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             Research has revealed that parents are generally right when witnessing the developmental disorders irrespective of the fact that they many not acknowledge the specific nature or degree of the problem. The pervasive developmental disorders or autism spectrum disorders, spans from a serious form, called autistic disorder, to a mild form known as Aperger syndrome. While a child has symptoms of each of these disorders but does not cater to the particular symptoms of either, it is known as Pervasive Developmental Disorder Not Otherwise Specified -- PDD-NOS. Other serious forms of disorder under the category of spectrum disorder considered very rare are Rett syndrome and childhood disintegrative disorder. Rett syndrome impacts exclusively the females and the symptoms occur normally after the normal development of 6 to 18 months. The mental and social development of the girl child goes on declining, her reaction to the parents is negligible and she withdraws from social contact. She stops talking and has no control over her feet and twists her hands. (Autism Spectrum Disorders (Pervasive Developmental Disorders)).

             Some of the problems associated with Rett syndrome can be treated. Physical, occupational and speech therapy can assist with problems of coordination, movement and speech. Scientists of the National Institute of Child Health and Human Development have found that a mutation in the sequence of a single gene can result in Rett Syndrome. Such findings may assist doctors slow or stop the onset of the syndrome. It may also give rise to methods of screening for Rett syndrome thus assisting the doctors to initiate treatment of such children much earlier and developing the quality of life of such children experience. A small number of children those have an autism spectrum disorder -- ASD symptoms cater to the criteria for Childhood Disintegrative Disorder. The CDD normally has a strong male preponderance.