Clinicopathological Classification of Dermatomyositis

Date: 2018-12-20
Number: 239
City: Hoofddorp, The Netherlands

239th ENMC workshop on the “Clinicopathological Classification of Dermatomyositis”
14-16 December 2018, Hoofddorp, The Netherlands

Organisers: Prof. W. Stenzel, Dr Y. Allenbach, Dr A. Mammen, Prof. O. Benveniste

Translations of the lay report:

Spanish by Albert Selva O Callaghan
Dutch by Ingrid de Groot and Marianne de Visser
Czech by Jiří Vencovský

Participants: Jiri Vencovksi, Czech Republic, Yves Allenbach, France, Olivier Benveniste, France, Olivier Boyer, France, Lisa Christopher-Stine, USA, Jan De Bleecker, Belgium, Ingrid De Groot, The Netherlands, Marianne de Visser, The Netherlands, Livia Casciola-Rosen, USA, Manabu Fujimoto, Japan, Cyril Gitiaux, France, Janine Lamb, United Kingdom, Ingrid Lundberg, Sweden, Andrew Mammen, USA, Ichizo Nishino, Japan, Albert Selva-O´Callaghan, Spain, Werner Stenzel, Germany, Guochun Wang, China, Lucy Wedderburn, United Kingdom, Victoria Werth, USA, Ocėane Landon-Cardinal, Canada, Josefine Radke, Germany, Jan Damoiseaux, The Netherlands

The 239th ENMC workshop on the “Clinicopathological Classification of Dermatomyositis” brought together experts from Europe, Japan, China, and the USA in the field of myositis. Neurologists, Rheumatologists, Dermatologists, Neuropathologists, Geneticists, Myopathologists and a patient found consensus on new diagnostic recommendations for dermatomyositis (DM).

All experts agreed on the importance of mandatory testing of myositis specific autoantibodies (MSA, e.g. TIF-1γ, Mi-2, NXP2, MDA5 and SAE) in the diagnostic workup of DM patients. Furthermore, they emphasized the importance of autoantibodies being sufficient to define certain subtypes of DM, which may have a characteristic clinical, pathological (i.e. caused by the disease) and even histological (i.e. the microscopic study of tissue) appearance. If the clinical presentation of a patient is classical, consisting of characteristic, DM-associated skin changes (e.g. DM-like rash), muscle weakness and detection of one DM-associated MSA, the diagnosis of DM may be made without a muscle biopsy. Moreover, the finding of characteristic skin changes, clinically and in a skin biopsy, in combination with MSA but without clinically overt muscle affection is also compatible with the diagnosis of DM. A more detailed definition of DM-like skin changes and histological criteria seen in the skin biopsy of an affected skin area in a DM patient will soon be published by an international expert team of dermatologists. It was clear to all experts that the muscle biopsy was and still is a very valuable tool and the gold standard in the diagnostic routine, which means that this procedure is widely recognized to be the best available test to diagnose DM. Novel methods whereby specific antigens in the patients´ tissues are found by the use of antibodies further increase the certainty of a correct histological diagnosis, however the diagnostic accuracy of autoantibody testing is not very high at present. Especially in TIF-1γ positive DM patients, the muscle biopsy combined with the patients´ age may help to stratify patients concerning their risk of already having or developing a malignancy. It became clear, that TIF-1γ should not be misinterpreted as a bona fide tumor marker. But older patients with TIF-1γ positive DM definitely need an oncological screening in routine care.

Additionally, the classification of the Anti-synthetase syndrome (ASS) was a matter of debate. Recent scientific data presented in the ENMC workshop, and being the topic of a previous ENMC workshop, clearly highlighted the differences of DM and ASS. All experts agreed on ASS being a distinct subtype, pathophysiologically clearly different from DM. Nevertheless, ASS should still be considered as DM-related syndrome since both entities may share similar clinical and pathological features. It was discussed, weather ASS patients should still be included in DM-related clinical trials. Although, there has to be a separate evaluation of ASS patients in terms of outcome and prognosis.


A full report will be published in Neuromuscular Disorders (pdf)

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