Description
The p.Gly179Ser variant in KCNQ1 has been reported in the heterozygous state in at least 3 individuals with autosomal dominant long QT syndrome (LQTS), one of whom had a more severe phenotype and carried a presumed pathogenic variant in another LQTS gene (Splawski 2000, Kapplinger 2009, Fernandes 2015, Natarajan 2016). It has also been reported in the homozygous or compound heterozygous state in 4 individuals with severe autosomal recessive LQTS (AR-LQTS) and segregated with AR-LQTS in 3 affected relatives from 2 families (Westenskow 2004, Giudicessi 2013, Vyas 2016, Bdier 2017). Individuals with AR-LQTS typically had a more severe phenotype with an earlier age of onset than heterozygotes, but none were reported to have hearing loss. Relatives of these individuals who were heterozygous carriers of this variant were often clinically asymptomatic or had modestly prolonged QT interval; however 1 heterozygous carrier experienced sudden cardiac death (Westenskow 2004, Giudicessi 2013, Bdier 2017), suggesting reduced penetrance and variable expressivity for the autosomal dominant form of LQTS associated with this variant. In vitro functional studies and computational prediction tools support an impact on protein function (Westenskow 2004, Huang 2018). This variant has been reported by other clinical laboratories in ClinVar (Variation ID 53063) and was absent from large population studies. In summary, this variant meets criteria to be classified as pathogenic for autosomal dominant and autosomal recessive LQTS. ACMG/AMP Criteria applied: PM3_Strong, PM2, PP1_Moderate, PP3, PS3_Supporting, PS4_Supporting.
| # | Sample | Method | Observation |
|---|
| Origin | Affected | Number tested | Tissue | Purpose | Method | Individuals | Allele frequency | Families | Co-occurrences |
|---|
| 1 | germline | unknown | not provided | not provided | not provided | | 2 | not provided | 2 | not provided |
