Two hundred and forty-one children with autism were ascertained and diagnosed (DSM-III criteria) in an epidemiologic survey of Utah. Pediatric and other pertinent medical records were abstracted for 233 patients and 66 of their siblings without autism for otitis media, upper respiratory, and other infections. A significantly greater number of children with autism had recurrent otitis media, upper respiratory and other infections than their nonautistic siblings. A greater number of children with autisru with recurrent infections had lower IQ scores, seizures, hearing deficits, delayed motor milestones, poorer speech, congenital anomalies, feeding problems, vomiting, diarrhea, and other types of infections than children with autism with mild or no infections. The only significant pre-, peri-, or postnatal risk factors between children with autism with recurrent, mild or no infection was an increase in the maternal-fetal incompatibility (ABO or Rh) in the recurrent infection group. Half the families with more than one child with autism had recurrent infections and 72% of those children with concurrent diseases which effect the CNS had recurrent infections. Methodological limitations are discussed.

The authors recently reported, in this journal, an epidemiologic survey of autism in Utah. Twenty (9.7%) of the 207 families ascertained had more than one autistic child. Analyses of these data revealed that autism is 215 times more frequent among the siblings of autistic patients than in the general population. The overall recurrence risk estimate (the chance that each sibling born after an autistic child will develop autism) is 8.6%. If the first autistic child is a male the recurrence risk estimate is 7%, and if a female 14.5%. These new recurrence risk estimates should be made available to all individuals who have autistic children and are interested in family planning.

To assess familial aggregation of autism, 86 autistic subjects were linked to the Utah Genealogical Database. Kinship coefficients were estimated for all possible pairs of autistic subjects and then averaged. Fifty replicate sets of matched control subjects (86 members in each set) were drawn randomly from the database, and the average kinship coefficient was computed for all possible pairs of individuals in each set. The average kinship coefficient for the autistic subjects was approximately 1/1,000, while the average kinship coefficients for the 50 control groups ranged from 4/100,000 to 1.6./10,000. These results indicate a strong tendency for autism to cluster in families. When kinship was analyzed by specific degrees of relationship, it was shown that the familial aggregation of autism is confined exclusively to sib pairs and does not extend to more remote degrees of relationship. This finding indicates that a single‐gene model is unlikely to account for most cases of autism.

The UCLA Registry for Genetic Studies in Autism was established in 1980 to test the hypothesis that genetic factors may be etiologically significant in subsets of patients. To date 61 pairs of twins have enrolled and 40 meet research diagnostic criteria for autism. The authors found a concordance for autism in these 40 pairs of 95.7% in the monozygotic twins (22 of 23) and 23.5% in the dizygotic twins (four of 17).

The authors conducted an epidemiologic survey in Utah using a four-level ascertainment system, blind current diagnostic assessments, and DSM-III criteria. Of 483 individuals ascertained, 241 were diagnosed as having autism. The best estimate for the prevalence rate was 4 per 10,000 population. Autism was not associated with parental education, occupation, racial origin, or religion. Sixty-six percent of the autistic subjects scored below 70 on standardized IQ tests, and females scored proportionately lower than males. Twenty (9.7%) of 207 families had more than one autistic sibling, which supports the authors' previous finding that there may be a familial subtype of autism.