Detection and sequences of human papillomavirus DNA in nongenital seborrhoeic keratosis of immunopotent individuals

BACKGROUND: The etiology of seborrhoeic keratosis (SK) is unknown. Its clinical and histopathological similarities to verrucae vulgaris and condyloma acuminatum prompted us to examine whether human papillomavirus (HPV) is present in SK lesions. In the present study, HPVs were frequently detected from genital lesions or hair follicle in immunocompromised host. OBJECTIVE: We analyzed 104 nongenital SK specimens diagnosed by clinical and histopathological examinations for HPV DNA in immunopotent individuals. METHOD: We analyzed SK specimens for HPV DNA using in situ hybridization (ISH), polymerase chain reaction (PCR), Southern blot hybridization, and sequencing of viral DNA of PCR-amplified fragments. And we also examined virion, which is the capsid protein of HPV in ISH-positive specimens by immunochemical examination. We identified eight mucosal and two cutaneous type HPVs. RESULT: ISH revealed that 30 of 104 (28.8%) SK samples contained HPV DNA. All ISH-positive specimens were demonstrated virion in the nuclei of the epidermal keratinocytes. PCR analysis showed that 87 (83.7%) samples contained HPV-18, 81 (77.9%) HPV-6, and 73 (70.2%) contained both HPV-18 and -6. The incidence of HPV-1 (7.7%) and HPV-2 (14.4%) was relatively low. All 20 normal controls were negative for HPV DNA by ISH but seven were positive by PCR sequencing. CONCLUSION: Our results suggest that HPV, possibly coinfection with HPV-6 and -18 and unknown type(s) of HPV, plays an important role in the pathogenesis of SK.