Childhood disintegrative disorder is also known as Heller's syndrome. It's a very rare condition in which children develop normally until at least two years of age, but then demonstrate a severe loss of social, communication and other skills.
Childhood disintegrative disorder is part of a larger category called autism spectrum disorder. However, unlike autism, someone with childhood disintegrative disorder shows severe regression after several years of normal development and a more dramatic loss of skills than a child with autism does. In addition, childhood disintegrative disorder can develop later than autism does.
Treatment for childhood disintegrative disorder involves a combination of medications, behavior therapy and other approaches.