Vitiligo: Mechanisms of Pathogenesis and Treatment.

Vitiligo is an autoimmune disease of the skin that targets pigment-producing melanocytes and results in patches of depigmentation that are visible as white spots. Recent research studies have yielded a strong mechanistic understanding of this disease. Autoreactive cytotoxic CD8+ T cells engage melanocytes and promote disease progression through the local production of IFN-γ, and IFN-γ-induced chemokines are then secreted from surrounding keratinocytes to further recruit T cells to the skin through a positive-feedback loop. Both topical and systemic treatments that block IFN-γ signaling can effectively reverse vitiligo in humans; however, disease relapse is common after stopping treatments. Autoreactive resident memory T cells are responsible for relapse, and new treatment strategies focus on eliminating these cells to promote long-lasting benefit. Here, we discuss basic, translational, and clinical research studies that provide insight into the pathogenesis of vitiligo, and how this insight has been utilized to create new targeted treatment strategies.

Resident memory CD8+ T cells in regional lymph nodes mediate immunity to metastatic melanoma.

The nature of the anti-tumor immune response changes as primary tumors progress and metastasize. We investigated the role of resident memory (Trm) and circulating memory (Tcirm) cells in anti-tumor responses at metastatic locations using a mouse model of melanoma-associated vitiligo. We found that the transcriptional characteristics of tumor-specific CD8+ T cells were defined by the tissue of occupancy. Parabiosis revealed that tumor-specific Trm and Tcirm compartments persisted throughout visceral organs, but Trm cells dominated lymph nodes (LNs). Single-cell RNA-sequencing profiles of Trm cells in LN and skin were distinct, and T cell clonotypes that occupied both tissues were overwhelmingly maintained as Trm in LNs. Whereas Tcirm cells prevented melanoma growth in the lungs, Trm afforded long-lived protection against melanoma seeding in LNs. Expanded Trm populations were also present in melanoma-involved LNs from patients, and their transcriptional signature predicted better survival. Thus, tumor-specific Trm cells persist in LNs, restricting metastatic cancer.

Endocrine Autoimmune Disease as a Fragility of Immune Surveillance against Hypersecreting Mutants.

Some endocrine organs are frequent targets of autoimmune attack. Here, we addressed the origin of autoimmune disease from the viewpoint of feedback control. Endocrine tissues maintain mass through feedback loops that balance cell proliferation and removal according to hormone-driven regulatory signals. We hypothesized the existence of a dedicated mechanism that detects and removes mutant cells that missense the signal and therefore hyperproliferate and hypersecrete with potential to disrupt organismal homeostasis. In this mechanism, hypersecreting cells are preferentially eliminated by autoreactive T cells at the cost of a fragility to autoimmune disease. The "autoimmune surveillance of hypersecreting mutants" (ASHM) hypothesis predicts the presence of autoreactive T cells in healthy individuals and the nature of self-antigens as peptides from hormone secretion pathway. It explains why some tissues get prevalent autoimmune disease, whereas others do not and instead show prevalent mutant-expansion disease (e.g., hyperparathyroidism). The ASHM hypothesis is testable, and we discuss experimental follow-up.

Inverse relationship between polygenic risk burden and age of onset of autoimmune vitiligo.

Vitiligo is a common autoimmune disease characterized by patches of depigmented skin and overlying hair due to destruction of melanocytes in the involved regions. We investigated the relationship between vitiligo risk and vitiligo age of onset (AOO) using a vitiligo polygenic risk score that incorporated the most significant SNPs from genome-wide association studies. We find that vitiligo genetic risk and AOO are strongly inversely correlated; subjects with higher common-variant polygenic risk tend to develop vitiligo at an earlier age. Nevertheless, the correlation is not simple. In individuals who carry a single high-risk major histocompatibility complex class II haplotype, the effect of additional polygenic risk on vitiligo AOO is reduced. Particularly among those with early-AOO vitiligo (onset ≤12 years of age), genetic risk can reflect contributions from high common-variant burden but also rare variants of high effect and sometimes both. While the heritability of vitiligo is relatively high, and we here show that genetic risk factors predict vitiligo AOO, vitiligo is never congenital, and thus environmental triggers also play an important role in disease onset.

