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. The gene discussed is APOBEC3B; the disease is infection.