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PubMed This is a summary of 15 peer-reviewed journal articles Updated
Neurology

How Rare Is SREAT? Incidence, Prevalence, and Causes

At a Glance

SREAT is considered very rare, with some medical literature estimating a prevalence of about 2.1 cases per 100,000 people. Its true frequency is uncertain because no single test confirms the diagnosis; researchers suspect an overactive immune system rather than a lifestyle-related cause.

In this answer

3 sections

01

Understanding the Rarity of SREAT

02

The Role of Antibodies and Autoimmunity

03

The Search for Triggers

Steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT), also known as Hashimoto’s encephalopathy, is generally considered a very rare condition. If you have been diagnosed with it, it is natural to wonder how common it is and why it happened to you. Some medical literature estimates the prevalence at roughly 2.1 cases per 100,000 people [1][2]. However, determining exact numbers is difficult because SREAT is challenging to diagnose consistently [3]. While the exact reason you developed SREAT is not entirely understood, researchers hypothesize it is an immune-mediated disorder—meaning it is driven by an overactive immune system—rather than a single specific trigger [4].

Understanding the Rarity of SREAT

SREAT is widely considered a rare disease, though calculating the exact incidence (how many new cases occur each year) and prevalence (how many people currently have it) is complicated [3].

One major reason for this difficulty is that there is no single validated biomarker or blood test that confirms SREAT [4]. SREAT is a clinical diagnosis of exclusion, meaning doctors must first rule out other, more common causes of encephalopathy (a broad medical term for brain dysfunction) [5]. A typical evaluation will ensure your symptoms are not caused by infections, untreated seizures, medication side effects, metabolic imbalances, or other types of autoimmune neurologic diseases [4][6]. Because this diagnostic process can vary, the numbers reported in studies often reflect hospital estimates rather than true general population statistics [7]. What is certain is that you are dealing with a highly uncommon condition.

The Role of Antibodies and Autoimmunity

Many people with SREAT have high levels of thyroid antibodies (like TPO antibodies) in their blood [5]. A common misconception is that these antibodies directly attack the brain. In reality, these antibodies are not specific to SREAT; they occur in many people without brain disease [6]. Research indicates that these antibodies are supportive clues—a red flag that your immune system is overactive—rather than the actual cause of the brain dysfunction [4][8]. Having elevated thyroid antibodies alone does not establish a diagnosis of SREAT.

Instead of a single cause, SREAT is thought to be tied to a generalized autoimmune tendency [4]. Some people who develop SREAT have an increased tendency toward autoimmunity and may have a personal or family history of other conditions, such as systemic lupus erythematosus (lupus) or other autoimmune disorders [9][10].

The Search for Triggers

Currently, there is no definitive known cause—such as a specific virus, diet, or environmental exposure—that triggers SREAT [11][12]. You did not cause this condition through your lifestyle or personal choices.

While the exact mechanism remains uncertain, researchers have proposed several theories. Some suspect that blood-brain barrier dysfunction (where the protective shield around the brain becomes leaky) or overactive immune cells may play a role [13][14]. These remain hypotheses, and the biological process of SREAT is still debated in the medical community.

Many reported patients improve with clinician-supervised immunotherapy, such as steroids [15]. However, outcomes vary: some people experience incomplete recovery or relapses, and steroids carry important risks that must be monitored [11]. Because there is no single cause, treatment and recovery are highly individualized.

Common questions in this guide

How common is SREAT?
SREAT is considered very rare. Some medical literature estimates its prevalence at roughly 2.1 cases per 100,000 people, but the true number may be different because the condition is difficult to diagnose consistently.
Why are SREAT incidence and prevalence hard to measure?
There is no single validated blood test or other marker that confirms SREAT. Doctors diagnose it after ruling out other causes of brain dysfunction, so studies may reflect hospital-based estimates rather than the number of cases in the general population.
Do high thyroid antibody levels prove that I have SREAT?
No. Thyroid antibodies, including thyroid peroxidase (TPO) antibodies, can be found in people who do not have brain disease, so they are clues rather than proof of SREAT. The diagnosis depends on the overall clinical evaluation and exclusion of other causes.
What is thought to cause SREAT, and did I do something to cause it?
The exact cause of SREAT is unknown, but researchers suspect that an overactive immune system and a general tendency toward autoimmunity may contribute. No specific virus, diet, environmental exposure, or lifestyle choice has been established as the cause, and you did not cause the condition through your personal choices.
Does having autoimmune disease in my family increase my risk of SREAT?
Some people with SREAT have a personal or family history of other autoimmune conditions, such as lupus. This may point to a broader tendency toward autoimmunity, but it does not prove that a relative's condition caused SREAT or that everyone with such a history will develop it.
Can SREAT improve with treatment, and can it come back?
Many reported patients improve with clinician-supervised immunotherapy, often including steroids, but recovery is not the same for everyone. Some people have incomplete recovery or relapses, and steroid-related risks need medical monitoring.

