Abstract
ObjectiveAnti-mitochondrial antibodies (AMAs) can be detected in some idiopathic inflammatory myopathy (IIM) patients. We aimed to investigate the clinical features of IIM patients with AMAs. MethodsWe retrospectively analysed 1,167 consecutive patients with IIM for AMA-associated myositis and compared them to age- and gender-matched AMA-negative IIM patients. ResultsTwenty-nine patients (2.5%) were identified with AMA-positive myositis; eight of them had primary biliary cholangitis (PBC). There were no significant differences in skin rash, dysphagia, interstitial lung disease, and muscle strength between AMA-positive patients and AMA-negative patients. Of 23 cases, 12 (52.2%) showed immune-mediated necrotizing myopathy (IMNM)-like pathological features. amongst AMA-positive patients, 11 of 16 patients with isolated anti-AMAs were classified as IMNM which was significantly higher than that of patients with coexistent anti-AMAs and myositis-specific antibodies (p = 0.026). Moreover, subclinical cardiac involvement was significantly more common in AMA-positive patients than in AMA-negative patients (21/29 VS 33/116, p<0.001). In addition, patients without PBC had a significantly higher incidence of abnormal echocardiography findings than that of patients with PBC (p = 0.009). Patients without heart abnormalities took significantly less time to achieve disease remission and prednisone tapering to <10 mg than patients with heart abnormalities (p = 0.000 and p = 0.001, respectively). ConclusionsIMNM was a major histopathological finding in IIM patients with isolated AMAs. AMAs were significantly associated with subclinical cardiac involvement in IIM. PBC seemed to be a protective factor for abnormal echocardiography findings in AMA-positive patients. Patients without heart involvement took less time to achieve disease remission and prednisone tapering off.
Highlights
Idiopathic inflammatory myopathy (IIM) is an autoimmune systemic disease that is characterised by skeletal muscle injury and multi-system involvement, including the skin, lung, heart, and oesophagus
There were no significant differences in skin rash, dysphagia, interstitial lung disease, and muscle strength between anti-mitochondrial antibody (AMA)-positive patients and disease controls. 12/23(52.2%) cases showed immune-mediated necrotizing myopathy (IMNM)-like pathological features
Among AMAs-positive patients, 11 of 16 patients with isolated anti-AMA were classified as IMNM which was significantly higher than that of patients with coexistent anti-AMAs and myositis-specific antibodies (p=0.026)
Summary
Idiopathic inflammatory myopathy (IIM) is an autoimmune systemic disease that is characterised by skeletal muscle injury and multi-system involvement, including the skin, lung, heart, and oesophagus. Many autoantibodies, including myositis-specific antibodies (MSAs) and myositis-related antibodies (MRAs), can be detected in the serum [1]. MSAs are closely related to distinct clinical characteristics [2, 3]. MRAs have been detected in other connective tissue diseases or overlap syndrome of IIM and other connective tissue diseases, it has been reported that some MRAs were associated with unique features in IIM. Anti-Ku antibody isolated from the serum in IIM was associated with concomitant severe interstitial lung disease (ILD) and immune-mediated necrotising myopathy [4]. Serum anti-Ro-52 antibody in dermatomyositis (DM) could develop rapidly progressive ILD, which mainly presents with organising pneumonia on high-resolution computed tomography [5, 6]
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