Autism

Autism

Autism is a childhood neurodevelopment disorder affecting approximately 1 in 70 children in the United States. The major neuropathological changes observed in autism are seen in the neuronal size of the limbic system, decreased numbers of Purkinje cells in the cerebellum, abnormalities in the brainstem, neocortex, amygdala, and hippocampus, features of cortical dysgenesis or migration disturbances, and alterations in GABAergic and cholinergic systems. Clinical autism is defined by the the presence of marked social deficits, specific language abnormalities, and stereotyped repetitive patterns of behavior.

Early Identification

Early identification of developmental disorders, in particular autism, before 2 years of age, is critical to the intervention and well-being of the infant. All infants should have developmental surveillance incorporated at every well-child preventive care. Preventive screening tests should be regularly started at 4 months of age with the Ages and Stages Questionnaire and the M-CHAT Screening Test at 18 months of age for Autism Spectrum Disorders. The detection of developmental disorders is an integral part of well-child care. Title V of the Social Security Act (42 USC Chapter 7, Subchapter V paragraph 701-710 [1989] and the Individuals with Disabilities Education Improvement Act (IDEA) of 2004 (Pub L No 108-446) reaffirm the mandate.

Vaccines and linkage with autism

A substantial vocal minority of American adults continue to hold influential misperceptions about the linkage of vaccines and autism. Refusal to vaccinate poses a serious public health risk for all, as heard immunity is required for a effective vaccination campaign.

Autism and thimerosal containing vaccines

Recent publications in the Proceeding National Academy of Sciences, Gadad_PNAS_2015_112(4) Administration of thimerosal-containing vaccines to infant rhesus macaques does not result in autism-like behavior or neuropathology.

Pregnancy Interval and Autism

Children born after an long interpregnancy interval of < 12 months or >= 72 months have a 2- to 3-fold interval increase of autism spectrum disorders as compared to children born after an interval of 36 to 47 months. The association mechanism is unknown and not explained by parental age, maternal antidepressant medication use, or changes in maternal weight before or changes during pregnancy.

Paternal Age and Autism

Current evidence from epidemiological data suggest (through association) advanced parental age in either the mother or father can lead to an increased risk of autism spectrum disorders. The genetic mechanism of increased risk for autism spectrum disorders is different in maternal and paternal figures. However, there currently is not any literature supporting advanced parental age and phenotypic severity of autism spectrum disorders.

Autism and Mercury Toxicity

Autism:
Motor –> stereotypes
Vision –> no abnormality
Speech –> delay, echolalia
Sensory –> hyper-responsiveness
Psychiatric –> socially aloof
Head size –> Large

Mercury toxicity:
Motor –> ataxia, dysarthria
Vision –> constricted visual fields
Speech –> dysarthria
Sensory –> peripheral neuropathy
Psychiatric: nonspecific depression, anxiety
Head size –> Small

Mercury Myth

When thimerosal or mercury was first thought as causing autism, the literature dispelled the myth. Epidemiological data revealed that even after removing thimerosal from vaccines, the rates of autism continued to rise. Although the diagnosis of autism spectrum disorders has expanded, increasing rates of diagnosis cannot be attributed to thimerosal since it is no longer included in vaccines.

Is Autism a Genetic Disorder?

Early twin studies initially indicated that autism is a heritable developmental disorder, with a heritability estimate of about 90%. However, larger and more recent studies have determined this genetic effect plays a smaller role than environmental influences. Recent studies have look at telomeres dysfunction and specifically how its length can predict an increased risk for autism spectrum disorders.