Dyspnea assessment in myotonic dystrophy type 1

In myotonic mystrophy type 1 (DM1), combining respiratory symptom screening and respiratory function testing, is crucial to identify the appropriate time for ventilatory support initiation. Dyspnea has been little investigated in DM1. To provide a multidimensional description of dyspnea, questionnaires assessing dyspnea were administered to 34 consecutive adult patients with DM1 (median (25th-75th centile) age of 36 (28-49), Vital Capacity (VC) of 74 (64-87)% of predicted value). Dyspnea scores were low whatever the questionnaire used: Multidimensional Dyspnea Profile score of 2(0-4.7)/50 for dyspnea sensory descriptor and of 0 (0-4.7)/60 for the emotional descriptor, Visual Analogue Scale score of 0 (0-0)/10 in sitting and supine position and Borg score after six-minute walk test (6MWT) of 2.2 (1.8-4.2)/10. Eleven patients (32%) reported disabling dyspnea in daily living (modified Medical Research Council (mMRC) score ≥ 2). In comparison with patients with mMRC score < 2, patients with mMRC score ≥ 2 had a more severe motor handicap (Muscular Impairment Rating score of 4.0 (4.0-4.0) vs 3.0 (2.0-3.5), p<0.01), a lower 6MWT distance (373 (260-424) vs 436 (346-499)m, p = 0.03) and a lower VC (64 (48-74)% vs 75 (69-89)%, p = 0.02). These data suggest that the mMRC scale might be an easy-to-use and useful tool to assess dyspnea in daily living in DM1 patients. However, the interest of integrating the mMRC dyspnea scale in clinical practice to guide therapeutic management of DM1 patients remains to be assessed in further studies.