A 6-year-old girl was admitted to the hospital with diffuse abdominal pain and discomfort during urination. She was diagnosed with gastroenteritis and urinary tract infection. Subsequently, the urine examination showed traces of proteins, some piocytes and Decoy cells, characteristics of a Polyoma virus infection. The diagnosis was confirmed by PCR in plasma and capsid antigen immunostaining in urine cells. Polyomavirus infection in children goes unnoticed unless the search for infected cells is carried out in the urine sediment. The viruses remain almost inactive until the adult life, where they can reactivate in immunocompromised individuals. In children with fever, painful urination, or increased nasopharyngeal secretion, it is important to always perform a study of the urinary sediment in search of Decoy cells, otherwise, primary Polyomavirus infections would go unnoticed. To our knowledge, only two cases of childhood primary infection have been reported so far, and this is the second.

Luis Alberto Palaoro is a renowned cytologist and researcher from the University of Buenos Aires, Argentina. He serves as a Consulting Professor at the School of Pharmacy and Biochemistry and Director of the Specialization Program in Cytology. His research focuses on Papillomavirus, Polyomavirus, and gynecological and testicular cancers. Recipient of three Lifetime Achievement Awards, he has authored seven scientific books, published over 100 research papers, and directed more than 150 graduate courses, making significant contributions to cytology and cancer research.