GNB5 and gnb5-related intellectual disability-cardiac arrhythmia syndrome: Consistent with previous reports,1–10 the carrier of a homozygous GNB5 missense variant on Ser81 presented with LADCI, the mild form of IDDCA (family W), while the nine individuals with biallelic loss-of-function (LoF) alleles due to truncating or splicing mutations displayed phenotypes corresponding to the severe end of the disease spectrum (families R and S, U and V, and X and Z).