CD49a Expression Defines Tissue-Resident CD8+ T Cells Poised for Cytotoxic Function in Human Skin.

Tissue-resident memory T (Trm) cells form a heterogeneous population that provides localized protection against pathogens. Here, we identify CD49a as a marker that differentiates CD8+ Trm cells on a compartmental and functional basis. In human skin epithelia, CD8+CD49a+ Trm cells produced interferon-γ, whereas CD8+CD49a- Trm cells produced interleukin-17 (IL-17). In addition, CD8+CD49a+ Trm cells from healthy skin rapidly induced the expression of the effector molecules perforin and granzyme B when stimulated with IL-15, thereby promoting a strong cytotoxic response. In skin from patients with vitiligo, where melanocytes are eradicated locally, CD8+CD49a+ Trm cells that constitutively expressed perforin and granzyme B accumulated both in the epidermis and dermis. Conversely, CD8+CD49a- Trm cells from psoriasis lesions predominantly generated IL-17 responses that promote local inflammation in this skin disease. Overall, CD49a expression delineates CD8+ Trm cell specialization in human epithelial barriers and correlates with the effector cell balance found in distinct inflammatory skin diseases.

The IFN-γ-CXCL9/CXCL10-CXCR3 axis in vitiligo: Pathological mechanism and treatment.

Vitiligo is a disease featuring distinct white patches that result from melanocyte destruction. The overall pathogenesis of vitiligo remains to be elucidated. Nevertheless, considerable research indicates that adaptive immune activation plays a key role in this process. Specifically, the interferon-gamma (IFN-γ), C-X-C motif chemokine ligands (CXCL9/10), and C-X-C motif chemokine receptor (CXCR3) signaling axis, collectively referred to as IFN-γ-CXCL9/10-CXCR3 or ICC axis, has emerged as a key mediator responsible for the recruitment of autoimmune CXCR3+ CD8+ T cells. These cells serve as executioners of melanocytes by promoting their detachment and apoptosis. Moreover, IFN-γ is generated by activated T cells to create a positive feedback loop, exacerbating the autoimmune response. This review not only delves into the mechanistic insights of the ICC axis but also explores the significant immunological effects of associated cytokines and their receptors. Additionally, the review provides a thorough comparison of existing and emerging treatment options that target the ICC axis for managing vitiligo. This review aims to foster further advancements in basic research within related fields and facilitate a deeper understanding of alternative treatment strategies targeting different elements of the axis.

Disorganisation of basement membrane zone architecture impairs melanocyte residence in vitiligo.

The basement membrane zone is the interface between the epidermis and dermis, and it is disrupted in several skin conditions. Here, we report the results of a comprehensive investigation into the structural and molecular factors of the basement membrane zone in vitiligo, a dermatological disorder characterised by depigmented patches on the skin. Using electron microscopy and immunofluorescence staining, we confirmed abnormal basement membrane zone morphology and disrupted basement membrane zone architecture in human vitiliginous skin. Furthermore, we identified elevated expression of matrix metalloproteinase 2 (MMP2) in human dermal fibroblasts as a key factor responsible for basement membrane zone matrix degradation. In our in vitro and ex vivo models, overexpression of MMP2 in fibroblasts led to basement membrane zone disruption and melanocyte disappearance. Importantly, we reveal that the loss of melanocytes in vitiligo is primarily linked to their weakened adhesion to the basement membrane, mediated by binding between integrin ß1 and laminin and discoidin domain receptor 1 and collagen IV. Finally, inhibition of matrix metalloproteinase 2 expression reversed depigmentation in a mouse model of vitiligo. In conclusion, our research shows the importance of basement membrane zone integrity in melanocyte residence and offers new avenues for therapeutic interventions to address this challenging skin condition. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

TRPM2-dependent autophagy inhibition exacerbates oxidative stress-induced CXCL16 secretion by keratinocytes in vitiligo.

