In clinical practice, detection of HCMV-specific IgM antibodies, as a rule, requires an interpretation, because it could be due not only to a PI, but also to: (i) NPI or persistence of IgM after PI; (ii) polyclonal activation or cross-reactivity during other infections, such as rubella, parvovirus B19, or others. This evidence concerns the gene CD40LG and infection.