BackgroudAnti-mitochondrial antibodies (AMAs) can be detected in some idiopathic in ammatory myopathy (IIM) patients. We aimed to investigate the clinical features of IIM patients with AMAs.
MethodsWe retrospectively analysed consecutive 1,167 patients with IIM for AMAs-associated myositis and compared them to age-and sex-matched AMA-negative patients.
ResultsTwenty-nine patients (2.5%) were identi ed with AMAs-positive myositis; eight of them had primary biliary cholangitis (PBC). There were no signi cant differences in skin rash, dysphagia, interstitial lung disease, and muscle strength between AMAs-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 classi ed as IMNM which was signi cantly higher than that of patients with coexistent anti-AMAs and myositis-speci c antibodies (p=0.026). Moreover, AMAs-positive patients had a signi cantly higher cardiac involvement ratio (P<0.001) compared to controls. Comparsion in AMAs-positive IIM patients show the incidence of abnormal echocardiography ndings was signi cantly higher in patients without primary biliary cholangitis (PBC) than in patients with PBC(P=0.009). Patients without heart abnormalities took signi cantly less time to achieve disease remission and prednisone tapering to <10 mg than patients with heart abnormalities (P<0.001 and P=0.001, respectively).
ConclusionsIMNM was a major histopathological nding in IIM patients with isolated anti-AMAs antibody. AMAs was signi cantly associated with cardiac involvement in IIM. PBC seemed to be a protective factor for abnormal echocardiography ndings in AMAs-positive patients. Patients without heart involvement took less time to achieve disease remission and prednisone tapering off.