**Question:** Most common complication of achalasia is:

A. Esophageal perforation
B. Malignant change in the esophagus
C. Esophageal stricture
D. Gastroesophageal reflux disease (GERD)

**Correct Answer:** B. Malignant change in the esophagus

**Core Concept:** Achalasia is a motor neuron disorder causing impaired relaxation of the lower esophageal sphincter (LES) and dilated esophagus. It is primarily caused by a deficiency of cholinergic neurons in the esophageal body and lower esophageal sphincter (LES).

**Why the Correct Answer is Right:** Achalasia is characterized by the absence of peristalsis and relaxation of LES, which leads to difficulties in swallowing (dysphagia) and regurgitation of food particles into the oral cavity. The long-term consequences of untreated achalasia include chronic inflammation, fibrosis, and subsequent malignant change in the esophageal wall.

**Why Each Wrong Option is Incorrect:**

A. Esophageal perforation: This complication is rare and typically occurs due to iatrogenic causes (e.g., endoscopy or surgery) rather than the primary condition itself.

B. Gastroesophageal reflux disease (GERD): GERD is a common complication of untreated achalasia, but it is not the most common complication. The correct answer is malignant change in the esophagus.

C. Esophageal stricture: Although esophageal stricture can occur as a complication of achalasia, it is not the most common complication. The correct answer is malignant change in the esophagus.

**Clinical Pearl:** The identification of the most common complication of achalasia is crucial for proper management and patient counselling. Early referral to a specialist (gastroenterologist or interventional radiologist) is essential for timely diagnosis and treatment, which includes medications (e.g., botulinum toxin injection), endoscopic myotomy, or surgical intervention (Heller myotomy).