Low prevalence of anti-small ubiquitin-like modifier activating enzyme antibodies in dermatomyositis patients

Background. The myositis-specific autoantibodies that characterize certain forms of inflammatory myopathy are useful in diagnosing dermatomyositis (DM) / polymyositis and predicting its prognosis. Autoantibodies to small ubiquitin-like modifier activating enzyme (SAE) have been identified as a DM-marker antibody in European Caucasians. Objective and methods. This study investigates the frequency and clinical characteristics of anti-SAE autoantibodies in Japanese patients with DM. Sera from 110 Japanese patients, including 13 with juvenile DM, were screened for anti-SAE antibodies by enzyme-linked immunosorbent assays. Positive sera were further examined by immunoblotting of the immunoprecipitates. Results. Only two patients (1.8%) were confirmed to have anti-SAE antibodies, and neither of these two patients had amyopathic or juvenile DM. One patient with anti-SAE had DM complicated with pulmonary arterial hypertension, and the other had cancer-associated DM. Both had hallmark cutaneous manifestations of DM. Conclusion. This is the first report of anti-SAE antibodies from an Asian single center cohort. Although Japanese patients with anti-SAE antibodies have a clinical phenotype similar to that of Caucasian patients, their frequency was lower in the Japanese patients than in the previously reported Caucasian patients.