Smith-Magenis Syndrome (SMS) is a rare genetic syndrome which results from an interstitial deletion in chromosome 17p11.2.
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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 1. Globally over 100 cases of the condition have been described in the medical literature 1.
Clinical presentation
Reported clinical manifestations of the syndrome include 1-3:
- 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 1.
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