Smith-Magenis Syndrome is a complex developmental disorder caused by a deletion in chromosome 17p11.2 or a mutation in the RAI1 gene. The estimated prevalence is 1:15,000-25,000 births.

Key Points

• Characterized by distinctive physical features
• Significant developmental delay and intellectual disability
• Severe sleep disturbance with inverted circadian rhythm
• Behavioral challenges including self-injury
• Requires comprehensive multidisciplinary care

Physical Features

Craniofacial

• Brachycephaly
• Broad, square face
• Midface hypoplasia
• Deep-set eyes
• Broad nasal bridge
• Prognathism with age
• Tented upper lip

Skeletal Features

• Short stature
• Brachydactyly
• Scoliosis (50%)
• Small hands and feet
• Clinodactyly

Other Systems

• Cardiovascular (30%)
  • Ventricular septal defects
  • Tetralogy of Fallot
  • Patent ductus arteriosus
• Ophthalmologic
  • Strabismus
  • Myopia
  • Iris abnormalities
• Otolaryngologic
  • Chronic otitis media
  • Hearing loss
  • Hoarse, deep voice

Diagnostic Approach

Genetic Testing

• Chromosomal microarray (CMA) - primary test
• Fluorescence in situ hybridization (FISH)
• RAI1 gene sequencing if deletion testing negative
• Multiple ligation-dependent probe amplification (MLPA)

Clinical Evaluation

• Detailed physical examination
• Developmental assessment
• Sleep study
• Behavioral evaluation
• Family history

Differential Diagnosis

• Down syndrome
• Prader-Willi syndrome
• Williams syndrome
• 1p36 deletion syndrome
• Fragile X syndrome

Multidisciplinary Care

Sleep Management

• Melatonin supplementation
• Strict sleep hygiene
• Beta-blockers (acebutolol)
• Environmental modifications
• Sleep study monitoring

Behavioral Interventions

• Applied Behavioral Analysis (ABA)
• Positive reinforcement strategies
• Environmental modifications
• Social skills training
• Parent training and support

Medical Management

• Endocrine
  • Growth hormone evaluation
  • Thyroid function monitoring
• Neurologic
  • Seizure management
  • Peripheral neuropathy assessment
• Orthopedic
  • Scoliosis monitoring
  • Physical therapy

Developmental & Behavioral Profile

Cognitive Development

• Mild to moderate intellectual disability
• Speech delay
• Better receptive than expressive language
• Relative strength in visual memory
• Challenges with abstract concepts

Behavioral Characteristics

• Self-injurious behaviors (90%)
  • Head banging
  • Self-hitting/biting
  • Skin picking
  • Nail yanking
• Stereotypic behaviors
  • Self-hugging
  • Hand licking and page flipping
  • Body rocking
• Attention seeking
• Sudden mood shifts
• Impulsivity

Monitoring & Prevention

Regular Assessments

• Annual physical examination
• Growth monitoring
• Developmental evaluation
• Behavioral assessment
• Sleep patterns evaluation

Specialty Monitoring

• Ophthalmology
  • Annual eye examination
  • Vision correction
• ENT/Audiology
  • Hearing evaluation every 1-2 years
  • Middle ear monitoring
• Orthopedics
  • Spine examination
  • Radiographs as needed
• Dental
  • Regular dental care
  • Orthodontic evaluation

Long-term Planning

• Educational support services
• Vocational training
• Transition planning
• Guardianship considerations
• Family support resources