HPV29-Associated Periungual Epidermoid/Verrucous Cyst

More than 230 human papillomavirus (HPV) types have been identified, and HPV infection has been implicated in the development of epidermoid cysts arising in hairless skin, such as the palms and soles. HPV-associated epidermoid cysts are defined by the presence of HPV DNA within the cyst epithelium, with HPV60 being the most frequently detected type. We report a rare case of an HPV29-associated periungual epidermoid/verrucous cyst with verrucous features in a healthy woman in her seventies. She presented with a painful keratotic lesion around the right third fingernail that had persisted for 2 years and was refractory to cryotherapy. Histopathological examination revealed a cystic structure lined by stratified squamous epithelium containing keratinized material, together with distinctive cytopathic changes in the cyst wall. DNA extracted from formalin-fixed paraffin-embedded tissue identified HPV29 by polymerase chain reaction and direct sequencing. RNA in situ hybridization demonstrated HPV29 E6/E7 mRNA signals throughout all layers of the cyst epithelium, indicating transcriptionally active infection. HPV29 is an alpha-papillomavirus that has only rarely been detected in cutaneous lesions. To our knowledge, this is the first report of an epidermoid/verrucous cyst caused by HPV29 and the first demonstration of transcriptionally active HPV29 infection by RNA in situ hybridization.