23/04/2023
Lichen planus pigmentosus (LPP) and erythema dyschromicum perstans (EDP) (also known as ashy dermatosis (AD)) are two conditions on the spectrum of dermal pigmentary disorders. LPP typically affects skin phototypes III-V and has involvement of sun exposed areas or intertriginous areas. It presents as irregularly shaped or oval grey-brown macules and patches that are typically asymptomatic, but can have mild pruritus and burning. EDP, on the other hand, presents as grey-brown macules and patches in sun-protected sites and may have an early inflammatory phase with an erythematous border. It is typically asymptomatic, but can also be mildly pruritic. There is significant histologic overlap between the two conditions including basal cell degeneration, a mild perivascular or band-like infiltrate in the upper dermis, and dermal melanophages. Multiple treatments for these conditions, including topical corticosteroids, topical calcineurin inhibitors, topical retinoids, chemical peels, minocycline, dapsone, hydroxychloroquine, isotretinoin, griseofulvin, and systemic steroids have been reported in the literature. However, none of these have been effective consistently. Tranexamic acid (TA) is a synthetic analog of lysine, and serves as a fibrinolytic agent by binding lysine sites on fibrinogen. Commonly used in surgery to prevent bleeding, it has recently been used in dermatology for the treatment of melasma. Melasma is a pigmentary disorder characterized by hyperpigmented patches in sun-exposed areas, often in response to hormones, sunlight, and other factors. The proposed mechanism of action of tranexamic acid in decreasing pigmentation in this condition is that it decreases inflammation by decreasing dermal angiogenesis and inhibits UV induced plasmin activity in keratinocytes. Plasmin activity can increase melanogenic factors, leading to increased pigmentation. In a study by Lee et al., when administered orally at a dose of 250mg twice daily over approximately 4 months, 89.7 % of patients had documented improvement in pigmentation. Of those who improved, the median lightening was approximately 50%, which is significant. Other studies have also shown promising results.
