The possible role of human papillomavirus infection in the development of lichen sclerosus.

Lichen sclerosus (LS) is a chronic inflammatory skin disease of unknown origin predominantly affecting the anogenital area that causes pruritus and pain and is associated with an increased risk of malignancy. In some cases, LS vanishes after application of imiquimod, raising the question whether human papillomavirus (HPV) may have an etiopathogenic role in anogenital LS. The databases MEDLINE and Embase were systematically searched using the PRISMA guidelines. Twenty-seven papers were included that reported the prevalence of HPV in LS and in LS associated with neoplasia. HPV was identified in 0-80% (median 22%) of all LS cases. The prevalence of HPV was higher among male patients with LS (median 29%) than among female patients (median 8%). HPV16 was the most prevalent genotype, but the distribution of genotypes indicates that even low-risk HPV can cause LS. The diverging detection rates are probably due to small sample sizes in the reviewed papers and different detection methods. Factors possibly underestimating the prevalence of HPV are a selective search for high-risk HPV, DNA destruction in fixed tissue, focally residing HPV, and possibly a clearing of HPV before the time of biopsy. Seventy-five percent of sexually active people acquire HPV during their lifetime, thus HPV alone is not a cause of LS. Genetic and immunological host factors and viral factors other than type are likely to contribute. Future studies should include patients with a short duration of symptoms, and biopsies should be multiple and fresh.