Pervasive Developmental Disorders is an umbrella term for a wide spectrum of disorders referred to as Autism or Autism Spectrum Disorders (ASD). The terms PDD and ASD are sometimes used interchangeably. They are a group of neurobiological disorders that affect a person’s ability to interact, communicate, relate, play, imagine, and learn. These disorders not only affect the development and function of the brain, but may possibly be related to differences in the immunological, gastrointestinal, and metabolic systems. Signs and symptoms are seen in early childhood and are visible in differences in very basic aspects of social interaction and communication, and in restricted interests and repetitive behaviors. The term “spectrum” is important in understanding autism because of the wide range of intensity, symptoms and behaviors, types of disorders, and considerable individual variation.