The patient's cell count and differential cell count were normal. His electrolyte levels were as follows: sodium, 135 mEq/L; potassium, 3.7 mEq/L; chloride, 97 mEq/L; and bicarbonate, 30 mmol/L. Other laboratory findings were as follows: BUN, 10 mg/dL; creatinine, 0.9 mg/dL; and calcium, 9.1 mg/dL. Posteroanterior and lateral plain films of the chest are shown in Figure 1. A CT scan of the chest showed a left-lower-lobe infiltrate with occasional air bronchograms that were suggestive of left-lower-lobe atelectasis and possible pneumonia. No pulmonary emboli were noted. No mediastinal lymph nodes or masses were noted. Arterial blood gas measurements were as follows: pH, 7.35; Pco2, 63 mm Hg; and Po2, 80 mm Hg. Pulmonary function test results are shown in Table 1. There was a 27% decrease in FVC (measured in upright vs supine positions). Fluoroscopy showed markedly limited movement of the right hemidiaphragm and a paralyzed (paradoxical motion) left hemidiaphragm. An electromyogram (EMG) demonstrated increased amplitude and duration of the motor unit potential of the thoracic paraspinal muscles. EMG manifestations as well as serology test results for Lambert-Eaton syndrome and myasthenia gravis were negative. MRIs of the brain, thoracic spine, and lumbar spine, and a CT scan of the cervical spine were unremarkable. Creatinine kinase levels, thyroid function test results, erythrocyte sedimentation rates, and serum protein electrophoresis findings were normal. The antinuclear antibody profile and the test results for anti-Jo antibodies were negative. The aldolase concentration was slightly elevated at 8.4 U/L (normal, 2 to 7 U/L).