Background: The relationship between childhood tic disorders and group A streptococcal (GAS) infections has been recently investigated by several research groups, but no systematic evaluation of laboratory indicators of GAS infections has been provided.
Objective: The aim of our study was to seek clinical and laboratory evidence of GAS infections in a large population of children affected with tic disorders.
Study design: This investigation was a case-control study: 150 consecutive children presenting with tics were investigated for clinical and laboratory signs of streptococcal infections on the occasion of their first neuropsychiatric consultation. To compare the rate of exposition to GAS in a similar population, a control group of 150 children without tic disorders was examined during the same period.
Results: In children with tics, mean antistreptolysin O (ASO) titer (434 +/- 338 IU) was significantly higher compared with that of control subjects (155 +/- 126 IU); 38% of the children with tics compared with 2% of the control subjects (P <.001) had ASO titers > or =500 IU. Twenty-six children with tics (17%) had throat cultures positive for GAS, but in all cases, only few colonies per plate were isolated. Among the strains isolated, no prevalent T pattern or M type was observed. In children with tics a positive correlation between ASO titers and severity of tic disorder (measured by the Yale Global Tic Severity Scale) was found.
Conclusion: Our results suggest that children with tic disorder could be a unique population in which GAS infection, or at least the exposure to streptococcal antigens, is correlated to the neurobehavioral disorder. Moreover, our data indicate a relationship between the severity of tic disorder and the magnitude of the serologic response to GAS antigens.