🏷

Classifications

Harrison's Part

🔗

Mappings

MONDO

MONDO:0016019 Rasmussen subacute encephalitis

MONDO:0016019 is the Rasmussen (subacute) encephalitis concept.

NCIT

NCIT:C125384 Rasmussen Subacute Encephalitis

MONDO:0016019 carries NCIT:C125384 as a cross-reference and takes its definition from that NCIT concept; the two labels agree.

ICD-11 Foundation

icd11f:182666470 Epilepsy due to Rasmussen encephalitis

The ICD-11 Foundation has no entity for Rasmussen encephalitis itself; it indexes the disorder only from the epilepsy side, as the epilepsy caused by it. Recorded as a closeMatch rather than an exactMatch because this entry is about the hemispheric encephalitis, of which the drug-resistant focal epilepsy is one consequence.

NCIT

NCIT:C125384 Rasmussen Subacute Encephalitis

MONDO:0016019 carries NCIT:C125384 as a cross-reference and takes its definition from that NCIT concept; the two labels agree.

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Discussions and Knowledge Gaps

3

Rasmussen encephalitis is driven by a T-cell response, but the inciting antigen (and whether an infection or a specific autoantigen initiates it) is unknown. Is there a definable target antigen or trigger, and would identifying it enable antigen-specific immunotherapy instead of broad immunosuppression or hemispherectomy?

KNOWLEDGE GAP OPEN re-unknown-antigenic-trigger

Attached to

pathophysiology#Immune Trigger and Adaptive Immune Activation

The absence of a known antigen is the central gap blocking targeted, hemisphere-sparing therapy; the immune attack is well characterized downstream, but its origin is not.

Proposed experiments

Target-antigen discovery study

re-antigen-discovery

Use T-cell receptor repertoire sequencing and antigen-screening of resected brain and blood from Rasmussen patients to search for a shared target antigen or trigger driving the clonal T-cell response.

Readouts

Shared TCR clonotypes and candidate target antigens

pathophysiology#Immune Trigger and Adaptive Immune Activation

Would support

pathophysiology#Immune Trigger and Adaptive Immune Activation

Immunotherapy can slow inflammatory progression but rarely stops the seizures, whereas hemispherectomy cures the seizures at the cost of a fixed neurological deficit. Can earlier or better-targeted immunotherapy (guided by imaging or immune biomarkers) defer or avoid hemispherectomy while preserving function, and what is the optimal timing of surgery?

KNOWLEDGE GAP OPEN re-immunotherapy-vs-surgery-timing

Attached to

pathophysiology#Progressive Neurological Decline pathophysiology#Drug-Resistant Focal Seizures and Epilepsia Partialis Continua

The trade-off between preserving hemispheric function and achieving seizure freedom is the central management dilemma, and the optimal timing and role of immunotherapy versus surgery are not resolved.

Proposed experiments

Immunotherapy timing and biomarker study

re-immunotherapy-timing-trial

Prospectively evaluate early immunotherapy regimens with serial MRI and immune biomarkers to test whether they slow progression enough to defer or avoid hemispherectomy while preserving neurological function.

Readouts

Progression, seizure, and function outcomes by immunotherapy timing

pathophysiology#Progressive Neurological Decline

Decision criterion

Preserved function with acceptable seizure control would support earlier immunotherapy as a hemisphere-sparing strategy.

Would support

pathophysiology#Progressive Neurological Decline

Show evidence (1 reference)

PMID:24457189 SUPPORT Human Clinical

"Cerebral hemispherectomy remains the only cure for seizures"

Frames the dilemma: surgery is curative for seizures but functionally costly, motivating better use of immunotherapy and timing.

Rasmussen encephalitis characteristically remains confined to a single cerebral hemisphere. What restricts the T-cell-mediated attack to one hemisphere and largely spares the other, and could that restriction be reinforced therapeutically?

KNOWLEDGE GAP OPEN re-unihemispheric-restriction

Attached to

pathophysiology#Progressive Unihemispheric Neuronal Loss and Gliosis

The unihemispheric confinement is both diagnostically defining and mechanistically puzzling; understanding what limits spread could reveal protective mechanisms and therapeutic targets.

Proposed experiments

Study of hemispheric confinement

re-hemispheric-restriction

Compare affected and unaffected hemispheres (imaging, immune, and, where available, tissue analyses) to identify factors that confine the inflammatory process to one hemisphere.

Readouts

Differences between affected and spared hemispheres

pathophysiology#Progressive Unihemispheric Neuronal Loss and Gliosis

Would support

pathophysiology#Progressive Unihemispheric Neuronal Loss and Gliosis

⚙

Pathophysiology

10

Immune Trigger and Adaptive Immune Activation

An unknown trigger initiates an adaptive immune response directed at one cerebral hemisphere. The inciting antigen is not established, but the downstream process is a cell-mediated (T-cell) attack. This node captures the single concept of the initiating immune activation.

Downstream

CD8+ Cytotoxic T-Cell Brain Infiltration Immune activation drives cytotoxic T-cell infiltration of the affected hemisphere.

Show evidence (1 reference)

PMID:24457189 SUPPORT Human Clinical

"Rasmussen's encephalitis is probably driven by a T-cell response to one or more antigenic epitopes"

The disorder is thought to be driven by a T-cell response to antigenic epitopes, with the inciting trigger not fully defined.

CD8+ Cytotoxic T-Cell Brain Infiltration

CD8+ cytotoxic T lymphocytes infiltrate the cortex of a single hemisphere and attack neurons and astrocytes, the central immunopathological lesion of Rasmussen encephalitis. This node captures the single concept of the T-cell-mediated attack.

CD8-positive cytotoxic T cell CL:0000625

T cell mediated cytotoxicity GO:0001913 ↑ INCREASED

Downstream

Microglial Activation and Neuroinflammation T-cell attack activates microglia and sustains neuroinflammation.

Cytotoxic T-Cell Attack on Astrocytes The same cytotoxic T-cell infiltrate engages astrocytes, not only neurons.

Show evidence (1 reference)

PMID:11891826 SUPPORT Human Clinical

"lymphocytic infiltrates that consisted mainly of CD3(+)CD8(+) T cells"

Immunohistochemistry showed the lymphocytic infiltrate is mainly CD8+ cytotoxic T cells, with granzyme-B polarized toward MHC-I+ neurons.

