**Core Concept**
Ichthyosis is a group of skin disorders characterized by dry, scaly, or thickened skin. It is caused by a combination of genetic and environmental factors that affect the skin's natural barrier function. The underlying pathophysiology involves impaired epidermal lipid synthesis, leading to abnormal skin permeability and hydration.

**Why the Correct Answer is Right**
The correct answer is related to the impaired synthesis of epidermal lipids, specifically ceramides, cholesterol, and fatty acids. These lipids are crucial for maintaining the skin's natural barrier function, and their deficiency leads to the characteristic symptoms of ichthyosis. The correct answer is related to the enzyme responsible for the synthesis of these lipids.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not directly relate to the pathophysiology of ichthyosis. While genetic mutations can contribute to the development of ichthyosis, this option is too broad and does not specify the underlying mechanism.
* **Option B:** This option is incorrect because it refers to a different group of skin disorders. Psoriasis is a chronic inflammatory skin disease characterized by thick, scaly skin, but it is not directly related to the impaired lipid synthesis seen in ichthyosis.
* **Option C:** This option is incorrect because it refers to a different underlying cause of skin disorders. Vitamin deficiencies can contribute to skin problems, but they are not the primary cause of ichthyosis.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that ichthyosis can be caused by a combination of genetic and environmental factors, including impaired epidermal lipid synthesis. This can lead to a range of symptoms, including dry, scaly skin, and increased skin permeability.

**Correct Answer:** C. Deficiency of the enzyme responsible for the synthesis of epidermal lipids.