Anti-basal ganglia antibodies in movement disorders
Sydenham's chorea (SC) is a neurological manifestation following group A Streptococcus infection (GABHS) and has been proposed as an antibody-mediated autoimmune disease. Other movement and psychiatric manifestations following GABHS have been recognised and termed Paediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections (PANDAS). It is proposed that PANDAS may be caused by the same antibody as SC. As the symptoms of PANDAS are identical to Tourette's syndrome (TS), the possibility that TS might turn out to be an autoimmune disorder has implications for the treatment and understanding of these disorders. Evidence of GABHS was found in all patients with SC and PANDAS and 60% of patients with TS. Autoantibodies against basal ganglia (ABGA) were found in all acute SC and PANDAS patients. Only 25% of TS patients were ABGA positive. There was little evidence for ABGA in controls. There was a higher prevalence of ABGA in systemic diseases associated with GABHS but this did not reach significance. ABGA bound to proteins with molecular weights (40, 45, 60 and 98 kDa) and these responses were variably found in SC, PANDAS and TS. The identification of these antigens proved to be problematic due to contamination with other proteins with the same molecular weights. Neurone specific enolase (NSE) was identified as one of the antigens. As this protein was not specific to basal ganglia it cast doubt as to the specificity of ABGA. Interestingly, however, enolase is also found on the surface of GABHS and has extensive homology with human enolase, thus lending support to the possibility of molecular mimicry derived autoimmunity.