Myositis

Myositis

The chronic inflammatory myopathies collectively called myositis can be sub-grouped into different diagnoses: polymyositis, dermatomyositis, inclusion body myositis, immune mediated necrotizing myopathy and anti-sythetase syndrome. The disease is rare and the incidence rate is around 10-cases/million inhabitants/year. In Sweden there are approximately 1400 persons with myositis. The disease may occur as an own entity but also with other rheumatic diseases. It may develop acute, or slowly and lead to pronounced muscle weakness and low muscle endurance. Muscles that are usually affected are thighs, shoulders, and neck with difficulties to stand up from sitting, climbing a ladder, combing the hair, or dressing, as a few examples. In the most severe forms problems with swallowing may occur. In many cases, an involvement of other organs than skeletal muscle is often seen. The most common is skin, joints, lungs, heart and the gastrointestinal tract. A general fatigue is also common. The cause of the disease is currently unknown, but there are several signs indicating activation of the immune system and both environmental factors such as smoking and certain genetic variants are risk factors.

The treatment traditionally consists of cortisone at high doses in combination with an immunosuppressant drug. With this treatment, most patients improve concerning muscle strength, skin rash and the inflammation in the lungs, however, many patients do not regain their former capacity. Common long-term effects of treatment and the chronic disease are osteoporosis, high blood pressure, diabetes, and cardiovascular disease. Therefor there is a high unmet need for new therapies. Our research group was the first in the world to demonstrate the positive effect of physical exercise on muscle strength and that this was associated with beneficial molecular changes in muscle tissue. These findings have led to a changed treatment recommendations by international experts to combine immunosuppressive therapy with exercise in patients with myositis.