Track: Basic Science

Abstract:

[Background] Post inflammatory hyperpigmentation (PIH) is an acquired hypermelanosis following cutaneous inflammation, exogenous stimuli, or dermatologic procedures. Depth of pigment deposition is prognostically important, influencing response to therapy. While epidermal PIH often improves with topical agents and peels, dermal PIH may be refractory, making pigment depth assessment essential for optimal laser selection. The aim of this study is to quantitatively characterize pigmentation and melanophage distribution in PIH across anatomical sites, inflammatory etiologies (lichenoid, interface, or spongiotic) and Fitzpatrick skin types (FST). [Methods] Fontana-Masson-stained biopsy specimens (n=96) obtained from an institutional database between 2013 to 2023 were analyzed using ImageJ software. Five parameters were measured: epidermal pigmentation intensity, dermal pigmentation intensity, melanophage area, melanophage count, and melanophage depth. Analyses included descriptive statistics, Kruskal-Wallis testing, and multivariate linear regression adjusted for inflammatory etiology, FST, and sun exposure. [Results] Epidermal pigmentation intensity varied significantly by etiology, FST, and sun exposure, with increased pigmentation scores in spongiotic dermatitis, FST 5–6, and sun-exposed sites (p<0.05). Dermal melanophage area and count showed significantly higher scores in patients with FST 5–6 (p< 0.05), but no significant differences were seen by etiology or sun exposure. Melanophage depth showed no significant variation by any variable. In adjusted analyses, FST 5–6 remained independently associated with increased melanophage area and count, while sun exposure was associated with increased dermal pigmentation. [Discussion] FST is positively correlated with dermal melanophage area and count in PIH, while melanophage depth is independent of skin type, etiology, and sun exposure. These findings may inform device selection and treatment parameters for PIH.

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Hye Jin Chung