Idiopathic inflammatory myopathies with anti-mitochondrial antibodies: Clinical features and treatment outcomes in a Chinese cohort

Abstract

Anti-mitochondrial antibodies, the hallmark of primary biliary cirrhosis, have been detected in many patients with idiopathic inflammatory myopathies and these anti-mitochondrial-antibody-associated idiopathic inflammatory myopathies frequently show unique characteristics. We detected anti-mitochondrial antibodies in Chinese idiopathic inflammatory myopathy and summarized the clinical findings of these antimitochondrial-antibody-positive patients. Of 136 patients, seven (5.15%) were found to be anti-mitochondrial-antibody-positive. Primary biliary cirrhosis was present in 2 of these 7 patients, chronic disease duration in 2 patients and asymmetrical muscle weakness in 4 patients. The mean disease course was 8.58 months, and the mean creatine kinase level was 2256.53 U/L. Myositis-specific antibodies were found in 3 patients. According to clinical features and muscle histopathological findings, 3 patients were classified as dermatomyositis, 2 as possible polymyositis and 2 as necrotizing autoimmune myopathy. Of the 6 anti-mitochondrial-antibody-positive patients receiving follow-ups of 12-83 months, they all showed marked clinical improvement. Our study indicates that anti-mitochondrial antibodies are relatively rare in Chinese idiopathic inflammatory myopathy patients. These patients generally show various clinical features and have favorable treatment outcomes. Anti-mitochondrial antibody testing may be helpful to confirm the diagnosis of idiopathic inflammatory myopathy, especially in patients with atypical manifestations.

Rimmed Vacuoles in Myositis Associated with Antimitochondrial Antibody

“…Previous studies of myositis associated with AMA have not revealed RV or other related findings. [1][2][3][4] Among idiopathic inflammatory myopathies, inclusion-body myositis commonly shows RV, but several other features in the present patient made this diagnosis less likely, including the lack of the characteristic distribution of muscle involvement (finger flexor and quadriceps muscles), no endomysial inflammatory cell infiltration surrounding or invading nonnecrotic muscle fibers, and the clearly favorable response to corticosteroid therapy. The pathogenesis of RV has been considered to be associated with the disruption of autophagy and the ubiquitin-proteasome system.…”

“…Myositis associated with antimitochondrial antibodies (AMAs) is characterized by proximal and axial muscle weakness and cardiac involvement. 1 2 3 4 The muscle pathology most commonly manifests as necrotizing myopathy with a variable extent of inflammatory cell infiltrates. Granulomatous inflammation has been observed in 25% of myositis patients.…”

Marked Respiratory Failure in an Ambulant Patient with Immune-mediated Necrotizing Myopathy and Anti-Kv1.4 and Anti-titin Antibodies

“…We therefore measured the antibodies against SRP and HMGCR, and the results were negative. In addition, anti-mitochondrial M2 and anti-ARS antibodies, which are associated with IMNM (11,12), were also negative. Therefore, we considered the case to be one of seronegative immune-mediated necrotizing myopathy.…”

Cardiac involvement with anti‐mitochondrial antibody‐positive myositis mimicking cardiac sarcoidosis

“…1 The frequency of AMA-positive Cardiac involvement with AMA-positive myositis myositis in idiopathic inflammatory myopathies is reported to vary depending on the country: Japan (11.3-19.5%), France (7.8%), China (5.15%), and North America (0.6%). 1,2,5,6 AMA-positive myositis is characterized by chronic progressive respiratory muscle weakness, muscular atrophy, and cardiac involvement. 1 Among these patients, 20-30% have cardiac involvement including arrhythmias and LV dysfunction.…”

“…AMA is most commonly found in association with primary biliary cirrhosis 6 ; however, it has also been linked to idiopathic inflammatory myopathies 1 . The frequency of AMA‐positive myositis in idiopathic inflammatory myopathies is reported to vary depending on the country: Japan (11.3–19.5%), France (7.8%), China (5.15%), and North America (0.6%) 1,2,5,6 . AMA‐positive myositis is characterized by chronic progressive respiratory muscle weakness, muscular atrophy, and cardiac involvement 1 .…”