**Core Concept**
Achalasia is a primary esophageal motor disorder characterized by the failure of the lower esophageal sphincter (LES) to relax, leading to dysphagia, regurgitation, and weight loss. The pathophysiology involves abnormal esophageal peristalsis, impaired LES relaxation, and increased LES pressure.

**Why the Correct Answer is Right**
Body peristalsis is not normal in achalasia; rather, it is often replaced by aperistalsis or simultaneous contractions. This is due to the degeneration of the myenteric plexus, which disrupts the normal coordination of esophageal muscle contractions. The loss of normal peristalsis contributes to the clinical symptoms of dysphagia and regurgitation. In contrast, LES pressure is increased in achalasia due to the failure of the LES to relax, and dilatation of the proximal esophagus is a common finding.

**Why Each Wrong Option is Incorrect**
**Option A:** Achalasia does not directly predispose to malignancy, although long-standing dysphagia may lead to complications like esophageal strictures or Barrett's esophagus, which may increase the risk of esophageal cancer. However, this is not a direct consequence of achalasia.
**Option C:** Increased LES pressure is a hallmark of achalasia, making this statement true, not false.
**Option D:** Dilatation of the proximal esophageal segment is a common finding in achalasia, making this statement true, not false.

**Clinical Pearl / High-Yield Fact**
Achalasia should be distinguished from other causes of dysphagia, such as esophageal carcinoma or stricture. A key diagnostic feature of achalasia is the failure of the LES to relax in response to swallowing or pharmacological stimuli, which can be assessed using manometry or barium swallow studies.

✓ Correct Answer: B. Body peristalsis is normal