Abstract
BackgroundAutism is a heritable developmental disorder of communication and socialization that has not been well studied in Hispanic populations. Therefore, we are collecting and evaluating all possible cases of autism from a population isolate in the Central Valley of Costa Rica (CVCR) for a clinical and genetic study.MethodsWe are assessing all subjects and parents, as appropriate, using the newly translated Spanish versions of the Autism Diagnostic Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS) as well as tests of intelligence and adaptive behavior. Detailed obstetric and family medical/psychiatric histories are taken. All cases are tested for Fragile X and will be extensively evaluated for cytogenetic abnormalities.ResultsTo date we have obtained clinical evaluations on over 76 cases of possible autism referred to our study and report data for the initial 35 complete cases. The mean age of the probands is 6.7 years, and 31 of the 35 cases are male. Twenty-one of the cases have IQs <50 and only 6 cases have IQs ≥ 70. Over half of the mothers had complications during pregnancy and/or delivery. No cases have tested positively for Fragile X or PKU. Chromosomal G-banding is not yet complete for all cases.ConclusionDiagnostic data gathered on cases of autism in the CVCR using Spanish versions of the ADI-R and ADOS look similar to that generated by studies of English-speaking cases. However, only 17% of our cases have IQs within the normal range, compared to the figure of 25% seen in most studies. This result reflects an ascertainment bias in that only severe cases of autism come to treatment in the CVCR because there are no government-sponsored support programs or early intervention programs providing an incentive to diagnose autism. The severity of mental retardation seen in most of our cases may also be exaggerated by the lack of early intervention programs and the use of IQ tests without Costa Rican norms. Still, we must formally train healthcare providers and teachers to recognize and refer autistic cases with normal or near normal IQs that are not seen in treatment.
Highlights
Autism is a heritable developmental disorder of communication and socialization that has not been well studied in Hispanic populations
Four studies indicate that siblings of autistic probands are at increased risk for Pervasive Developmental Disorder Not Otherwise Specified (PDDNOS) and Asperger's Disorder, suggesting that these disorders exist on a continuum [3,4,5,6]
One family later declined to participate because of the mother's health, two cases have been excluded by genealogy, one case was too retarded to determine a diagnosis, one case has RETT syndrome (AU043), and the other excluded case is an autistic child with Moebius syndrome (AU044)
Summary
Autism is a heritable developmental disorder of communication and socialization that has not been well studied in Hispanic populations. A mutation in the Neuroligin 3 gene on Xq13 has been identified in a sibship where one brother has autism and the other has Asperger's [7] This mutation was inherited from the mother and changes a highly conserved arginine residue to cysteine (R451C), resulting in retention of the protein in the endoplasmic reticulum and reduced binding with its presynaptic partner beta neurexin-1 [8]. Mutations in this gene may not explain a substantial portion of the population risk for autism, the finding provides definitive proof for the genetic basis of autism spectrum disorders (ASD) and encouragement for ongoing genetic studies such as ours
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