PANDAS: Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections

Article written in collaboration with @sangyemenla

Abstract

PANDAS (Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections) is a pediatric neuropsychiatric condition characterized by the acute and sudden onset of obsessive-compulsive symptoms and/or tics following an infection caused by Group A Streptococcus pyogenes. The underlying mechanism is autoimmune in nature: antibodies produced in response to the infection mistakenly attack neuronal structures, particularly the basal ganglia. This review examines the neurobiological basis of the disorder, its diagnostic criteria, clinical presentation, overlaps with related conditions such as PANS and Sydenham's chorea, and the main treatment approaches, with particular attention to the role of the psychologist in managing the child and their family.

Keywords: PANDAS, PANS, streptococcus, obsessive-compulsive disorder, autoimmunity, pediatric neuropsychiatry, Sydenham's chorea, clinical psychology.

Introduction

The relationship between infections and neuropsychiatric disorders has been one of the most stimulating and controversial areas of research in developmental neuroscience and psychiatry over the past few decades. PANDAS represents a paradigmatic example of this relationship: a relatively common bacterial infection — streptococcal pharyngitis — can trigger, in genetically predisposed children, an immunological cascade with dramatic and often debilitating psychiatric consequences (Swedo et al., 1998).

The PANDAS hypothesis was first formulated by the National Institute of Mental Health (NIMH) in the late 1990s, based on clinical observations revealing a precise temporal correlation between Group A Streptococcus pyogenes (GAS) infectious episodes and the sudden onset of obsessive-compulsive disorder (OCD) and/or tics in prepubertal children (Swedo et al., 1998). Since then, the scientific community has continued to debate the existence, nosological boundaries, and pathogenetic mechanisms of this condition, generating a rich and sometimes contradictory body of literature (Wilbur et al., 2019).

A nationwide study conducted in Denmark examined key aspects of the PANDAS hypothesis in a sample of over one million individuals, confirming a significant association between streptococcal pharyngeal infection and the subsequent development of mental disorders — particularly OCD and tics — with a peak risk in the weeks immediately following the infection (Orlovska et al., 2017). These epidemiological findings strengthen the biological plausibility of the hypothesis, although they are not conclusive with regard to causal mechanisms.

Neurobiological Basis: The Autoimmune Mechanism

PANDAS is not a direct infectious disease of the central nervous system. The bacterium does not invade the brain; rather, the child's immune system — in the act of defending itself — produces antibodies that, through a mechanism of molecular mimicry, mistake certain neuronal proteins for bacterial antigens. This immunological cross-reactivity leads the antibodies to attack the body's own brain structures, particularly the basal ganglia — subcortical structures involved in the regulation of movement, repetitive behaviour, and impulse control (Cunningham et al., 2006).

A crucial element is the permeability of the blood-brain barrier (BBB) in childhood. In children, the BBB has not yet fully matured, making it more permeable to the passage of immunological molecules — including immunoglobulins — compared to adults. With puberty, the immune system consolidates and the barrier strengthens, which explains why PANDAS tends to resolve or no longer present after adolescence. This has significant prognostic implications and provides an optimistic orientation for long-term management of the disorder.

Anti-neuronal antibodies detected in PANDAS patients react with dopaminergic D1 and D2 receptors in the basal ganglia, altering dopaminergic and glutamatergic neurotransmission in cortico-striato-thalamo-cortical (CSTC) circuits. These circuits, already implicated in the pathophysiology of OCD and Tourette syndrome, appear to be the shared neurobiological substrate of the clinical manifestations typical of PANDAS (Cunningham et al., 2006; Swedo et al., 1998).

Diagnostic Criteria and Clinical Presentation

The diagnosis of PANDAS is based on clinical criteria, in the absence of a specific biomarker or definitive diagnostic test. The five criteria originally proposed by Swedo et al. (1998) remain the primary reference: 

1. Presence of OCD and/or tics; 

2. Prepubertal onset; 

3. Acute onset of symptoms or episodic course with remissions and relapses;

4. Temporal association with documented GAS infection;

5. Presence of associated neurological abnormalities, including motor hyperactivity, choreoathetosis, or emotional lability.

The sudden and dramatic onset is perhaps the most clinically characteristic and disruptive feature. Parents often report that their child — completely asymptomatic the day before — woke up with intrusive obsessive rituals, irrational fears, motor or vocal tics, and an anguish that seems incomprehensible and disproportionate. This acute onset contrasts sharply with the gradual emergence typical of idiopathic OCD and constitutes a primary clinical signal (Wilbur et al., 2019).

