Influence of oral isotretinoin treatment on the composition of comedonal lipids. Implications for comedogenesis in acne vulgaris.

One of the primary events in the pathogenesis of acne vulgaris is abnormal follicular keratinization. Since oral isotretinoin therapy reduces follicular hyperkeratinization in acne, our study has been designed to determine whether epidermal lipid composition of the epithelium of sebaceous follicles is affected by isotretinoin treatment. Noninflamed early comedones obtained from ten patients with nodulocystic acne before and after the 6th week of isotretinoin therapy (mean daily dose 0.7 mg/kg b. wt.) were used as probes of the hyperkeratinizing follicular epithelium. Comedonal lipids were analyzed by high-performance thin-layer chromatography. Oral isotretinoin caused a decrease of the comedonal glyceride fraction by 36% (P less than 0.01), whereas free sterols and total ceramides increased by 34% (P less than 0.10) and 19%, respectively. The changes of comedonal lipids were associated with a significant elevation of the free sterols/cholesterol sulfate ratio of 86% from pretreatment levels (P less than 0.05). The isotretinoin-induced changes of the comedonal lipid composition in direction to a pattern of epidermal lipids of normal desquamating stratum corneum are discussed as a possible comedolytic mechanism of oral isotretinoin treatment.