Autistic Spectrum Disorders

What are Autistic Spectrum Disorders?

1. Introduction

2. Epidemiology

3. Etiology

4. References

Contents

1. Introduction

Autism is a neurodevelopmental disorder characterized by impaired social interaction and communication, repetitive and stereotyped patterns of behavior, and uneven intellectual development often with mental retardation. Symptoms begin in early childhood. The cause in most children is unknown, although evidence supports a genetic component; in some, autism may be caused by a medical condition. Diagnosis is based on developmental history and observation. Treatment consists of behavioral management and sometimes drug therapy.

2. Epidemiology

Autism is the most common of the disorders called pervasive developmental disorders. Given the wide clinical variability of these conditions, many people also refer to PDDs as "autism spectrum disorders." Estimates of prevalence range from 5/10,000 to 50/1000. Autism is 2 to 4 times more common in boys. In the past decade, there has been a rapid rise in the diagnosis of autism spectrum disorders, partially because of changes in diagnostic criteria.


3. Etiology

Most cases of autism spectrum disorders are unrelated to diseases that affect the brain. However, some cases have occurred with congenital rubella syndrome, cytomegalic inclusion disease, phenylketonuria, and fragile X syndrome.

Strong evidence supports a genetic component. Parents of one child with a PDD have a risk 50 to 100 times greater of having a subsequent child with a PDD. The concordance rate of autism is high in monozygotic twins. Research on families has suggested several potential target gene areas, including those related to neurotransmitter receptors (GABA) and CNS structural control (HOX genes). Environmental causes (including vaccination and various diets) have been suspected but are unproven.

Abnormalities of brain structure and function probably underlie much of the pathogenesis of autism. Some children with autism have enlarged ventricles, some have hypoplasia of the cerebellar vermis, and others have abnormalities of brainstem nuclei.

4. References:

American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision. Washington, DC, American Psychiatric Association.