A genotype-phenotype correlation does not seem to exist, especially as one individual with isolated CCDD was compound heterozygous for two apparently COL25A1 null alleles, such as the nonsense variant c.1489G > T; p.(Gly497*) in exon 28 and the intragenic ~124-kb deletion [2, 3]. Here, COL25A1 is linked to atrial conduction disease.