Molecular structure and concentration of melanin in the stratum corneum of patients with melasma.

Melasma is an abnormal acquired hyperpigmentation of the face of unknown origin, it is considered a single disease and very little has been found regarding its pathogenesis. It is usually assumed that melasma is due to excessive melanin production, but excessive retention or abnormal metabolism of this molecule has not yet been considered. In order to search for an alternate explanation for the excessive pigmentation in melasma the molecular structure and concentration of melanin in the stratum corneum of patients with melasma was analyzed using Raman spectroscopy and optical transmission spectroscopy, respectively. From this study it became apparent that in melasma melanin is concentrated in the deeper layers of the skin but its exteriorization remains the same as for healthy skin. Raman spectroscopy measurements showed degraded molecules of melanin in some subjects, which may help explain the variable success rate of the standard therapy.