A syndrome of abnormal physical, developmental, and behavioral features due to microdeletion of chromosome 17. Behavioral problems include affective lability, temper tantrums, impulsivity, anxiety, physical aggression, destruction, argumentativeness, and sleep difficulties.
Smith-Magenis Syndrome is a multiple congenital anomaly chromosomal disorder associated with deletion in the proximal arm of Chromosome 17. Albeit underdiagnosed, SMS is considered a rare genetic disorder when compared to other genetic abnormalities with an approximate incidence of 1 in 25,000. The clinical phenotype of SMS is marked by brachycephaly, midface hypoplesia, prognatism, hoarse voice, speech delay with or without hearing loss, sleep disturbances, psychomotor and growth retardation, intellectual impairment, and behavior problems including hyperactivity, aggression, onychotillomania, self-hugging, and inappropriate insertion of foreign objects into body orifices. In some cases, children with a complete deletion of arm 17 are more severely afflicted with facial malformations, cleft palate, and major congenital malformations of the heart, skeletal, and genitourinary systems. The overall intellectual level of these children has been reported to be within the deficient range. Within this range, most investigations have revealed intellectual skills in the moderate range of mental deficiency. With regard to adaptation, the adaptive level of children with SMS is usually in the impaired range (low) across all domains (communicative, daily living skills, and social; Dykens et al., 1987).