Microglial Activation and Neuroinflammation

Activated microglia form microglial nodules and, with the T-cell infiltrate, sustain chronic neuroinflammation in the affected hemisphere. This node captures the single concept of the innate/neuroinflammatory amplification.

Microglial cell CL:0000129

Inflammatory response GO:0006954 ↑ INCREASED

Downstream

Progressive Unihemispheric Neuronal Loss and Gliosis Sustained cytotoxic inflammation destroys neurons and drives astrogliosis.

Astrocytic MHC Class I Upregulation Astrocytes within the inflamed hemisphere come to display MHC class I.

Show evidence (1 reference)

PMID:11891826 SUPPORT Human Clinical

"unihemispheric lymphocytic infiltrates, microglial nodules, and neuronal loss"

Microglial nodules are a defining neuropathological feature of the affected hemisphere, establishing microglial activation as part of the lesion.

Astrocytic MHC Class I Upregulation

Astrocytes in the affected hemisphere display major histocompatibility complex class I, the molecular precondition that makes them recognizable to CD8+ cytotoxic T lymphocytes. This node captures the single concept of astrocytic MHC class I display.

Astrocyte CL:0000127

antigen processing and presentation via MHC class I GO:0002474 ↑ INCREASED

Downstream

Cytotoxic T-Cell Attack on Astrocytes MHC class I display licenses cytotoxic T-cell recognition of astrocytes.

Show evidence (1 reference)

PMID:17503512 SUPPORT Human Clinical

"Astrocytes in these tissues showed major histocompatibility complex class I expression."

Direct in situ observation that astrocytes in Rasmussen encephalitis tissue express MHC class I, which is what renders them targetable by CD8+ cytotoxic T cells.

Cytotoxic T-Cell Attack on Astrocytes

CD8+ cytotoxic T lymphocytes engage astrocytes directly, with granzyme-B granules polarized toward the astrocytic membrane. This node captures the single concept of the cytotoxic attack on astrocytes, the feature that distinguishes Rasmussen encephalitis from generic T-cell encephalitis.

CD8-positive cytotoxic T cell CL:0000625 Astrocyte CL:0000127

T cell mediated cytotoxicity GO:0001913 ↑ INCREASED

Downstream

Astrocytic Apoptosis and Loss Cytotoxic attack drives astrocytes into apoptosis and depletes them.

Show evidence (2 references)

PMID:17503512 SUPPORT Human Clinical

"Granzyme-B(+) granules in these lymphocytes were polarized and faced the astrocytic membranes."

Polarization of cytotoxic granules toward the astrocytic membrane is the morphological signature of an active cytotoxic attack directed at astrocytes rather than incidental lymphocyte proximity.

PMID:17503512 SUPPORT Human Clinical

"No evidence was found for an antibody-mediated destruction."

The study explicitly excludes the competing GluR3-antibody-mediated mechanism for astrocytic loss, which is why this node is modeled as a cell-mediated cytotoxic attack rather than an antibody-mediated one.

Astrocytic Apoptosis and Loss

Astrocytes undergo apoptosis and are progressively lost from cortical and white matter areas of the affected hemisphere, a change specific to Rasmussen encephalitis and absent from other epilepsy pathologies. This node captures the single concept of astrocyte depletion.

Astrocyte CL:0000127

astrocyte apoptotic process GO:0006915 ↑ INCREASED

Downstream

Unihemispheric Cortical Hyperexcitability Loss of astrocytic support may contribute to cortical hyperexcitability and seizure induction.

Progressive Unihemispheric Neuronal Loss and Gliosis Astrocyte depletion may enhance neuronal death beyond the direct T-cell-mediated killing of neurons.

Show evidence (2 references)

PMID:17503512 SUPPORT Human Clinical

"Astrocytic apoptosis and subsequent loss of these cells is a specific feature of RE. Such lesions are not found in the control groups."

Astrocytic apoptosis and loss is reported as specific to Rasmussen encephalitis and absent in healthy controls, paraneoplastic encephalomyelitis, Ammon's horn sclerosis, and focal cortical dysplasia, establishing it as a disease-defining node rather than generic inflammatory collateral.

PMID:17503512 SUPPORT Human Clinical

"In RE, astrocytic apoptosis and loss was present both in cortical and in white matter areas."

Documents the anatomical distribution of astrocyte loss across both grey and white matter of the affected hemisphere.

Progressive Unihemispheric Neuronal Loss and Gliosis

Chronic cytotoxic inflammation causes progressive neuronal loss and reactive astrogliosis confined to one hemisphere, producing the characteristic progressive unilateral hemispheric atrophy. This node captures the single concept of the resulting tissue destruction.

Neuron CL:0000540

Downstream

Unihemispheric Cortical Hyperexcitability The inflamed, injured cortex becomes epileptogenic and hyperexcitable.

Progressive Neurological Decline Progressive hemispheric destruction produces hemiparesis and cognitive decline.

Show evidence (1 reference)

PMID:11891826 SUPPORT Human Clinical

"a T-cell-mediated cytotoxic reaction induces neuronal death in Rasmussen's encephalitis"

Cytotoxic T cells directly induce neuronal death, driving the progressive hemispheric destruction.

Unihemispheric Cortical Hyperexcitability

The inflamed and injured cortex of the affected hemisphere is intensely hyperexcitable and prone to continuous focal discharge. This node captures the single concept of network hyperexcitability and conforms to the shared epilepsy final common pathway.

Neuron CL:0000540

Downstream

Drug-Resistant Focal Seizures and Epilepsia Partialis Continua Cortical hyperexcitability generates continuous, drug-resistant focal seizures.

Show evidence (1 reference)

PMID:24457189 SUPPORT Human Clinical

"unilateral inflammation of the cerebral cortex, drug-resistant epilepsy"

PARTIAL: the review establishes that the inflamed unilateral cortex coexists with drug-resistant epilepsy, which makes that cortex the presumed epileptogenic substrate. It does not describe cortical hyperexcitability, the state this node asserts, so the support is indirect.

Drug-Resistant Focal Seizures and Epilepsia Partialis Continua

The clinical hallmark is drug-resistant focal seizures, characteristically epilepsia partialis continua (continuous focal motor seizures). This node captures the single concept of the seizure endpoint and conforms to the shared epilepsy final common pathway.

Neuron CL:0000540

Show evidence (1 reference)

PMID:24457189 SUPPORT Human Clinical

"Rasmussen's encephalitis is a rare chronic neurological disorder, characterised by unilateral inflammation of the cerebral cortex, drug-resistant epilepsy"

Drug-resistant epilepsy is one of the three defining clinical features of Rasmussen encephalitis.

