Systemic sclerosis (SSc) is a rare and complex autoimmune disease. Although its etiology remains unknown, various environmental factors, including certain microorganisms, can represent potential triggers of SSc in individuals with a permissive genetic background. Patients show a wide spectrum of clinical features including periodontitis, which is an inflammatory disease of the tooth-supporting tissues resulting from dysbiosis of the periodontal microbiota guided by inflammophilic bacteria. The microbiota plays a fundamental role in the induction, training, and function of the host immune system. Numerous studies have highlighted the impact of an altered microbiota, i.e. dysbiosis, on the pathogenesis of immune-mediated diseases. Indeed, commensals are important to maintain immune homeostasis and changes in the microbial composition can be responsible for a loss of tolerance. SSc has been shown to be associated with gut dysbiosis and a depletion of commensals. However, although the oral cavity is one of the two largest microbial habitats, only one study (only focusing on Lactobacillus species) has investigated the oral microbiota in SSc. As periodontal dysbiosis is known to induce low-grade systemic inflammation and represents a risk factor for the development of various autoimmune diseases, the relationship between periodontal microbiota composition and SSc merits further exploration. The aim of this pilot study is to characterize the taxonomic composition and metabolic pathways of the periodontal microbiota in SSc patients and age and sex-matched controls.