Gastroesophageal Reflux Disease (GERD): This is often the most common cause of dysphagia with a normal upper endoscopy, as the symptoms can be due to reflux and not necessarily to visible mucosal damage.

Eosinophilic Esophagitis: Although endoscopy may appear normal, this condition can cause dysphagia due to esophageal inflammation and narrowing. Diagnosis is often made through biopsy.
Functional Dysphagia: This condition involves difficulty swallowing without an obvious physical cause, which could include issues with the coordination of swallowing muscles.
Scleroderma/Esophageal Sclerosis: This autoimmune disorder can lead to esophageal dysmotility, causing dysphagia. The endoscopy might appear normal, but manometry can reveal motility issues.

Esophageal Cancer: Although less likely, especially with a normal endoscopy, it's crucial not to miss this diagnosis. Certain types of esophageal cancer might not be visible or might cause symptoms before they are visible on endoscopy.
Achalasia: A motility disorder of the esophagus that can cause dysphagia. It's essential to consider this diagnosis, as it requires specific treatment and can be diagnosed with manometry.
Ingested Foreign Body: Though typically associated with acute symptoms, a chronic foreign body could potentially cause dysphagia with a normal-appearing endoscopy if the object does not cause significant mucosal damage.

Esophageal Ring or Web: These are mucosal structures that can cause intermittent dysphagia. They might not always be visible on endoscopy, especially if they are not causing significant obstruction at the time of the procedure.
Chagas Disease: Caused by Trypanosoma cruzi, this parasitic infection can lead to esophageal dysmotility and dysphagia, particularly in individuals from endemic areas.
Esophageal Spasm: Abnormal contractions of the esophagus can cause chest pain and dysphagia. This condition might not have visible findings on endoscopy but can be diagnosed with manometry.