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Childhood development occurs in biological, psychological, social, and emotional domains, and progresses from complete dependence to autonomy. Development—while predictable and linear—does not progress synchronously for each individual. Disparities in the progression of abilities should be recognized early and intervention started as soon as possible.

Intelligence is the ability to learn, reason, problem solve, and navigate the world independently. Adaptive behavior refers to the skills to successfully function in the community. It is comprised of conceptual skills such as language and literacy; social skills such as interpersonal interactions, self-awareness, and self-esteem; and practical skills such as activities of daily living, instrumental activities of daily living, and occupational skills. Global developmental delay describes delay in children less than 5 years of age in 2 or more developmental domains noted above. This delay is thought to be a predictor of future intellectual disability (ID), but not all children with global developmental delay progress to the diagnosis of ID. ID is a neurodevelopmental disorder described as deficits in both cognitive intelligence and adaptive skills occurring before the age of 18 years. ID is anticipated to be lifelong. It is estimated that 1% to 3% of the general population is affected with ID. Many conditions are associated with ID, and so the presentation is variable. Therefore, treatment strategies must be flexible and individualized.

Individuals with ID, particularly those with higher severity disabilities, have less frequent receipt of recommended preventive care and a greater mortality rate compared to the general population. Routine care as well as treatment of associated limitations and concurrent disorders is therefore crucial. The current emphasis of treatment for ID is habilitation, or promoting function to achieve the highest capability and minimizing or preventing deterioration. Most systems prioritize keeping children in their homes or communities and not in institutions. It should be stressed that the sooner the recognition of developmental delay and the initiation of treatment occur, the better the outcome will be. This chapter focuses on the evaluation and management of intellectual and developmental disabilities for children with medical complexity.


Preventive care is the backbone of clinical services for children. Well-child visits occur frequently in the first 2 years and provide an excellent opportunity for surveillance of developmental progression and detection of delays. Developmental delays in the older child may present as behavior concerns or school failure. Once an abnormality is detected, the clinician can then evaluate the types and degree of delay and begin to consider differential diagnoses.

A general approach should begin with a thorough history and physical examination. Complete prenatal and birth histories should be reviewed for factors associated with genetic or metabolic disorders, birth trauma, or substance abuse. The past medical history should be reviewed for developmental milestones, abnormalities in newborn screening, established or suspected diagnoses, healthcare utilization patterns, and previous concern for developmental disorder. The family history ...

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