Which condition features decreased mobility of the lower two-thirds of the esophagus with constriction of the lower esophageal sphincter?

The condition characterized by decreased mobility of the lower two-thirds of the esophagus, along with constriction of the lower esophageal sphincter, is achalasia. This disorder affects the ability of the esophagus to move food into the stomach and can lead to symptoms such as difficulty swallowing, chest pain, and regurgitation. In achalasia, the lower esophageal sphincter fails to relax properly, which creates a blockage that hinders the passage of food.

Aphthous stomatitis primarily refers to small, painful ulcers within the mouth and does not pertain to esophageal function. Colorectal cancer involves the lower part of the digestive tract and does not directly relate to conditions affecting the esophagus. Diarrhea is a symptom rather than a specific disease and does not involve the esophageal motility or sphincter function at all. Therefore, achalasia is the only condition listed that directly describes the symptoms of decreased esophageal mobility and lower esophageal sphincter constriction.