It is a developmental disorder that affects many parts of the body. The major features of this condition include mild to moderate intellectual disability, delayed speech and language skills, distinctive facial features, sleep disturbances, and behavioral problems. Most people with SMS have a deletion of genetic material in each cell from a specific region of chromosome
Symptoms and Causes
The major features of Smith-Magenis syndrome include mild to moderate intellectual disability, delayed speech and motor skills, dental abnormalities, behavioral problems, distinctive facial features, sleep disturbances, skeletal abnormalities.
Facial features in people with SMS may be subtle in early childhood, but usually become more apparent with age. They may include:
- A broad, square-shaped face with deep-set eyes, full cheeks, and a prominent lower jaw
- A “flattened” appearance to the middle of the face and the bridge of the nose
- A downward-turned mouth with a full, outward-curving upper lip
While people with SMS often have affectionate, engaging personalities, most also have behavioral problems. These may include:
- Frequent temper tantrums and outbursts
- Difficulty paying attention
- Self-injury, including biting, hitting, head-banging, and skin picking
- Repetitive self-hugging (a trait that may be unique to SMS)
- Compulsively licking the fingers and flipping pages of books (a behavior known as ‘lick and flip’)
Additional features of SMS may include short stature, scoliosis, reduced sensitivity to pain and temperature, chronic ear infections, obesity, and a hoarse voice.
The oral motor and swallowing/feeding difficulties typically begin within the first year of life and improve throughout childhood with therapeutic interventions. Frequently, sucking abilities are poor and transitioning to specific food textures are often challenging for parents. Although infrequent, it is not uncommon for children to develop failure to thrive if feeding issues are severe. These may require alternate feeding sources or feeding supplements to assist with growth and development. Services to enhance children with these difficulties can be obtained with specialists such as gastroenterologists, nutritionists, speech-language pathologists and other professionals within early intervention programs. Chewing and mastication are often delayed and food refusals and transitions can be difficult. Often delays in oral motor movements contribute to these problems. Speech Pathology therapeutic interventions can assist with these and can help with oral motor skill development necessary for these functional skills.
In addition to the oral motor and swallowing/feeding delays, communication skills are frequently delayed in SMS children. These skills are important for expressing needs and wants, interacting with family members, fostering education/social development and transferring into work environments. Expressive speech skills are often delayed and frequently verbal speech is unintelligible. It is not uncommon that verbal speech is absent until early school age years.