Vitiligo is a depigmented skin disease due to the destruction of melanocytes. Under oxidative stress, keratinocyte-derived chemokine C-X-C motif ligand 16 (CXCL16) plays a critical role in recruiting CD8+ T cells, which kill melanocytes. Autophagy serves as a protective cell survival mechanism and impairment of autophagy has been linked to increased secretion of the proinflammatory cytokines. However, the role of autophagy in the secretion of CXCL16 under oxidative stress has not been investigated. Herein, we initially found that autophagy was suppressed in both keratinocytes of vitiligo lesions and keratinocytes exposed to oxidative stress in vitro. Autophagy inhibition also promoted CXCL16 secretion. Furthermore, upregulated transient receptor potential cation channel subfamily M member 2 (TRPM2) functioned as an upstream oxidative stress sensor to inhibit autophagy. Moreover, TRPM2-mediated Ca2+ influx activated calpain to shear autophagy related 5 (Atg5) and Atg12-Atg5 conjugate formation was blocked to inhibit autophagy under oxidative stress. More importantly, Atg5 downregulation enhanced the binding of interferon regulatory factor 3 (IRF3) to the CXCL16 promoter region by activating Tank-binding kinase 1 (TBK1), thus promoting CXCL16 secretion. These findings suggested that TRPM2-restrained autophagy promotes CXCL16 secretion via the Atg5-TBK1-IRF3 signaling pathway under oxidative stress. Inhibition of TRPM2 may serve as a potential target for the treatment of vitiligo. © 2024 The Pathological Society of Great Britain and Ireland.

Improvements in immune/melanocyte biomarkers with JAK3/TEC family kinase inhibitor ritlecitinib in vitiligo.

BACKGROUND: Vitiligo is an autoimmune depigmenting disorder with no effective and safe treatments. Its pathogenesis is not fully elucidated. OBJECTIVE: This substudy of a randomized, double-blind, placebo-controlled phase 2b trial (NCT03715829) evaluated effects of ritlecitinib, an oral JAK3/TEC family kinase inhibitor, on skin and blood biomarkers in participants with nonsegmental vitiligo (NSV). METHODS: Sixty-five adults with NSV participated in the substudy and received daily treatment for 24 weeks with placebo (n = 14) or ritlecitinib with or without a 4-week loading dose: 200 (loading dose)/50 mg (n = 13), 100/50 mg (n = 12), 50 mg (n = 11), 30 mg (n = 8), or 10 mg (n = 6). Skin (lesional and nonlesional) biopsy samples were obtained at baseline and at 4 and 24 weeks. Changes from baseline to weeks 4 and 24 in skin and blood molecular and cellular biomarkers were evaluated by RNA sequencing, quantitative real-time PCR, proteomic analysis, and flow cytometry. RESULTS: Ritlecitinib-treated groups showed downregulation of immune biomarkers and upregulation of melanocyte-related markers at weeks 4 and 24 compared to baseline and/or placebo. Significant reductions were seen in CD3+/CD8+ T-cell infiltrates, with significant increases in melanocyte markers (tyrosinase; Melan-A) in NSV lesions in the 50 mg ritlecitinib groups (both P < .05). There was significant, dose-dependent downregulation in T-cell activation, NK, cytotoxic, and regulatory markers in lesional skin (IL-2, IL2-RA, IL-15, CCR7, CD5, CRTAM, NCR1, XCL1, KIR3DL1, FASLG, KLRD; P < .05). TH1 and TH2 markers were also downregulated in lesional skin and blood in a dose-dependent manner (P < .05). Changes in immune biomarkers correlated with clinical response. CONCLUSIONS: Ritlecitinib significantly downregulated proinflammatory biomarkers and increased melanocyte products in skin and blood of participants with NSV, suggesting its potential in treatment. Ritlecitinib-mediated changes positively correlated with clinical response.

