Prevalence and clinical relevance of systematically tested antimitochondrial antibodies in systemic sclerosis

Introduction Antimitochondrial antibodies (AMA), the hallmark of primary biliary cholangitis (PBC), have been inconsistently reported and poorly characterized in systemic sclerosis (SSc). Although recently linked to subclinical dysmotility in a cohort enriched for gastrointestinal (GI) involvement, data on the prevalence and clinical relevance of AMA in real-life SSc cohorts remain limited. Methods A retrospective cross-sectional study was conducted on consecutive SSc patients followed at a referral center for the disease. Patients were tested for serum AMA according to reference standards, including HEp-2 immunofluorescent screening and ELISA confirmation (anti-E2 pyruvate dehydrogenase). Patients' features were compared between AMA-positive and -negative cases. Results Among 165 SSc patients (20% diffuse cutaneous disease, 33% interstitial lung disease, 7.3% pulmonary arterial hypertension; 51% positive for anticentromere antibodies, 29% anti-topoisomerase I, 12% anti-RNA polymerase III), 37 (22%) were AMA-positive. While strongly associated with PBC, AMA were not linked to significant differences in cutaneous, vascular, pulmonary, or myocardial involvement. However, AMA were associated with GI vascular involvement (OR 13.3, 95% CI 2.53-95.0; p = 0.002), including gastric antral vascular ectasia (OR 7.99, 95% CI 1.05-72.5; p = 0.045), independently from PBC or symptoms of SSc-GI involvement. These complications are clinically relevant, as they may lead to GI bleeding and refractory iron-deficiency anemia. Conclusion In our cohort of SSc patients systematically screened for autoantibodies, we found a high prevalence of AMA and identified a novel putative association with GI vascular involvement, which warrants confirmation in independent studies.