PANDAS
These criteria describe a neuropsychiatric syndrome with the presence of obsessive-compulsive disorder (OCD) or tic disorder and a temporal association of symptom onset with group A streptococcal (GAS) infection.

PANDAS can be diagnosed when all of the five symptoms are present.

The PANDAS diagnostic criteria
I. Presence of OCD or a tic disorder
II. Prepubertal symptom onset
III. Acute symptom onset and episodic (relapsing-remitting) course
IV Temporal association between Group A streptococcal infection and symptom onset/exacerbations
V Association with neurological signs (motor hyperactivity or choreiform movements)

The crucial difference between typical OCD and OCD seen in cases of PANDAS is the sudden onset of initial OCD symptoms in the latter. This abrupt onset is in stark contrast to the gradual development of obsessions-compulsions experienced by children with childhood OCD rather than PANDAS [2-5].

PANS
The PANS criteria describe a clinically distinct presentation, which includes the abrupt onset (< 3 months) of OCD or a severely restricted food intake (tic disorder is not required) with a concurrent development or exacerbation of other neuropsychiatric symptoms [5, 6, 8]. PANS is triggered by preceding infections that are not limited to GAS [6, 7]. Other known medical diseases should be ruled out before a diagnosis of PANS is reached; hence PANS is a diagnosis of exclusion.

The PANS diagnostic criteria. There is no age limit.

I.Abrupt, dramatic onset of obsessive-compulsive disorder or severely restricted food intake.
II. Concurrent presence of additional neuropsychiatric symptoms, (with similarly severe and acute onset), from at least two of the following seven categories:
1. Anxiety
2. Emotional lability and/or depression
3. Irritability, aggression, and/or severely oppositional behaviours
4. Behavioural (developmental) regression
5. Deterioration in school performance (related to attention deficit/hyperactivity disorder [ADHD]-like symptoms, memory deficits, cognitive changes)
6. Sensory or motor abnormalities
7. Somatic signs and symptoms, including sleep disturbances, enuresis, or urinary frequency
III. Symptoms are not better explained by a known neurologic or medical disorder, such as Sydenham’s Chorea.

The individual PANS symptoms overlap with a variety of psychiatric disorders, such as OCD, Tourette’s Syndrome, ADHD, depression, bipolar disorder, schizophrenia and lupus cerebritis; as well as Autism, ODD or sensory processing disorder [6, 12-16].

However, it is the acuity of onset – or acute exacerbation of – and simultaneous presentation of symptoms in multiple domains that differentiate PANS from these psychiatric conditions [6].

The symptom profiles of patients with PANS often have a “relapsing/remitting” course with rapid progression to maximum symptom severity and rapid return to previous function over hours or days, sometimes without therapy [17]. Some patients present with a chronic-static/progressive course [18].

Many children with PANS are extremely ill, with extreme compulsions (licking shoes, barking), motor and phonic tics, behavioural regression, hallucinations, separation anxiety (often associated with obsessional thoughts about a parent’s death) and terrifying episodes of extreme anxiety or aggression [6, 9]. Some children display severe psychotic symptoms [10, 11]. The behavioural manifestations often prompt rapid referral to psychological or psychiatric services, but all patients should receive a full medical evaluation.

Successfully established multidisciplinary PANS/PANDAS clinics and teams, their assessment protocols and outcomes have been documented by specialist clinics in Stockholm [18, 22-24], Gothenburg [25], Stanford [10, 26-28], Florida [2], Genoa [29], Florence [30] and Rome [31, 32].

Recommended investigations and test panels to support clinicians in the identification and management of PANDAS/PANS patients have been described [6, 29, 33]. In the light of increasing evidence for secondary immune-mediated forms of OCD, the Immuno-Neuropsychiatry Group of the European College of Neuropsychopharmacology (ECNP), have produced a first proposal of clinical criteria for the definition of secondary autoimmune OCD – including PANS/PANDAS – and its clinical investigation [5].

Two sets of peer-reviewed published guidelines for the treatment of PANS/PANDAS exist, representing recommendations from responsible bodies of clinicians. A UK Clinical Guideline Development Group commences work on a UK consensus guideline in Spring 2024 which will work towards ending the current variation in the diagnosis and management of people presenting with symptoms of PANS and PANDAS in the UK.

PANS research consortium treatment guidelines

The PANS research consortium guidelines, published in 2017, represent a national standard of care and best evidenced treatment guidelines for PANS/PANDAS [34-36]. An overview of these treatment guidelines is available [37].

Development of these guidelines was undertaken by three workgroups of the PANS/PANDAS Clinical Research Consortium. They separately addressed 1) use of psychiatric medications and behavioral interventions; 2) use of antimicrobials; and 3) use of anti-inflammatory and immunomodulating therapies. Each workgroup first reviewed the published literature and then drew upon their combined clinical experience with more than 1,000 children with PANS/PANDAS to formulate an initial set of recommendations, which were then sent to a separate group of expert clinicians for critical review and comment [37, 38].

The resulting peer-reviewed and published PANS Research consortium guidelines were contributed to by 44 named contributors representing 23 highly respected academic institutions from across the US, Canada and Australia. These included not only clinicians with expertise in the diagnosis and treatment of PANS/PANDAS, but also experts in the fields of child psychiatry, paediatrics, infectious diseases, microbiology, neurology, neuroimmunology, immunology and rheumatology. As such, the PANS Research consortium treatment guidelines represent recommendations from a multidisciplinary and responsible body of clinicians with experience in appropriately treating patients with PANS/PANDAS.

The Pandas Physicians Network, an inter-disciplinary group with expertise in the medical sub-specialties that are relevant to PANS and PANDAS who include the contributors to the PANS Research consortium guidelines, provide evidenced information on the treatment of PANS/PANDAS via their website – including a treatment flowchart www.pandasppn.org/flowchart/

A detailed review of patients seen by the Stanford Immune Behavioral Health/PANS Clinic [28] has shown that PANS children are more sensitive to the side effects of psychiatric medications than in children with other, non-PANS, diagnoses (OCD, anxiety, depression, and aggression), and that adverse reactions to SSRIs can occur in a large proportion of PANS children if normal doses are used, particularly in the first instance. Paradoxical response to psychotropic medications may be an indication that a PANS diagnosis requires consideration [9, 40, 41].

Estimation of the actual prevalence of PANDAS is not well described and this is complicated by inconsistencies of inclusion criteria and methodologies in various studies [19, 20]. With epidemiological data of related conditions such as Tourette’s Disorder and OCD finding that 0.3%-3% of children are affected with these conditions, it follows that a smaller subset may then fulfil criteria for PANDAS [21, 19].
With the backing of NHS England, the PANS PANDAS Steering Group are embarking on work to roll out a nationwide surveillance study, designed to identify the number of children and young people presenting to healthcare professionals with symptoms matching the diagnostic criteria for PANS and PANDAS..