Resident memory T cells in nonlesional skin and healed lesions of patients with chronic inflammatory diseases: Appearances can be deceptive.

Tissue-resident memory T (TRM) cells serve as a first line of defense in peripheral tissues to protect the organism against foreign pathogens. However, autoreactive TRM cells are increasingly implicated in autoimmunity, as evidenced in chronic autoimmune and inflammatory skin conditions. This highlights the need to characterize their phenotype and understand their role for the purpose of targeting them specifically without affecting local immunity. To date, the investigation of TRM cells in human skin diseases has focused mainly on lesional tissues of patients. Accumulating evidence suggests that self-reactive TRM cells are still present in clinically healed lesions of patients and play a role in disease flares, but TRM cells also populate skin that is apparently normal. This review discusses the ontogeny of TRM cells in the skin as well as recent insights regarding the presence of self-reactive TRM cells in both clinically healed skin and nonlesional skin of patients with autoimmune and inflammatory skin conditions, with a particular focus on psoriasis, atopic dermatitis, and vitiligo.

Autoimmune adverse event following COVID-19 vaccination in Seoul, South Korea.

BACKGROUND: There is growing evidence that the coronavirus disease 2019 (COVID-19) vaccination can affect the regulation of the immune system, leading to the development of autoimmune diseases. However, the autoimmune adverse events (AEs) after COVID-19 vaccination remain largely unclear. OBJECTIVE: We sought to investigate the autoimmune AEs after COVID-19 vaccination from a population-based cohort in South Korea. METHODS: A total of 4,203,887 participants, representing 50% of the population residing in Seoul, were recruited from the National Health Insurance Service database and then divided into 2 groups on the basis of COVID-19 vaccination. The cumulative incidence, hazard ratios (HRs), and 95% CIs of autoimmune AEs were assessed following COVID-19 vaccination. RESULTS: The incidence of vitiligo has been observed to be significantly higher in the vaccination group compared with the no vaccination group. The cumulative incidence of vitiligo began to show a significant difference starting 2 weeks after vaccination, and it reached 2.2% in the vaccination group and 0.6% in the no vaccination group by 3 months after COVID-19 vaccination. Vitiligo (HR, 2.714; 95% CI, 1.777-4.146) was an increased risk among autoimmune AEs. Furthermore, the risk of vitiligo was the highest for heterologous vaccination (HR, 3.890; 95% CI, 2.303-6.573) compared with using cDNA vaccine (HR, 2.861; 95% CI, 1.838-4.453) or mRNA vaccine (HR, 2.475; 95% CI, 1.607-3.813). CONCLUSIONS: Vitiligo as an autoimmune AE was noted to be substantially higher in the COVID-19-vaccinated group compared with the controls. Therefore, the occurrence of vitiligo could be considered as one of the significant AEs post-COVID-19 vaccination.

Identification and validation of RNA-binding protein SLC3A2 regulates melanocyte ferroptosis in vitiligo by integrated analysis of single-cell and bulk RNA-sequencing.

