<b><i>Background:</i></b> Acne inversa/hidradenitis suppurativa (HS) is a chronic, recurrent inflammatory disease of the skin that can significantly affect patients’ quality of life. The etiology and pathogenesis of HS are unclear and gene mutations might play a role. <b><i>Summary:</i></b> The primary focus of the review is on aggregating the gene mutations reported, summarizing the structure of γ-secretase and analyzing and speculating about the mechanism and the underlying relations between gene mutation and functional changes of protein. The systematic literature review was done by searching the PubMed, Embase, and Web of Science databases. γ-Secretase is an intramembrane protease complex responsible for the intramembranous cleavage of more than 30 type-1 transmembrane proteins including amyloid precursor protein and Notch receptors. The protein complex consists of four hydrophobic proteins: presenilin, presenilin enhancer-2 (PSENEN), nicastrin, and anterior pharynx defective 1 (APH1). To date, 57 mutations of γ-secretase genes have been reported in 70 patients or families worldwide, including 39 in NCSTN, 14 in PSENEN, and 4 in PSEN1, of which 17 are frameshifts, 15 result in nonsense mutations, 13 in missense mutations, and 12 are splice site mutations. Given the structure of γ-secretase and analysis of related mutation loci of NCSTN, PSENEN, and PSEN1, mutations in γ-secretase genes could affect activation of presenilin, prevent substrate binding, and hinder intramembrane cleavage of select proteins.

Melasma is an acquired, benign, and chronic hypermelanosis characterized by irregular light brown to dark brown patches of hyperpigmentation on the skin. Its prevalence varies according to ethnic background, skin phototype, and intensity of sun exposure. 1 The precise incidence of melasma remains unknown but both males and females can be affected in nearly every racial subgroup. Melasma is more common in darker skin types, particularly Fitzpatrick skin types III and IV, and often lasts for many years after pregnancy. 2 Melasma appears as light brown to dark, muddy brown macules and patches on the face, especially the forehead, malar areas, and chin, and it may last for decades, impacting on quality of life in those affected patients, such as emotional well-being and social life. 3 Interestingly, the negative effect on quality of life with melasma such as depression was not correlated with the severity of melasma, suggesting that even a small amount of pigmentation may have a significant emotional role. 2 The pathogenesis of melasma is complex, and its treatment remains challenging. While sun exposure, pregnancy and oral contraceptives are thought to be risk factors, much remains to be elucidated. 4 Therapeutic innovation for melasma remains a goal for dermatologists worldwide. There are many treatment options for melasma, including topical drugs, oral drugs, chemical peels, and laser and light treatments. 5

Background: Inflammation and postinflammatory hyperpigmentation (PIH) are two adverse side effects of ablative fractional CO 2 laser (ablative Fr CO 2 ) treatment for both rejuvenation and acne scars. Aims: To evaluate the efficacy of fusidic acid cream versus erythromycin ointment as postoperative therapy in patients who underwent ablative Fr CO 2 treatment for atrophic acne scars. Methods: Sixty Chinese patients who fulfilled the study criteria were recruited and randomly assigned to an experimental group treated with fusidic acid cream or a control group treated with erythromycin ointment. Postoperative treatment lasted for 7 days in each group. Each patient had two follow-up visits at 8 and 12 weeks. In total, three patients dropped out of the study, one in the experimental group at week 8 and two in the control group at weeks 8 and 12. Baseline and postoperative inflammation and PIH were assessed by facial examination, photographs, and questionnaires. Besides, PIH was evaluated by the Hyperpigmentation Activity and Severity Index (HASI) and a five-point grading system.Results: Moderate-to-severe PIH was observed in both groups. However, the mean HASI score and severity of PIH in the experimental group were lower than those of the control group at weeks 8 and 12 (P < 0.05). In the control group, one patient developed postoperative abscesses and one had papules, whereas no inflammation was observed in the experimental group participants. Conclusion:Fusidic acid cream shows promise as a common treatment after ablative Fr CO 2 therapy to reduce postoperative inflammation and PIH.