Observations on the classification of the inflammatory myopathies.

This brief review considers historical approaches to the classification of the inflammatory myopathies. The last 25 years have seen advances in our knowledge of the underlying immune mechanism but the initial trigger for the idiopathic inflammatory myopathies remains unknown. Existing classifications have their limitations, but with the absence of a "gold standard" a definitive classification is not yet possible. Despite these problems, a working classification is possible that is valuable for everyday clinical practice.