**Core Concept**
Protein-energy malnutrition (PEM) affects various bodily systems, including the integumentary system. Skin changes in PEM are primarily due to the deficiency of essential nutrients required for skin health and integrity. These changes can range from mild to severe and are often indicative of the underlying nutritional status.

**Why the Correct Answer is Right**
The skin changes seen in PEM can be attributed to the deficiency of proteins, essential fatty acids, and vitamins. Proteins are crucial for maintaining skin structure and function, while essential fatty acids are necessary for the integrity of the skin's lipid bilayer. Vitamins, such as vitamin A, play a vital role in skin health, including the maintenance of the epidermal barrier and the prevention of skin infections. The deficiency of these nutrients can lead to various skin changes, including dry skin, hair loss, and impaired wound healing.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because protein is a critical component of skin structure and function. Protein deficiency can lead to skin changes such as dryness, thinning, and fragility.
**Option B:** This option is incorrect because essential fatty acids are necessary for the integrity of the skin's lipid bilayer. Deficiency of essential fatty acids can lead to skin changes such as dryness, scaling, and impaired barrier function.
**Option C:** This option is incorrect because vitamin A is essential for skin health, including the maintenance of the epidermal barrier and the prevention of skin infections. Deficiency of vitamin A can lead to skin changes such as dryness, scaling, and impaired wound healing.

**Clinical Pearl / High-Yield Fact**
It's essential to note that skin changes can be an early indicator of protein-energy malnutrition. A thorough physical examination, including skin assessment, can help identify individuals at risk of PEM.

**Correct Answer:** D.