Clinical score for early diagnosis of myotonic dystrophy type 2

Abstract

Background and aims: Myotonic dystrophy type 2 (DM2) is a rare, multisystemic, autosomal dominant disease with highly variable clinical presentation. DM2 is considered to be highly under-diagnosed. The aim of this study was to determine which symptoms, signs and diagnostic findings in patients referred to neurological outpatient units are the most indicative to arouse suspicion of DM2. We tried to make a useful and easy-to-administer clinical scoring system for early diagnosis of DM2 - DM2 Early Diagnosis Score (DM2-EDS). Methods: 291 patients with a clinical suspicion of DM2 were included: 69 were genetically confirmed to have DM2 and 222 patients were DM2 negative. Relevant history, neurological, and para-clinical data were obtained from the electronic medical records. Results: Following parameters appeared as significant predictors of DM2 diagnosis: cataracts (beta=0.410, p<0.001), myotonia on needle EMG (beta=0.298, p<0.001), hand tremor (beta=0.211, p=0.001), positive family history (beta=0.171, p=0.012), and calf hypertrophy (beta=0.120, p=0.043). In the final DM2-EDS, presence of these symptoms was associated with following values: cataracts 3.4, myotonia 2.5, tremor 1.7, family history 1.4, and calf hypertrophy 1.0. Cut-off value of 3.25 of maximum 10 points had sensitivity of 84% and specificity of 81% to diagnose DM2, while cut-off value of 4.6 points had sensitivity of 81% and specificity of 95% in early diagnosis of DM2. Conclusion: Significant predictors of DM2 diagnosis in neurology outpatient unit were identified. We made an easy-to-administer DM2-EDS score for early diagnosis of DM2