Melasma, one of the most common acquired hyperpigmentary disorders among Asians, remains a therapeutic challenge. Although much is known about its predisposing and aggravating factors, including female gender, genetics, sun-exposure and hormonal influence, its pathogenetic mechanisms are not fully understood; however much progress has been made in recent years.
What began as an immunohistopathological understanding of this condition, from the increase in melanogenesis and melanocytosis to the disturbance of the basement membrane and increase in dermal vasculature and mast cells, has evolved into molecular elucidation of the signaling pathways. Upregulation of melanin biosynthesis-related genes and melanocyte markers demonstrated through transcription analysis of melasma lesions, participation of non-coding RNA like H19 gene, involvement of the Wnt signaling pathways (reduced WIF-1 expression), and overexpression of VEGF are some examples. However these innovative findings have not or are yet to be translated into clinical interventions.
Skin lightening agents and sun-protection still remain as the therapeutic mainstay for melasma. Combination therapy based on Kligman formula has achieved better results than monotherapy. However a subset of patients with melasma remains refractory to this intervention. Addition of oral tranexamic acid can be helpful, and its benefits have been consistently reproduced by different investigators. How this antifibrinolytic agent works in reducing melanogenesis specific to melasma still bewilders researchers, but its effects on mast cells and dermal vasculature have been demonstrated. The demand for laser and light interventions for treatment of melasma is high, driven partially by the economic returns of such procedures. The results from intense pulse light are inconsistent, but low-fluence, repeated “laser toning” has achieved satisfactory lightening of melasma but with possible risks of rebound hyperpigmentation and guttate leukoderma. Fractional laser ablation, whether carbon dioxide or thulium fiber, has also shown to be beneficial.
Despite all these interventions, melasma relapses and continues to vex patients and challenge clinicians. It remains an art to treat melasma.