BACKGROUND: The pathogenesis of vitiligo remains unclear. The genes encoding vitiligo-related RNA-binding proteins (RBPs) and their underlying pathogenic mechanism have not been determined. RESULTS: Single-cell transcriptome sequencing (scRNA-seq) data from the CNCB database was obtained to identify distinct cell types and subpopulations and the relative proportion changes in vitiligo and healthy samples. We identified 14 different cell types and 28 cell subpopulations. The proportion of each cell subpopulation significantly differed between the patients with vitiligo and healthy groups. Using RBP genes for unsupervised clustering, we obtained the specific RBP genes of different cell types in vitiligo and healthy groups. The RBP gene expression was highly heterogeneous; there were significant differences in some cell types, such as keratinocytes, Langerhans, and melanocytes, while there were no significant differences in other cells, such as T cells and fibroblasts, in the two groups. The melanocyte-specific RBP genes were enriched in the apoptosis and immune-related pathways in the patients with vitiligo. Combined with the bulk RNA-seq data of melanocytes, key RBP genes related to melanocytes were identified, including eight upregulated RBP genes (CDKN2A, HLA-A, RPL12, RPL29, RPL31, RPS19, RPS21, and RPS28) and one downregulated RBP gene (SLC3A2). Cell experiments were conducted to explore the role of the key RBP gene SLC3A2 in vitiligo. Cell experiments confirmed that melanocyte proliferation decreased, whereas apoptosis increased, after SLC3A2 knockdown. SLC3A2 knockdown in melanocytes also decreased the SOD activity and melanin content; increased the Fe2+, ROS, and MDA content; significantly increased the expression levels of TYR and COX2; and decreased the expression levels of glutathione and GPX4. CONCLUSION: We identified the RBP genes of different cell subsets in patients with vitiligo and confirmed that downregulating SLC3A2 can promote ferroptosis in melanocytes. These findings provide new insights into the pathogenesis of vitiligo.

From mice to men: An assessment of preclinical model systems for the study of vitiligo.

Vitiligo is an autoimmune skin disease of multiple etiology, for which there is no complete cure. This chronic depigmentation is characterized by epidermal melanocyte loss, and causes disfigurement and significant psychosocial distress. Mouse models have been extensively employed to further our understanding of complex disease mechanisms in vitiligo, as well as to provide a preclinical platform for clinical interventional research on potential treatment strategies in humans. The current mouse models can be categorized into three groups: spontaneous mouse models, induced mouse models, and transgenic mice. Despite their limitations, these models allow us to understand the pathology processes of vitiligo at molecule, cell, tissue, organ, and system levels, and have been used to test prospective drugs. In this review, we comprehensively evaluate existing murine systems of vitiligo and elucidate their respective characteristics, aiming to offer a panorama for researchers to select the appropriate mouse models for their study.

Abnormal metabolism in melanocytes participates in the activation of dendritic cell in halo nevus.

A comprehensive analysis of spatial transcriptomics was carried out to better understand the progress of halo nevus. We found that halo nevus was characterized by overactive immune responses, triggered by chemokines and dendritic cells (DCs), T cells, and macrophages. Consequently, we observed abnormal cell death, such as apoptosis and disulfidptosis in halo nevus, some were closely related to immunity. Interestingly, we identified aberrant metabolites such as uridine diphosphate glucose (UDP-G) within the halo nevus. UDP-G, accompanied by the infiltration of DCs and T cells, exhibited correlations with certain forms of cell death. Subsequent experiments confirmed that UDP-G was increased in vitiligo serum and could activate DCs. We also confirmed that oxidative response is an inducer of UDP-G. In summary, the immune response in halo nevus, including DC activation, was accompanied by abnormal cell death and metabolites. Especially, melanocyte-derived UDP-G may play a crucial role in DC activation.

Role of fibroblasts in nonfibrotic autoimmune skin diseases.

Autoimmune diseases, a disease characterized by immune imbalance caused by the human immune system mistakenly attacking its own components, include vitiligo, psoriasis and atopic dermatitis (AD). Previous studies on autoimmune diseases have focused mainly on immune cells, keratinocytes and endothelial cells. Fibroblasts, the main cells that secrete the extracellular matrix (ECM) in the dermis, have been studied thoroughly in terms of fibrosis and wound healing. However, an increasing number of studies have shown that fibroblasts play an important role in nonfibrotic autoimmune skin diseases. In this article, the previously reported role of fibroblasts in nonfibrous autoimmune skin diseases such as psoriasis, vitiligo and AD is summarized to provide new ideas for the treatment of this disease.

Multi-center retrospective review of vitiligo-like lesions in breast cancer patients treated with cyclin-dependent kinase 4 and 6 inhibitors.