Progressive Neurological Decline

Progressive hemiparesis (contralateral to the affected hemisphere), cognitive decline, and, when the dominant hemisphere is involved, language impairment result from the ongoing hemispheric destruction. This node captures the single concept of the neurological deterioration.

Neuron CL:0000540

Show evidence (1 reference)

PMID:24457189 SUPPORT Human Clinical

"progressive neurological and cognitive deterioration"

Progressive neurological and cognitive deterioration is a defining feature of the disorder and the clinical endpoint of hemispheric destruction.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

5

Nervous System 3

Drug-Resistant Focal Seizures Focal-onset seizure HP:0007359

Show evidence (1 reference)

PMID:24457189 SUPPORT Human Clinical

"characterised by unilateral inflammation of the cerebral cortex, drug-resistant epilepsy, and progressive neurological and cognitive deterioration"

The review defines the triad of unilateral cortical inflammation, drug-resistant epilepsy, and progressive neurological/cognitive decline.

Progressive Hemiparesis HP:0001269

Show evidence (1 reference)

PMID:15689357 SUPPORT Human Clinical

"unilateral hemispheric atrophy, associated progressive neurological dysfunction and intractable seizures"

The European consensus statement reports progressive neurological dysfunction accompanying unilateral hemispheric atrophy. It supports progressive focal neurological deficit generally; the abstract does not name hemiparesis specifically, hence PARTIAL.

Unilateral Cerebral Atrophy HP:0002059

Show evidence (1 reference)

PMID:15689357 SUPPORT Human Clinical

"immune-mediated brain disorder leading to unilateral hemispheric atrophy"

The European consensus statement identifies unilateral hemispheric atrophy as the characteristic structural outcome of the disease.

Other 2

Epilepsia Partialis Continua HP:0012847

Progressive Cognitive Decline Progressive encephalopathy HP:0002448

Show evidence (1 reference)

PMID:24457189 SUPPORT Human Clinical

"drug-resistant epilepsy, and progressive neurological and cognitive deterioration"

The review names progressive neurological and cognitive deterioration as a defining clinical feature of Rasmussen encephalitis.

💊

Medical Actions

3

Functional Hemispherectomy (Hemispherotomy)

Action: surgical procedure Ontology label: Surgical Procedure NCIT:C15329

Functional hemispherectomy/hemispherotomy - surgically disconnecting the affected hemisphere - is the only reliably seizure-terminating treatment and is the definitive therapy for drug-resistant Rasmussen encephalitis, at the cost of a fixed contralateral hemiparesis and (for the dominant hemisphere) language considerations.

Show evidence (1 reference)

PMID:24457189 SUPPORT Human Clinical

"Cerebral hemispherectomy remains the only cure for seizures"

Hemispherectomy is the only reliably curative treatment for the seizures, at the cost of fixed functional deficits.

Immunotherapy

Action: Pharmacotherapy NCIT:C15986

Agent: methylprednisolone NCIT:C647 rituximab NCIT:C1702

Immunomodulatory therapy (corticosteroids, intravenous immunoglobulin, and agents such as tacrolimus or rituximab) can slow inflammatory progression and is used particularly early or to delay surgery, but does not reliably stop seizures.

Show evidence (1 reference)

PMID:24457189 SUPPORT Human Clinical

"Immunomodulatory treatments seem to slow rather than halt disease progression in Rasmussen's encephalitis, without changing the eventual outcome."

The Lancet Neurology review states that immunomodulatory treatment slows but does not halt progression and does not change the eventual outcome, supporting both the utility of immunotherapy and the caveat that it does not reliably stop seizures.

Antiseizure Medication

Action: Pharmacotherapy NCIT:C15986

Antiseizure medications are used but rarely control the seizures, especially epilepsia partialis continua.

Show evidence (1 reference)

PMID:35131107 SUPPORT Human Clinical

"Antiseizure medications are generally unable to stop seizures."

A systematic review of medical treatment in Rasmussen encephalitis states directly that antiseizure medications generally fail to stop seizures, supporting the description of this treatment as used but rarely controlling the seizures.

📊

Prevalence

1

Children (worldwide)

Unknown Ultra Rare

Rasmussen encephalitis is a rare, sporadic disorder of childhood, with population estimates on the order of only a few cases per ten million children; a precise, well-established rate is not available. Onset is typically in mid-childhood.

📊

Related Datasets

4

Brain Molecular Mechanisms in Rasmussen Encephalitis geo:GSE310367

Objective: Identify molecular mechanisms in brain tissue of Rasmussen encephalitis (RE) when compared to people with non-RE epilepsy (PWE) and control cases using whole exome sequencing (WES), RNAseq, and proteomics. Methods: Frozen brain tissue (ages 2-19 years) was obtained from control autopsy (n=14), surgical PWE (n=10), and surgical RE cases (n=27). We evaluated WES variants in RE associated with epilepsy, seizures, RE, and human leukocyte antigens (HLAs). Differential expression was evaluated by RNAseq (adjusted p<0.05) and label-free quantitative mass spectrometry (false discovery rate<5%) in the three groups.

human BULK RNA SEQ n=49

PMID:36336987

Identified by GEO DataSets index search for Rasmussen Encephalitis (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-08-01. Title, sample count, and organism are GEO's own values.

Comparison of cortical grey matter from Rasmussen Encephalitis patients and age-matched epileptic controls geo:GSE121010

We performed whole-genome transcriptome analysis of Rasmussen Encephalitis of the early disease stages for an overview of differentially expressed pathways leading to widespread neuroinflammation and degeneration.

human MICROARRAY n=24

PMID:30663001

Identified by GEO DataSets index search for Rasmussen Encephalitis (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-08-01. Title, sample count, and organism are GEO's own values.

Molecular and spatial heterogeneity of microglia in Rasmussen encephalitis geo:GSE213364

Rasmussen encephalitis (RE) is a rare childhood neurological disease characterized by progressive unilateral loss of function, hemispheric atrophy and drug-resistant epilepsy. Affected brain tissue shows signs of infiltrating cytotoxic T-cells, microglial activation, and neuronal death, implicating an inflammatory disease process. Recent studies have identified molecular correlates of inflammation in RE, but cell-type-specific mechanisms remain unclear. We used single-nucleus RNA-sequencing (snRNA-seq) to assess gene expression across multiple cell types in brain tissue resected from two children with RE.

human MULTI OMICS n=6

PMID:36411471

Identified by GEO DataSets index search for Rasmussen Encephalitis (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-08-01. Title, sample count, and organism are GEO's own values.

