The purpose of this study is to determine if human immunoglobulin given by mouth twice a day is effective in treating the persistent gastrointestinal (GI) problems such as diarrhea, constipation, abdominal pain, and bloating, in children with autism.

Autistic GI Dysfunction (AGID) is a term that describes a constellation of GI signs and symptoms often found in children with autistic disorder, including abdominal pain, constipation, chronic diarrhea, alternating constipation and diarrhea, gaseousness, bloating, and reflux.

The objective of this study is to assess the potential efficacy of oral immunoglobulin in reducing a wide range of GI symptoms in children and adolescents diagnosed with autistic disorder.

Inclusion Criteria:

• Male or female from 2 years to 18 years of age (up to, but not inclusive of the 18th birthday)
• Diagnosis of autistic disorder corroborated by an Autism Diagnostic Interview - Revised (ADI-R) assessment performed by a certified investigator
• Physician Clinical Global Impression of Severity (of Autistic Disorder)
• History of chronic, persistent gastrointestinal disturbance
• No elective changes in medication, diet intervention, or behavioral therapy during the study (18 weeks total)

Exclusion Criteria:

• Evidence of a gastrointestinal infection or GI abnormality
• A known diagnosis of other gastrointestinal pathology
• Antibiotic and/or antifungal (e.g. nystatin) medication
• Chelation therapy
• Medication affecting gastrointestinal transit
• Planned use of prohibited drugs or agents that could affect GI transit
• Changes in diet intervention within 30 days prior to the screening visit
• Changes in alternative medical therapies or dietary supplements within 30 days prior to the screening visit
• Adding and/or changing behavior modification or psychotherapy during participation in the study
• Adding or changing psychotropic medication during participation in the study
• DSM-IV diagnosis of a pervasive developmental disorder other than autistic disorder
• Evidence of a seizure disorder, diagnosis of fragile X syndrome, tuberous sclerosis complex, liver disease, pancreatic disease, cystic fibrosis, or chronic infection
• Previous gastrointestinal surgery
• Pregnancy
• Participation in another investigational study
• Significant deviation from normal laboratory test values at baseline
• IgA deficiency (serum IgA < 5 mg/dL)
• A history of severe hypersensitivity to human immunoglobulin
• Treatment with any human immunoglobulin and/or immunoglobulin products
• Any concurrent medication that would compromise subject's tolerance of drug or compliance with the protocol