Likewise, no specific gene has been targeted to cause autism. New evidence reveals that the serotonin-transpoter gene may be related to the cause of this disease (Rapin 101). Complications in birth are also taken into consideration. Prenatal factors are intrauterine rubella, tuberous sclerosis, chromosomal abnormalities, and brain abnormalities. Perinatal factors have little to no effect on autism. Postnatal factors include untreated phenylketonuria, infantile spasms, focal brain lesion, and rarely herpes simplex encephalitis and other rare diseases or syndromes. Evidence that genetics is an important, but not exclusive cause, of so-called primary autism includes a three to eight percent risk of recurrence in families with one affected child (Rapin 100).
Autism isn't just one disease but a category of complicated syndromes. Three of the most definable syndromes are Rett's, Asperger's, and Landua-Kleffner. Rett's syndrome is only found in females and most are retarded. This syndrome develops between the ages of six months to eighteen months. Rett's begins with a normal state of development, then the victim regresses in skills such as speech, hand movements, and social skills, along with other signs of central nervous system dysfunction. Females with Rett's are most prone to having seizures. Asperger's syndrome is affective in both males and females. After the first few years of life, victims will lose everything they have learned, but will eventually progress again. People with Asperger's appear to have more verbal and recognition skills. They also usually show strong interest in subway, bus, and train schedules and maps. Asperger's syndrome is probably the closest to primary autism. Landua-Kleffner syndrome is also found in males and females. Victims with this disorder appear normal until between the ages of three to seven, which is when regression is noticeable. They lose the ability to talk and show great social withdrawal.