Genetic Markers Among the Israeli Druze Minority Population With End-Stage Kidney Disease

RATIONALE & OBJECTIVE

Genetic etiologies have been identified among approximately 10% of adults with chronic kidney disease (CKD). However, data are lacking regarding the prevalence of monogenic etiologies especially among members of minority groups. This study characterized the genetic markers among members of an Israeli minority group with end-stage kidney disease (ESKD).

STUDY DESIGN

A national-multicenter cross-sectional study of Israeli Druze patients (an Arabic-speaking Near-Eastern transnational population isolate) who are receiving maintenance dialysis for ESKD. All study participants underwent exome sequencing.

SETTING & PARTICIPANTS

We recruited 94 adults with ESKD, comprising 97% of the total 97 Druze individuals throughout Israel being treated with dialysis during the study period.

PREDICTORS

Demographics and clinical characteristics of kidney disease.

OUTCOME

Genetic markers.

ANALYTICAL APPROACH

Whole-exome sequencing and the relationship of markers to clinical phenotypes.

RESULTS

We identified genetic etiologies in 17 of 94 participants (18%). None had a previous molecular diagnosis. A novel, population-specific, WDR19 homozygous pathogenic variant (p.Cys293Tyr) was the most common genetic finding. Other monogenic etiologies included PKD1, PKD2, type IV collagen mutations, and monogenic forms of noncommunicable diseases. The pre-exome clinical diagnosis corresponded to the final molecular diagnosis in fewer than half of the participants.

LIMITATIONS

This study was limited to Druze individuals, so its generalizability may be limited.

CONCLUSIONS

Exome sequencing identified a genetic diagnosis in approximately 18% of Druze individuals with ESKD. These results support conducting genetic analyses in minority populations with high rates of CKD and for whom phenotypic disease specificity may be low.

PLAIN-LANGUAGE SUMMARY

Chronic kidney disease (CKD) affects many people worldwide and has multiple genetic causes. However, there is limited information on the prevalence of genetic etiologies, especially among minority populations. Our national-multicenter study focused on Israeli Druze patients. Using exome-sequencing, we identified previously undetected genetic causes in nearly 20% of patients, including a new and population-specific WDR19 homozygous pathogenic variant. This mutation has not been previously described; it is extremely rare globally but is common among the Druze, which highlights the importance of studying minority populations with high rates of CKD. Our findings provide insights into the genetic basis of end-stage kidney disease in the Israeli Druze, expand the WDR19 phenotypic spectrum, and emphasize the potential value of genetic testing in such populations.

MO046: Exome sequencing of Israeli Druze individuals on dialysis reveals common as well as population- specific monogenic etiologies in ∼30%

BACKGROUND AND AIMS

Genetic etiologies are estimated to affect ∼10% of adults with advanced CKD. However, significant population disparities in genetic kidney disease exist and population-based screening are lacking especially among minority groups. The Druze population is a middle-eastern minority with high rates of end-stage renal disease (ESRD) and consanguinity, which suggests high rates of population-specific monogenic CKD etiologies. We therefore hypothesized that by exome sequencing we will identify a unique distribution of monogenic ESRD causes as compared with prior studies and that important ramifications for clinical practice may ensue.

METHOD

We initiated a national multicenter study of all Israeli dialysis units in order to provide comprehensive evidence for ESRD's genetic basis (Israeli ESRD Genetic Consortium Cohort). Specifically, during 2020, we recruited 97% (n = 94) of Israeli Druze individuals on dialysis from 12 different hospitals and community-based units. We conducted exome sequencing and diagnostic analysis for all patients. We assessed the diagnostic yield of genetic analysis and its relation to baseline clinical phenotypes.

RESULTS

Overall, the cohort consists of 94 individuals from 91 different families with first-degree consanguinity rate of 28%. Participants mean age was 62 years (ranging from 18 to 88 years). Most common primary clinical diagnoses were diabetic kidney disease, nephropathy of unknown origin, glomerular or cystic kidney disease, together encompassing 90% of all cases. None had previous molecular diagnosis. Using exome sequencing, we identified a genetic etiology in 27 out of 94 (28.7%) participants. We identified WDR19 (NPHP13) homozygous mutation c.878G > A (p.C293Y) as the most common genetic diagnosis (5.3%). Follow-up clinical characterization revealed that all affected individuals exhibited non-syndromic adulthood-onset ESRD, supporting a profound mutation-dependent phenotypic heterogeneity and weak pre-exome phenotypic specificity. Other prevalent genetic diagnoses included type IV collagen, PKD1, PKD2 and UMOD mutations as well as monogenic forms of diabetes and hyperlipidemia. Molecular diagnosis corresponded to the pre-exome clinical diagnosis in only one-third of the participants.

CONCLUSION

Exome sequencing in Druze with ESRD yields a genetic diagnosis in just <30% of cases with WDR19 mutation being the most prevalent single-gene etiology. These results, which remarkably inform clinical management, emphasize the importance of revealing population-specific mutations given the underutilization of genetic testing, particularly among adult minorities.