Autism (also called autistic disorder, infantile autism, Kanner's syndrome or Kanner syndrome) is a neurodevelopmental disorder that manifests itself before the age of three years. Children with autism are marked by impaired social interaction, impaired communication, and restricted and repetitive behavior. These three characteristics reflect Leo Kanner's first reports of autism emphasizing "autistic aloneness" and "insistence on sameness". Autism spectrum disorders or ASD is mainly characterized by difficulties in social interaction, communication challenges and to engage in repetitive behaviors. However, the symptoms and severity can vary widely across different areas. For a few of them, it may be mild challenges but for others, the symptoms may be severe when lack of proper communication and repetitive behaviors interface with everyday life.
Rett syndrome is a neurodevelopmental disorder that is classified as a pervasive developmental disorder by the DSM-IV. Many argue that this is a misclassification just as it would be to include such disorders as fragile X syndrome, tuberous sclerosis, or Down syndrome where one can see autistic features. The symptoms of this disorder are most easily confused with those of Angelman syndrome and autism. The clinical features include a deceleration of the rate of head growth (including microcephaly in some) and small hands and feet. Stereotypic, repetitive hand movements such as mouthing or wringing are also noted. Symptoms of the disease include cognitive impairment and problems with socialization, the latter during the regression period. Socialization typically improves by the time they enter school. Girls with Rett syndrome are very prone to gastrointestinal disorders and up to 80% have seizures. They typically have few or no verbal skills, and about 50% of females are not ambulatory. Scoliosis, growth failure, and constipation are very common and can be problematic. Rett syndrome or RS occurs exclusively in females. This kind of syndrome is related to different mutations in MECP2 gene that codes for methyl-CpG binding protein-2 (MECP2). Recently, the scientists have suggested that MECP2 is expressed in glial cells and neurons and someday it may be possible to reverse the disorder even after birth when behavioral symptoms occur.
Asperger syndrome (also Asperger's syndrome or Asperger's disorder) is one of several autism spectrum disorders characterized by difficulties in social communication and reciprocal social skills and in restricted and stereotyped interests and activities. Asperger syndrome is distinguished from the other autism spectrum disorders by having no general delay in language or cognitive development. The extent of the overlap between Asperger syndrome and high-functioning autism (HFA—autism unaccompanied by mental retardation) is unclear. Asperger syndrome is distinguished by a pattern of symptoms rather than one single symptom. It is characterized by impairments in social interaction, and repetitive and stereotyped behaviours and interests, without significant delay in language or cognitive development. Intense preoccupation with a narrow subject, one-sided verbosity, restricted prosody and intonation, and motor clumsiness are typical of the condition, but are not required for diagnosis. Asperger’s syndrome is the most interesting label in psychiatry. Children with this kind of syndrome are known with a mild autism, often with physically clumsy, but there are many verbal prodigies speaking complex sentences at an early age. Children with Asperger's syndrome have normal to above-average intelligence but can have difficulties in social interactions and have pervasive interests in special topics.
Childhood disintegrative disorder has some similarity to autism, but an apparent period of fairly normal development is often noted before a regression in skills or a series of regressions in skills. Many children are already somewhat delayed when the illness becomes apparent, but these delays are not always obvious in young children. The age at which this regression can occur varies, and can be from age 2-10 with the definition of this onset depending largely on opinion. Regression can be very sudden, and the child may even voice concern about what is happening, much to the parent's surprise. Some children describe or appear to be reacting to hallucinations, but the most obvious symptom is that skills apparently attained are lost. This has been described by many writers as a devastating condition, affecting both the family and the individual's future. As is the case with all pervasive developmental disorder categories, there is considerable controversy around the right treatment for those diagnosed with childhood disintegrative disorder. CDD is usually considered a low-functioning form of autistic spectrum disorder. However, autism never shows the severe regression after several years of normal development that can characterise as CDD. Children with CDD show a dramatic loss of skills compared with children with autism. CDD can also tend to develop later than autism up to the age of 10 years.
Pervasive developmental disorder not otherwise specified (PDD-NOS) is a diagnosis for people who are well-described by the pervasive developmental disorder label, but who don't line up well with the other four pervasive developmental disorders diagnoses. It is usually milder than autism, with some symptoms present, and others absent. Usually, the issues focus more on social interaction.
Controversies in autism
There is considerable disagreement over the exact nature of autism; however, it is generally considered to be a neurodevelopmental condition that manifests in markedly abnormal social interaction, communication ability, patterns of interests, and patterns of behavior. It encompasses a wide range of atypical conditions, none of which is well understood. Although there are common and specific physical conditions comorbid to autism spectrum disorders, not all people diagnosed with autism spectrum disorders experience these. The diagnostic criteria, as of 2006, are still generally limited to psychiatric and cognitive evaluation methods with IQ score and a particular patterns of abilities (common to those with autism) featuring strongly in the formal diagnosis of autism and distinguishing it from Asperger syndrome at the time of diagnosis.