An article published in the International Journal of Molecular Sciences described melasma as a commonly acquired hypermelanosis that affects sun-exposed areas of the skin, with frequent facial involvement. Its histologic manifestations are evident in the epidermis, extracellular matrix and the dermis. In addition to epidermal pigmentation, pathologic findings of melasma include extracellular matrix abnormality, especially solar elastosis.

The authors reported that the disrupted basement membrane has been described in melasma with variable incidences. In the dermis, an increase in vascularity and in the number of mast cells were observed, indicating that dermal factors have critical roles in the pathogenesis of melasma, despite the fact that melasma is characterized by epidermal hyperpigmentation.

Source: International Journal of Molecular Sciences. 2016 Jun; 17(6): 824. Published online 2016 May 26. doi: 10.3390/ijms17060824