Polymyositis, invasion of non-necrotic muscle fibres, and the art of repetition.

A dispute has erupted over the diagnostic criteria for polymyositis, a disorder characterised by progressive muscle weakness and the presence of inflammatory infiltrates in skeletal muscle tissue that could leave many myositis patients diagnostically adrift and excluded from receiving potentially effective treatment. It might also lead to the results of clinical studies performed by one specialist not being accepted by another because of disagreement over the diagnostic criteria used. The dispute focuses on the histopathological characteristics of polymyositis and whether the presence of inflammatory infiltrates invading non-necrotic muscle fibres is a prerequisite for the diagnosis. To examine the validity of this presumed histological characteristic of polymyositis, we traced the original source of this statement by performing a structured literature search. We subsequently studied the original source in the light of present day knowledge onmyositis.