Pulmonary function and ventilatory response to chemical stimuli in familial myopathy

We studied the pulmonary function and ventilatory response to carbon dioxide and hypoxia in three sisters aged 16, 13, and 10 years who presented with droopy eyelids, external ophthalmoplegia, hearing loss, speech difficulty, and truncal muscular weakness. Pulmonary function test results showed decreased maximum static pressure, reduced vital capacity and total lung capacity, normal functional residual capacity, elevated residual volume, and reduced dynamic pulmonary volumes. The degree of functional abnormality paralleled the severity of clinical manifestations. The characteristic picture of pulmonary functional abnormality was distinct from either restrictive disorders of pulmonary origin or obstructive pulmonary diseases. The ventilatory response to hypoxia was markedly diminished and hypercapnic response was moderately diminished in all three patients.