Some conditions may have symptoms similar to autism; therefore, professionals must be diligent when determining a diagnosis and its treatment.

Following is a list of related syndromes/disorders that manifest behaviors similar to those of autism and/or are more prevalent in individuals with autism:

Congenital Rubella Syndrome: Helen Keller National Center for Deaf-Blind Youths and Adults

Cornelia deLange Sydrome: Cornelia deLange Syndrome Foundation

Down Syndrome: National Down Syndrome Society

Fragile X Syndrome: National Fragile X Foundation

Klüver-Bucy Syndrome: National Institute of Neurological Disorders and Stroke

Landau-Kleffner Syndrome: National Institute of Neurological Disorders and Stroke

Lesch-Nyhan Syndrome: Lesch-Nyhan Disease network

Untreated Phenylketonuria (PKU): National PKU Alliance

Prader-Willi Syndrome: Prader-Willi Syndrome Association

Rett Syndrome: International Rett Syndrome Foundation

Tourette Syndrome: Tourette Syndrome Association

Tuberous Sclerosis: Tuberous Sclerosis Alliance

Williams Syndrome: Williams Syndrome Association

Although autism is commonly thought of as a mental health disorder, it is a whole-body condition and can manifest through a number of physical symptoms and characteristics.