Phenotype and genotype of autosomal dominant tubulointerstitial kidney disease in a Japanese cohort.

Background: Autosomal dominant tubulointerstitial kidney disease (ADTKD) is characterized by tubular atrophy, interstitial fibrosis, and progressive kidney dysfunction. Its causative genes include UMOD, MUC1, REN, HNF1B, and SEC61A1. ADTKD contributes to unexplained chronic kidney disease (CKD), and many cases remain genetically undiagnosed. This study aimed to elucidate the clinical features of patients genetically diagnosed with ADTKD in Japan.

Methods: We included individuals with suspected congenital anomalies of the kidney and urinary tract, nephronophthisis, polycystic kidney disease, or ADTKD. Genetic analyses using direct sequencing, short-read next-generation sequencing (SRS), and/or long-read next-generation sequencing (LRS) were performed on 1097 families. Patients with ADTKD-HNF1B were excluded due to prior reporting.

Results: Variants in UMOD, MUC1, REN, and SEC61A1 were identified in 52 patients from 40 families (18, 16, 5, and 1 family, respectively). The median age at diagnosis was 38.5 years, and the urinary protein-to-creatinine ratio was 0.05 g/gCr. End-stage kidney disease was present at diagnosis in 37% of patients. Genetic testing was performed in 58% due to suspected ADTKD based on pathology or clinical course and in 38% due to unexplained CKD. Kidney biopsies were performed in 55%, with ADTKD confirmed pathologically in 41%. SRS and LRS were used in 55% and 30% of all families, respectively; for ADTKD-MUC1, 75% of families were analyzed using LRS.

Conclusions: Clinical and pathological diagnosis of ADTKD remains challenging, emphasizing the importance of comprehensive genetic testing. Enhanced access to advanced genetic testing such as LRS is essential to improve diagnostic precision and management.