Efficacy of Topical Hydroquinone 4% with or without Intradermal Autologous Platelet-rich Plasma in Lichen Planus Pigmentosus: A Split-face Randomized Controlled Trial

Abstract

Lichen planus pigmentosus (LPP) is a chronic acquired hyperpigmentation disorder predominantly affecting sun-exposed areas of the face and neck, for which effective treatment remains challenging. Platelet-rich plasma (PRP) contains growth factors and bioactive mediators, including transforming growth factor-β1 (TGF-β1) and macromolecular activators of phagocytosis, which may modulate melanocyte activity, inflammation, and dermal pigment clearance. This study evaluated whether intradermal autologous PRP provides additive benefit when combined with topical 4% hydroquinone (HQ) in patients with LPP.

In this randomized, single-blinded, split-face controlled trial, 15 patients received intradermal PRP injections on one randomly assigned side of the face at baseline, week 2, and week 4, while both sides received nightly topical 4% HQ throughout the 20-week study period. Outcomes included the melanin index measured by Mexameter®, the hemi-modified acquired macular hyperpigmentation and severity index (DPASI), patient satisfaction, and adverse events, assessed through week 20.

Both treatment arms showed significant reductions in melanin index from baseline to week 20. Earlier reductions were observed on the PRP-treated side, particularly among patients with mild disease and those naïve to PRP. These findings are consistent with PRP-mediated modulation of melanocyte activity and inflammatory pathways. However, no statistically significant between-side differences were detected at any time point, and effect sizes were small. DPASI scores improved modestly in both groups without significant intergroup differences, while patient satisfaction favored the PRP-treated side. Adverse effects were mild and transient.

In conclusion, PRP may exert early localized biological effects on pigmentation through growth factor-mediated mechanisms but did not confer a sustained or clinically dominant advantage over HQ monotherapy. PRP appears to be best positioned as a safe adjunctive therapy in selected patients with LPP.