A child with autism was found to have complete IgA deficiency (serum IgA <6 mg/dL; normal 33-235 mg/dL), Candidiasis of the gastrointestinal tract based on evaluation of stool testing and elevated urine arabinose, and elevated serum antibodies to wheat and dairy products. The pretreatment urinary arabinose concentration (341 mmol/mol creatinine in this child was nearly six times the mean value (60.4 mmol/mol creatinine, n=20) of normal children and over ten times the median value (31.0 mmol/mol creatinine) of normal controls. After antifungal therapy for four months, the urine was retested. At that time the urine arabinose was measured at 51 mmol/mol creatinine, a value only 15% of the baseline sample. Restriction of wheat and dairy products from the diet and antifungal therapy led to a significant decrease in autistic behaviors and increased rate of learning. The Childhood Autism Rating Scale (CARS), an observational measure of various aspects of autism, for the child has decreased from a rating of 43 (severely autistic) prior to introduction of these therapies to a value of 29 (nonautistic) after therapy.