Suggested evaluation of children with intellectual disability

Key steps in the evaluation of a child with DD/MR/ID include:

• Clinical history
• Family history
• Dysmorphologic examination
• Neurologic examination
• Karyotype
• FISH for subtelomere abnormalities
• Consider fragile X molecular genetic testing
• Consider further molecular genetic testing
• Consider brain imaging (MRI)
• Consider metabolic testing

In 1997, the American Academy of Pediatrics (AAP) published a policy statement on the clinical evaluation of the child with mental retardation or developmental delay. ([Curry: 1997]) Dysmorphology and neurology exams and genetic testing are recommended, while recognizing financial factors and distance from genetic sub-specialists may preclude such evaluation.

A dysmorphology exam by a clinical geneticist aims to identify an etiology or a genetic syndrome. A neurologic exam aims to identify etiologic clues, such as muscle weakness, spasticity, microcephaly, etc. Positive findings may lead to additional testing, such as an EEG in an patient with seizures, or a brain MRI in a child with spasticity and mental retardation.

Cytogenetic studies with high-resolution karyotyping are recommended for those for whom an etiology is not identifiable. This technique will identify a cause in approximately 10% of children with intellectual disability. If the diagnosis remains obscure, fluorescent in situ hybridization (FISH) techniques for submicroscopic subtelomeric rearrangements are recommended (allowing etiologic diagnosis in another 7.4%). [Curry: 1997] Fragile X testing, especially in boys, is also recommended. Microarray comparative genomic hybridization might be helpful in selected children. Although it is unknown what etiologic proportion this might be able to identify, this test is becoming increasingly common.

See Clinical Genetic Evaluation Algorithm (AAP) ( 520 KB) for a testing algorithm for a genetic basis for ID.