Muscle Pathological Features and Extra-Muscle Involvement in Idiopathic Inflammatory Myopathies With Anti-Mitochondrial Antibody

Abstract

BackgroudAnti-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.Methods We 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 identified with AMAs-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 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 classified as IMNM which was significantly higher than that of patients with coexistent anti-AMAs and myositis-specific antibodies (p=0.026). Moreover, AMAs-positive patients had a significantly higher cardiac involvement ratio (P<0.001) compared to controls. Comparsion in AMAs-positive IIM patients show the incidence of abnormal echocardiography findings was significantly higher in patients without primary biliary cholangitis (PBC) than in 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<0.001 and P=0.001, respectively).ConclusionsIMNM was a major histopathological finding in IIM patients with isolated anti-AMAs antibody. AMAs was significantly associated with cardiac involvement in IIM. PBC seemed to be a protective factor for abnormal echocardiography findings in AMAs-positive patients. Patients without heart involvement took less time to achieve disease remission and prednisone tapering off.

Refractory ventricular tachycardia and heart failure due to anti-mitochondrial antibody-positive inflammatory myopathy

“…Two Chinese patient cohorts reported the positive ratio varied from 2.5 -5% [6,7]. In addition, it was identified that IMNM was the major histopathological finding in AMAs-positive IIM, which is consistent with the current report [6].…”

“…A study from Japan reported 11.3% myositis patients had positive AMAs and the incidence ratio of males to females varies from 9:15−1:6 [5]. Two Chinese patient cohorts reported the positive ratio varied from 2.5 -5% [6,7]. In addition, it was identified that IMNM was the major histopathological finding in AMAs-positive IIM, which is consistent with the current report [6].…”

The effect of immunosuppressive therapy on cardiac involvements in anti‐mitochondrial antibody‐positive myositis

“…Recently, the AMA‐M2 subtype was identified as an associated factor for cardiac involvement in a multicentre cross‐sectional study 19 . AMAs were detected in about 5%–10% of inflammatory myositis and the cardiac involvement was more frequent in the AMA‐positive myositis than other inflammatory myositis with a 30%–70% incidence rate 4,8,9,20–22 . The first symptoms were cardiovascular in about 50% of cases with cardiac involvement 22 .…”

“…19 AMAs were detected in about 5%-10% of inflammatory myositis and the cardiac involvement was more frequent in the AMA-positive myositis than other inflammatory myositis with a 30%-70% incidence rate. 4,8,9,[20][21][22] The first symptoms were cardiovascular in about 50% of cases with cardiac involvement. 22 In our study, the most frequent initial symptom was dyspnoea (60%), and 87% of the patients first visited the cardiovascular department.…”

“…7 Serum AMA-M2 levels were measured by MESACUP-2 Test Mitochondria M2 kit (Medical and Biological Laboratories) or Elia M2 Well (Thermo Fisher Scientific). Following previous reports, 4,[8][9][10] we included patients who were positive for these tests in this study and called them 'AMApositive myositis'. Cardiac involvement was defined as one or more of the following: arrhythmia, reduced left ventricular ejection fraction (LVEF) < 50%, and LV wall motion abnormality.…”