SCN5A mutations in 442 neonates and children: genotype-phenotype correlation and identification of higher-risk subgroups.

Aims: To clarify the clinical characteristics and outcomes of children with SCN5A-mediated disease and to improve theirrisk stratification. Methods and results: A multicentre, international, retrospective cohort study was conducted in 25 tertiary hospitals in 13 countries between1990 and 2015. All patients <_16 years of age diagnosed with a genetically confirmed SCN5A mutation wereincluded in the analysis. There was no restriction made based on their clinical diagnosis. A total of 442 children{55.7% boys, 40.3% probands, median age: 8.0 [interquartile range (IQR) 9.5] years} from 350 families wereincluded; 67.9% were asymptomatic at diagnosis. Four main phenotypes were identified: isolated progressive cardiacconduction disorders (25.6%), overlap phenotype (15.6%), isolated long QT syndrome type 3 (10.6%), and isolatedBrugada syndrome type 1 (1.8%); 44.3% had a negative electrocardiogram phenotype. During a medianfollow-up of 5.9 (IQR 5.9) years, 272 cardiac events (CEs) occurred in 139 (31.5%) patients. Patients whose mutationlocalized in the C-terminus had a lower risk. Compound genotype, both gain- and loss-of-function SCN5A mutation,age <_1 year at diagnosis in probands and age <_1 year at diagnosis in non-probands were independent predictorsof CE.Conclusion In this large paediatric cohort of SCN5A mutation-positive subjects, cardiac conduction disorders were the mostprevalent phenotype; CEs occurred in about one-third of genotype-positive children, and several independent riskfactors were identified, including age <_1 year at diagnosis, compound mutation, and mutation with both gain- andloss-of-function.