More than 10 disease-modifying therapies (DMT) are approved by the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA) for the treatment of multiple sclerosis (MS) and new therapeutic options are on the horizon. Due to different underlying therapeutic mechanisms, a more individualized selection of DMTs in MS is possible, taking into account the patient's current situation. Therefore, concomitant treatment of various comorbid conditions, including autoimmune mediated disorders such as rheumatoid arthritis, should be considered in MS patients. Because the pathomechanisms of autoimmunity partially overlap, DMT could also treat concomitant inflammatory diseases and simplify the patient's treatment. In contrast, the exacerbation and even new occurrence of several autoimmune diseases have been reported as a result of immunomodulatory treatment of MS. To simplify treatment and avoid disease exacerbation, knowledge of the beneficial and adverse effects of DMT in other autoimmune disorders is critical. Therefore, we conducted a literature search and described the beneficial and adverse effects of approved and currently studied DMT in a large number of comorbid autoimmune diseases, including rheumatoid arthritis, ankylosing spondylitis, inflammatory bowel diseases, cutaneous disorders including psoriasis, Sjögren´s syndrome, systemic lupus erythematosus, systemic vasculitis, autoimmune hepatitis, and ocular autoimmune disorders. Our review aims to facilitate the selection of an appropriate DMT in patients with MS and comorbid autoimmune diseases.

Ulcerating skin lesions are manifestations of human ISG15 deficiency, a type I interferonopathy. However, chronic inflammation may not be their exclusive cause. We describe two siblings with recurrent skin ulcers that healed with scar formation upon corticosteroid treatment. Both had a homozygous nonsense mutation in the ISG15 gene, leading to unstable ISG15 protein lacking the functional domain. We characterized ISG15^–/– dermal fibroblasts, HaCaT keratinocytes, and human induced pluripotent stem cell–derived vascular endothelial cells. ISG15-deficient cells exhibited the expected hyperinflammatory phenotype, but also dysregulated expression of molecules critical for connective tissue and epidermis integrity, including reduced collagens and adhesion molecules, but increased matrix metalloproteinases. ISG15^–/– fibroblasts exhibited elevated ROS levels and reduced ROS scavenger expression. As opposed to hyperinflammation, defective collagen and integrin synthesis was not rescued by conjugation-deficient ISG15. Cell migration was retarded in ISG15^–/– fibroblasts and HaCaT keratinocytes, but normalized under ruxolitinib treatment. Desmosome density was reduced in an ISG15^–/– 3D epidermis model. Additionally, there were loose architecture and reduced collagen and desmoglein expression, which could be reversed by treatment with ruxolitinib/doxycycline/TGF-β1. These results reveal critical roles of ISG15 in maintaining cell migration and epidermis and connective tissue homeostasis, whereby the latter likely requires its conjugation to yet unidentified targets.

A wide variety of immunomodulatory therapies are already available for the treatment of multiple sclerosis (MS). Through fundamental insights from basic research with a gain of knowledge in the pathological processes underlying MS, the exploration of additional medical compounds within clinical trials has been ignited. Emerging novel medications with innovative mechanisms of action are being introduced. Those mechanisms of action include a broad therapeutic spectrum of substances targeting various protein kinases, some of which could also be used for the treatment of other autoimmune-mediated diseases. The advancement of new compounds could therefore enable a more personalized approach in treating MS, taking into consideration patients' co-existing autoimmune-mediated diseases. In this review, we discuss potential compounds targeting protein kinases, currently under investigation in clinical trials for various autoimmune diseases that could become viable treatment options for MS and comorbid autoimmune conditions in the future.

Background/Objectives: Cutaneous side effects are the most common immune-related adverse events (irAEs) caused by immune checkpoint inhibitors (ICIs) and affect 70–90% of patients. Besides diverse types of exanthema, rare skin toxicity includes bullous dermatoses in 0.3% of cases. Systemic steroids are the first-line treatment for immune-related bullous pemphigoid (irBP); however, some cases are corticosteroid-resistant. IrBP is one of the irAEs most frequently chronic and associated with long-term steroid use. However, steroids may interfere with tumor response. Therefore, alternative treatment strategies for irBP are desperately needed. Dupilumab, a monoclonal antibody blocking the receptor binding of interleukin-4 (IL-4) and interleukin-13 (IL-13), has been successfully used to treat spontaneous forms of bullous pemphigoid (BP). In this study, we analyzed the gene expression profiles of BP and irBP. Patients and Methods: A retrospective multicenter study evaluated the gene expression profiles of irBP and BP in comparison to healthy controls. Gene expression analyses of skin biopsies were performed using NanoString technology from patients with BP (n = 17), irBP (n = 19), and healthy skin (n = 24) after the patients had consented to participate in this study, and differentially expressed genes (DEGs) were determined using Rosalind software. Results: Compared to healthy skin, BP showed 167 DEGs, and irBP revealed 99 DEGs. Some of the DEGs from irBP and BP vs. healthy skin overlapped. Specifically, IL-4- and IL-13-associated genes were upregulated in both irBP and BP compared to healthy skin. Interestingly, expression profiles of BP vs. irBP also showed 13 DEGs. Conclusions: These findings suggest a possibility for therapeutic efficacy of IL-4 and IL-13 inhibitors in the treatment of irBP.