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. 2020 Nov 26;9(12):3846.
doi: 10.3390/jcm9123846.

Clinical Implications and Gender Differences of KCNQ1 p.Gly168Arg Pathogenic Variant in Long QT Syndrome

Rebeca Lorca  1   2   3 , Alejandro Junco-Vicente  2 , Maria Martin-Fernandez  2   3 , Isaac Pascual  2   3 , Andrea Aparicio  2 , Noemi Barja  2   3 , Elias Cuesta-LLavona  1   3 , Luis Roces  4 , Pablo Avanzas  2   3 , Cesar Moris  1   2   3 , Eliecer Coto  1   3 , José Julían Rodríguez Reguero  1   2   3 , Juan Gómez  1   3
Affiliations

Clinical Implications and Gender Differences of KCNQ1 p.Gly168Arg Pathogenic Variant in Long QT Syndrome

Rebeca Lorca et al. J Clin Med. .

Abstract

Background: Long QT syndrome (LQTS) is an inheritable arrhythmogenic disorder associated with life-threatening arrhythmic events (LAEs). In general, patients with LQTS2 (KCNH2) and LQTS3 (SCN5A) are considered to be a greater risk of LAEs than LQTS1 (KCNQ1) patients. Gender differences are also important. Series analyzing families with the same pathogenic variants may help in the progress of elaborating strong specific genotype-phenotype management strategies. In this manuscript, we describe the phenotype of seven unrelated families, carriers of the KCNQ1 G168R pathogenic variant.

Methods: we identified all consecutive index cases referred for genetic testing with LQTS diagnosis carriers of KCNQ1 G168R variant. Genetic and clinical screening for all available relatives was performed.

Results: we evaluated seven unrelated families, with a total 34 KCNQ1 G168R carriers (two obligated carriers died without available EKGs to evaluate the phenotype). All index cases but one were women and three of them presented with aborted sudden cardiac death (SCD) or syncope. The presence of sudden death in these families is notable, with a total of nine unexplained sudden deaths and four aborted SCD. Phenotype penetrance was 100% in women and 37.5% in men.

Conclusions: KCNQ1 G168R is a pathogenic variant, with a high penetrance among women and mild penetrance among men. Risk for LAEs in this variant seems not negligible, especially among woman, and risk stratification should always be carefully evaluated.

Keywords: genetic testing; inheritable arrhythmogenic disorder; long QT syndrome.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
KCNQ1 G168R carriers: Family pedigrees. SD, sudden death. Age of deceased in patients due to SD, in brackets. Symbols denote sex and disease status: +, carriers; −, noncarriers; without sign, genetic status unknown; box, male; circle, female; black darkened, long QT syndrome phenotype (prolonged QTc in electrocardiogram); grey darkened, unexplained SD; symbol clear, negative phenotype (normal QTc); ?, unknown phenotype; slashed, deceased; arrow, proband.
Figure 1
Figure 1
KCNQ1 G168R carriers: Family pedigrees. SD, sudden death. Age of deceased in patients due to SD, in brackets. Symbols denote sex and disease status: +, carriers; −, noncarriers; without sign, genetic status unknown; box, male; circle, female; black darkened, long QT syndrome phenotype (prolonged QTc in electrocardiogram); grey darkened, unexplained SD; symbol clear, negative phenotype (normal QTc); ?, unknown phenotype; slashed, deceased; arrow, proband.
Figure 2
Figure 2
Two EKGs from Family 4. (A) Patient IV.5: genotype and phenotype positives. (B) Patient V.4: positive genotype and negative phenotype.
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