HLA Polymorphism in Regressive and Non‐Regressive Autism: A Preliminary Study

Autism spectrum disorders (ASD) comprises heterogeneous neurodevelopmental conditions with symptom onset usually during infancy. However, about 10%–30% of affected cases experience a loss of language and social skills around 18–30 months, so‐called regressive autism. In this subset with regression, immune dysfunctions including inflammation and autoimmunity have been proposed to be at risk factors. Given the implication of the human histocompatibility antigens (HLA) system in various aspects of immune responses, including autoimmunity, and in ASD, we investigate here the distribution of the HLA Class I and Class II haplotypes in 131 children with ASD meeting DSM‐IV TR criteria, with and without regression. We found that 62 of the 98 non‐regressive ASD patients carry the HLA‐DPA1*01‐DPB1*04 sub‐haplotype as compared to 14 of the 33 patients with regression (63% vs. 43% respectively, Pc = 0.02), suggesting that this HLA haplotype may exert a protective effect against regression. Similarly, the HLA‐DPA1*01‐DPB1*04 has also been found to be more represented in healthy controls as compared to patients affected with common nonpsychiatric autoimmune disorders. Overall our findings suggest a possible involvement of HLA polymorphism in the context of regressive ASD. Autism Res 2020, 13: 182–186. © 2019 The Authors. Autism Research published by International Society for Autism Research published by Wiley Periodicals, Inc. Lay Summary Immune dysfunctions including inflammatory and autoimmune processes have been reported in autism, particularly in regressive forms. In this study, we analyzed the distribution of HLA haplotypes among children with autism spectrum disorder (ASD), with and without regression from Sweden and observed that HLA‐DPA1*01‐DPB1*04 sub‐haplotype was less represented in patients with regressive autism as compared with those without regression. Such possible protective effect, also observed in other common autoimmune disorders, may constitute a link between HLA‐mediated immune processes and regressive ASD.