Infections and Systemic Sclerosis

Systemic sclerosis (SSc) is a chronic autoimmune disease with microangiopathy, inflammation, autoantibodies production, and fibrosis. Despite progress in the understanding of main SSc pathogenesis pathways, the causes of the disease have not yet been clarified. A higher incidence of antibodies to infective microorganisms has been reported in SSc patients. In genetically predisposed patients, viruses (mainly hPVB19, hCMV, and EBV) have been suggested to be implicated in the emergence of SSc. The mechanism of viral invasion and behavior in the affected host’s immune cells and realization of autoimmune mechanisms such as adjuvant effect, molecular mimicry, microchimerism, and auto-reactivity may serve as a ground for this proposal. Bacterial infections have a major negative input on the course and outcome of SSc. Digital and skin ulcers, respiratory system, and upper gastrointestinal tract are the main gateways for pathological microorganisms’ colonization and infective inflammation. For some pathogens such as S. aureus, there is an ability to invade endothelial and epithelial cells as well as fibroblasts with severe alteration in their function, abnormal senescence, and death that result in ineffective wound healing. A broad use of DMARDs and biologic agents in the last decades and progress with transplantation procedures increase the possibility of typical and atypical bacterial and viral infections. Awareness of main SSc infectious complications will serve the clinical approach, with early recognition, proper treatment, and better outcome. Whether infection is a consequence of an abnormal host defense or serves as a trigger in the emergence of SSc in individuals with genetic and epigenetic background remains a question that needs to be resolved. Since the beginning of the COVID-19 pandemic, several issues have arisen regarding the ability of the new coronavirus or the innovative mRNA vaccine to cause SSc or to cause worsening of symptoms in a patient with an existing SSc, the similarity between pulmonary findings and microangiopathy in SSc and COVID-19, the safety of anti-coronavirus treatments among SSc patients, and the place of immunosuppressive treatment during the actual pandemic. In this chapter, we will discuss the relationship between viral and bacterial infections in SSc, prevalence, significance, consequences, prophylaxis, and more.