Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS): An Evolving Concept.

Pediatric autoimmune neuropsychiatric disorders associated with streptococcus infections (PANDAS) originated from the observational work of Swedo and collaborators, who formalized their definition in 1998 in a set of operational criteria. The application of these criteria, which focuses on tics and obsessive-compulsive symptoms as core symptoms, has encountered difficulties, eventually leading to a high rate of misdiagnosis. In particular, the core feature represented by the association between newly diagnosed infections and neuropsychiatric symptom relapses in youths with this diagnosis could not be demonstrated by longitudinal studies. Exploratory studies aiming to identify clinical or cognitive features that could discriminate PANDAS from other pediatric obsessive-compulsive and tic disorders present methodological limitations, and therefore are not conclusive. Other behavioral features, in addition to obsessive-compulsive symptoms and tics, have been included in pediatric acute-onset neuropsychiatric syndromes (PANS) and childhood acute neuropsychiatric syndromes (CANS), two new concepts recently proposed in order to define a much broader clinical spectrum encompassing etiologically diverse entities. Given the uncertainties on the clinical definition of PANDAS, it is not surprising that evidence in support of a post-infectious, immune-mediated pathophysiology is also insufficient. Anti-dopamine receptor antibodies might be relevant to both Sydenham's chorea (SC)-the prototypical post-streptococcal neuropsychiatric disorder-and some rare forms of encephalitis targeting the basal ganglia specifically, but studies exploring their association with children fulfilling Swedo's criteria for PANDAS have been inconclusive. Moreover, we lack evidence in favor of the efficacy of antibiotic prophylaxis or tonsillectomy in patients fulfilling Swedo's criteria for PANDAS, whereas a response to immune-mediated treatments like intravenous immunoglobulins has been documented by one study, but needs replication in larger trials. Overall, the available evidence does not convincingly support the concept that PANDAS are a well-defined, isolated clinical entity subdued by definite pathophysiological mechanisms; larger, prospective studies are necessary to reshape the nosography and disease mechanisms of post-streptococcal acute neuropsychiatric disorders other than SC. Research is also under way to shed further light on a possible relationship between streptococcal infections, other biological and psychosocial stressors, and the complex pathobiology of chronic tic disorders.