Most patients present with mild-to-moderate intellectual disability, delayed speech and language skills, distinctive facial features (flat head, square head, and deep-set eyes), dental abnormalities, sleep disturbances, attention deficit disorders, and autism spectrum disorder. Some patients present with short stature, scoliosis, pain and temperature sensory loss, hoarse voice, and ocular abnormalities. Rarely, patients have a heart or kidney defect.
Approximately 1 in 25 000 patients are diagnosed. However, many individuals with the disorder are undiagnosed, making it an underreported condition.
Most patients have deletion of some genetic materials specific to chromosome 17. A minority of SMS patients have RA11 gene mutation.
SMS is typically not inherited, as most patients have no family history. It usually the result of a genetic change during the development of reproductive cells (eggs or sperm) or in early fetal development.
Treatment requires a multi-disciplinary team of specialists to build a comprehensive and individualized plan for each patient. Treatment is supportive and geared toward symptoms. Early intervention ensures that affected patients reach their highest potential. Special remedial education, speech and language therapy, occupational therapy, and sensory integration therapy are options. Medications may be used to treat symptoms. Feeding difficulties should be identified and properly addressed. Because SMS is a highly variable disease, prognosis is also variable.
For more information, see OMIM.
Q93.88 – Other microdeletions
401315004 – Smith-Magenis syndrome