The genetic landscape of autosomal dominant polycystic kidney disease in Kuwait

Background Autosomal dominant polycystic kidney disease (ADPKD) is the most common renal monogenic disease, characterized by bilateral accumulation of renal fluid-filled cysts leading to progressive renal volume enlargement and gradual impairment of kidney function, often resulting in end-stage renal disease. Kuwait could provide valuable genetic insights about ADPKD, including intrafamilial phenotypic variation, given its large household size. This study aims to provide a comprehensive description of the pathogenic variants linked to ADPKD in the Kuwaiti population using multiple genetic analysis modalities and to describe and analyse the ADPKD phenotypic spectrum in terms of kidney function, kidney volume and renal survival. Methods A total of 126 ADPKD patients from 11 multiplex families and 25 singletons were recruited into the study. A combination of targeted next-generation sequencing (tNGS), long-range polymerase chain reaction, Sanger sequencing and multiplex ligation-dependent probe amplification were utilized for genetic diagnosis. Clinical evaluation was conducted through renal function testing and ultrasonographic kidney volume analysis. Results We identified 29 ADPKD pathogenic mutations from 36 families achieving an overall molecular genetic diagnostic rate of 112/126 (88.9%), including 29/36 (80.6%) in families. A total of 28/36 (77.8%) families had pathogenic mutations in PKD1, of which 17/28 (60.7%) were truncating, and 1/36 (2.8%) had a pathogenic variant in the IFT140 gene. A total of 20/29 (69%) of the identified ADPKD mutations were novel and described for the first time, including a TSC2-PKD1 contiguous syndrome. Clinical analysis indicated that genetically unresolved ADPKD cases had no apparent association between kidney volume and age. Conclusion We describe for the first time the genetic landscape of ADPKD in Kuwait. The observed genetic heterogeneity underlining ADPKD along with the wide phenotypic spectrum reveal the level of complexity in disease pathophysiology. ADPKD genetic testing could improve the care of patients through improved disease prognostication, guided treatment and genetic counselling. However, to fulfil the potential of genetic testing, it is important to overcome the hurdle of genetically unresolved ADPKD cases. Lay Summary We explored the genetic landscape of autosomal dominant polycystic kidney disease (ADPKD) cases in Kuwait. Although genetic analysis revealed the causes of the majority of cases, 19.4% of the cases remain genetically unsolved. The observed genetic heterogeneity of ADPKD along with the wide phenotypic spectrum reveal the level of complexity in disease pathophysiology. ADPKD genetic testing could improve the care of patients through improved disease prognostication, treatment guidance, support of clinical trials and aid in genetic counselling. However, it is also important to overcome the hurdle of genetically unsolved ADPKD cases thorough improved genetic testing pipelines to ensure more effective implementation of ADPKD genetic testing in clinical setups.

Automated summary

This study describes the genetic landscape of autosomal dominant polycystic kidney disease (ADPKD) in Kuwait, revealing the genetic heterogeneity and wide phenotypic spectrum of the disease. ADPKD genetic testing could improve patient care, but the hurdle of genetically unsolved cases needs to be overcome.