Autism overview

# Overview
Autism is a brain development disorder that impairs social interaction and communication, and causes restricted and repetitive behavior, all starting before a child is three years old. This set of signs distinguishes autism from milder autism spectrum disorders (ASD) such as Asperger syndrome. Autism has a strong genetic basis, although the genetics of autism are complex and it is unclear whether ASD is explained more by multigene interactions or by rare mutations. In rare cases, autism is strongly associated with agents that cause birth defects. Other proposed causes, such as childhood vaccines, are controversial and the vaccine hypotheses lack convincing scientific evidence. Most recent reviews estimate a prevalence of 100- 200 cases per 100,000 people for autism, and about 600 per 100,000 for ASD, with ASD averaging a 4.3:1 male-to-female ratio. The number of people known to have autism has increased dramatically since the 1980s, at least partially due to changes in diagnostic practice; the question of whether actual prevalence has increased is unresolved. Autism affects many parts of the brain; how this occurs is poorly understood. Parents usually notice signs in the first two years of their child's life. Early behavioral or cognitive intervention can help children gain self-care, social, and communication skills. There is no cure. Few children with autism live independently after reaching adulthood, but some become successful, and an autistic culture has developed, with some seeking a cure and others believing that autism is a condition rather than a disorder.

# Historical Perspective
The first reported case of autism dates back to 1798, discovered by a medical student, Jean Itard, who treated the patient using a behavioral program. In 1943, Leo Kanner first described 11 cases of autism in his paper called autistic disturbances of affective contact. In 1910, Eugen Bleuler, a Swiss psychiatrist coined the term autism form latin word autismus. In 1981, Asperger was the first to separate Asperger syndrome, from autism.

# Classification
DSM 5 categorized autism under autistic spectrum disorders/pervasive developmental disorders (PDD). Autistic spectrum of disorders are characterized by widespread abnormalities of social interactions, communication associated with severely restricted interests and repetitive behavior and can be classified into 5 types.

# Pathophysiology
Despite extensive investigation, the occurrence of autism is not well understood. Its mechanism can be divided into two areas: the pathophysiology of brain structures and processes associated with autism, and the neuropsychological linkages between brain structures and behaviors. The behaviors appear to have multiple pathophysiologies.

# Causes
Autism and autism spectrum disorders are complex neuro developmental disorders. Many causes of autism have been proposed, but its theory of causation is still incomplete. Heritability contributes about 90% of the risk of a child developing autism, but the genetics of autism are complex and typically it is unclear which genes are responsible. In rare cases, autism is strongly associated with agents that cause birth defects. Many other causes have been proposed, such as exposure of children to vaccines; these proposals are controversial and the vaccine hypotheses have no convincing scientific evidence.

# Differentiating Autism from other Diseases
Diagnosis of autism is based on behavior, but not cause or mechanism. Autism must be differentiated from other group of diseases with similar neurological presentations such as lack of social or emotional reciprocity, stereotyped and repetitive use of language or idiosyncratic language, and persistent preoccupation with parts of objects. Most common differential include Reitts disorders, other differentials include Leigh syndrome, Niemann-Pick disease type C, infantile muscle spasms.

# Epidemiology and Demographics
Most recent reviews estimate a prevalence of 100- 200 cases per 100,000 people for autism, and about 600 per 100,000 for ASD, with ASD averaging a 4.3:1 male-to-female ratio. The number of people known to have autism has increased dramatically since the 1980s, at least partly due to changes in diagnostic practice; the question of whether actual prevalence has increased is unresolved.

# Risk Factors
Common risk factors in the development of autism include male gender, advanced maternal and paternal age, low birth weight, hypoxia during childbirth, and family history schizophrenia.

# Screening
The American Academy of Pediatrics recommends that all children be screened for ASD at the 18- and 24-months using autism-specific formal screening tests.

