Idiopathic inflammatory myopathies are a group of connective tissue diseases characterized by nonsuppurative inflammation of the striated muscle. At present, the diagnostic criteria for polymyositis/dermatomyositis classification proposed by Bohan and Peter in 1976 is mainly used clinically. In clinical observations, it is found that myopathy involves not only skin and muscle but also affects many systems of the body. Interstitial lung disease occupies an important part, and it is an important cause of death of patients with inflammatory myopathy. Patients with idiopathic myositis should be examined as early as possible by high-resolution CT to improve the detection rate of myositis-associated interstitial lung disease and start treatment as soon as possible. At the same time, the patients with myositis have different clinical manifestations due to specific antibodies in the serum; some specific antibodies may indicate poor prognosis and poor treatment response. Timely screening of patients with positive myositis-specific antibodies in patients with the pulmonary interstitial disease can help the patient’s diagnosis and treatment process.
Objective To explore the clinical characteristics of patients with connective tissue disease with positive anti-small ubiquitin-like modifier activating enzyme (SAE) antibodies. MethodsRetrospectively select the patients who completed the screening of myositis autoantibodies in West China Hospital of Sichuan University between January 1, 2015 and May 30, 2021. Meanwhile, patients with positive anti-SAE antibodies were screened out. According to the clinical data of anti-SAE antibodies positive patients, they were divided into the following groups: tumor group and non-tumor group, ILD group and non-ILD group, inflammatory myopathy group and non-inflammatory myopathy group. Clinical symptoms, signs, laboratory examinations, imaging examinations and other clinical data of the above patients were collected. Results A total of 1 594 patients were screened for myositis autoantibodies, of which 56 were positive for anti-SAE antibodies, with a positive rate of 3.5%. In 56 patients, 32.1% in skin involvement, 35.7% in muscle involvement, 12.5% in joint involvement, 5.4% in dysphagia, 5.4% in weight loss, 58.9% in patients with interstitial lung disease (ILD) and 12.5% in patients with tumor history. There was no significant difference in age, sex, skin involvement, muscle involvement, joint involvement and respiratory system involvement between the tumor group and the non-tumor group (P>0.05). Except for age, the frequency of muscle involvement, and positive rate of anti-Ro-52 antibody, there was no significant difference in other indicators between the ILD group and the non-ILD group (P>0.05). Except for the positive rate of ILD, the frequency of skin involvement, the frequency of muscle involvement, the level of creatine kinase and hydroxybutyrate dehydrogenase (P<0.05), there was no significant difference in other indexes between the non-inflammatory myopathy group and the inflammatory myopathy group (P>0.05). Conclusions The patients with positive anti-SAE antibodies mainly present skin and muscle symptoms, and are prone to ILD, malignant tumor and dysphagia. Patients with positive anti-SAE antibodies and ILD were older, had less muscle damage, and had a higher positive rate of anti-Ro-52 antibody. Anti-SAE antibodies appear not only in patients with inflammatory myopathy, but also in non-inflammatory myopathy, often associated with a higher frequency of ILD and less muscle involvement.