**5. Conclusions**

Dysphagia is common in patients with IIM, with an estimated overall prevalence rate of 36% and a particularly high prevalence in IBM. Factors with increased risk of dysphagia include malignancy and NXP2 autoantibodies. A refined instrumental assessment is more sensitive to detect dysphagia and should be included in the diagnostic work-up of swallowing impairment. Dysphagia in IIM is caused by inflammatory involvement of the swallowing muscles, which can lead to reduced pharyngeal contractility, cricopharyngeal dysfunction, reduced laryngeal elevation and esophageal hypomotility. In IIM, impaired deglutition can lead to life-threatening complications such as aspiration pneumonia and increasing mortality. Standard immunomodulatory therapy can improve swallowing function and dysphagia should, therefore, be included as a therapeutic target. Further positive therapeutic effects may result from the treatment of malignancy or from interventions targeting the cricopharyngeal muscle such as myotomy, dilatation or botulinum toxin injection.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2077-0383/9/7/2150/s1, Table S1: Articles reporting on epidemiology and prevalence, Table S2: Articles reporting on pathophysiology, Table S3: Articles reporting on outcome; Table S4: Articles reporting on therapeutic effects; Document S1: included studies with prevalence and CI in a forest plot and a funnel-plot for all meta-analysis;

**Author Contributions:** Conceptualization and study design, B.L.; formal analysis, B.L.; data curation, B.L.; writing—original draft preparation, B.L.; writing—review and editing, M.P. and T.R. and P.M. and I.C. and S.S.-K. and T.W. and S.G.M. and H.W. and R.D.; visualization, B.L.; supervision, R.D. and M.P.; All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** We are especially grateful to Hanna Labeit, who helped to create the illustration. The authors acknowledge support from the Open Access Publication Fund of the University of Muenster.

**Conflicts of Interest:** Wiendl receives honoraria for acting as a member of Scientific Advisory Boards Biogen, Evgen, Genzyme, MedDay Pharmaceuticals, Merck Serono, Novartis, Roche Pharma AG, and Sanofi-Aventis as well as speaker honoraria and travel support from Alexion, Biogen, Cognomed, F. Hoffmann-La Roche Ltd., Gemeinnützige Hertie-Stiftung, Merck Serono, Novartis, Roche Pharma AG, Genzyme, TEVA, and Wiendl is acting as a paid consultant for Abbvie, Actelion, Biogen, IGES, Johnson & Johnson, Novartis, Roche, Sanofi-Aventis, and the Swiss Multiple Sclerosis Society. His research is funded by the German Ministry for Education and Research (BMBF), Deutsche Forschungsgesellschaft (DFG), Else Kröner Fresenius Foundation, Fresenius Foundation, the European Union, Hertie Foundation, NRW Ministry of Education and Research, Interdisciplinary Center for Clinical Studies (IZKF) Muenster and RE Children's Foundation, Biogen, GlaxoSmithKline GmbH, Roche Pharma AG, Sanofi-Genzyme. All other authors declare no conflict of interest.

#### **References**


© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

### *Registered Report*
