• There is no known reason why more males have autistic disorder than females. However, there is one theory. Chromosomes determine gender in humans. Females have two X chromosomes while males have one X and one Y chromosome. Changes in genes on the X chromosome cause disease in males more often than females because males have only one X chromosome. If a gene on their only X chromosome doesn't work properly, they don't have an extra copy (like females do) to make up for it. Since males have autistic disorder more often than females, researchers have thought that autistic disorder might be associated with a gene on the X chromosome. However, research to date has not found an association between the X chromosome and autistic disorder.

  REFERENCE:

  1. Cuccaro M.L., Wolpert C.M., McClintock D.E., Abramson R., Beaty L.M., Storoschuk S., Zimmerman A., Frye V., Porter N., Cook E., Stevenson R., DeLong G.R., Wright H.H., Pericak-Vance, M.A. Familial aggregation in autistic disorder: Evidence against X-linkage as a major genetic etiology. American Society of Human Genetics 1996.
  
  
  
  2. Hallmayer J., Spiker D., Lotspeich L., McMahon W.M., Petersen P.B., Nicholas P., Pingree C., Ciaranello R.D. Male-to-male transmission in extended pedigrees with multiple cases of autistic disorder. American Journal of Medical Genetics. 67:13-18, 1996.

Asperger Disorder
Individuals with Asperger disorder do not have a delay in spoken language development, but can have serious deficits in social and communication skills.

Pervasive Developmental Disorder Not Otherwise Specified (PDD/NOS)
Is a diagnosis often considered for children who show some signs of autistic disorder, but who do not meet the specific diagnostic criteria for the other PDDs.

Rett Disorder
Rett disorder is among the most common genetic cause of profound intellectual and physical disability in girls, occurring more commonly than 1 in 10,000 female births.

Childhood Disintegrative Disorder
Children with childhood disintegrative disorder develop normally for a relatively prolonged period before developing a condition that resembles autistic disorder.