Levels of cognitive and linguistic development in Angelman syndrome: a study of 20 children.

Angelman syndrome (AS) is a genetic disorder associated with severe developmental delay. The purpose of this study was to investigate cognitive and linguistic development in AS. Piaget's developmental model was used to evaluate the test results. The participants comprised 20 children (14 boys and 6 girls) aged 2-14 years (median age 7.4 years). AS was diagnosed either according to typical clinical criteria or confirmatory genetic testing. Cognitive functioning was evaluated with Griffiths' Mental Development Scale. Language development was also evaluated with Receptive-Expressive Emergent Language Scale 2 (REEL-2). Cognitive functioning, based on results on the Performance Scale, never exceeded Piaget's sensorimotor stage, 0-2 years. The median mental age for language development was 9 months. Expressive verbal vocabulary consisted of less than 2 words (n = 11), 2-3 words (n = 7) and 4-5 words (n = 2). Analyses according to REEL-2 did not indicate a consistent discrepancy between impressive and expressive language.