Melasma is a common acquired condition of symmetric hyperpigmentation, typically occurring on the face, with higher prevalence in females and darker skin types. Multiple etiologies, including light exposure, hormonal influences, and family history, have been implicated in the pathogenesis of this disorder. Overall prevalence ranges widely at 1–50%, since values are typically calculated within a specific ethnic population within a geographic region. Histologically, melasma can display increased epidermal and/or dermal pigmentation, enlarged melanocytes, increased melanosomes, solar elastosis, dermal blood vessels, and, occasionally, perivascular lymphohistiocytic infiltrates. Various topical, oral, and procedural therapies have been successfully used to treat melasma. Traditional topical therapies including hydroquinone, tretinoin, corticosteroids, and triple combination creams; however, other synthetic and natural topical compounds have also shown varying efficacies. Promising oral therapies for melasma include tranexamic acid, Polypodium leucotomos, and glutathione. Procedures, including chemical peels, microneedling, radiofrequency, and lasers, are also often used as primary or adjunctive treatments for melasma. Notably, combination therapies within or across treatment modalities generally result in better efficacies than monotherapies. This review serves as a comprehensive update on the current understanding of the epidemiology, pathogenesis, clinical and histologic features of melasma, as well as treatments for this common, yet therapeutically challenging, condition.

Microneedling appears to be an overall effective and safe therapeutic option for numerous dermatologic conditions. Larger and more randomized controlled trials are needed to provide greater data on the use of microneedling for different dermatologic conditions in different skin types.

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Vitiligo, an acquired depigmentation disorder, manifests as white macules on the skin and can cause significant psychological stress and stigmatization. Recent advances have shed light on key components that drive disease onset and progression as well as therapeutic approaches. Vitiligo can be triggered by stress to the melanin pigment-producing cells of the skin, the melanocytes. The triggers, which range from sunburn to mechanical trauma and chemical exposures, ultimately cause an autoimmune response that targets melanocytes, driving progressive skin depigmentation. The most significant progress in our understanding of disease etiology has been made on three fronts: (1) identifying cellular responses to stress, including antioxidant pathways and the unfolded protein response (UPR), as key players in disease onset, (2) characterizing immune responses that target melanocytes and drive disease progression, and (3) identifying major susceptibility genes. The current model for vitiligo pathogenesis postulates that oxidative stress causes cellular disruptions, including interruption of protein maturation in the endoplasmic reticulum (ER), leading to the activation of the UPR and expression of UPR-regulated chemokines such as interleukin 6 (IL-6) and IL-8. These chemokines recruit immune components to the skin, causing melanocytes to be targeted for destruction. Oxidative stress can further increase melanocyte targeting by promoting antigen presentation. Two key components of the autoimmune response that promote disease progression are the interferon (IFN)-γ/CXCL10 axis and IL-17-mediated responses. Several genome-wide association studies support a role for these pathways, with the antioxidant gene NRF2, UPR gene XBP1, and numerous immune-related genes including class I and class II major histocompatibility genes associated with a risk for developing vitiligo. Novel approaches to promote repigmentation in vitiligo are being investigated and may yield effective, long-lasting therapies.

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