Subclinical neurovascular and immune correlates of post-COVID-19 syndrome detected by retinal imaging.

Melasma is a chronic acquired hyperpigmentation disorder characterized by symmetrical brown to gray-brown macules and patches predominantly affecting sun-exposed facial areas. It arises from a complex interplay of genetic predisposition, ultraviolet radiation exposure, hormonal influences, and vascular factors, with recent evidence highlighting a central role for dermal photoaging, including solar elastosis, increased vascularity, and senescent fibroblast accumulation. Melasma is classified by distribution into centrofacial, malar, and mandibular patterns and by Wood's lamp examination into epidermal, dermal, or mixed forms. Objective severity is commonly assessed using the modified Melasma Area and Severity Index (mMASI) and provides improved practicality while maintaining strong correlation with imaging-based pigmentation metrics. Treatment selection is further influenced by Fitzpatrick skin phototype, with Phototypes III and IV exhibiting both the highest global melasma burden and increased susceptibility to postinflammatory hyperpigmentation, which poses additional challenges when using energy-based devices. Melasma shows variable global prevalence, ranging from 0.18% in the general United States population to as high as 41% in high-risk Asian populations, with a marked female predominance. In East Asian populations, it is one of the most common pigmentary disorders and is frequently associated with sun exposure, hormonal factors, and inflammatory features.