Musculoskeletal pain in patients with myotonic dystrophy type 2

Background: Myotonic dystrophy type 2/proximal myotonic myopathy (DM2/PROMM) is an autosomal dominant multisystem disorder. Musculoskeletal pain is one of its frequent symptoms but also occurs in other chronic noninflammatory muscle disorders (OMD). Objectives: To characterize the phenotype of DM2/PROMM-associated musculoskeletal pain and to test whether it shows features distinct from OMD. Setting: Outpatient clinic for patients with neuromuscular disorders, university hospital. Patients: Twenty-four patients with DM2/PROMM (12 women and 12 men; median age, 57 years) and 24 age-and sex-matched patients with OMD consecutively recruited during a 3-year period were examined for musculoskeletal pain. Methods: Standardized pain assessment; McGill Pain Questionnaire; depression score; and quantification of pain thresholds to blunt pressure on limb muscles with an algometer. Results: Unlike patients with OMD who have musculoskeletal pain, patients with DM2/PROMM distinguished a wide spectrum of coexisting pain types. The major pain type in patients with DM2/PROMM was exercise-related, temperature-modulated, and palpation-induced, whereas, cramps were rare. In 8 of the patients with DM2/PROMM and in 3 of the patients with OMD, musculoskeletal pain was the most disabling symptom. Conclusion: Besides many similarities, DM2/PROMM-associated musculoskeletal pain shows features distinct from OMD.