Molecular Mechanisms in Rasmussen Encephalitis massive:MSV000089203

Rasmussen encephalitis is a unilateral encephalitis characterized by treatment-resistant epilepsy and progressive cognitive and motor decline. MRI reveals inflammation and neuropathology reveals reactive astrocytes, microglial activation, microglial nodules, T cell infiltration, and neuronal loss.

Located via OmicsDI, which aggregates across omics repositories; this record comes from massive. Only repositories with no other discovery route in this project and with a working accession resolver are curated from OmicsDI -- GEO, ArrayExpress, PRIDE, MetaboLights and EGA hits are excluded as duplicates of dedicated passes. Matched because the disease is named in the dataset's own title ("Rasmussen Encephalitis"). Retrieved 2026-08-02.

{ }

Source YAML

click to show

name: Rasmussen Encephalitis
creation_date: "2026-07-18T00:00:00Z"
category: Complex
description: >-
  Rasmussen encephalitis is a rare, acquired, progressive inflammatory disorder
  that affects a single cerebral hemisphere, usually beginning in childhood.
  Unlike the genetic developmental and epileptic encephalopathies, it is an
  immune-mediated (predominantly CD8+ cytotoxic T-cell-driven) chronic
  encephalitis of unknown trigger. Progressive unihemispheric inflammation,
  microglial activation, and neuronal loss produce drug-resistant focal
  seizures - characteristically epilepsia partialis continua - together with
  progressive hemiparesis, cognitive decline, and atrophy of the affected
  hemisphere. Antiseizure medications rarely control the seizures;
  immunotherapy can slow progression, but functional hemispherectomy
  (hemispherotomy) is the only reliably seizure-terminating treatment.
parents:
- Epilepsy
- Neurological Disease
synonyms:
- Rasmussen syndrome
- Rasmussen subacute encephalitis
- Chronic focal encephalitis
disease_term:
  preferred_term: Rasmussen subacute encephalitis
  term:
    id: MONDO:0016019
    label: Rasmussen subacute encephalitis
mappings:
  icd11f_mappings:
  - term:
      id: icd11f:182666470
      label: Epilepsy due to Rasmussen encephalitis
    mapping_predicate: skos:closeMatch
    mapping_source: manual curation
    mapping_justification: >-
      The ICD-11 Foundation has no entity for Rasmussen encephalitis itself; it
      indexes the disorder only from the epilepsy side, as the epilepsy caused
      by it. Recorded as a closeMatch rather than an exactMatch because this
      entry is about the hemispheric encephalitis, of which the drug-resistant
      focal epilepsy is one consequence.
  mondo_mappings:
  - term:
      id: MONDO:0016019
      label: Rasmussen subacute encephalitis
    mapping_predicate: skos:exactMatch
    mapping_source: MONDO
    mapping_justification: >-
      MONDO:0016019 is the Rasmussen (subacute) encephalitis concept.
  ncit_mappings:
  - term:
      id: NCIT:C125384
      label: Rasmussen Subacute Encephalitis
    mapping_predicate: skos:exactMatch
    mapping_source: MONDO:0016019
    mapping_justification: >-
      MONDO:0016019 carries NCIT:C125384 as a cross-reference and takes its
      definition from that NCIT concept; the two labels agree.
    consistency:
    - reference: MONDO:0016019
      consistent: CONSISTENT
      notes: "xref: NCIT:C125384"
pathophysiology:
- name: Immune Trigger and Adaptive Immune Activation
  description: >-
    An unknown trigger initiates an adaptive immune response directed at one
    cerebral hemisphere. The inciting antigen is not established, but the
    downstream process is a cell-mediated (T-cell) attack. This node captures
    the single concept of the initiating immune activation.
  role: trigger
  biological_scale: CELLULAR
  evidence:
  - reference: PMID:24457189
    reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Rasmussen's encephalitis is probably driven by a T-cell response to one or more antigenic epitopes"
    explanation: >-
      The disorder is thought to be driven by a T-cell response to antigenic
      epitopes, with the inciting trigger not fully defined.
  downstream:
  - target: CD8+ Cytotoxic T-Cell Brain Infiltration
    causal_link_type: DIRECT
    description: >-
      Immune activation drives cytotoxic T-cell infiltration of the affected
      hemisphere.
    evidence:
    - reference: PMID:24457189
      reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Neuropathological and immunological studies support the notion that Rasmussen's encephalitis is probably driven by a T-cell response to one or more antigenic epitopes"
      explanation: >-
        Attributing the disease process to an antigen-directed T-cell response is
        what places cytotoxic T-cell infiltration downstream of the initiating
        immune activation. PARTIAL rather than SUPPORT because the review states
        the driving response, not the infiltration event itself, and hedges it as
        "probably".
- name: CD8+ Cytotoxic T-Cell Brain Infiltration
  description: >-
    CD8+ cytotoxic T lymphocytes infiltrate the cortex of a single hemisphere
    and attack neurons and astrocytes, the central immunopathological lesion of
    Rasmussen encephalitis. This node captures the single concept of the
    T-cell-mediated attack.
  role: mediator
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: CD8-positive cytotoxic T cell
    term:
      id: CL:0000625
      label: CD8-positive, alpha-beta T cell
  biological_processes:
  - preferred_term: T cell mediated cytotoxicity
    term:
      id: GO:0001913
      label: T cell mediated cytotoxicity
    modifier: INCREASED
  evidence:
  - reference: PMID:11891826
    reference_title: "Destruction of neurons by cytotoxic T cells: a new pathogenic mechanism in Rasmussen's encephalitis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "lymphocytic infiltrates that consisted mainly of CD3(+)CD8(+) T cells"
    explanation: >-
      Immunohistochemistry showed the lymphocytic infiltrate is mainly CD8+
      cytotoxic T cells, with granzyme-B polarized toward MHC-I+ neurons.
  downstream:
  - target: Microglial Activation and Neuroinflammation
    causal_link_type: DIRECT
    description: >-
      T-cell attack activates microglia and sustains neuroinflammation.
    evidence:
    - reference: PMID:24457189
      reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "initial damage to the brain is mediated by T cells and microglia"
      explanation: >-
        Histopathology-clinical correlation places T cells and microglia together
        in the early damaging lesion. PARTIAL because co-occurrence in the early
        lesion is indirect evidence for the directional T-cell-to-microglia
        amplification step, which the review does not state as such.
  - target: Cytotoxic T-Cell Attack on Astrocytes
    causal_link_type: DIRECT
    description: >-
      The same cytotoxic T-cell infiltrate engages astrocytes, not only neurons.
    evidence:
    - reference: PMID:17503512
      reference_title: "Astrocytes are a specific immunological target in Rasmussen's encephalitis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "granzyme-B(+) lymphocytes were found in close apposition to astrocytes bordering astrocyte-deficient lesions"
