**Core Concept:** Crouzon syndrome is a genetic disorder characterized by early fusion of cranial sutures and abnormal facial development. It is a subtype of Apert syndrome, a group of craniosynostosis disorders.

**Why the Correct Answer is Right:** Crouzon syndrome is primarily caused by mutations in the FGFR2 gene, which encodes a protein called fibroblast growth factor receptor 2 (FGFR2). This protein plays a critical role in the regulation of bone and cartilage development during embryonic growth. In individuals with Crouzon syndrome, the mutated FGFR2 protein results in premature closure of cranial sutures (craniosynostosis) and abnormal facial development.

**Why Each Wrong Option is Incorrect:**

A. Autosomal dominant inheritance: Crouzon syndrome is caused by mutations in the FGFR2 gene, which is located on chromosome 10 and follows autosomal dominant inheritance pattern. However, the correct answer is X-linked dominant inheritance.

B. Autosomal recessive inheritance: Similarly to option A, Crouzon syndrome is caused by mutations in a single gene (FGFR2) and does not follow autosomal recessive inheritance.

C. X-linked dominant inheritance: As mentioned above, Crouzon syndrome follows X-linked dominant inheritance.

D. Chromosomal abnormality: Crouzon syndrome is caused by mutations in a single gene (FGFR2), not chromosomal abnormalities.

**Clinical Pearl/High-Yield Fact:** Understanding the inheritance patterns of genetic disorders is crucial for genetic counseling and anticipating future generations' risks. Remember that Crouzon syndrome is X-linked dominant and Apert syndrome is autosomal dominant.