As an individual with autism, I have learned that, unfortunately, some therapists and physicians are unaware of autistics' overly acute senses, specifically hyperacute hearing. For example, the birthday party fun of noise-makers for a normal child was torture for me. There are many first-person reports of people with autism who, like me, find certain loud sounds intolerable.

Some children and adults with autism also have visual sensitivity problems. I enjoyed visually stimulating things such as flags or automatic supermarket doors, but individuals with severe visual sensitivities cannot tolerate even fluorescent lights. In her book, Somebody Somewhere, autistic Donna Williams describes how the flicker from fluorescent lights causes her visual overload. A study conducted by Coleman et al indicates that fluorescent lights can increase repetitive behavior in children with autism.

Autistic sensory problems are highly variable. When I was a child, I liked to play with running water; however, another child with autism may not be able to tolerate the same sound. I was attracted to automatic supermarket doors and I liked to watch them move. Another autistic child or adult may scream and run away from these same automatic doors because sudden movement hurts his or her eyes. Maybe a small anomaly in my visual processing caused me to be attracted to the movement of the doors. A greater anomaly may cause another individual to avoid the same stimulus. Waterhouse et al found it puzzling that I was attracted to strong visual stimuli, yet high-pitched auditory stimuli hurt my ears.

While the etiologies of pervasive developmental disorders (PDDs) appear complicated, multifactorial, and relatively poorly understood research over the last 30 to 40 years has implicated certain neurochemicals in the pathophysiology of these diseases. From these studies, a great deal of evidence has emerged supporting a role for serotonergic dysfunction in individuals with autism and related disorders. Recent clinical trials of drugs influencing serotonergic systems have demonstrated promising effects in children, adolescents, and adults with PDDs.

The literature on neuropsychiatric, neuropsychological, and neuroimaging findings in autism and Asperger's disorder is briefly reviewed. Neurological soft sign, neuropsychological, and positron-emission tomography findings in one patient with Asperger's disorder and one patient with autism are highlighted, discussed as examples of heterogeneity, and integrated with the relevant literature.

Recent studies of the pathogenesis of autism have suggested that this disorder may have an autoimmune basis in some patients. Observations have been made regarding cellular and humoral immune dysfunction, abnormalities associated with the complement system and major histocompatibility complex gene expression, differences in soluble mediators of the immune response, and the presence of antibrain and antimyelin autoantibodies. In this article, we review these experimental and clinical observations, and examine preliminary efforts using immunomodulatory therapies to treat autism.