PURPOSE: Cutaneous adverse effects from cyclin-dependent 4 and 6 kinase inhibitors (CDK4/6i) used in metastatic breast cancer are prevalent and well described. Vitiligo-like lesions have been reported and are rare. They can negatively impact patients' quality of life and may be associated with survival benefits. We describe the clinical characteristics of vitiligo-like lesions in an international cohort of patients treated with CDK4/6i to help improve recognition and management. METHODS: Retrospective review of patients diagnosed with vitiligo-like lesions from CDK4/6i from five academic institutions in the USA and Europe was performed. Ten patients were included in the study. RESULTS: Median age of our patients was 55 (range 37-86). Median progression-free survival was 24 months in 5 patients. The median time to rash was 10 months. Sun-exposed areas such as the arms and face were the most affected areas. Multiple skin-directed therapies such as topicals, laser, and phototherapy were trialed with minor success. Mild repigmentation was seen in one patient treated with ruxolitinib cream. CDK4/6 treatment was discontinued due to the vitiligo-like lesions in one patient. CONCLUSION: Clinical characteristics are similar to previously reported findings in case reports and series. We add topical ruxolitinib as a potential treatment option for these patients and include data regarding progression-free survival that should continue to be collected. No definitive conclusions can be made regarding survival benefits from our cohort. Clinicians should refer these patients to dermatologists to aid with management.

Clinical Findings in a Series of Thirty Eight Patients with Williams-Beuren Syndrome.

INTRODUCTION: Williams-Beuren syndrome is a contiguous gene syndrome caused by microdeletion of the locus 7q11.23. It is a clinically recognizable condition whose cardinal features include growth deficiency, variable degrees of neurodevelopmental disorders, congenital cardiac defects, outgoing personality, and typical facies. Case Series Presentation: This retrospective study analyzed 38 consecutive patients in a single center for rare diseases, diagnosed by Preus criteria modified by the Sugayama scoring system, comprising 17 male and 21 female individuals aged 1 month to 55 years. Cases were divided into two groups concerning (a) exclusive clinical diagnosis or (b) clinical diagnosis followed by a laboratory cytogenetic or cytogenomic test; except for hypertension, no significant difference was seen among both groups. The most frequent findings were intellectual deficiency, developmental delay, typical facies, and overfriendliness, all above 80% of the total sample. On the other hand, supravalvar aortic stenosis was found in only 32.4%, while other congenital heart diseases were seen in 56.7% of the sample. Unusual features included one individual with 13 pairs of ribs, another with unilateral microphthalmia, and three with unilateral renal agenesis. Comorbidities comprised 9 cases of hypothyroidism and 1 case each of precocious puberty, segmental vitiligo, type 1 diabetes mellitus, and congenital adrenal hyperplasia. CONCLUSION: Preus criteria modified by the Sugayama scoring system are still efficient and helpful for clinical diagnosis. This is the second report on microphthalmia and the first study describing the association between vitiligo, type 1 diabetes mellitus, and congenital adrenal hyperplasia in individuals with Williams-Beuren syndrome.

The impact on the quality of life and sleep complaints in a vitiligo sample and the influence of inflammatory cytokines in the interaction between vitiligo and sleep.

