Understanding the Numbers: Why PANS/PANDAS is Classified as a Rare Disease
Since the recent announcement that PANS (Pediatric Acute-onset Neuropsychiatric Syndrome) has officially joined the 2020 listing of PANDAS on the NIH Genetic and Rare Diseases (GARD) directory, the PACE Foundation has received inquiries from our community about PANS/PANDAS prevalence, federal recognition, and what the word “rare” really means.
For many families, that label lands with a thud. It can feel validating and alarming at the same time. On one hand, rare disease recognition is a major policy and research milestone. On the other, parents understandably worry that “rare” will be misread by local physicians, school systems, or hospital networks as meaning “unlikely,” “too obscure to evaluate,” or somehow less urgent.
If you are a caregiver who has spent months or years fighting to be heard, only to be told your child’s symptoms are “one in a million,” “behavioral,” or “not something we see,” we want to say this clearly: your experience is real, and the fear of being dismissed is real too. In day to day life, these disorders do not feel rare. They feel relentless.
Improving and expanding access to specialized care is the heartbeat of the PACE Foundation. We take pride in our track record of opening multidisciplinary clinics along with funding and facilitating breakthrough research, but we also recognize that our work is far from over. We lean into the most current, evidence-based data because it gives our advocacy the scientific weight required to change institutional policies and improve lives.
In this article, we’ll walk through how prevalence estimates changed, what the Wald et al. (2023) data adds to the conversation, and why the rare disease classification under the Orphan Drug Act helps to unlock better research, better protocols, and better access to care.
The Evolution of a Number: From 1 in 200 to Today
For years, the figure most commonly cited by advocacy groups was that PANS/PANDAS affects roughly 1 in 200 children. Importantly, this was used as a prevalence estimate, meaning the total number of children living with the condition at a given time, not the number of newly diagnosed cases each year.
But where did that number come from? In a recent letter to the PACE Foundation, Dr. Sue Swedo (the visionary researcher who first defined PANS/PANDAS at the NIH) shared the history behind that initial estimate, joined by a group of multidisciplinary clinical leaders who listed their names in support of the letter.
In the early days of research, Dr. Swedo and her team at the NIMH focused on childhood-onset Obsessive Compulsive Disorder (OCD), which affects about 1% of children. They noticed that a subset of these children had an abrupt, “overnight” onset accompanied by physical signs like choreiform movements. By extrapolating these clinical observations onto the broader population of children with OCD, they arrived at an estimate between 1 in 200 to 1 in 500.
However, as Dr. Swedo notes, that early number was influenced by environmental factors unique to the regions where the data was gathered, specifically the DC Metro area and central Florida. These areas happened to have unusually high rates of “rheumatogenic” strains of Group A Streptococcus at the time, which led to a disproportionately high incidence of post-streptococcal sequelae, including PANDAS.
A Milestone in Precision: The Wald et al. (2023) Study
As science progresses, our tools for measuring disease frequency become more refined. We have moved from early “guess-timates” to rigorous, population-based epidemiological studies. The most significant of these is the Wald et al. (2023) study, which performed a retrospective review of nearly 96,000 medical records in a general pediatric population across three large U.S. academic medical centers.
Why this study matters
The findings provided a more refined lens for how we talk about PANS/PANDAS prevalence:
- The Incidence: The study found a pooled annual incidence of approximately 1 in 11,700 children. In other words, this figure reflects new cases diagnosed each year, not the total number of children living with PANS/PANDAS at any one time.
- The Specificity: When researchers applied the acute-onset diagnostic criteria for PANS and PANDAS, the number of confirmed cases was lower than the number of children presenting with non-acute onset symptoms.
- The Prevalence Context: When accounting for the duration of illness, that annual incidence translates to an estimated prevalence of approximately 96,000 children in the U.S. living with PANS/PANDAS at a given time.
- The Implication: Better prevalence data helps families, clinicians, and policymakers speak with more precision when advocating for recognition, treatment pathways, and research investment.
It is important to make a distinction here. In Dr. Swedo’s letter, she references epidemiologic field studies of OCD and clinical observations made during her time at the NIMH, which revealed that OCD affects approximately 1% of children and adolescents. While nearly 1% of children may experience these symptoms, only a fraction meet the full, acute-onset, complex criteria for a PANS/PANDAS diagnosis requiring intensive medical intervention.
Global research is expanding, not shrinking
Just as importantly, the rare disease designation is not pushing PANS/PANDAS out of the scientific spotlight. It is doing the opposite. As prevalence estimates become more precise, they are attracting more serious epidemiologic work across multiple countries.
A 2024 Canadian study by Goren et al. reported an estimated prevalence of roughly 1 in 60,000 children, adding international support to the conclusion that PANS/PANDAS falls within a rare disease framework.
A 2025 Swedish prevalence report from SANE (pending scientific journal publication) estimated a prevalence of approximately 64 in 100,000 children in Sweden after targeted physician education and improved case recognition. Though these regional figures can differ, they all remain well within rare disease territory when considered against established rare disease thresholds.
