Dopaminergic receptor gene polymorphisms in children affected by ADHD/ASD overlapping.

Background: Several studies have shown a genetic role in the pathogenesis of many childhood psychiatric disorders. The most common childhood psychiatric disorder is the attention deficit hyperactivity disorder (ADHD) and some reports showed the co-­occurance in ADHD children and Autism Spectrum Disorders (ASD). Many investigators focused their attention on polymorphisms affecting gene regions coding for dopamine receptors. In this study we evaluate the association of three single-­nucleotide polymorphisms (SNPs) with clinically significant level of autistic symptoms among children with ADHD. Methods: We enrolled 150 children who were divided into four groups: children with ADHD, children with ASD, children with co-­occurance of ADHD/ASD, and control subjects. We investigated rs265975 C/T (174862195C>T) for dopamine receptor D1 gene, rs1076560 C/A (113283688C>A) and rs1079597 G/A (113296286C>T) for dopamine receptor D2 gene utilizing previous DNA extraction and amplification, restriction enzymes that recognized one of two allelic variants. Results: Our results demonstrated that homozygosis T/T for rs265975 had a lower frequency in ADHD patients compared to other groups,whereas small differences were seen in heterozygosis C/T. Both heterozygosis C/A for rs1076560 and heterozygosis G/A for rs1079597 showed higher frequency in ASD group with respect to control children and ADHD patients, whereas in ADHD/ASD group a ratio 3:1 vs unaffected people was seen. The same trend, but with slight differences, was observed in homozygosis A/A for rs1076560 and rs1079597. Conclusions: These preliminary data pointing to differences between ADHD/ASD and other groups must be confirmed and encourage us to enlarge our study populations