Lichen sclerosus (LS) is a chronic inflammatory dermatosis that results in white plaques with epidermal atrophy and scarring. Lichen sclerosus has both genital and extragenital presentations and also goes by the names lichen sclerosus et atrophicus (dermatological literature), balanitis xerotica obliterans (glans penis presentation), and kraurosis vulvae (older description of vulvar presentation). An increased risk of squamous cell carcinoma may exist in genital disease, but the precise increase in risk and what cofactors (human papillomavirus infection or prior radiotherapy) may be involved are not yet completely defined. In patients who have been treated for vulvar cancer, the presence or absence of lichen sclerosus does not appear to affect the timing of recurrence. In large series, genital presentations, both vulvar and penile, outnumber extragenital reports by more than 5:1.
Inflammation and altered fibroblast function in the papillary dermis leads to fibrosis of the upper dermis. Genital skin and mucosa are affected most frequently, but extragenital lichen sclerosus does occur, and even rare oral presentations are reported. The role that hypoxia and ischemia have in the initial cellular and vascular damage is supported by the finding of increased glut-1 and decreased vascular endothelial growth factor (VEGF) expression in affected skin.  The effect of cell-mediated cytotoxicity has been better defined at the biochemical level.  Systemic disease or involvement of other organ systems, unlike scleroderma, is not described, although many more authors are describing lichen sclerosus and scleroderma as closely related entities; many cases of coexistent lichen sclerosus/scleroderma having been reported.
The population rate is unknown. Male genital lichen sclerosus is seen almost exclusively in uncircumcised or incompletely circumcised men and boys. The rate of circumcision in a given population would thus influence the rate in this subset.
Lichen sclerosus, both genital and extragenital, has no known racial predilection. A genetic predisposition, based on family clustering, is apparent. 
The male-to-female ratio is 1:6, with female genital cases making up the bulk of reports.
Up to 15% of cases are in children with the majority being vulvar presentations. A study of foreskins submitted after therapeutic circumcision for phimosis revealed many cases of unrecognized lichen sclerosus. Extragenital lichen sclerosus is rare in children.
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