      explanation: >-
        Granzyme-B-positive lymphocytes sit directly against astrocytes at the
        edge of astrocyte-depleted lesions, placing the cytotoxic infiltrate in
        physical contact with astrocytes and establishing this edge.
- name: Microglial Activation and Neuroinflammation
  description: >-
    Activated microglia form microglial nodules and, with the T-cell
    infiltrate, sustain chronic neuroinflammation in the affected hemisphere.
    This node captures the single concept of the innate/neuroinflammatory
    amplification.
  role: mediator
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: Microglial cell
    term:
      id: CL:0000129
      label: microglial cell
  biological_processes:
  - preferred_term: Inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
    modifier: INCREASED
  evidence:
  - reference: PMID:11891826
    reference_title: "Destruction of neurons by cytotoxic T cells: a new pathogenic mechanism in Rasmussen's encephalitis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "unihemispheric lymphocytic infiltrates, microglial nodules, and neuronal loss"
    explanation: >-
      Microglial nodules are a defining neuropathological feature of the affected
      hemisphere, establishing microglial activation as part of the lesion.
  downstream:
  - target: Progressive Unihemispheric Neuronal Loss and Gliosis
    causal_link_type: DIRECT
    description: >-
      Sustained cytotoxic inflammation destroys neurons and drives astrogliosis.
    evidence:
    - reference: PMID:11891826
      reference_title: "Destruction of neurons by cytotoxic T cells: a new pathogenic mechanism in Rasmussen's encephalitis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "unihemispheric lymphocytic infiltrates, microglial nodules, and neuronal loss leading to the destruction of the affected hemisphere"
      explanation: >-
        The inflammatory infiltrate and microglial nodules are described as
        leading to neuronal loss and destruction of the affected hemisphere.
  - target: Astrocytic MHC Class I Upregulation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Astrocytes within the inflamed hemisphere come to display MHC class I.
    evidence:
    - reference: PMID:17503512
      reference_title: "Astrocytes are a specific immunological target in Rasmussen's encephalitis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Astrocytes in these tissues showed major histocompatibility complex class I expression."
      explanation: >-
        PARTIAL, and the link type is deliberately
        INDIRECT_UNKNOWN_INTERMEDIATES: the study documents MHC class I
        expression on astrocytes inside inflamed Rasmussen cortex, but it does
        not identify the signal that induces it. This edge encodes the
        inflammatory context in which the MHC class I display arises, not a
        demonstrated induction by microglial activation.
- name: Astrocytic MHC Class I Upregulation
  description: >-
    Astrocytes in the affected hemisphere display major histocompatibility
    complex class I, the molecular precondition that makes them recognizable to
    CD8+ cytotoxic T lymphocytes. This node captures the single concept of
    astrocytic MHC class I display.
  role: mediator
  biological_scale: MOLECULAR
  cell_types:
  - preferred_term: Astrocyte
    term:
      id: CL:0000127
      label: astrocyte
  biological_processes:
  - preferred_term: antigen processing and presentation via MHC class I
    term:
      id: GO:0002474
      label: antigen processing and presentation of peptide antigen via MHC class I
    modifier: INCREASED
  evidence:
  - reference: PMID:17503512
    reference_title: "Astrocytes are a specific immunological target in Rasmussen's encephalitis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Astrocytes in these tissues showed major histocompatibility complex class I expression."
    explanation: >-
      Direct in situ observation that astrocytes in Rasmussen encephalitis
      tissue express MHC class I, which is what renders them targetable by CD8+
      cytotoxic T cells.
  downstream:
  - target: Cytotoxic T-Cell Attack on Astrocytes
    causal_link_type: DIRECT
    description: >-
      MHC class I display licenses cytotoxic T-cell recognition of astrocytes.
    evidence:
    - reference: PMID:17503512
      reference_title: "Astrocytes are a specific immunological target in Rasmussen's encephalitis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Astrocytes in these tissues showed major histocompatibility complex class I expression. Furthermore, granzyme-B(+) lymphocytes were found in close apposition to astrocytes bordering astrocyte-deficient lesions."
      explanation: >-
        PARTIAL: the study establishes both ends of this edge in the same
        tissue - MHC class I-positive astrocytes and granzyme-B-positive
        lymphocytes apposed to them - but does not experimentally demonstrate
        that MHC class I display is what enables the attack. That step is
        standard CD8+ T-cell immunobiology rather than a finding of this paper.
- name: Cytotoxic T-Cell Attack on Astrocytes
  description: >-
    CD8+ cytotoxic T lymphocytes engage astrocytes directly, with granzyme-B
    granules polarized toward the astrocytic membrane. This node captures the
    single concept of the cytotoxic attack on astrocytes, the feature that
    distinguishes Rasmussen encephalitis from generic T-cell encephalitis.
  role: mediator
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: CD8-positive cytotoxic T cell
    term:
      id: CL:0000625
      label: CD8-positive, alpha-beta T cell
  - preferred_term: Astrocyte
    term:
      id: CL:0000127
      label: astrocyte
  biological_processes:
  - preferred_term: T cell mediated cytotoxicity
    term:
      id: GO:0001913
      label: T cell mediated cytotoxicity
    modifier: INCREASED
  evidence:
  - reference: PMID:17503512
    reference_title: "Astrocytes are a specific immunological target in Rasmussen's encephalitis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Granzyme-B(+) granules in these lymphocytes were polarized and faced the astrocytic membranes."
    explanation: >-
      Polarization of cytotoxic granules toward the astrocytic membrane is the
      morphological signature of an active cytotoxic attack directed at
      astrocytes rather than incidental lymphocyte proximity.
  - reference: PMID:17503512
    reference_title: "Astrocytes are a specific immunological target in Rasmussen's encephalitis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "No evidence was found for an antibody-mediated destruction."
    explanation: >-
      The study explicitly excludes the competing GluR3-antibody-mediated
      mechanism for astrocytic loss, which is why this node is modeled as a
      cell-mediated cytotoxic attack rather than an antibody-mediated one.
  downstream:
  - target: Astrocytic Apoptosis and Loss
    causal_link_type: DIRECT
    description: >-
      Cytotoxic attack drives astrocytes into apoptosis and depletes them.
    evidence:
    - reference: PMID:17503512
