Characteristics of SMS

imgCharact1A distinct pattern of physical and behavioral characteristics are present in people with SMS. An individual with SMS may have just a few or many of the features listed below:

Major Physical Features (> 75% of affected individuals)

  • Characteristic facial appearance; flattened mid-face, down-turned mouth, prominent and often rosy cheeks; prominent jaw in older children and adults; dark eyebrows that meet in midline (synophrys). (Note: these facial characteristics can be subtle.)
  • Low muscle tone (hypotonia)
  • Oral-sensory motor dysfunction (poor suck/swallow, decreased tongue strength & movement, open mouth posture, frequent drooling, textural aversions)
  • Middle ear problems (chronic ear infections) and laryngeal anomalies
  • Hoarse voice, hypernasal speech
  • Short fingers and toes
  • Hyporeflexia
  • Signs of peripheral neuropathy
  • Markedly flat feet
  • Distinct, broad-based gait (walking pattern)
  • Decreased sensitivity to pain

Major Developmental & Behavioral Features* (> 75% of affected individuals)

  • Developmental delay
  • Variable levels of intellectual disability (mild - moderate)
  • Generalized complacency/lethargy (infancy)
  • Mouthing objects or hands that persists beyond early childhood
  • Speech delay and articulation problems
  • Sensory integration issues
  • Teeth grinding
  • Delayed toileting skills (delayed potty training and/or persistence of nighttime bedwetting (enuresis) for age)
  • Maladaptive behaviors such as: hyperactivity, impulsivity, attention seeking (especially from adults); easy excitability or distractibility; sudden mood shifts; explosive outbursts; prolonged tantrums; and aggressive or destructive behavior
  • Sleep disturbance (chronic)
    • Frequent nighttime awakenings
    • Increased daytime sleepiness/naps
    • Early morning awake times (5:30 a.m. - 6:30 a.m.)
  • Inverted circadian rhythm of melatonin
  • Stereotypic/repetitive behaviors such as arm hugging/hand squeezing when excited, “lick and flip” behavior (i.e., quick flipping pages of books/magazines with/without licking finger)
  • Self-injurious behaviors: head banging, hand biting, picking at skin, sores and nails, pulling off finger- and toenails (older ages), inserting foreign object into ears, nose or other body orifices.
  • Positive behavioral features
    • Endearing/appealing personalities
    • Excellent long term memory for names, places, events
    • Great sense of humor

Common Features (50% - 75% of affected individuals)

  • Hearing impairment (conductive with/without sensorineural hearing loss)
  • Short stature (especially in early childhood)
  • Scoliosis (curvature of the spine)
  • Eye problems, including strabismus (an eye that turns in or out), myopia (nearsightedness), small cornea (microcornea) and/or iris anomalies
  • History of constipation
  • Hypercholesterolemia/hypertriglyceridemia
  • Abnormal EEG without seizures

Characteristic During Infancy

  • “Cherubic” facial appearance (rosy cheeked- appearance)
  • Happy disposition
  • Infrequent crying and diminished vocalizations for age
  • Low muscle tone (hypotonia) persisting into childhood
  • Feeding problems (poor suck/swallow, transitioning from pureed to textured foods)
  • Delayed gross motor and fine motor skills

imgCharact2Less Common Features (25% - 50% of affected individuals)

  • Congenital heart defects / murmurs
  • Lowered immune function
  • Seizures
  • Thyroid function adnormalities

Occasional Features (<25% of affected individuals)

  • Renal/urinary trace abnormalities
  • Forearm abnormalities
  • Cleft lip/palate
  • Retinal detachment

* While it is possible that a person with SMS could never show significant behavioral problems, some degree of self-injurious behavior and sleep disturbance occurs in most SMS individuals. Despite their very difficult behaviors, children and adults with SMS are very affectionate and have engaging personalities and much untapped potential.

* Note: Individuals with SMS are often diagnosed with psychiatric diagnoses based on DMSIV criteria (dual diagnosis), including: attention deficit/hyperactivity disorder (ADHD), attention deficit disorder (ADD), obsessive compulsive disorder (OCD), oppositional defiant disorder (ODD), etc.