Why these differences matter
These numbers may reflect differences in study design, physician awareness, referral patterns, regional clustering, and how actively clinicians were trained to recognize the condition. In other words, broader global research is helping us understand that prevalence can look different depending on where and how you study it, while still supporting the central point that these disorders are rare and deserving of attention.
Research is ongoing and accelerating
This is also not the end of the story. Research is actively accelerating. A PACE and NIH-funded prospective study led by Dr. Wald at the University of Wisconsin in collaboration with Dartmouth College is now tracking incidence and outcomes in real time. That kind of prospective work is exactly what families and clinicians have been asking for: better data, better follow-up, and a clearer picture of how children do over time.
Taken together, the Wald data, the Canadian findings, the Swedish report, and the ongoing NIH-funded prospective work all point in the same direction: rare disease recognition helps bring more high-level scientific attention to PANS/PANDAS, not less.
Quick takeaway for busy parents
- A lower prevalence estimate does not mean your child’s suffering is less serious.
- It does mean researchers are getting more accurate about who meets full diagnostic criteria.
- It also means more international teams are now studying PANS/PANDAS with greater rigor.
- That kind of precision is what drives stronger studies, clearer protocols, and ultimately better care.
The Math of “Rare”: Why the 200,000 Threshold Matters
In the United States, the legal definition of a rare disease is one that affects fewer than 200,000 people at any given time. This isn’t an arbitrary number, it is the threshold set by the Orphan Drug Act.
Even if we use liberal estimates that include every child and teenager in the U.S. (ages 3–19) who might be currently struggling with the condition, Dr. Swedo’s letter points out that the total count would be approximately 96,000 individuals. This is well under the 200,000 threshold.
By acknowledging that PANS/PANDAS is a rare disease, we are not saying it is unimportant. We are saying it meets the criteria for specific federal protections and incentives.
Why the “Rare” Label is a Strategic Win for Families
You might ask: How does a rare label help my child get treated at our local hospital tomorrow?
That is the right question. And it is exactly why this conversation matters.
The reality is that for years, PANS has existed in a “medical no-man’s land.” Although PANDAS has been listed on Orphanet since 2006, and on GARD since 2020, PANS was not. Pharmaceutical companies have little incentive to fund the massive clinical trials needed to get treatments like IVIG or specialized anti-inflammatories FDA-approved specifically for this condition.
Why this matters in real life
For families, this is not just a policy issue. It affects whether a physician takes the condition seriously, whether a hospital builds a pathway for evaluation, whether insurance sees treatment as medically necessary, and whether researchers can pursue studies with enough support to change standards of care.
The rare disease designation changes the game in three critical ways:
1. The Orphan Drug Act
This act provides incentives for pharmaceutical companies to develop treatments for small patient populations. This includes tax credits for clinical trials, seven years of marketing exclusivity, and, most importantly, a waiver of the almost $5 million user fee required simply to submit a trial for FDA review. This is the primary way to get universal insurance for IVIG and other treatments that families so desperately need.
2. Standardization of Care
When a disease is listed on GARD, it forces the medical community to move toward evidence-based PANS protocols. It helps us fight “medical gaslighting” by providing a federal repository of information that says, “Yes, this is a recognized medical entity.” It supports our mission to build a national network of CPAE Centers of Excellence where families can access multidisciplinary pediatric care.
3. Research Funding
Agencies like the NIH and the Department of Defense (DoD) have specific budget carves-outs for rare disease research. Being on the GARD list makes PANS/PANDAS eligible for funding streams that were previously out of reach.
Validation: Rare Does Not Mean Insignificant
We know that many of you are facing children’s hospitals that refuse to recognize the disorder or physicians who cite outdated reports to justify dismissal. The “rare” designation is not a white flag of surrender to these barriers; it is a battering ram.
By aligning with the rare disease community, we are joining forces with thousands of other “rare” warriors who have successfully fought for insurance mandates, federal research dollars, and physician education. We are moving from a “controversial” diagnosis to a formally recognized rare neuroimmune disorder.
Our goal at the PACE Foundation remains the same: to ensure that every child has a pathway to neuroimmune disorder recovery and can return to their baseline.
Understanding the Path Forward
The classification of PANS/PANDAS as rare isn’t a sign that fewer children are sick: it’s a sign that our research is getting better at identifying who truly has this specific autoimmune syndrome. This accuracy allows us to target treatments more effectively and advocate with more authority.
As Dr. Swedo concluded in her letter: “The rarity of PANS and PANDAS should not detract from our zeal in finding effective intervention and prevention strategies. Affected children suffer terribly and their families suffer along with them… The toll is tremendous and demands our best efforts.”
We are listening to your concerns. We know the road to care is still far too steep. But by securing this GARD designation, a stronger foundation has been established for the clinical infrastructure that will eventually serve every family, in every state.
In my own experience this will not help many desperate families. Clinicians will just dismiss because of the rare category. This is exactly what happened to my boy. Left to suffer at crisis level for 3 years because Dr’s view was Pans Pandas is rare, it can’t be! Then luckily on transition to adult services a psychiatrist who actually listened treated him with immune modulating treatments and 3 months later my boy says “It feels like im back” no longer in crisis.
If you truly want to help, please listen to families.
Thanyou