Reader Response: Lack of Association of Group A Streptococcal Infections and Onset of Tics: European Multicenter Tics in Children Study

Schrag et al.¹ reported that Group A streptococcal (GAS) exposure is unrelated to tics in children at risk for tic disorders. The critical limitations of this study are that only children with genetic risks for tics were studied, and information about risk for autoimmunity, infection susceptibility, and antibiotics use is absent.¹ The European Multicenter Tics in Children Study (EMTICS) home page states that many patients refused to participate when told that antibiotic use would be limited. This would introduce a negative selection bias against families who perceive themselves as high risk and patients procuring antibiotics outside the trial.² GAS infections trigger autoimmune disorders through mechanisms mediated by superantigens and adaptive immunity.³ Studies in rodent models for GAS-induced neuropsychiatric symptoms showed that Th17 lymphocytes and autoantibodies, generated in response to multiple infections, targeted the brain and triggered neuroinflammation. They also caused blood-brain barrier damage and neuronal circuitry dysfunction, which elicited behavioral abnormalities.⁴ We have witnessed the transformative effect of antibiotic treatment in a small group of patients with Obsessive-Compulsive Disorder (OCD) and/or movement disorders secondary to GAS infections.⁵ Consequently, we are concerned that results from the EMTICS study may be incorrectly extrapolated to children and adolescents with acute onset of tics, resulting in effective treatment being withheld.