Assessing the Efficacy and Safety Profiles of 0.025% Tretinoin in Treating Axillary Hyperpigmentation with Acanthosis Nigricans: a Randomized Double-blinded Study

Acanthosis nigricans (AN) is a dermatological condition, marked by hyperpigmentation and skin thickening, frequently affecting body folds like the axillae. Treatment options for axillary hyperpigmentation remain underexplored. This study evaluated the efficacy of 0.025% tretinoin cream in treating axillary hyperpigmentation associated with AN. In a randomized, intra-individual, split-side design study, participants applied 0.025% tretinoin cream on one axilla and a cream-based on the other. The study spanned 12 weeks, with topical application for the first 8 weeks, followed by a 4-week cessation period. Efficacy was measured using the melanin (M) index via narrowband reflectance spectrophotometry. Overall success was evaluated through investigator- and participant-global evaluation (IGE and PGE) scales, with adverse effects monitored. Twenty participants completed the study. The 0.025% tretinoin cream significantly reduced hyperpigmentation compared to the control (p < 0.001). By week 8, the mean M index reduction with tretinoin was 28.05%±12.20%, versus 6.55%±12.66% with the control. Hyperpigmentation reappeared partially after treatment cessation. By week 8, 75% of participants in the tretinoin group achieved more than 75% improvement in IGE, compared to 35% in the cream-based group. Similarly, 75% of the tretinoin group reported more than 75% improvement in PGE, whereas only 15% of the cream-based group achieved more than 50% improvement. Adverse effects were mild and included slight erythema, peeling, and itching. The 0.025% tretinoin cream significantly improved AN patients' axillary hyperpigmentation, demonstrating a safe and effective treatment option with minimal side effects.