Common features include: characteristic, yet subtle, facial appearance, infant feeding problems, low muscle tone, developmental delay, variable levels of mental retardation, early speech/language delay, middle ear problems, skeletal anomalies and decreased sensitivity to pain.
The syndrome also includes a distinct pattern of neurobehavioral features characterized by chronic sleep disturbances, arm hugging/hand squeezing, hyperactivity and attention problems, prolonged tantrums, sudden mood changes and/or explosive outbursts and self-injurious behaviors.