Assessment of children in the autistic spectrum disorder that carry the Thr92Ala-DIO2 polymorphism

Abstract

Introduction: A polymorphism in the type 2 deiodinase (Thr92Ala-DIO2) gene has been associated with behavioral and cognitive dysfunction as well as neurodegeneration and oxidative stress in the central nervous system.

Objective: To test whether the minor allele (Ala92) frequency (MAF) is increased in children in the autism spectrum disorder (ASD), and whether carriers of the minor allele exhibit more severe symptoms and/or worse adaptive behavior.

Study design: ASD children were evaluated at baseline and yearly throughout the study by psychologists using the following tools: autism behavior checklist, Vineland Adaptative Behaviour Scales II, non-verbal intelligence test SON-R 2^1/2-7, SON-R 6-40, Weschler scale for intelligence, and autism treatment evaluation checklist.

Settings: Academic outpatient mental health facility in Sao Paulo, Brazil.

Participants: ASD boys and girls younger than 18 years of age. 132 consecutive ASD children, mostly boys (~ 80%); ~ 50% was classified as verbal. Exclusion criteria were coexistence of sensory and/or physical impairment, or any associated genetic syndromes.

Results: Median follow-up was for an uninterrupted period of 937 days (139-1375 days), which did not vary significantly among the genotypes. The MAF was 47% in ASD patients vs. 51% in a local reference population with similar ethnic background; the clinical severity and progression were not affected by the minor allele. Carriers of the minor allele exhibited higher adaptive behavior in the domains "daily living skills" and "communication", which correlated positively with the dose of the minor allele.

Conclusion: The MAF is not different in ASD children, but carriers of the Thr92Ala-DIO2 polymorphism exhibited higher adaptive behavior.

Keywords: Austism Spectrum Disorder; D2; Polymorphism; Vineland.