Clinical Utility of Genetic Testing with Geographical Locations in ADPKD: Describing New Variants

TL;DR

This study identifies new genetic variants in ADPKD patients and explores their geographical distribution and impact on kidney survival.

Contribution

The study reports 33 new PKD1 and six new PKD2 gene variants in ADPKD, contributing to a more detailed genetic map of the disease.

Findings

33 new PKD1 gene variants and six new PKD2 gene variants were identified, likely affecting protein function.

Truncated PKD1 variants were associated with lower renal survival compared to missense variants.

Geographical distribution of variants was analyzed, aiding in understanding disease patterns.

Abstract

Background: Our study aims to comment on all ADPKD variants identified in our health area and explain how they are distributed geographically, to identify new variants, and relate the more frequent variants with their renal phenotype in terms of kidney survival. Materials and Methods: We identified patients suffering from ADPKD in a specialized consultation unit; genealogical trees were constructed from the proband. According to the ultrasound-defined modified Ravine–Pei criteria, relatives classified as at risk were offered participation in the genetic study. Socio-demographic, clinical, and genetic factors related to the impact of the variant on the survival of the kidney and the patient, such as age at RRT beginning and age of death, were recorded. Results: In 37 families, 33 new variants of the PKD1 gene were identified, which probably produce a truncated protein. These variants included 2 large deletions, 19 frameshifts, and 12 stop-codons, all of which had not been previously described in the databases. In 10 families, six new probably pathogenic variants in the PKD2 gene were identified. These included three substitutions; two deletions, one of which was intronic and not associated with any family; and one duplication. A total of 11 missense variants in the PKD1 gene were grouped in 14 families and classified as probably pathogenic. We found that 33 VUS were grouped into 18 families and were not described in the databases, while another 15 were without grouping, and there was only 1 in the PKD2 gene. Some of these variants were present in patients with a different pathogenic variant (described or not), and the variant was probably benign. Renal survival curves were compared to nonsense versus missense variants on the PKD1 gene to check if there were any differences. A group of 328 patients with a nonsense variant was compared with a group of 264 with a missense variant; mean renal survival for truncated variants was lower (53.1 ± 0.46 years versus non-truncated variant 59.1 ± 1.36 years; Log Rank, Breslow, and Tarone Ware, p < 0.05). Conclusions: To learn more about ADPKD, it is necessary to understand genetics. By describing new genetic variants, we are approaching creation of an accurate genetic map of the disease in our country, which could have prognostic and therapeutic implications in the future.

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