Cytomegalovirus inclusions have been reported in perineal ulcers from immunosuppressed adults. The importance of this finding is unknown. We report the first pediatric case of cutaneous cytomegalovirus infection in an infant with congenital human immunodeficiency virus infection, presenting as a diaper dermatitis. Cytomegalovirus was cultured from the skin biopsy specimen, and characteristic inclusions were seen on hematoxylin-eosin-stained sections. Results of this biopsy specimen analysis prompted further investigation revealing disseminated cytomegalovirus infection, including retinitis. Aggressive pursuit of a pathogen in common conditions such as diaper dermatitis is strongly recommended in immunosuppressed pediatric patients.