Puzzling dyspnea caused by respiratory muscle weakness.

Dyspnea is common in advanced stages of neuromuscular disorders, but it is infrequently the presenting symptom. However, dyspnea is a frequent complaint in a primary care setting but is rarely caused by a respiratory muscle weakness. Consequently, the diagnosis of respiratory muscle weakness often is delayed. First symptoms may occur when respiratory muscles are under increased load, such as when standing in the water higher than the chest, swimming, or in the supine position. We describe a patient in whom dyspnea was the first symptom of amyotrophic lateral sclerosis to remind clinicians of clinical features of respiratory muscle weakness and to help avoid the delay in diagnosis.