Treatment of Acquired Dermal Macular Hyperpigmentation With Oral Isotretinoin: A Multi‐Institutional Retrospective Study of 121 Cases

The term acquired dermal macular hyperpigmentation (ADMH) was introduced to unify Riehl's melanosis (RM), lichen planus pigmentosus (LPP), and related entities. These are cosmetically distressing pigmentary disorders that pose therapeutic challenges. To investigate the efficacy and safety of oral isotretinoin in treating ADMH, we conducted a muticenter retrospective study of patients with ADMH treated with oral isotretinoin between 2014 and 2024. Patients from Australia, China, Europe, India, Middle East, North America, and North Africa were included. Patients lost to follow-up before two visits were excluded. The response was graded by a 5-point Investigator's Global Assessment (IGA) scale. A total of 121 patients were included. Most patients (64.5%) were treated with a dose of 20 mg/d for an average of 8 months. Oral isotretinoin improved the severity of pigmentation in all RM and 85 (90.4%) LPP patients, with 17 (63.0%) RM and 31 (33.0%) LPP patients achieving marked improvement. RM patients responded better than LPP patients (p = 0.005). Patients with localized lesions (p = 0.0012), disease duration of less than 5 years (p = 0.046 for RM, p = 0.0272 for LPP), Fitzpatrick skin phototypes III-VI (p = 0.0081), or longer duration of treatment (p = 0.0178) responded better. Oral isotretinoin appears to be a promising treatment modality for ADMH.