Pediatric acute-onset neuropsychiatric syndrome (PANS) is a disorder characterized by the sudden onset of obsessive-compulsive (OCD) symptoms or eating restrictions, concomitant with acute behavioral deterioration and/or motor/sensory changes in at least two of seven domains. Those domains are anxiety, emotional lability and/or depression, irritability, aggressive or oppositional behavior, academic decline, cognitive decline, and sleep disruption. The diagnosis necessitates a course that follows a relapsing–remitting pattern. In the case of post-puberty chronicity residual symptoms and their severity increases.

OCD and tic disorders are hypothesized to arise in a subset of children as a result of a post-streptococcal autoimmune process. The earlier PANDAS hypothesis was unconfirmed and unsupported by data, and two new categories were proposed: PANS and CANS (childhood acute neuropsychiatric syndrome). The CANS/PANS hypotheses include different possible mechanisms underlying acute-onset neuropsychiatric conditions. PANDAS, PANS and CANS are the focus of clinical and laboratory research but remain unproven.