As CMV IgM antibodies can persist for months after primary infection or reappear during recurrent infection,[10,11] urine CMV culture positivity and positive blood CMV antigen are confirmatory of the diagnosis of true CMV infection in practice.[12] In the present study, among 40 pediatric patients with EBV and CMV IgM dual positivity during the acute phase of infectious mononucleosis, only 3 patients (7.5%) were positive for the additional serum CMV antigenemia assay, urine CMV PCR or urine CMV culture. The gene discussed is CD40LG; the disease is cytomegalovirus infection.