Dermatomyositis. Diagnosis and evaluation of dermatomyositis, polymyositis, and inclusion-body myositis.

In diseases of an unknown etiology, such as the idiopathic inflammatory myopathies, we must tackle first of all the question of classification and the degree of disease activity before we can institute treatment. The majority of idiopathic inflammatory myopathies are diagnosed clinically and confirmed by biopsy. The presently applicable methods of diagnosis and evaluation of idiopathic inflammatory myopathy have certain limitations, and hence it is necessary to apply new methods of rating the disease activities. Magnetic resonance imaging (MRI) and 99m-technetium muscle-scanning are the latest noninvasive methods for evaluation of disease activities with myositis. Future laboratory methods to determine the numerous myositis-specific autoantibodies will probably enable identification of subsets of these diseases.