Abstract
A 69-year-old woman with left-sided breast cancer developed elevated creatine kinase levels and muscle weakness in her extremities after treatment with pembrolizumab. The patient was diagnosed with immune checkpoint inhibitor (ICI)-related myositis. Although the patient had no symptoms of dysphagia, we evaluated her swallowing function because esophageal dysfunction is a known complication of idiopathic inflammatory myopathy. A videofluoroscopic swallowing study detected barium residues in the lower esophagus. Furthermore, high-resolution manometry showed impaired upper esophageal sphincter opening and absence of esophageal peristalsis, which improved partially after immunotherapy. These findings suggest that esophageal dysfunction may be an unrecognized complication of ICI-related myositis.