In terms of differential diagnosis, it is essential to rule out other causes of acute-onset OCD or tics, including primary neurological disorders, psychosis, substance use, or other autoimmune processes of the central nervous system. Antistreptococcal antibody levels (ASLO and anti-DNase B) can support the diagnosis, but elevated titres only indicate past contact with the bacterium and do not necessarily attest to a clinically active ongoing infection. This point, often misunderstood, is of great importance when communicating with families (Wilbur et al., 2019).

From PANDAS to PANS: A Broader Framework

The limitations of the PANDAS construct — in particular its exclusivity regarding the streptococcal trigger — led to the proposal of the broader term PANS (Pediatric Acute-onset Neuropsychiatric Syndrome). PANS describes the same clinical presentation (acute onset of OCD and behavioural regression in childhood) but accommodates different aetiological triggers, including viral infections (influenza, Mycoplasma pneumoniae, varicella), metabolic factors, and environmental causes not yet fully identified (Wilbur et al., 2019).

The conceptual shift from PANDAS to PANS reflects growing awareness that the underlying pathogenetic mechanism — an inflammatory or autoimmune response involving the central nervous system — can be activated by multiple agents. This has important therapeutic implications: treatment is not limited to controlling the streptococcal infection but requires multidisciplinary management that considers the full clinical history and potential triggers for each individual patient.

Sydenham's Chorea: A Sister Disease

Sydenham's chorea (SC), historically known as St. Vitus' dance, is another post-streptococcal autoimmune neurological manifestation, classically classified as a complication of acute rheumatic fever. It is characterised by involuntary, rapid, purposeless movements of the face, limbs, and trunk, typically associated with emotional lability, irritability, and, in some cases, obsessive-compulsive symptoms (Cunningham et al., 2006).

Unlike PANDAS, which tends to resolve with post-pubertal immune maturation, the neurological damage associated with SC can recur in adulthood. A paradigmatic example is chorea gravidarum, a form of chorea that manifests during pregnancy in women with a previous history of SC, presumably due to the immunological and hormonal changes associated with gestation. This highlights the importance of long-term follow-up even after the apparent resolution of symptoms.

The neurobiological overlap between PANDAS and SC — both mediated by antibodies attacking the basal ganglia following GAS infection — supports the idea that these conditions belong to a clinical continuum, rather than being separate and distinct entities. The study of anti-neuronal antibodies present in SC has helped illuminate the possible molecular mechanisms of PANDAS (Cunningham et al., 2006).

Treatment: A Multimodal Approach

In the absence of shared guidelines and high-level evidence-based recommendations, the treatment of PANDAS is based on a pragmatic and multimodal approach, articulated across three main levels: management of the underlying infection, immunomodulatory treatment, and psychological/psychiatric intervention (Wilbur et al., 2019).

Antibiotic Treatment

Treating each documented streptococcal infection with an appropriate antibiotic therapy (usually amoxicillin or penicillin) constitutes the first level of intervention. In cases of frequent relapses, long-term antibiotic prophylaxis has been proposed, although this approach remains controversial due to concerns about bacterial resistance and the lack of large-scale randomised controlled trials (Wilbur et al., 2019).

Immunomodulatory Interventions

In more severe and treatment-resistant cases, immunomodulatory treatments such as plasmapheresis and intravenous immunoglobulins (IVIG) have been used, with the aim of reducing the anti-neuronal antibody burden. A randomised controlled trial by Perlmutter et al. (1999) showed significant improvements in children treated with these approaches compared to placebo, although the generalisability of these findings remains limited by sample size and the complexity of the procedures.

The Role of Psychological Intervention

Regardless of the stage of illness, Cognitive-Behavioural Therapy (CBT) — and in particular Exposure and Response Prevention (ERP) for OCD — represents a first-line intervention, recommended for its efficacy profile and minimal invasiveness. CBT targets the maintenance mechanisms of OCD and avoidance behaviours without interfering with the underlying biological processes, and can be integrated at any point in the care pathway (Wilbur et al., 2019).

Selective serotonin reuptake inhibitors (SSRIs) may be considered in cases of severe OCD or those poorly responsive to CBT alone. However, it is worth noting that children with PANDAS may show increased sensitivity to SSRI side effects, with potential behavioural activation or agitation at standard doses, requiring a particularly cautious approach to drug titration (Wilbur et al., 2019).

