Respiratory manifestations of rigid spine syndrome.

Thoracic abnormalities and respiratory muscle function were investigated in nine patients with rigid spine syndrome. A severe restrictive chest wall defect and limited mobility of the spine associated with clinically significant respiratory muscle weakness were present in all patients. Respiratory muscle strength and endurance were less than 60% of control values. Slight to moderate scoliosis was present in five patients and absent in four. Scoliosis appeared to have only a minor additional effect on respiratory muscle function. Six patients were emaciated, and one patient was underweight, but no relationship was seen between body mass index and respiratory muscle strength. Respiratory muscle function was more impaired in patients with hypoventilation than in normocapnic patients. Respiratory muscle involvement appears to be a significant feature of rigid spine syndrome, terminating in hypercapnic ventilatory failure in some patients.