**Core Concept**
Harlequin ichthyosis is a rare genetic disorder characterized by severe scaling of the skin, leading to a characteristic "harlequin" appearance. It is caused by mutations in the ABCA12 gene, which plays a crucial role in the normal functioning of the epidermal lamellar body. This disorder is a result of impaired lipid metabolism and transport in the skin.

**Why the Correct Answer is Right**
The correct answer is autosomal recessive because the ABCA12 gene is located on an autosome (non-sex chromosome) and mutations in both copies of the gene (one from each parent) are required to express the disorder. This is in contrast to autosomal dominant disorders, where a single copy of the mutated gene is sufficient for expression. The ABCA12 gene is crucial for the proper functioning of the epidermal lamellar body, which is responsible for the production and secretion of lipids in the skin.

**Why Each Wrong Option is Incorrect**
**Option A:** X-linked recessive - This option is incorrect because the ABCA12 gene is not located on a sex chromosome and mutations in the gene do not show a sex-linked pattern of inheritance.
**Option B:** Autosomal dominant - This option is incorrect because mutations in both copies of the ABCA12 gene are required to express the disorder, not just one copy.
**Option C:** Mitochondrial inheritance - This option is incorrect because the ABCA12 gene is not located in the mitochondria and mutations in the gene do not show a pattern of mitochondrial inheritance.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that Harlequin ichthyosis is a rare and severe disorder that requires prompt medical attention. Early diagnosis and management can improve the quality of life for affected individuals.

**Correct Answer: C. Autosomal recessive.**