**Core Concept**
Perleche, also known as angular cheilitis, is a condition characterized by inflammation of the corners of the mouth, often accompanied by pain and crusting. It is commonly associated with nutritional deficiencies and oral candidiasis.

**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of perleche, which often involves an overgrowth of Candida albicans, a type of fungus. This occurs due to an imbalance in the oral microbiome, often resulting from factors such as poor oral hygiene, ill-fitting dentures, or nutritional deficiencies (e.g., vitamin B2 deficiency). Candida albicans adheres to the mucosal surface and secretes enzymes to break down the mucin, leading to inflammation and the characteristic symptoms of perleche.

**Why Each Wrong Option is Incorrect**
**Option A:** Not relevant to the pathophysiology of perleche.
**Option B:** While malnutrition can contribute to perleche, it is not the primary cause.
**Option C:** This option is not directly related to the etiology of perleche.

**Clinical Pearl / High-Yield Fact**
Perleche can be a symptom of underlying nutritional deficiencies, particularly vitamin B2 (riboflavin) deficiency, which can be treated with supplementation.

**Correct Answer:** D. Candida albicans