Resource : Definitions of Disabilities

These are the examples of common developmental disabilities. If you notice the signs of developmental disabilities, it is critical to discuss with a specialist such as a special education teacher, doctor, psychologist, or therapist who has knowledge in developmental disabilities and receive appropriate diagnosis. Appropriate treatment and intervention strategies vary by individual needs. Please discuss details with a specialist.

Pervasive Developmental Disorder; PDD

Pervasive Developmental Disorder (PDD) is a group of disabilities that are characterized by social, communication, and langauge difficulties due to the differences in brain function. Individuals with PDD may have limited areas of interest and persistent preoccupation with some objects or subjects. There are many types of PDD, which widely vary in abilities, intelligence, and behaviors.

Types of Pervasive Developmental Disorder


In principle, the signs of autism appear before age 3. Some of these signs include not being interested in others, communication difficulties, and limited areas of interest.

Rett Syndrome
Rett syndrome is more common in females than in males, and the signs of Rett syndrome usually appear between 6 to 18 months. Some signs of Rett syndrome are the delays in intelligence, language, or physical development and unpurposeful use of hands, including hand wringing, hand clasping, hand clapping or tapping, or repeatedly moving hands toward month.
Childhood Disintegrative Disorder; CDD

Children with Child Disintegrative Disorder (CDD) follow typical developmental stages by age 2; however, between age 3 to 10, some signs of CDD start to appear gradually. One of the characteristics of CDD is to lose already acquired skills. For instance, children who already learned basic speech may lose the speech skills after the onset of symptoms.

High-functioning Autism
Individuals with high-functioning autism have average or above-average intelligence, and mainly have problems with socialization and communication. Asperger syndrome has similar symptoms, but less severe than high-functioning autism.