Rare Genetic Mutations Associated with Long QT Syndrome in Hong Kong Chinese Patients.

Congenital long QT syndrome (LQTS) is a type of cardiac ion channelopathy that increases the susceptibility of the affected individuals to spontaneous ventricular tachycardia/fibrillation or even sudden cardiac death. More than 17 subtypes have been identified. This was a systematic review of the published case series or reports on the clinical characteristics, genetic basis, and patient outcomes from Hong Kong with rare genetic variants of LQTS which fall outside the traditional LQTS classification system. PubMed and Zenodo were searched from the corresponding inception until January 15, 2022. Twenty-four studies were identified. Of these, one article met the inclusion criteria. The article included a case series of six patients from a cohort with 134 patients. They had either asymptomatic LQTS with HCN4 mutations (n = 1, c.1471G>A, QTc: 420 ms with prolonged QTc of 670 ms during the recovery phase of treadmill test), RYR2 (n = 1, c.7060G>A, QTc: 480 ms) or SCN10A (n = 2, c.3542C>T, QTc: 439 ms-480 ms), or LQTS with multiorgan syndromes with GATA3 mutations (n = 1, c. 815C>T, Barakat syndrome: Sensorineural deafness, hypoparathyroidism, and renal disease, QTc: 450-489 ms), or SLC6A8 (n = 1, c.691_693del; X-linked creatine transporter deficiency, with c.6065A>G mutation in AKAP9, known modifier of LQTS; QTc: 485 ms). In addition, rare genetic variants in non-LQTS causative genes were identified. Future studies should be conducted to compare the variants and investigate their functional consequences. [ABSTRACT FROM AUTHOR]