Question: How are CDD and Rett syndrome different from other autism spectrum disorders?
Answer: Childhood disintegrative disorder is much rarer than autism spectrum disorders, in general. It is less likely, also, to occur in girls. Rett syndrome, on the other hand, almost always occurs in girls. It has a known genetic basis, in most cases, unlike other autism spectrum disorders. It is less common than autistic disorder. And it is also characterized by distinctive hang-wringing movements.