According to the Centers for Disease Control and Prevention, the prevalence of ASD in the United States may be as high as 1 in 150 children.

The disorder is divided into five subtypes, including autism prope(see info at end of article for more).

Pathogenesis of ASD may be environmental and/or biological.

Experts suspect that many genes may play a role in the etiology of ASD.

Eli Hatchwell, M.D., Ph.D., Associate Professor of Pathology at Stony Brook University Medical Center, and colleagues have found that a disruption of the Contactin 4 gene on chromosome 3 may be linked to autism spectrum disorder (ASD). What causes ASD, a developmental disorder of the central nervous system, is largely unknown. Dr. Hatchwell’s finding suggests that mutations affecting Contactin 4 may be relevant to ASD pathogenesis, and thus a potential biomarker for some individuals with the disorder. Details of the study are reported in the early online edition of the Journal of Medical Genetics.

A total of 92 patients with ASD from the Cody Center participated in the genetics study. The participants came from 81 families. Genomic DNA was analyzed from all subjects and, where relevant, from their biological parents. More than 500 normal control patients were included in the analysis.

A whole genome analysis of the 92 subjects revealed that three subjects had chromosome 3 copy number variations that disrupted the same gene, Contactin 4. A deletion was detected in two subjects (siblings), and a duplication was found in a third, unrelated, individual. Subsequent array analysis of parental DNA indicated that both variations were paternally inherited, specifically inherited from fathers without a history of ASD.

 The mutations found in Dr. Hatchwell’s study directly interrupt Contactin 4. The gene codes for an axon-associated cell adhesion molecule that is expressed in the brain and is known to be important in axonal development. According to Dr. Hatchwell, when mutations are found that explain just one percent of a given ASD population, the results are significant, as ASD likely has a multitude of genetic causes. For example, a recent study reported in the New England Journal of Medicine showed that copy number variations of chromosome 16p11.2 accounted for one percent of all cases of the syndrome. Dr. Hatchwell explains that the genetic analysis with the Cody Center patients, detailed in the article entitled “Disruption of Contactin 4 in 3 Subjects with Autism Spectrum Disorder,” is highly significant in that two of 81 families (2.5 percent) presented with a disruption of Contactin 4.

The study was supported in part by grants from the Cody Center for Autism and Developmental Disabilities, National Alliance for Autism Research, National Institute of Neurological Diseases and Stroke, the National Cancer Institute, and the General Clinical Research Center at SBUMC.

About Autism
Autism is one of a group of disorders known as autism spectrum disorders (ASDs). ASDs are developmental disabilities that cause substantial impairments in social interaction and communication and the presence of unusual behaviors and interests. Many people with ASDs also have unusual ways of learning, paying attention, and reacting to different sensations. The thinking and learning abilities of people with ASDs can vary—from gifted to severely challenged. An ASD begins before the age of 3 and lasts throughout a person's life.

ASDs include

•  Asperger's Disorder. A child with asperger's disorder has the same common problems as children with autism however they don't have language development problems of a autistic child.

  Childhood Disintegrative Disorder (CDD). Childhood disintegrative disorder (CDD) is a developmental disorder that resembles autism. It is characterized by at least two years of normal development, followed by loss of language, social skills, and motor skills before age ten. Other names for childhood disintegrative disorder are Heller's syndrome, dementia infantilis, and disintegrative psychosis.Rett's Disorder – The symptoms of this disorder are most easily confused with those of 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 and hand washing are also noted. Symptoms of the disorder include cognitive impairment and problems with socialization, the latter during the regression period. Motor involvement is quite striking and profound mental retardation is typical. Characteristic hand-washing stereotypes develop. Rett’s syndrome occurs primarily in girls, who also are very prone to gastrointestinal disorders and seizures. Lack of verbal skills, They typically have no verbal skills, scoliosis, growth failure, and constipation are also very common and can be problematic.

• Pervasive Developmental Disorder and not otherwise specified (PDD-NOS) - This child has autism but doesn't meet the criteria for high functioning autism.
  

These conditions all have some of the same symptoms, but they differ in terms of when the symptoms start, how severe they are, and the exact nature of the symptoms.