The Role of the Psychologist: Beyond the Symptom

A PANDAS diagnosis has a profound and pervasive impact on the family system. The sudden and often incomprehensible onset of symptoms generates disorientation, fear, and guilt in parents. Many families describe a lengthy journey through medical consultations before receiving a diagnosis, with the risk that symptoms are mistakenly attributed to psychogenic causes, parenting issues, or primary psychiatric disorders (Wilbur et al., 2019).

The psychologist plays a central role at several levels. On the psychoeducational level, they help the family understand the neurobiological nature of the disorder, distinguishing symptomatic — and therefore involuntary — behaviours from volitional ones, thereby reducing the risk of punitive responses that can worsen the clinical picture. On the clinical level, they conduct CBT with the child and monitor symptom progression over time. On the systemic level, they facilitate coordination with the school and other professionals involved, promoting an integrated network of care.

The emotional burden on caregivers should not be underestimated. Research on the family impact of paediatric neuropsychiatric disorders documents high levels of parental stress, reduced family quality of life, and the risk of anxious and depressive symptoms emerging in parents themselves. Psychological support for the parental couple and, where indicated, family psychotherapy therefore constitute integral components of a comprehensive care plan.

Controversies and Future Perspectives

PANDAS remains one of the most debated diagnoses in paediatric neuropsychiatry. The main areas of controversy concern: the specificity of the causal association with streptococcus compared to other infections; the nature of reliable biological markers for diagnosis; the true prevalence in the paediatric population; and the distinction between PANDAS as a discrete entity and OCD with infectious precipitating factors (Wilbur et al., 2019).

The epidemiological study by Orlovska et al. (2017), conducted on a sample of over one million Danish individuals, found an association between streptococcal pharyngeal infection and mental disorders even in adult subjects, suggesting that the link between immunology and psychopathology may extend beyond childhood. This opens new scenarios for understanding subgroups of adult patients with later-onset OCD or tics.

Future research will need to address the need for prospective studies with large samples, standardised diagnostic criteria, and reliable biomarkers. The field of psychoneuroimmunology offers a promising theoretical framework for understanding how inflammatory processes may influence neurological and psychopathological development, with implications that extend well beyond PANDAS.

Conclusions

PANDAS represents a paradigmatic example of how biological processes — in this case a post-infectious immune response — can translate into complex and debilitating psychiatric manifestations. Understanding this disorder requires a genuinely biopsychosocial approach: biological with regard to the pathogenetic mechanisms, psychological in terms of treatment and support, and social in managing the family and school context.

For mental health professionals, PANDAS raises a fundamental and methodologically fertile question: how many behaviours we attribute to psychological or relational dynamics have, in fact, biological substrates not yet identified? Interdisciplinary openness — across psychology, immunology, neurology, and paediatrics — is not merely desirable but necessary to do justice to the complexity of the children and families facing this condition.

References

Cunningham, M. W., Cox, C. J., & Bhatt, D. (2006). Antineuronal antibodies in movement and psychiatric disorders. Annals of the New York Academy of Sciences, 1062(1), 241–253. https://doi.org/10.1196/annals.1358.028

Orlovska, S., Vestergaard, C. H., Bech, B. H., Nordentoft, M., Vestergaard, M., & Benros, M. E. (2017). Association of streptococcal throat infection with mental disorders: Testing key aspects of the PANDAS hypothesis in a nationwide study. JAMA Psychiatry, 74(7), 740–746. https://doi.org/10.1001/jamapsychiatry.2017.0995

Perlmutter, S. J., Leitman, S. F., Garvey, M. A., Hamburger, S., Feldman, E., Leonard, H. L., & Swedo, S. E. (1999). Therapeutic plasma exchange and intravenous immunoglobulin for obsessive-compulsive disorder and tic disorders in childhood. The Lancet, 354(9185), 1153–1158. https://doi.org/10.1016/S0140-6736(99)05155-2

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Wilbur, C., Bitnun, A., Kronenberg, S., Laxer, R. M., Levy, D. M., Logan, W. J., Shouldice, M., Yeh, E. A., & Canadian Pediatric Society (2019). PANDAS/PANS in childhood: Controversies and evidence. Paediatrics & Child Health, 24(2), 85–91. https://doi.org/10.1093/pch/pxy145