Immune dysregulation in pediatric tic disorders: mechanisms, biomarkers, and therapeutic frontiers

Tic Disorders (TDs) are common neurodevelopmental disorders characterized by complex pathophysiological mechanisms. A growing body of evidence in recent years suggests that immune system dysregulation plays a critical role in the pathogenesis and clinical course of TDs in a subset of pediatric patients. This review aims to systematically summarize the current understanding of the core mechanisms of immune dysregulation in pediatric TDs, potential biomarkers, and related therapeutic frontiers. We detail three core pathophysiological pathways, Post infectious autoimmunity, represented by the Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS) and Pediatric Acute-onset Neuropsychiatric Syndrome (PANS) models. Its core mechanism involves the production of autoantibodies induced by molecular mimicry, which target basal ganglia neurons, such as cholinergic interneurons and dopamine receptors. Neuroinflammation is another critical pathway. This process involves T helper 17 (Th17) cell-mediated disruption of the blood-brain barrier and microglial activation. It is further characterized by elevated pro-inflammatory cytokines, such as Tumor Necrosis Factor-alpha (TNF-α) and Interleukin-12 (IL-12). Microbiota-gut-brain axis dysregulation, wherein gut dysbiosis and compromised intestinal barrier function influence central nervous system (CNS) function through the neuro immune endocrine network. Building upon this framework, we evaluate potential biomarkers across various dimensions, including the findings and limitations in serology (cytokines), cerebrospinal fluid analysis (oligoclonal bands, MCP-1), neuroimaging (volumetric changes in the basal ganglia and PET imaging of neuroinflammation), and genetics (variations in the IL-1RN gene). Finally, we discuss the evolution from conventional treatments to emerging immune-targeted therapies. This encompasses core immunomodulatory therapies (Intravenous Immunoglobulin (IVIG) and plasmapheresis) and promising future strategies, such as fecal microbiota transplantation (FMT), targeted B-cell therapies, and small-molecule anti-inflammatory drugs. In conclusion, a deeper understanding of the immunological basis of TDs is paving the way for the development of more precise diagnostic tools and novel, individualized immunomodulatory interventions.