      reference_title: "Astrocytes are a specific immunological target in Rasmussen's encephalitis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We suggest a specific attack by cytotoxic T lymphocytes as a possible mechanism responsible for astrocytic degeneration in RE."
      explanation: >-
        PARTIAL because the authors state this as a suggested possible
        mechanism rather than a demonstrated one. The supporting morphology
        (granzyme-B polarization against MHC class I-positive astrocytes at the
        margins of astrocyte-deficient lesions) is strong but correlative.
- name: Astrocytic Apoptosis and Loss
  description: >-
    Astrocytes undergo apoptosis and are progressively lost from cortical and
    white matter areas of the affected hemisphere, a change specific to
    Rasmussen encephalitis and absent from other epilepsy pathologies. This node
    captures the single concept of astrocyte depletion.
  role: mediator
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: Astrocyte
    term:
      id: CL:0000127
      label: astrocyte
  biological_processes:
  - preferred_term: astrocyte apoptotic process
    term:
      id: GO:0006915
      label: apoptotic process
    modifier: INCREASED
  evidence:
  - reference: PMID:17503512
    reference_title: "Astrocytes are a specific immunological target in Rasmussen's encephalitis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Astrocytic apoptosis and subsequent loss of these cells is a specific feature of RE. Such lesions are not found in the control groups."
    explanation: >-
      Astrocytic apoptosis and loss is reported as specific to Rasmussen
      encephalitis and absent in healthy controls, paraneoplastic
      encephalomyelitis, Ammon's horn sclerosis, and focal cortical dysplasia,
      establishing it as a disease-defining node rather than generic
      inflammatory collateral.
  - reference: PMID:17503512
    reference_title: "Astrocytes are a specific immunological target in Rasmussen's encephalitis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In RE, astrocytic apoptosis and loss was present both in cortical and in white matter areas."
    explanation: >-
      Documents the anatomical distribution of astrocyte loss across both grey
      and white matter of the affected hemisphere.
  downstream:
  - target: Unihemispheric Cortical Hyperexcitability
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Loss of astrocytic support may contribute to cortical hyperexcitability
      and seizure induction.
    evidence:
    - reference: PMID:17503512
      reference_title: "Astrocytes are a specific immunological target in Rasmussen's encephalitis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The loss of astrocytes might play a role in neuronal dysfunction, seizure induction, and enhancement of neuronal cell death."
      explanation: >-
        PARTIAL and deliberately hedged: the authors write "might play a role".
        Astrocytes govern extracellular potassium and glutamate buffering, so
        their loss is a plausible route to hyperexcitability, but this paper
        proposes rather than demonstrates the link and does not identify the
        intervening steps.
  - target: Progressive Unihemispheric Neuronal Loss and Gliosis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Astrocyte depletion may enhance neuronal death beyond the direct
      T-cell-mediated killing of neurons.
    evidence:
    - reference: PMID:17503512
      reference_title: "Astrocytes are a specific immunological target in Rasmussen's encephalitis."
      supports: SUPPORT
      directness: INDIRECT
      evidence_source: HUMAN_CLINICAL
      snippet: "The loss of astrocytes might play a role in neuronal dysfunction, seizure induction, and enhancement of neuronal cell death."
      explanation: >-
        INDIRECT: the same hedged interpretation sentence. It nominates
        astrocyte loss as an amplifier of neuronal cell death without
        establishing the magnitude or the mechanism, so this edge is modeled as
        a contributing route alongside the direct cytotoxic killing of neurons.
- name: Progressive Unihemispheric Neuronal Loss and Gliosis
  description: >-
    Chronic cytotoxic inflammation causes progressive neuronal loss and reactive
    astrogliosis confined to one hemisphere, producing the characteristic
    progressive unilateral hemispheric atrophy. This node captures the single
    concept of the resulting tissue destruction.
  role: mediator
  biological_scale: TISSUE
  cell_types:
  - preferred_term: Neuron
    term:
      id: CL:0000540
      label: neuron
  evidence:
  - reference: PMID:11891826
    reference_title: "Destruction of neurons by cytotoxic T cells: a new pathogenic mechanism in Rasmussen's encephalitis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a T-cell-mediated cytotoxic reaction induces neuronal death in Rasmussen's encephalitis"
    explanation: >-
      Cytotoxic T cells directly induce neuronal death, driving the progressive
      hemispheric destruction.
  downstream:
  - target: Unihemispheric Cortical Hyperexcitability
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      The inflamed, injured cortex becomes epileptogenic and hyperexcitable.
    intermediate_mechanisms:
    - Loss of inhibitory interneurons and reactive astrogliosis in the damaged
      cortex, degrading local inhibitory tone
    - Cytokine-mediated modulation of glutamatergic and GABAergic
      neurotransmission by the sustained inflammatory infiltrate
    evidence:
    - reference: PMID:24457189
      reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "characterised by unilateral inflammation of the cerebral cortex, drug-resistant epilepsy"
      explanation: >-
        PARTIAL, and deliberately so: this is a definitional sentence listing
        unilateral cortical inflammation and drug-resistant epilepsy as
        co-occurring features of the disorder. It does not assert that the
        injured cortex becomes hyperexcitable, which is the claim this edge
        makes; it only establishes that the two ends of the edge are both
        present in the disease.
  - target: Progressive Neurological Decline
    causal_link_type: DIRECT
    description: >-
      Progressive hemispheric destruction produces hemiparesis and cognitive
      decline.
    evidence:
    - reference: PMID:24457189
      reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "unilateral inflammation of the cerebral cortex, drug-resistant epilepsy, and progressive neurological and cognitive deterioration"
      explanation: >-
        PARTIAL: this is the same definitional listing of disease features. It
        establishes that hemispheric destruction and progressive neurological
        and cognitive deterioration co-occur, but does not assert that the
        former causes the latter, which is what this edge claims.
- name: Unihemispheric Cortical Hyperexcitability
  description: >-
    The inflamed and injured cortex of the affected hemisphere is intensely
    hyperexcitable and prone to continuous focal discharge. This node captures
    the single concept of network hyperexcitability and conforms to the shared
    epilepsy final common pathway.
  role: central_effector
