How does Graves disease affect the respiratory system, and what is the link between Graves disease and recurrent aspiration pneumonia? The respiratory system is commonly impacted by Graves disease, as evidenced by the fact that nearly 90% of patients complain of dyspnea at the time of diagnosis. This is most often attributed to the hypermetabolic and neuromuscular effects of increased thyroid hormone levels. In a smaller number of patients, dyspnea, cough, and dysphagia may occur from direct impingement of the upper airway or esophagus by an enlarging cervical or retrosternal goiter. The increased metabolic rate associated with thyrotoxicosis results in excess carbon dioxide production and therefore increased alveolar ventilation. In addition, patients with thyrotoxicosis exhibit increased ventilatory responsiveness to carbon dioxide and hypoxia resulting in further increases in tachypnea and dyspnea. Graves disease also causes reversible skeletal muscle weakness in 50% of patients from a neuromyopathy that remains poorly understood. Typically, proximal muscles exhibit nontender weakness with normal blood muscle enzyme levels and nonspecific electromyography findings. In approximately 25% of patients, both the diaphragm and abdominal expiratory muscles can be affected, resulting in diminished inspiratory and expiratory muscle function that can be severe enough to reduce the vital capacity and lung compliance and thus contribute to respiratory symptoms. In a smaller number of Graves disease patients, pulmonary complications can result from aspiration secondary to dysphagia from pharyngeal muscle weakness. Although Graves disease can very rarely be associated with myasthenia gravis, most patients with nongoiter-related dysphagia appear to have a bulbar myopathy that may complicate a generalized myopathy or may occur in isolation without evidence of other skeletal muscle involvement. In some of these patients, recurrent aspiration pneumonia was the presenting abnormality leading to the correct diagnosis. For example Marks et al reported a 56-year-old woman with a 3-year history of tremor, weight loss without muscle weakness, and frequent episodes of choking with eating associated with at least three pneumonias in dependent lung lobes. Graves disease was diagnosed, and barium swallow revealed aspiration. All symptoms resolved with carbimazole, repeat barium swallow was normal, and she remained free of pneumonia over the subsequent 3 years of follow-up. As described by Chiu et al, some of these patients appear to have an additional contribution from thyrotoxic esophageal dysmotility. The mechanism of this is unknown but, similar to the cases of bulbar myopathy, successful treatment of the thyrotoxicosis results in normalization of swallowing function and cessation of recurrent pneumonia.