Smith-Magenis syndrome is a genetic disability due to a microdeletion or abnormality of chromosome 17. The major features of Smith-Magenis Syndrome (SMS) include mild to moderate intellectual disability, delayed speech and language skills, distinctive facial features, sleep disturbances, and behavioural problems.
Individuals with Smith-Magenis Syndrome are characterised by a short flat head, prominent forehead, broad square face, deep-set eyes, underdeveloped midface, broad nasal bridge, short nose, tented upper lip, and a chin that is small in infancy and becomes relatively prominent with age. These facial differences can be subtle in early childhood, but they usually become more distinctive in later childhood and adulthood. Dental abnormalities are also common.
During infancy quite often there are feeding problems, failure to thrive, weak muscle tone, prolonged napping and lethargy. Then later in childhood and adulthood there can be the development of disturbed sleep patterns (difficulty falling asleep, regular waking throughout the night and sleepiness in the day), as well as behavioural problems.
These behaviour problems can be exhibited in a variety of ways, frequent temper tantrums, impulsivity, anxiety, distractibility, aggression and self-injurious behaviours including self-hitting, self-biting, and skin picking.
In addition to the above challenging behaviours, there are stereotypical behaviours including ‘self-hugging’ hand licking and page flipping (“lick and flip”) behaviour, mouthing objects, insertion of hand in mouth, teeth grinding, body rocking, and spinning or twirling objects.
Other signs and symptoms of Smith-Magenis syndrome include short stature, abnormal curvature of the spine (scoliosis), reduced sensitivity to pain and temperature, possible toileting difficulties and a hoarse voice. Some individuals also have ear abnormalities that lead to hearing loss and also possible vision difficulties. Although less common, heart and kidney defects have also been reported in Individuals with Smith-Magenis syndrome.