Table 2.

Clinical Features of Smith-Magenis Syndrome

FrequencySystemFinding
>75% of
individuals		Craniofacial/
Skeletal/
Growth
  • Brachycephaly
  • Midface retrusion
  • Relative prognathism w/age
  • Broad, square-shaped face
  • Everted, "tented" vermilion of the upper lip
  • Deep-set, close-spaced eyes
  • Short broad hands
  • Dental anomalies (missing premolars; taurodontism)
  • >90%ile for weight, w/abdominal fat deposition (esp after age 10 yrs)
Neurobehavioral
  • Infantile hypotonia
  • Generalized complacency/lethargy (infancy)
  • Oral sensorimotor dysfunction (early childhood)
  • Sensory processing issues
  • Developmental delay / cognitive impairment
  • Speech/language impairment
  • Sleep disturbance
  • Inverted circadian rhythm of melatonin
  • Attention-seeking behaviors
  • Inattention ± hyperactivity
  • Tantrums, behavioral dysregulation
  • Impulsivity
  • Stereotypic behaviors
  • Self-injurious behaviors
  • Hyporeflexia
  • Signs of peripheral neuropathy
Otolaryngologic
  • Middle-ear & laryngeal anomalies
  • Hearing loss (79%)
  • Hyperacusis (74%)
  • Hoarse, deep voice
Common
(50%-75% of
individuals)
  • Short stature
  • Scoliosis
  • Mild ventriculomegaly of brain
  • Hyperacusis
  • Tracheobronchial problems
  • Velopharyngeal insufficiency
  • Ocular abnormalities (strabismus, myopia, iris anomalies, &/or microcornea)
  • REM sleep abnormalities
  • Hypercholesterolemia/hypertriglyceridemia
  • Chronic constipation
  • Abnormal EEG w/out overt seizures
  • Features of autism spectrum disorder
Less common
(25%-50% of
individuals)
  • Cardiac defects
  • Thyroid function abnormalities
  • Seizures (11%-30%)
  • Immune function abnormalities (esp low IgA)
Occasional
(<25% of
individuals)
  • Renal / urinary tract abnormalities
  • EEG abnormalities in absence of clinical seizures 1
  • Forearm abnormalities
  • Cleft lip/palate
  • Retinal detachment

From: Smith-Magenis Syndrome

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