Pathology Diagnosis of Idiopathic Inflammatory Myopathies

Number 205
Date 1 April 2014

Location: Naarden, The Netherlands

This workshop was co-sponsored by the European Science Foundation and the Dutch ZonMw Foundation


The idiopathic inflammatory myopathies (‘myositis’) are not one single disease but encompass a group of diseases with variable clinical characteristics. A muscle biopsy is usually needed for a precise diagnosis. The identification of disease subgroups is extremely important for assessing treatment options and prognosis in the individual patient, yet classification criteria have not been standardized and validated.  A first ENMC workshop on myositis muscle pathology was held in 2012 and led to recommendations for a minimum diagnostic set of histopathological stainings and a working document on how to best define and score disease signs. At the end of the first workshop, participants agreed unanimously that continuing toward a standardized diagnostic work up is absolutely crucial to better patient care in the future.

The group of world experts on muscle pathology of patients with myositis now reconvened in Naarden to fine-tune the propositions from the first workshop.  Consensus was sought on how and what to analyze in muscle biopsies of patients suspected of having an inflammatory myopathy and how to provide accurate description of disease subtypes. It was discussed how to translate these recommendations into a comprehensive diagnostic tool that could be widely implemented. A virtual microscopy platform was used to validate the drafted morphological criteria in digitalized muscle biopsies from 24 selected patients which were assessed prior to the workshop. At the end of the workshop a consensus text was drafted stipulating the work up of muscle biopsy specimens and a working document for scoring pathological features. It was concluded that important progress was made toward the final goal being the drafting of a standardized scoring procedure for the idiopathic inflammatory myopathies. Participants reaffirmed their willingness to continue efforts in this respect.

A full report is published in Neuromuscular Disorders (pdf)