Characteristics/Symptoms

Characteristic facial appearance (may be subtle)
Low muscle tone (hypotonia)
Oral-sensory motor dysfunction
- Poor suck/swallow
- Decreased tongue strength and movement
- Open mouth posture
- Frequent drooling
- Possible aversion to certain textures
Below normal or absent reflexes
Peripheral neuropathy (weakness, numbness, and pain typically in hands and feet)
Distinct, broad-based gait (walking pattern)
Decreased sensitivity to pain
Short stature
Small hands and feet
- Markedly flat or highly arched feet
Abnormalities of the larynx
- Polyps
- Nodules
- Edema
- Partial vocal cord paralysis
- Horse deep voice
- Hypernasal speech
- Velopharyngeal insufficiency (impoper closing in the soft palate) and/or structural vocal fold abnormalities
Middle ear abnormalities
- Hearing loss
  - Ear infections can lead to conductive hearing loss
  - Hyperacusis (oversensitivity to certain frequencies and sounds) is common
Missing teeth
Major developmental and behavioral features (>75% of affected individuals)

Positive behavior
- Endearing/appealing personalities
- Excellent long term memory for names, places, events
- Great sense of humor
Developmental delay and variable intellectual disability (usually mild to moderate)
Tendancy to mouth objects or hands. This may persist beyond early childhood.
Speech delay and articulation problems
Autism or autistic-like features
Sensory integration issues
Tendancy to grind teeth
Delayed toileting skills
Challenging behaviors
- Hyperactivity
- Impulsivity
- Attention seeking (especially from adults)
- Easy excitability or distractibility
- Sudden mood shifts
- Explosive outbursts
- Prolonged tantrums
- Aggressive or destructive behavior
Chronic sleep disturbances
- Frequent nighttime awakenings
- Increased daytime sleepiness/naps
- Early morning waking times (5:30 a.m. - 6:30 a.m.)
Other stereotypic or repetitive behaviors include:
- Arm hugging/hand squeezing when excited
- “Lick and flip” behavior (compulsively lick their fingers and flip through pages)
Self-injurious behaviors
- Head banging
- Hand biting
- Picking at skin, sores, and nails
- Pulling off fingernails and toenails
- Inserting foreign object into ears, nose, or other body orifices.

Major physical traits and behaviors