INTRODUCTION: Vitiligo is an autoimmune dermatosis that affects quality of life, which englobes sleep quality. Sleep regulates the immune system, including inflammatory cytokines, and other pathways, which may influence vitiligo pathogenesis. OBJECTIVES: To analyze levels of immune serum components (cytokines) in a vitiligo group, and assess whether there was any association with sleep. METHODS: This study comprised 30 vitiligo patients and 26 control individuals. Quality of life and sleep questionnaires were completed [Dermatology Life Quality Index (DLQI), Short-Form Health Survey (SF-36), Pittsburgh Sleep Quality Index (PSQI) and Insomnia Severity Index (ISI)]. Seven cytokines have been measured: IFN-γ, interleukin (IL)-4, IL-6, IL-10, IL-17A, IL-12 p40 and TNF-α. RESULTS: The mean age of the vitiligo group was 47.7 years-old, with prevalence of females (66.7 %). Mucosal (70 %), acral (60 %) and focal subtype (53.3 %) predominated. Signs of vitiligo activity were identified in 63.3 % of the disease sample. Total PSQI scores and scores for domain 4 (sleep efficiency) were statistically worse in vitiligo group. The SF-36 and ISI total scores were worse in the vitiligo group, although not statistically significant compared with controls. Four SF-36 domains were statistically worse in vitiligo sample, and the DLQI mean score was mild to moderate (5.57). Cytokine levels were not different between groups, or when associated with PSQI. Higher ISI scores (more severe insomnia) were related to increased IL-17A. Higher IL-4, IL-6 and IL-10 levels were associated with previous phototherapy. CONCLUSIONS: Poor sleep and impaired aspects of quality of life predominated in the vitiligo sample. Insomnia was related to IL-17A increase in vitiligo. Increased levels of IL-4, IL-6 and IL-10 were related to previous ultraviolet B narrow band (UVB-NB) phototherapy, suggesting an interaction of this treatment on immune system. Sleep disruption and the course of vitiligo may have common pathways in respect of circadian cytokines, which may represent an important subject in vitiligo management.

The underestimated role of mitochondria in vitiligo: From oxidative stress to inflammation and cell death.

Vitiligo is an acquired depigmentary disorder characterized by the depletion of melanocytes in the skin. Mitochondria shoulder multiple functions in cells, such as production of ATP, maintenance of redox balance, initiation of inflammation and regulation of cell death. Increasing evidence has implicated the involvement of mitochondria in the pathogenesis of vitiligo. Mitochondria alteration will cause the abnormalities of mitochondria functions mentioned above, ultimately leading to melanocyte loss through various cell death modes. Nuclear factor erythroid 2-related factor 2 (Nrf2) plays a critical role in mitochondrial homeostasis, and the downregulation of Nrf2 in vitiligo may correlate with mitochondria damage, making both mitochondria and Nrf2 promising targets in treatment of vitiligo. In this review, we aim to discuss the alterations of mitochondria and its role in the pathogenesis of vitiligo.

Efficacy and safety of ritlecitinib in vitiligo patients across Fitzpatrick skin types with biomarker analyses.

Efficacy and safety of ritlecitinib (an oral JAK3/TEC family kinase inhibitor) were evaluated in patients with nonsegmental vitiligo (NSV) across Fitzpatrick skin types (FSTs). Patients with FST I-III ('light skin'; n = 247) and FST IV-VI ('dark skin'; n = 117) received once-daily ritlecitinib 50 mg (with/without 4-week loading dose), low-dose ritlecitinib or placebo for 24 weeks. At baseline, patients with light skin displayed higher CLM-1 and NCR1 serum levels than patients with dark skin (p < 0.05). At 24 weeks, ritlecitinib 50 mg improved the extent of depigmentation measured by percent change from baseline in facial-vitiligo area scoring index (placebo-adjusted mean difference [90% CI]) in patients with light (-15.2 [-24.7, -5.8]; p = 0.004) and dark (-37.4 [-50.3, -24.4]; p < 0.0001) skin, with continuous re-pigmentation through week 48. Treatment-emergent adverse events were similar across FSTs. At weeks 4 and 24, ritlecitinib 50 mg reduced CXCL11 serum levels (p < 0.001) in patients with light skin, whereas patients with dark skin had increased levels at week 4 (p = 0.05) and no significant change at week 24. Ritlecitinib 50 mg decreased IL-9 and IL-22 expression levels in dark skin compared with light skin (qPCR; p < 0.05). These differences in immune dysregulations may explain why NSV patients with dark skin respond to therapy earlier than patients with light skin.