BAG3 and familial dilated cardiomyopathy: BAG3 variants, including the missense BAG3 c.626C>T; p.(Pro209Leu) (proline-to-leucine substitution at codon 209, impairing co-chaperone function), are linked to early-onset DCM, VAs, and progression to advanced heart failure, with ventricular ectopy, LV dilatation, and myocardial fibrosis on CMR emerging as key markers of risk [23].