Lung and respiratory muscle function in facioscapulohumeral muscular dystrophy

Pulmonary dysfunction is not a well-recognized feature of facioscapulohumeral muscular dystrophy (FSHD). The aim of this study was to establish the prevalence and type of pulmonary and respiratory muscle dysfunction in FSHD. Sixteen patients with moderately advanced FSHD and 16 healthy controls were evaluated. Standard lung and respiratory muscle function tests were performed. Diaphragm muscle inspiratory action was evaluated with transdiaphragmatic pressure measurements. Lung function tests showed an increased residual volume in five patients. There was a significant difference in global respiratory muscle function in patients versus controls; weakness was mild, and it affected expiratory more than inspiratory muscles. There was no significant difference in the diaphragm inspiratory action of patients versus controls. The dystrophic process that underlies FSHD did not significantly involve the muscles of the diaphragm, but it caused mild global respiratory muscle weakness that affected expiratory more than inspiratory muscles. It is probably not necessary to routinely monitor respiratory muscle function in ambulant FSHD patients who lack symptoms or signs of respiratory impairment.