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School of Medicine
NeuroLogic - Giving Myositis Research Muscle
NeuroLogic Winter 2013
Giving Myositis Research Muscle
Date: January 1, 2013
Andrew Mammen's work with muscle samples from patients aims to demystify myositis and other autoimmune diseases.
Over the five years that the Johns Hopkins Myositis Center has been in existence, hundreds of patients with this condition have found it to be an incredibly rich resource, says neurologist and center co-director Andrew Mammen. Few other medical centers around the country have such broad expertise in treating this rare collection of autoimmune muscle diseases, he says, as well as the willingness to collaborate so closely among the different disciplines needed to help these patients, including neurology, rheumatology and pulmonology.
But the center has also been a boon for Mammen and other researchers interested in better understanding this condition and other autoimmune disorders.
“Most patients who come to the clinic are involved in our studies,” he explains. “They’ve been extremely helpful in moving our research forward.”
When patients come to the center, they spend the morning receiving a full medical work-up tailored to their specific symptoms. Most receive muscle biopsies, blood tests, MRIs, electromyographies and nerve-conduction studies to evaluate the levels of inflammation throughout their bodies and how well their nerves and muscles are functioning. Some also receive tests to evaluate their lungs and skin, which can also be affected by myositis. In the afternoon, the center’s diverse group of physicians from different specialties evaluates each patient’s test results and collectively recommends a comprehensive treatment.
As part of this work-up, Mammen says, patients are often asked to volunteer for studies. Their involvement may be as simple as signing a waiver that allows their tissue samples to be used for research purposes.
Myositis is unlike other autoimmune diseases, Mammen explains, in that the tissue under attack is easily accessible, and biopsies cause no lasting harm. When patients give muscle samples for testing, there’s typically plenty left over for research purposes. “It’s a good system to study autoimmunity precisely because muscle is the affected tissue,” he says. “In lupus, you don’t have lots of kidney left over from biopsies, and in multiple sclerosis, you don’t often biopsy brain tissue. Myositis gives us the unusual opportunity to look directly at the tissue being attacked.”
Those research efforts have paid off in a big way. Recently, Mammen and his colleagues discovered a new form of autoimmune muscle disease triggered by statin use. Between 5 percent and 10 percent of the 300 million patients nationwide who take statins develop muscular side effects; only a small fraction have symptoms that don’t recede when they stop taking statins. These patients often have to go on immune-suppressing medications to treat their conditions.
Using tissue from 1,000 patients from the center, Mammen and his team, including co-Myositis Director Lisa Christopher-Stine, showed that this unusual problem occurs in genetically susceptible patients and is triggered by statin use. The disrupted gene, which codes for a protein called HMG coA-reductase, is also a target for statins. The finding makes this condition one of the only autoimmune disorders in which scientists know both the problematic gene and the environmental trigger, Mammen says. Such knowledge wouldn’t be possible without the help of the center’s willing patients.
“Just three years ago,” he says, “people didn’t know that statins cause autoimmune disease. Our discovery happened remarkably quickly. Having the center and our patients made this possible.”
He adds that the center’s patients may help researchers make discoveries about other autoimmune conditions as well.
“We think insights we get with myositis,” Mammen says, “will carry over to help us understand a host of other autoimmune diseases.”
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