A 34-year-old woman had worsening intermittent retrosternal dysphagia but no heartburn, nausea, vomiting, abdominal pain, weight loss, or changes in bowel habits; ranitidine (150 mg twice daily) provided no relief. CBC results were normal; esophagogastroduodenoscopy showed esophageal furrows and rings, and esophageal biopsy showed intraepithelial eosinophils. What is the diagnosis and what would you do next?