**Core Concept**
Skin pigmentation and ichthyosis are side effects associated with the use of certain medications that interfere with the normal function of the skin's outermost layer, the stratum corneum. This is primarily due to the inhibition of enzymes involved in the breakdown and repair of skin lipids and proteins.

**Why the Correct Answer is Right**
The correct answer is associated with the use of **isotretinoin**, a derivative of vitamin A. Isotretinoin works by inhibiting the enzyme **acetyl-CoA carboxylase**, which is essential for the synthesis of fatty acids and the subsequent formation of skin lipids. This disruption leads to the characteristic side effects of skin dryness, pigmentation changes, and ichthyosis. The inhibition of **retinoic acid receptors** also contributes to the teratogenic effects of isotretinoin.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while other retinoids may exhibit some similar side effects, they are not as strongly associated with skin pigmentation and ichthyosis as isotretinoin.
**Option B:** This option is incorrect because amiodarone, an antiarrhythmic medication, can cause skin pigmentation changes, but it is not typically associated with ichthyosis.

**Clinical Pearl / High-Yield Fact**
Isotretinoin is a teratogenic medication that requires strict contraception in female patients to prevent severe birth defects. This medication is primarily used to treat severe acne, particularly in cases resistant to other treatments.

**Correct Answer:** C. Isotretinoin.