  biological_scale: TISSUE
  conforms_to: "epilepsy_excitation_inhibition_imbalance#Neuronal Hyperexcitability and Hypersynchrony"
  cell_types:
  - preferred_term: Neuron
    term:
      id: CL:0000540
      label: neuron
  evidence:
  - reference: PMID:24457189
    reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "unilateral inflammation of the cerebral cortex, drug-resistant epilepsy"
    explanation: >-
      PARTIAL: the review establishes that the inflamed unilateral cortex
      coexists with drug-resistant epilepsy, which makes that cortex the
      presumed epileptogenic substrate. It does not describe cortical
      hyperexcitability, the state this node asserts, so the support is
      indirect.
  downstream:
  - target: Drug-Resistant Focal Seizures and Epilepsia Partialis Continua
    causal_link_type: DIRECT
    description: >-
      Cortical hyperexcitability generates continuous, drug-resistant focal
      seizures.
    evidence:
    - reference: PMID:24457189
      reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "unilateral inflammation of the cerebral cortex, drug-resistant epilepsy"
      explanation: >-
        PARTIAL: the drug-resistant epilepsy at this edge's target is documented,
        but the review does not attribute it to hyperexcitability of the inflamed
        cortex, which is the causal step this edge asserts.
- name: Drug-Resistant Focal Seizures and Epilepsia Partialis Continua
  description: >-
    The clinical hallmark is drug-resistant focal seizures, characteristically
    epilepsia partialis continua (continuous focal motor seizures). This node
    captures the single concept of the seizure endpoint and conforms to the
    shared epilepsy final common pathway.
  role: consequence
  biological_scale: ORGANISM
  conforms_to: "epilepsy_excitation_inhibition_imbalance#Recurrent Unprovoked Seizures"
  cell_types:
  - preferred_term: Neuron
    term:
      id: CL:0000540
      label: neuron
  evidence:
  - reference: PMID:24457189
    reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Rasmussen's encephalitis is a rare chronic neurological disorder, characterised by unilateral inflammation of the cerebral cortex, drug-resistant epilepsy"
    explanation: >-
      Drug-resistant epilepsy is one of the three defining clinical features of
      Rasmussen encephalitis.
- name: Progressive Neurological Decline
  description: >-
    Progressive hemiparesis (contralateral to the affected hemisphere), cognitive
    decline, and, when the dominant hemisphere is involved, language impairment
    result from the ongoing hemispheric destruction. This node captures the
    single concept of the neurological deterioration.
  role: effector
  biological_scale: ORGANISM
  cell_types:
  - preferred_term: Neuron
    term:
      id: CL:0000540
      label: neuron
  evidence:
  - reference: PMID:24457189
    reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "progressive neurological and cognitive deterioration"
    explanation: >-
      Progressive neurological and cognitive deterioration is a defining feature
      of the disorder and the clinical endpoint of hemispheric destruction.
phenotypes:
- name: Epilepsia Partialis Continua
  description: >-
    Continuous focal motor seizures (epilepsia partialis continua) are the
    characteristic seizure manifestation.
  phenotype_term:
    preferred_term: Epilepsia partialis continua
    term:
      id: HP:0012847
      label: Epilepsia partialis continua
- name: Drug-Resistant Focal Seizures
  description: >-
    Focal-onset seizures that are typically refractory to antiseizure
    medication.
  phenotype_term:
    preferred_term: Focal-onset seizure
    term:
      id: HP:0007359
      label: Focal-onset seizure
  evidence:
  - reference: PMID:24457189
    reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "characterised by unilateral inflammation of the cerebral cortex, drug-resistant epilepsy, and progressive neurological and cognitive deterioration"
    explanation: >-
      The review defines the triad of unilateral cortical inflammation,
      drug-resistant epilepsy, and progressive neurological/cognitive decline.
- name: Progressive Hemiparesis
  description: >-
    Progressive hemiparesis contralateral to the affected hemisphere develops as
    the disease advances.
  phenotype_term:
    preferred_term: Hemiparesis
    term:
      id: HP:0001269
      label: Hemiparesis
  evidence:
  - reference: PMID:15689357
    reference_title: "Pathogenesis, diagnosis and treatment of Rasmussen encephalitis: a European consensus statement."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "unilateral hemispheric atrophy, associated progressive neurological dysfunction and intractable seizures"
    explanation: >-
      The European consensus statement reports progressive neurological
      dysfunction accompanying unilateral hemispheric atrophy. It supports
      progressive focal neurological deficit generally; the abstract does not
      name hemiparesis specifically, hence PARTIAL.
- name: Progressive Cognitive Decline
  description: >-
    Progressive cognitive decline and encephalopathy accompany disease
    progression.
  phenotype_term:
    preferred_term: Progressive encephalopathy
    term:
      id: HP:0002448
      label: Progressive encephalopathy
  evidence:
  - reference: PMID:24457189
    reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "drug-resistant epilepsy, and progressive neurological and cognitive deterioration"
    explanation: >-
      The review names progressive neurological and cognitive deterioration as
      a defining clinical feature of Rasmussen encephalitis.
- name: Unilateral Cerebral Atrophy
  description: >-
    Progressive atrophy of the affected cerebral hemisphere is seen on imaging.
  phenotype_term:
    preferred_term: Cerebral atrophy
    term:
      id: HP:0002059
      label: Cerebral atrophy
  evidence:
  - reference: PMID:15689357
    reference_title: "Pathogenesis, diagnosis and treatment of Rasmussen encephalitis: a European consensus statement."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "immune-mediated brain disorder leading to unilateral hemispheric atrophy"
    explanation: >-
      The European consensus statement identifies unilateral hemispheric
      atrophy as the characteristic structural outcome of the disease.
prevalence:
- population: Children (worldwide)
  measure_type: UNKNOWN
  prevalence_class: ULTRA_RARE
  notes: >-
    Rasmussen encephalitis is a rare, sporadic disorder of childhood, with
    population estimates on the order of only a few cases per ten million
    children; a precise, well-established rate is not available. Onset is
    typically in mid-childhood.
treatments:
- name: Functional Hemispherectomy (Hemispherotomy)
  description: >-
    Functional hemispherectomy/hemispherotomy - surgically disconnecting the
    affected hemisphere - is the only reliably seizure-terminating treatment and
    is the definitive therapy for drug-resistant Rasmussen encephalitis, at the
    cost of a fixed contralateral hemiparesis and (for the dominant hemisphere)
    language considerations.
  treatment_term:
