Which type of inheritance does Aicardi syndrome fall into?

• A. X-linked dominant
• B. X-linked recessive
• C. Autosomal dominant
• D. Autosomal recessive

Answer: (A)

Aicardi syndrome is classified as an X-linked dominant condition. This means that the gene responsible for the disorder is located on the X chromosome, and it only takes one copy of the mutated gene for the condition to manifest in females, who have two X chromosomes. In males, who have one X and one Y chromosome, a mutation on the X chromosome is typically lethal, which is why Aicardi syndrome primarily affects females.

The hallmark features of Aicardi syndrome include agenesis of the corpus callosum, seizures, and chorioretinal lacunae. Understanding the inheritance pattern is crucial for genetic counseling and risk assessment, especially since the condition arises from a mutation that is passed through maternal genes.

This X-linked dominant inheritance pattern contrasts with the other types of inheritance listed. For example, X-linked recessive conditions require two copies of the mutated gene in females (one on each X chromosome) for the condition to manifest, making them different from Aicardi syndrome, which appears with only one affected copy. Autosomal dominant and recessive forms involve genes located on the autosomes (non-sex chromosomes) and follow different inheritance rules related to the number of alleles required to express the trait.