Distinctiveness and correlates of maladaptive behaviour in children and adolescents with Smith-Magenis syndrome

This two-part study examines the distinctiveness and correlates of maladapt ive behaviour in 35 children and adolescents with Smith-Magenis syndrome, a developmental disorder caused by an interstitial deletion of chromosome 17 (p11.2). Study I compares Child Behavior Checklist scores in 35 children w ith Smith-Magenis syndrome to age- and gender-matched subjects with Prader- Willi syndrome and mixed intellectual disability. Subjects with Smith-Magen is syndrome had significantly higher levels of maladaptive behaviour than t he other groups. Although some problems were shared across groups, 12 behav iours differentiated the three groups with 100% accuracy. Study 2 assessed the frequency and correlates of self-injurious and stereotypical behaviours , including unusual features such as nail-yanking, inserting objects into b odily orifices, self-hugging and a 'lick-and flip' behaviour. Nail-yanking and bodily insertions were less common than other types of self-injury, and self-hugs and the 'lick-and flip' stereotypies were seen in about half the sample. Although age and degree of delay were correlated with problem beha viours, sleep disturbance emerged as the strongest predictor of maladaptive behaviour. The implications are discussed for clinical diagnostic ambiguit ies between the Smith-Magenis and Prader-Willi syndromes, and for intervent ion.