Advances in Pulmonary Care in Duchenne Muscular Dystrophy

D uchenne muscular dystrophy (DMD) is a degenerative neuromuscular disease leading to progressive muscle weakness and loss. This review discusses advances in understanding the natural history of DMD, as well as recent pharmacotherapies. Decline in expiratory and inspiratory pulmonary function results in ineffective airway clearance, sleep-disordered breathing and nocturnal and daytime respiratory failure. Routine measures of pulmonary function include forced vital capacity (FVC) and peak expiratory flow (PEF). Both measures follow parallel trajectories and relentlessly decline, reaching the lower limit of normal of 80% of predicted at early teenage years. Moreover, decline in PEF and FVC are closely correlated with respiratory complications and clinically relevant thresholds for FVC are defined in standard of care recommendations. Glucocorticoids (GCs) delay the onset of pulmonary function decline, but once patients have reached the 80% of predicted threshold the decline of FVC and PEF in GC users and patients not using GCs is comparable. In the successful phase III DELOS trial in DMD patients not using GCs, the short-chain benzoquinone idebenone (Raxone®, Santhera Pharmaceuticals, Liestal, Switzerland) has demonstrated statistically significant and clinically relevant efficacy on expiratory and inspiratory function in patients in the pulmonary function decline stage. These results indicate that idebenone can modify the natural course of respiratory disease progression, which is relevant in clinical practice where loss of respiratory function continues to be a predominant cause of early morbidity and mortality in DMD.