What is the primary cause of achalasia?

Achalasia is primarily caused by the degeneration of the lower esophageal sphincter nerves, specifically the ganglion cells in the myenteric plexus. This degeneration impairs the ability of the lower esophageal sphincter to relax properly during swallowing, which leads to a functional obstruction. The absence of normal esophageal peristalsis further complicates the condition, as the esophagus cannot effectively move food into the stomach.

Other options describe possible conditions or abnormalities related to the esophagus but do not capture the fundamental pathophysiology of achalasia. Structural abnormalities may occur as a consequence of the disease or from other conditions but are not the primary cause. Inflammation and cancer can affect esophageal function but are not considered the underlying cause of achalasia. Overall, the crucial aspect of achalasia lies in the nerve degeneration that specifically affects the lower esophageal sphincter and contributes to its inadequate function.