Low-dose excimer 308-nm laser for treatment of lichen planopilaris.

L ichen planopilaris (LPP) is a difficult-to-treat, chronic, inflammatory autoimmune disease targeting the hair follicle that eventually leads to permanent irreversible scarring alopecia. It commonly affects adult women on the central scalp with multifocal patches, perifollicular erythema, hyperkeratosis, and subjective complaints like pruritus or pain. Recently, a deficiency of the peroxisome proliferatoractivated receptor (PPAR) and disturbed lipid metabolism in the pilosebaceous unit were identified in LPP, with subsequent lymphocyte recruitment and upregulated cytokine expression provoking loss of adhesion of follicular keratinocytes. Based on this finding, treatment with the PPAR agonist pioglitazone was successfully tried in some cases, in addition to other current treatment options such as intralesional steroids, doxycycline, hydroxychloroquine, mycophenolate mofetil. For chronic inflammation, we hypothesized that UV-B excimer laser treatment might also be effective in LPP, since it has proven beneficial for certain inflammatory skin disorders that are mediated by lymphocytes and are responsive to psoralen plus UV-A therapy.