency virus (HIV). Twenty-one (58.3%) of the cases had unknown aetiology after the exclusion of other non-genetic causes, nine of whom underwent genetic testing yielding a genetic diagnosis for 3 (33.3%) of the 9: 2 (22.2%) children were homozygous for NPHS1 p.R460Q and one for NPHS2 p.V260E. There were no differences in age of diagnosis, age at kidney failure, age of death or kidney function markers between the group of infants with CNS attributed to infection and those without infection (p> 0.05). Infants with monogenic CNS experienced, on average, an earlier diagnosis (mean age 28 days, SD 11)) than those with infection-associated CNS (43 days, SD 19.11). Conclusion: South African black children are diagnosed with high rates of CNS attributed to untreated maternal CMV and HIV infections likely resulting from limited prenatal maternal care in this population. The diagnostic genetic yield was much less than expected compared to larger studies in Western settings, indicating a need for further investigation of the genetic landscape of CNS in African populations.