Lung and respiratory muscle function in limb girdle muscular dystrophy

Pulmonary involvement is frequently observed in patients with limb girdle muscular dystrophy and occurs early in the disease. The aim of this study was to establish the prevalence of pulmonary dysfunction; the type of dysfunction; and any correlation between patient age, disease duration, or limb weakness and lung or respiratory muscle dysfunction.

Twenty patients with strictly delineated limb girdle muscular dystrophy and 20 healthy controls were evaluated. Full inspiration chest radiographs were obtained. Standard lung and respiratory muscle function tests were performed and the data were statistically analysed.

The mean age of the patients was 40.6 years, the mean disease duration was 18.9 years, and the mean average muscle score (a numerical expression of limb weakness) was 5.73 out of 10. Chest radiography showed unilateral paresis of the diaphragm in three patients. Increased residual volumes, with either increased or decreased total lung capacity, correlated inversely with disease duration. Respiratory muscle weakness was common but mild. Expiratory muscle function was more impaired than inspiratory muscle function and correlated positively with expiratory reserve volume.

Respiratory muscle strength is commonly impaired in limb girdle muscle dystrophy. A dissociation of the limb and mild respiratory muscle involvement is observed; wheelchair restriction does not predict worsening of pulmonary function, and patient age, disease duration, or degree of limb weakness do not predict pulmonary morbidity. The diaphragm is not disproportionately affected by the dystrophic process compared with limb muscles.