CD44 and lichen sclerosus et atrophicus: Topical application of one of these retinoids, retinaldehyde (RAL), a natural retinoid immediate precursor of retinoic acid (RA), restores the epidermal thickness and CD44 expression which are correlated with clinical improvement in lichen sclerosus et atrophicus (LSA) lesions [9], where the epidermal expression of CD44 has been shown to be decreased or absent [10].