Lichen sclerosus. Light micrograph of a section through skin affected by lichen sclerosus et atrophicus (LS). LS is an uncommon disease of unknown cause that results in thin, smooth, white patches (plaques) on the skin around the genitals. The disease causes thinning and wasting (atrophy) of the epidermis (dark pink, top). This atrophy is associated with hyalinization of the underlying dermis (light pink).