We read with interest a recent article in CHEST (June 2001)1that considered pectus excavatum as the cause of hypercapnic respiratory failure. Patients with generalized neuromuscular weakness that results in scoliosis, such as those with Duchenne muscular dystrophy2and those with pectus due to the generalized weakness associated with spinal muscular atrophy type 1 (SMA1),3 develop hypercapnic respiratory failure. Also, even when not associated with generalized weakness, thoracic deformity from kyphoscoliosis, when severe enough, itself can result in hypoventilation. However, in the cases of patients with Duchenne muscular dystrophy and SMA1, the ultimate cause of the skeletal impairment is muscular. Likewise, idiopathic scoliosis may be due to paraspinal muscle weakness, just as the pectus in these patients may be due to, or at least may be associated with, intercostal muscular impairment. Although diaphragmatic function was tested in these patients with pectus, the values of the sniff test were not given. An assessment of maximum inspiratory pressures would reflect the strength of inspiratory muscles, including those of the rib cage. If the root cause of the problem is an underlying muscular impairment, then the hypercapnia may be due more to that condition, and the pectus deformity may be only secondary, just as it is for patients with SMA1. The fact that the patient had a history of being easily fatigued and frail as a child implies a possible neurologic or muscular disorder that worsened with time.