Abstract
• Chronic muscle inflammation in polymyositis or dermatomyositis causes muscle weakness and fatigue. • The chronic inflammation could lead to a catabolic state and additional loss of muscle mass. • The chronic muscle inflammation could induce a metabolic myopathy. • Body weight may not be reliable to measure muscle loss, rather measurement of body composition is recommended. •For patients with polymyositis or dermatomyositis it is important to provide the body with the right amount of macronutrients and trace elements for maintenance and improvement of body functions. • One recommendation is supplementation with calcium and vitamin D. • Another recommendation is regular physical exercise that during limited periods can be combined with supplements such as creatine, if done under the care of a physician.