Autosomal Recessive Adolescent Syndromic Nephronophthisis Caused by a Novel Compound Heterozygous Pathogenic Variant

BACKGROUND Nephronophthisis, an autosomal recessive ciliopathy involving mutations in primary cilium genes, is characterized by chronic tubulointerstitial nephritis and a defective urine concentrating capacity. It accounts for about 5% of renal failure in children and adolescents and usually progresses to end-stage renal disease before the age of 30 years. Nephronophthisis is associated with extrarenal manifestations, including retinitis pigmentosa in Senior-Loken syndrome (SLS), and liver fibrosis in 10-20% of cases. While some presenting patterns could be characteristic, patients may have atypical presentation, making diagnosis difficult. Tubulointerstitial fibrosis is the predominant feature on histology and as such, diagnosis depends mostly on genetic testing. Despite advances in renal genomics over the years with a better understanding of primary cilia and ciliary theory, about 40% of nephronophthisis cases go undiagnosed. As the underlying genetic etiologies are not fully understood, morphologic pathologic findings are non-specific, and treatment options are limited to dialysis and transplantation. CASE REPORT We describe a unique case of a patient with adolescent nephronophthisis who presented with advanced chronic kidney disease and severe pancytopenia, who progressed to end-stage renal disease at the age of 19, and was found to have syndromic nephronophthisis with compound heterozygous inheritance. CONCLUSIONS This report highlights the atypical presentation patterns that can be seen in syndromic nephronophthisis, the importance of genetic diagnosis when there is a high index of suspicion, and the need to further study genetic variants to better understand and diagnose the disease and to develop targeted therapy.