Which of the following is NOT a commonly associated diagnosis with intellectual disability?

• A. Alzheimer disease
• B. Autism spectrum disorder
• C. Down syndrome
• D. Fragile X syndrome

Answer: (A)

People with intellectual disability often have other developmental or genetic conditions. Down syndrome is a common genetic cause of intellectual disability, Fragile X syndrome is another well-known single-gene cause, and autism spectrum disorder frequently co-occurs with or is seen alongside intellectual disability. Alzheimer disease, however, is a degenerative disease of aging and is not a usual accompanying diagnosis with intellectual disability. (Note: in Down syndrome, risk of Alzheimer’s disease increases with age, but that’s a separate, later-life development rather than a common early association with intellectual disability.)