Given the assumed underreporting of Myotonic dystrophy type 2 (DM2) in the Netherlands combined with the predominant role of pain in DM2 as well as in fibromyalgia syndrome (FMS), the authors hypothesized that there will be an excess prevalence of DM2 in patients with (suspected) FMS. They aimed to determine the prevalence of DM2 in patients with suspected FMS. A prevalence of 2% was considered a relevant excess frequency. Between November 2011 and April 2014, 398 patients with suspected FMS who had been assessed by a rheumatologist participated in this cross-sectional study. 95% of the study population was female, with a mean age of 42 years. The final ICD-9 diagnoses were collected, in 96% the diagnosis was FMS. 92% met the 2010 American College of Rheumatology (ACR) diagnostic criteria for FMS. A questionnaire including neuromuscular symptoms was completed. Creatine kinase was determined, and genetic testing for DM2 was conducted in all patients. DM2 was established in only one patient (0.25%, 95% CI 0.04-1.4%), thus disapproving the authors’ hypothesis of a relevant prevalence of 2%. These results suggest that patients with suspected FMS should not routinely be tested for DM2.
