Background: The aggregation of autoimmune diseases in relatives (AID-R) of patients with systemic sclerosis (SSc) has been reported.
Objectives: To analyze the prevalence of autoimmune diseases in SSc relatives and to compare their features to those of SSc patients without AID-R (controls).
Methods: A case-control analysis compared SSc patients with AID-R to those without AID-R (25 patients) with similar disease duration.
Results: Among 322 patients, 25 (7.7%; 21 females, 41.4 ± 15.6 years of age, disease duration 11 ± 8.6 years) had AID-R (21 had a first-degree relative, 4 had a second-degree relative, and 2 had both). Fourteen patients (56%) and five controls (20%) had an additional autoimmune disease (P < 0.009). Diffuse SSc (48% vs. 24%) and arthritis (72% vs. 28%) were more frequent among the patients with AID-R than the controls (P < 0.05). No significant differences were found regarding lung, heart, vascular, and digestive system involvement. The mean number of additional autoimmune diseases was 0.84 ± 0.94 in AID-R vs. 0.24 ± 0.52 in controls (P < 0.038). The mean number of autoantibodies was 2.8 ± 1.5 and 2.2 ± 0.9 (P < 0.047). Five patients died during follow-up, four of whom had AID-R. Relatives of SSc patients had diverse autoimmune diseases; the prevalence of SSc in scleroderma relatives was 1.86% (2 in first-degree and 6 in second-degree relatives). SSc patients with AID-R had an obvious tendency to polyautoimmunity.
Conclusions: A precise family history is an important clue in prognosis and prediction of autoimmune diseases in SSc patients and their relatives.