Objective. Major findings concerning the phenotype and psychoneurological symptoms of the Smith-Magenis syndrome (SMS) are presented.
Review. The Smith-Magenis syndrome (SMS) is a complex neurobehavioral, contiguous gene syndrome ascribed to interstitial microdeletion of chromosome 17, band p11.2, or - rarely - to mutations of RAI1 gene located in this region. The estimated frequency of SMS is 1 in 25000, but this may be an underestimate. The syndrome is characterized by distinctive facial features, hoarse, nasal voice, short hands and feet with brachydactyly, developmental retardation, cognitive impairment, behavioural and neurological abnormalities (including, among others, inattention, hyperactivity, impulsivity, aggression). Hearing loss, ocular problems, congenital heart and urinary tract defects are also reported. Self-injurious behaviours, including inserting foreign objects into body orifices (polyemoilokomania) and yanking finger nails and/ or toenails (onchyotillomania), as well as two stereotypic behaviours, self-hugging and the so-called,, lick and flip " behaviour, (i.e. hand licking and page flipping with no attention to the text) are thought to be specific to SMS. Patients with SMS also suffer from long-term sleep disturbances associated with inverted circadian melatonin rhythm (with high hormone levels during the day and low at night). Diagnosis of SMS is difficult and often delayed until the characteristic physical and behavioural phenotypes become evident. The Smith-Magenis syndrome may be misdiagnosed with other contiguous gene syndromes (Down 's syndrome, DiGeorge syndrome, Williams syndrome, Prader-Willi syndrome, fragile X chromosome syndrome), autism, or attention deficit/hyperactivity disorder (ADHD).