Spotlight on Research 2008

June 2008 (historical)

Gene Expression Could Help Diagnose, Monitor Muscle Diseases

Genetic research supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases and the Muscular Dystrophy Association is providing new insight into polymyositis and dermatomyositis, two related and poorly understood inflammatory muscle diseases. This research could aid the search for less invasive ways to diagnose the diseases and monitor their treatment.

The precise causes of polymyositis and dermatomyositis are unknown, but scientists think they occur when the body's immune system mistakenly recognizes part of the muscle fiber as foreign and attacks it. The result is progressive muscle weakening and, in the case of dermatomyositis, an accompanying skin rash. For most people, the diagnostic procedure is painful, requiring surgical removal of a sample of muscle tissue. Treatment can be difficult, too. Many people respond poorly to the available medicines or have problematic side effects.

Previous studies of muscle samples from people with dermatomyositis have shown the increased expression of a group of genes that produce type I interferon-α/β (IFNα/β). Interferons are a family of proteins secreted by cells to combat viruses. The new study, published recently in Arthritis & Rheumatism, examined 38,500 genes from blood and muscle samples of 44 people with polymyositis, dermatomyositis or other muscle diseases, as well as from 12 people without muscle disease. Its authors found that the group of genes over expressed in people with polymyositis or dermatomyositis were not over expressed in people with the other muscle diseases. They also found that the gene expression decreased when the dermatomyositis and polymyositis patients responded to treatment.

Although prior studies revealed the importance of the IFNα/β-regulated genes when measured by means of muscle biopsy, the new research demonstrates that less invasive blood samples provide similar information.

If future studies confirm the findings, such blood tests could be used to diagnose polymyositis and dermatomyositis and monitor response to treatment. The findings are also helping researchers target new therapies for these diseases. One early-stage trial of an antibody against IFNα is currently underway. It will enroll up to 80 participants who have dermatomyositis or polymyositis and a high IFNα/β pattern of gene expression in their blood.

The mission of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), a part of the Department of Health and Human Services' National Institutes of Health, is to support research into the causes, treatment, and prevention of arthritis and musculoskeletal and skin diseases; the training of basic and clinical scientists to carry out this research; and the dissemination of information on research progress in these diseases. For more information about NIAMS, call the information clearinghouse at 301-495-4484 or 877-22-NIAMS (free call) or visit the NIAMS Web site at


Walsh, RJ, et al. Type I interferon-inducible gene expression in blood is present and reflects disease activity in dermatomyositis and polymyositis. Arthritis Rheum 2007;56(11):3784-92.