**Core Concept**
Ichthyosis is a group of skin disorders characterized by dry, scaly, and thickened skin, often resulting from impaired skin barrier function. The underlying pathophysiology involves abnormal keratinization and desquamation of skin cells. This can be due to genetic mutations, nutritional deficiencies, or medication side effects.

**Why the Correct Answer is Right**
The correct answer is likely a medication that affects skin cell turnover or lipid metabolism. For example, isotretinoin, a vitamin A derivative used in the treatment of acne, can cause ichthyosis as a side effect. Isotretinoin inhibits the enzyme acyl-CoA:diacylglycerol acyltransferase (DGAT), which plays a crucial role in triglyceride synthesis and skin lipid metabolism. This leads to an imbalance in skin lipids, resulting in dry, scaly skin.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the development of ichthyosis.
* **Option B:** While some medications can cause skin dryness, they are not typically associated with ichthyosis.
* **Option C:** This option is not a known cause of ichthyosis.

**Clinical Pearl / High-Yield Fact**
Isotretinoin-induced ichthyosis can be a significant concern in patients undergoing long-term treatment for acne. It is essential to monitor patients for skin changes and adjust treatment plans accordingly.

**Correct Answer: C. Isotretinoin. Isotretinoin-induced ichthyosis can be a significant concern in patients undergoing long-term treatment for acne.**