Which disorder is associated with severe intellectual disability?

Carpenter Syndrome is associated with severe intellectual disability, making it the correct choice in this context. This syndrome, which is caused by mutations in specific genes, is a type of craniosynostosis syndrome. Individuals with Carpenter Syndrome may experience intellectual disability in addition to other physical anomalies such as fused fingers and toes, and certain craniofacial features.

Pfeifer Syndrome, while it can lead to developmental delays and some intellectual challenges, does not typically result in severe intellectual disability as commonly seen in Carpenter Syndrome. Crouzon Syndrome primarily affects the skull shape due to early closure of cranial sutures but is not characterized by severe intellectual impairment; many individuals have normal cognitive function. Saethre-Chotzen Syndrome, like Crouzon, presents with craniosynostosis but is not generally associated with severe intellectual disability, and cognitive abilities can range from normal to mildly impaired.

Thus, Carpenter Syndrome stands out due to its strong association with significant intellectual disability, making it the most accurate answer to the question posed.