Smith-Magenis syndrome
Smith-Magenis Syndrome (SMS) is a rare genetic syndrome which results from an interstitial deletion in chromosome 17p11.2.
Terminology
The condition is known by several other names which are all similar variants related to its underlying karyotype: 17p deletion syndrome, 17p11.2 monosomy, chromosome 17p deletion syndrome and partial monosomy 17p.
Epidemiology
Smith-Magenis syndrome is an uncommon and rarely diagnosed condition with limited data available to accurately quantify incidence. The limited available data suggests an incidence in the region of 1:25,000 individuals . Globally over 100 cases of the condition have been described in the medical literature .
Clinical presentation
Reported clinical manifestations of the syndrome include :
- intellectual disability
- delayed speech
- delayed language skills
- sleep disturbance (reverse circadian rhythm)
- behavioral problems
- short stature
- brachydactyly and more rarely polydactyly
- scoliosis
- hoarse voice
- facial features
- square-shaped face
- deep-set eyes
- mandibular prominence
- buccal prominence
- midface flattening
- dental abnormalities
- cardiac defects (rare)
- renal defects (rare)
Pathology
Fluorescence in situ hybridization (FISH) or a comparative genomic hybridization array can be used to confirm a clinically suspected diagnosis in approximately 95% of affected individuals. The remaining 5% may warrant sequencing analysis of the RAI1 gene .
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