Alongside the development of early-onset severe DCM associated with biallelic mutations, missense and splice donor RPL3L variants such as p.Val262Met, p.Ala75Val and c.1167+1G>A have also been associated with prolonged electrocardiographic P-wave duration and atrial fibrillation (AF) [11,12], while the p.R242W variant has been identified as a modifier for catecholaminergic polymorphic ventricular tachycardia (CPVT) seen in siblings carrying a homozygous agrin (AGRN) gene variant [13]. The gene discussed is AGRN; the disease is familial dilated cardiomyopathy.