Which conditions are associated with Down syndrome?

• A. Leukemia, obstructive sleep apnea, thyroid dysfunction, and early onset Alzheimer's
• B. Diabetes mellitus
• C. Asthma and allergies
• D. Hypertension

Answer: (A)

Down syndrome is associated with several well-recognized medical comorbidities that reflect how the extra chromosome 21 affects development and metabolism. Leukemia risk is heightened in children with Down syndrome, particularly certain aggressive forms like acute lymphoblastic leukemia and acute megakaryoblastic leukemia. Obstructive sleep apnea is common because of structural and functional factors such as hypotonia, midface hypoplasia, and airway anatomy that predispose to airway collapse during sleep. Thyroid dysfunction, especially hypothyroidism, occurs relatively frequently in Down syndrome and can impact growth and cognitive development if not treated. There is also a higher risk of early-onset Alzheimer disease later in life, linked to the APP gene on chromosome 21, which increases amyloid production and accelerates cognitive decline compared with the typical population.

Other options may be seen in individuals with Down syndrome but are not as characteristic or commonly emphasized as these four. Diabetes mellitus and asthma/allergies can occur in the general population and may be present, but they are not hallmark associations of Down syndrome. Hypertension is not a classic or defining association either.

Therefore, the combination of leukemia, obstructive sleep apnea, thyroid dysfunction, and early onset Alzheimer's disease best reflects the conditions associated with Down syndrome.