# Natural History, Complications and Prognosis
ASD is a chronic illness with core features persisting throughout life, although presentation may vary according to the age, level of maturity, environment. Infantsare affected most severely. There is developmental delay and regression of language. Indifference and lack of interest (which is commonly found in ASD) may also seem like a delay in behavior. Some individuals may have a higher level of functioning despite social awkwardness (called savants). Autism patients may develop many syndromes and exhibit signs and symptoms of the respective syndrome, leading to complications. Higher socioeconomic status, acquisition of language skill at an early age, higher IQ and absence of underlying genetic or metabolic disorder are all associated with better outcomes in patients suffering from autism.

# Diagnosis

## Diagnostic Criteria
The diagnosis of autism is made on the basis of DSM-V Diagnostic Criteria for Autism Spectrum Disorder.

## History and Symptoms
Autism is distinguished by a pattern of symptoms rather than one single symptom. The main characteristics are impairments in social interaction, impairments in communication, restricted interests and repetitive behavior. Other aspects, such as atypical eating, are also common but are not essential for diagnosis. Individual symptoms of autism occur in the general population and appear not to associate highly, without a sharp line separating pathological severity from common traits.

## Physical examination
Physical examination of patients with autism is usually remarkable for repetitive behavior, dyspraxia, abnormal gait, and abnormality of motor functions. The signs of autism are present since birth but initial signs are visible by the age of 6-12 months. Most of the clinical signs of autism are identified by three years of age.

## Laboratory Findings
Clinical genetics evaluations are often done once ASD is diagnosed, particularly when other symptoms already suggest a genetic cause. Although genetic technology allows clinical geneticists to link an estimated 40% of cases to genetic causes, consensus guidelines in the U.S. and UK are limited to high-resolution chromosome and fragile X testing. As new genetic tests are developed several ethical, legal, and social issues will emerge. Commercial availability of tests may precede adequate understanding of how to use test results, given the complexity of autism's genetics. Metabolic tests are sometimes helpful, but are not routine.

## CT
There are no CT scan findings associated with autism

## MRI
There are no MRI findings associated with autism

## Other Diagnostic studies
Other diagnostic studies for autism include electroencephalography, polysomnography, metabolic testing, and genetic testing to rule out other conditions.

## Other imaging studies
Positron emission tomography (PET scan), single-photon emission CT scanning (SPECT) may show some deficits, but these findings are nonspecific to diagnose autism spectrum disorder

# Treatment

## Medical Therapy
Many medications are used to treat problems associated with ASD. More than half of U.S. children diagnosed with ASD are prescribed psychoactive drugs or anticonvulsants, with the most common drug classes being antidepressants, stimulants, and antipsychotics. Aside from antipsychotics, there is scant reliable research about the effectiveness or safety of drug treatments for adolescents and adults with ASD. A person with ASD may respond atypically to medications, the medications can have adverse effects, and no known medication relieves autism's core symptoms of social and communication impairments.

## Behavorial Therapy
The main goals of treatment are to lessen associated deficits and family distress, and to increase quality of life and functional independence. No single treatment is best and treatment is typically tailored to the child's needs. Intensive, sustained special education programs and behavior therapy early in life can help children acquire self-care, social, and job skills, and often improve functioning and decrease symptom severity and maladaptive behaviors; claims that intervention by age two to three years is crucial are not substantiated.

## Cost-Effectiveness of Therapy
Treatment is expensive; indirect costs are more so. A U.S. study estimated an average cost of $3.2 million in 2003 U.S. dollars for someone born in 2000, with about 10% medical care, 30% extra education and other care, and 60% lost economic productivity. Publicly supported programs are often inadequate or inappropriate for a given child, and unreimbursed out-of-pocket medical or therapy expenses are associated with likelihood of family financial problems; a 2008 U.S. study found a 14% average loss of annual income in families of children with ASD. After childhood, key treatment issues include residential care, job training and placement, sexuality, social skills, and estate planning.