Introduction: According to the literature, organ‑specific antibodies may be present in the course of systemic sclerosis (SSc).

Objectives: The aim of this study was to assess the prevalence of antithyroid antibodies (antithyroid peroxidase antibodies [anti‑TPO] and antithyroglobulin antibodies) and of antimitochondrial antibodies (AMAs), as well as to evaluate their clinical significance in patients with SSc.

Patients and methods: The study involved 86 consecutive in‑hospital patients with SSc (32 patients with diffuse cutaneous SSc [dcSSc] and 54 with limited cutaneous SSc [lcSSc]). Patients were observed for autoimmune thyroid diseases (ATDs) and primary biliary cirrhosis (PBC). Serum samples were obtained from each patient.

Results: Positive antithyroid antibody titers were observed in 27 patients (31%) and positive AMA titers—in 11 patients (13%). ATD was diagnosed in 26 patients (30%) and PBC—in 10 patients (12%) with SSc. No significant differences in the prevalence of antithyroid antibodies were found between patients with dcSSc and those with lcSSc, but the prevalence of AMAs was significantly higher in patients with lcSSc compared with those with dcSSc. The prevalence of anti‑Ro‑52 antibodies was significantly higher in the SSc group with positive anti‑TPO antibody titers compared with the SSc group with negative anti‑TPO antibody titers. The prevalence of anticentromere antibodies (ACAs) was significantly higher in the SSc group with positive AMA titers compared with the SSc group with negative AMA titers.

Conclusions: The prevalence of organ‑specific antibodies in SSc patients is relatively high. The prevalence of AMAs is higher in patients with lcSSc than in those with dcSSc and is strongly associated with the presence of ACAs. Patients with SSc should be evaluated for coexisting ATDs and PBC.