Related questions

Are Seizures, Tremors, and Ataxia Common in SREAT? Can SREAT Cause Only Psychiatric Symptoms Like Psychosis? Do Thyroid Antibodies Cause Brain Inflammation in SREAT? Can Thyroid Antibody Levels Predict SREAT Relapses? How Is SREAT Differentiated From Dementia and CJD?
Show more
How to Evaluate a Neurologist's SREAT and AE Expertise Is a Normal Brain MRI Common in Hashimoto's Encephalopathy? What Are SREAT Clinical Subtypes and Onset Patterns? Can Delayed SREAT Cause Long-Term Cognitive Effects? What Are SREAT Second-Line Treatments After Steroids Fail? SREAT Relapse vs. Steroid Withdrawal: Warning Signs What Do CSF and Spinal Tap Results Show for SREAT? How long does steroid treatment for SREAT usually last? What Specialists Manage Hashimoto's Encephalopathy? Why Is TSH Usually Normal in Hashimoto's Encephalopathy?

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References

References (15)
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    Steroid-responsive Encephalopathy Associated with Autoimmune Thyroiditis: A Case Fulfilling Definite Graus Criteria.

    Ammari S, Ibrahim N, Karuchola S, Ouais S

    Journal of community hospital internal medicine perspectives 2026; (16(4)):115-119 doi:10.55729/2000-9666.1618.

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    Hashimoto's encephalopathy in a patient with septal panniculitis: a case report.

    Cosso C, Ghio M, Cutolo M

    Reumatismo 2018; (70(4)):268-269 doi:10.4081/reumatismo.2018.1090.

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    Debut with psychotic symptoms of Hashimoto encephalopathy: A case report.

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    Medwave 2022; (22(9)):e2566 doi:10.5867/medwave.2022.09.2566.

    PMID: 36260762
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    Brain dysfunction and thyroid antibodies: autoimmune diagnosis and misdiagnosis.

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    Brain communications 2021; (3(2)):fcaa233 doi:10.1093/braincomms/fcaa233.

    PMID: 34061124
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    Steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT): Characteristics, treatment and outcome in 251 cases from the literature.

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    Autoimmunity reviews 2016; (15(12)):1129-1133 doi:10.1016/j.autrev.2016.09.008.

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    Hashimoto encephalopathy in the 21st century.

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    Neurology 2020; (94(2)):e217-e224 doi:10.1212/WNL.0000000000008785.

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    Clinical presentations and treatment outcomes of Hashimoto encephalopathy at Siriraj Hospital - Thailand's largest national tertiary referral center.

    Dumrikarnlert C, Thakolwiboon S, Senanarong V

    BMC neurology 2023; (23(1)):334 doi:10.1186/s12883-023-03305-4.

    PMID: 37737161
  8. 8

    Initial serum thyroid peroxidase antibodies and long-term outcomes in SREAT.

    Litmeier S, Prüss H, Witsch E, Witsch J

    Acta neurologica Scandinavica 2016; (134(6)):452-457 doi:10.1111/ane.12556.

    PMID: 26757046
  9. 9

    A Challenging Diagnosis of Steroid-Responsive Encephalopathy Associated With Autoimmune Thyroiditis (SREAT) in a Systemic Lupus Erythematosus (SLE) Patient With Hashimoto Encephalopathy (HE): A Case Report.

    Genidy R, Abbas A, Adi AAK, et al.

    Cureus 2024; (16(11)):e73262 doi:10.7759/cureus.73262.

    PMID: 39655145
  10. 10

    Delirious Mania Associated with Autoimmune Gastrothyroidal Syndrome of a Mid-Life Female: The Role of Hashimoto Encephalopathy and a 3-Year Follow-Up including Serum Autoantibody Levels.

    Bonnet U, Selle C, Kuhlmann R

    Case reports in psychiatry 2016; (2016()):4168050 doi:10.1155/2016/4168050.

    PMID: 27688922
  11. 11

    Thyroid gland and brain: Enigma of Hashimoto's encephalopathy.

    Churilov LP, Sobolevskaia PA, Stroev YI

    Best practice & research. Clinical endocrinology & metabolism 2019; (33(6)):101364 doi:10.1016/j.beem.2019.101364.

    PMID: 31801687
  12. 12

    Steroid-Responsive Encephalopathy Associated with Autoimmune Thyroiditis Presenting with Fever and Confusion.

    Liyanage CK, Munasinghe TMJ, Paramanantham A

    Case reports in neurological medicine 2017; (2017()):3790741 doi:10.1155/2017/3790741.

    PMID: 29234548
  13. 13

    An observational study on the association of anti-thyroid autoantibodies with clinical, EEG, MRI, FDG-PET, cerebrospinal fluid and anti-neuronal antibody findings in 530 patients with schizophreniform and affective disorders.

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    Psychoneuroendocrinology 2021; (131()):105320 doi:10.1016/j.psyneuen.2021.105320.

    PMID: 34171794
  14. 14

    Patients with a relapsing course of steroid-responsive encephalopathy associated with autoimmune thyroiditis exhibit persistent intrathecal CD4+ T-cell activation.

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    Hashimoto's Encephalopathy Masquerading as Rapidly Progressive Dementia and Extrapyramidal Failure.

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    Journal of neurosciences in rural practice 2022; (13(1)):101-104 doi:10.1055/s-0041-1741487.

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This page explains SREAT prevalence and possible causes for informational purposes only and is not medical advice. Your treating clinician should interpret your diagnosis, antibody results, treatment response, and care plan.