High prevalence of serum folate receptor autoantibodies in children with autism spectrum disorders. 
Supplementation of folic acid by pregnant mothers is thought to lower the risk of autism spectrum disorders (ASDs) in the offspring.  Folic acid is taken up by cells via receptors with high affinity for folate and reduced folic acid derivatives.  However, this is blocked by the presence of folate receptor autoantibodies (FRAA).  Cerebral FRAA have been detected with high frequency in children with ASDs, suggesting the existence of a link between folic acid uptake and disease aetiology.  We investigated the frequency of FRAA in serum samples from 40 children with ASDs and 42 gender- and age-matched children with typical development (TD).  Serum FRAA concentrations were measured by enzyme-linked immunosorbent assay.  We found a significant difference in the frequency of serum FRAA in the two study cohorts.  Serum FRAA were present in 77.5% (31/40) of children with ASDs compared with 54.8% (23/42) of TD children (p = 0.03746, Fischer's exact test).  Thus, serum FRAA are more prevalent in children with ASDs than in TD children.  Our data suggest that children with ASDs may have defects in folic acid absorption that play a role in the onset of ASDs.