Progress in inflammatory myopathies: good but not good enough
- Neuromuscular Diseases Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Building 10, Room 4N248, 10 Center Dr. MSC 1382, Bethesda, MD 20892–1382, USA
- Dr M C Dalakas dalakasm{at}ninds.nih.gov
During the past decade there have been remarkable achievements in the immunopathogenesis of the inflammatory myopathies that laid the grounds for more effective therapeutic interventions. This editorial summarises where we stand today in our understanding of these disorders and their treatment, identifies key biological issues that need further study, and considers possibilities of applying new and more specific therapeutic interventions.
Classification, nomenclature, and clinical diagnostic challenges
The inflammatory myopathies comprise three major and distinct subsets: dermatomyositis (DM), polymyositis (PM), and sporadic inclusion body myositis (s-IBM) (table 1). All three have in common the presence of moderate to severe muscle weakness and endomysial inflammation, but each subset retains characteristic clinical, immunopathological, and morphological features.1 2
- In this window
- In a new window
Inflammatory myopathies
DERMATOMYOSITIS
Dermatomyositis is a distinct disease that affects muscle and skin. Involvement of the muscle results in mild to severe myopathy; involvement of the skin causes a heliotropic rash on the face and knuckles and a flat red rash on the trunk, knees, neck, chest, and back. When the muscle strength is normal, the term dermatomyositis sine myositis is used even though muscle biopsy shows the same changes as in patients with clinical signs of myositis. Dermatomyositis, but not PM or IBM, may overlap with scleroderma and mixed connective tissue disease.1 Unique for DM is its frequent association with malignancies. Putative cancer peptides that share antigenic epitopes with the muscle or endomysial capillaries have not yet been identified.
POLYMYOSITIS
Polymyositis remains a challenge in definition and diagnosis. It is a diagnosis of exclusion and must be considered in every patient with acquired myopathy of subacute onset who does not have family history, exposure to myotoxic drugs or toxins, another acquired muscle disease caused by endocrine, metabolic or neurogenic causes, IBM, or dystrophy (table 1). Exclusion of the last two conditions is crucial because they account for most patients with the …
