Breathlessness Assessment in Adult Patients With Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is one of the most common neuromuscular diseases in adults. As respiratory dysfunction is the most common cause of death in patients with DM1, a respiratory disease progression must be monitored combining symptom screening and respiratory function testing, in order to identify the appropriate time to initiate non invasive ventilation (NIV). Dyspnea, one of the main respiratory symptoms, has been little studied in patients with DM1. The main objective of this study is to provide the first multidimensional description of dyspnea in patients with DM1. The secondary objectives are: * To compare respiratory symptoms according to the presence or not of criteria from respiratory function testing to initiate NIV * To assess associations between dyspnea and respiratory function testing * To assess associations between dyspnea and number of Cytosine Thymine Guanine (CTG) repeats * To assess associations between dyspnea and muscular strength * To assess associations between dyspnea and BMI * To assess associations between dyspnea and anxiety or depression * To assess associations between dyspnea and cognitive impairment * To assess associations between dyspnea and quality of life.