Although p.Cys217Tyr is not a de novo variant, taking into account the infection-related onset of DCM in early childhood, we suggest that the specific genotype/haplotype in the APOBEC3 family (i.e., a single copy of APOBEC3B damaged by the missense variant together with APOBEC3H hapIV) may have contributed to cardiomyopathy in this patient. This evidence concerns the gene APOBEC3B and familial dilated cardiomyopathy.