Autism Characteristics:

Autism is a highly variable neurodevelopmental disorder[17] that first appears during infancy or childhood, and generally follows a steady course without remission.[18] Overt symptoms gradually begin after the age of six months, become established by age two or three years,[19] and tend to continue through adulthood, although often in more muted form.[20] It is distinguished not by a single symptom, but by a characteristic triad of symptoms: impairments in social interaction; impairments in communication; and restricted interests and repetitive behavior. Other aspects, such as atypical eating, are also common but are not essential for diagnosis.[21] Autism's individual symptoms occur in the general population and appear not to associate highly, without a sharp line separating pathologically severe from common traits.[22]

Wikipedia. Wikimedia Foundation, n.d. Web. 13 Mar. 2014. http://en.wikipedia.org/wiki/Autism#cite_note-23