1. Rett Syndrome, Childhood Disintegrative Disorder, Pervasive Developmental Disorder – Not Otherwise Specified (PDD – NOS)

2. Defintion
Rett syndrome is a distinct neurological condition that begins between 5 and 30 months of age following an apparently normal early infancy.

3. Features
The baby’s head growth slows, purposeful use of the hands is replaced with stereotypic hand movements (e.g., wringing and mouthing),
there is a gradual onset of unsteadiness and awkward gait, and
severe impairments in language and cognitive abilities ensue.

4. Continued… Seizures are common. Rett syndrome primarily affects girls.
* Although it is on the ASD continuum, Rett’s syndrome is considered to be a distinct neurological condition. *

5. Childhood Disintegrative Disorder
Childhood disintegrative disorder shares behavioral characteristics with autistic disorder, but the condition does not begin until after age 2 and sometimes not until the child has reached age 10.
Medical complications are common, and the prognosis for significant improvement is usually very poor.

6. Pervasive Developmental Disorder – Not Otherwise Specified (PDD-NOS).
Children who meet some, but not all of the qualitative or quantitative criteria for autistic disorder are often diagnosed as having pervasive developmental disorder—not otherwise specified (PDD-NOS).
All children with PDD-NOS have significant impairments in socialization with difficulties in either communication or restricted interests.

7. Continued…
The boundaries for PDD-NOS are not well defined, and children with socialization problems as the result of other conditions may be misdiagnosed.