Summary
Patients with autoimmune myositis experience an attack of the muscle by the immune system, leading to muscle inflammation and weakness. There are several types of myositis, each marked by a specific antibody biomarker that may help give rheumatologists clues about potential future symptoms, effective treatments, and long-term disease prognosis. A team of researcher from the Johns Hopkins Division of Rheumatology, led by Jemima Albayda, MD and Lisa Christopher-Stine, MD, MPH, has verified that an antibody biomarker in a group of patients with myositis is associated with cardiac involvement. This confirms a previous report from 2012 noting similar findings which were unknown to the Hopkins research team at the time of their discovery (Maeda MH, et al. Inflammatory myopathy associated with antimitochondrial antibodies. Brain 2012;135:1767-1777). These antibodies bind to a protein in the mitochondria, the energy producing factory of the cell. Usually, these antibodies are found in people with primary biliary cirrhosis, a disease where the immune system causes damage to the liver. These antibodies were also found by Dr. Christopher-Stine’s team, to be present in the blood of people with myositis who have chronic inflammation of the skeletal muscle, as well as cardiac involvement which is presumed to be inflammatory in nature.
Why was this study done?
Dr. Christopher-Stine and her team treat patients with many different forms of myositis, in the Johns Hopkins Myositis Center. Over time, they began to notice that some of their myositis patients had severe heart disease, but none of the known antibody biomarkers. They went on to find that many of these patients were positive for antimitochondrial antibodies or AMA. Based on this initial finding, the team sought to review all cases in which myositis patients had AMA and describe the clinical features of this disease subset.
How was this study done?
The research team identified patients seen at the Myositis Center who were positive for AMA and had inflammatory muscle disease. They reviewed the patients’ records to collect information on their clinical symptoms, laboratory tests, MRI images, electrophysiologic tests, and muscle biopsy results.
What were the major findings?
The researchers found that patients with AMA associated myositis often experienced a chronic disease course, with years of worsening muscle weakness prior to their diagnosis. This often led to a difficulty in doctors arriving at the correct diagnosis of myositis, and patients had severe muscle atrophy (wasting away due to underuse) by the time they were diagnosed by a rheumatologist. Heart disease was seen in 71% of these patients and took the form of myocarditis (inflammation of the heart), severe arrhythmias, or cardiomyopathy (enlargement of the heart). Although the heart disease was often not recognized to be related to the myositis, treatments that suppressed the immune system led to improvements in these symptoms.
What is the impact of this work?
This study describes a clear association of AMA with a chronic autoimmune myositis in which patients experience prominent and severe heart disease. Given the increasing evidence for such a distinct clinical entity, the authors propose that AMA should be added to the growing list of myositis-associated antibodies. They should be searched for in myositis patients with a history of severe arrhythmias, cardiomyopathy, or myocarditis. Conversely, if AMAs are noted in myositis patients, a thorough cardiac evaluation should be undertaken including EKG and echocardiography at the minimum. Early recognition of this rare form of myositis is important since prompt treatment with medications that suppress the immune system may dramatically improve disease prognosis in these patients.
This research was supported by:
The Johns Hopkins Rheumatic Disease Research Core Center (P30-AR053503) from the US National Institutes of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health; Stabler Foundation; and Huayi and Siuling Zhang Discovery Fund
Link to original research article:
Inflammatory myopathy associated with antimitochondrial antibodies: A distinct phenotype with cardiac involvement. Albayda J, Khan A, Casciola-Rosen L, Corse AM, Paik JJ, Christopher-Stine L. Semin Arthritis Rheum. 2017 Jun 13. pii: S0049-0172(17)30239-1. doi: 10.1016/j.semarthrit.2017.06.004. [Epub ahead of print]
EDIT 10/24/2017 : This article was updated to clarify that this clincial entity was previously described by Maeda, MH, et al in the 2012 issue of Brain. As such, all claims regarding the novelty of this finding in the JHU cohort have been removed from this article.