    preferred_term: surgical procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  evidence:
  - reference: PMID:24457189
    reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cerebral hemispherectomy remains the only cure for seizures"
    explanation: >-
      Hemispherectomy is the only reliably curative treatment for the seizures,
      at the cost of fixed functional deficits.
- name: Immunotherapy
  description: >-
    Immunomodulatory therapy (corticosteroids, intravenous immunoglobulin, and
    agents such as tacrolimus or rituximab) can slow inflammatory progression
    and is used particularly early or to delay surgery, but does not reliably
    stop seizures.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: methylprednisolone
      term:
        id: NCIT:C647
        label: Methylprednisolone
    - preferred_term: rituximab
      term:
        id: NCIT:C1702
        label: Rituximab
  evidence:
  - reference: PMID:24457189
    reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Immunomodulatory treatments seem to slow rather than halt disease progression in Rasmussen's encephalitis, without changing the eventual outcome."
    explanation: >-
      The Lancet Neurology review states that immunomodulatory treatment slows
      but does not halt progression and does not change the eventual outcome,
      supporting both the utility of immunotherapy and the caveat that it does
      not reliably stop seizures.
- name: Antiseizure Medication
  description: >-
    Antiseizure medications are used but rarely control the seizures, especially
    epilepsia partialis continua.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  evidence:
  - reference: PMID:35131107
    reference_title: "Medical treatment of Rasmussen's Encephalitis: A systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Antiseizure medications are generally unable to stop seizures."
    explanation: >-
      A systematic review of medical treatment in Rasmussen encephalitis states
      directly that antiseizure medications generally fail to stop seizures,
      supporting the description of this treatment as used but rarely
      controlling the seizures.
classifications:
  harrisons_chapter:
  - classification_value: NEUROLOGIC
    evidence:
    - reference: PMID:24457189
      reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Rasmussen's encephalitis is a rare chronic neurological disorder, characterised by unilateral inflammation of the cerebral cortex, drug-resistant epilepsy, and progressive neurological and cognitive deterioration"
      explanation: >-
        Lancet Neurology review characterises Rasmussen encephalitis as a
        chronic neurological disorder presenting with drug-resistant epilepsy
        and progressive neurological deterioration, placing its primary
        clinical home in Harrison's Neurologic Disorders Part.
  - classification_value: IMMUNE_RHEUMATOLOGIC
    evidence:
    - reference: PMID:24457189
      reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Neuropathological and immunological studies support the notion that Rasmussen's encephalitis is probably driven by a T-cell response to one or more antigenic epitopes"
      explanation: >-
        The same review attributes the disorder to a T-cell-mediated immune
        response against brain antigens, so the entity also belongs in
        Harrison's Immune-Mediated, Inflammatory, and Rheumatologic Part.
datasets:
- accession: geo:GSE310367
  title: Brain Molecular Mechanisms in Rasmussen Encephalitis
  description: 'Objective: Identify molecular mechanisms in brain tissue of Rasmussen encephalitis (RE) when compared to people with non-RE epilepsy (PWE) and control cases using whole exome sequencing (WES), RNAseq, and proteomics. Methods: Frozen brain tissue (ages 2-19 years) was obtained from control autopsy (n=14), surgical PWE (n=10), and surgical RE cases (n=27). We evaluated WES variants in RE associated with epilepsy, seizures, RE, and human leukocyte antigens (HLAs). Differential expression was evaluated by RNAseq (adjusted p<0.05) and label-free quantitative mass spectrometry (false discovery rate<5%) in the three groups.'
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: BULK_RNA_SEQ
  sample_count: 49
  publication: PMID:36336987
  notes: Identified by GEO DataSets index search for Rasmussen Encephalitis (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-08-01. Title, sample count, and organism are GEO's own values.
- accession: geo:GSE121010
  title: Comparison of cortical grey matter from Rasmussen Encephalitis patients and age-matched epileptic controls
  description: We performed whole-genome transcriptome analysis of Rasmussen Encephalitis of the early disease stages for an overview of differentially expressed pathways leading to widespread neuroinflammation and degeneration.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: MICROARRAY
  sample_count: 24
  publication: PMID:30663001
  notes: Identified by GEO DataSets index search for Rasmussen Encephalitis (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-08-01. Title, sample count, and organism are GEO's own values.
- accession: geo:GSE213364
  title: Molecular and spatial heterogeneity of microglia in Rasmussen encephalitis
  description: Rasmussen encephalitis (RE) is a rare childhood neurological disease characterized by progressive unilateral loss of function, hemispheric atrophy and drug-resistant epilepsy. Affected brain tissue shows signs of infiltrating cytotoxic T-cells, microglial activation, and neuronal death, implicating an inflammatory disease process. Recent studies have identified molecular correlates of inflammation in RE, but cell-type-specific mechanisms remain unclear. We used single-nucleus RNA-sequencing (snRNA-seq) to assess gene expression across multiple cell types in brain tissue resected from two children with RE.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: MULTI_OMICS
  sample_count: 6
  publication: PMID:36411471
  notes: Identified by GEO DataSets index search for Rasmussen Encephalitis (scripts/discover_datasets.py); accession and metadata verified against NCBI E-utilities on 2026-08-01. Title, sample count, and organism are GEO's own values.
- accession: massive:MSV000089203
  title: Molecular Mechanisms in Rasmussen Encephalitis
  description: Rasmussen encephalitis is a unilateral encephalitis characterized by treatment-resistant epilepsy and progressive cognitive and motor decline. MRI reveals inflammation and neuropathology reveals reactive astrocytes, microglial activation, microglial nodules, T cell infiltration, and neuronal loss.
  notes: Located via OmicsDI, which aggregates across omics repositories; this record comes from massive. Only repositories with no other discovery route in this project and with a working accession resolver are curated from OmicsDI -- GEO, ArrayExpress, PRIDE, MetaboLights and EGA hits are excluded as duplicates of dedicated passes. Matched because the disease is named in the dataset's own title ("Rasmussen Encephalitis"). Retrieved 2026-08-02.
discussions:
- discussion_id: re-unknown-antigenic-trigger
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - "pathophysiology#Immune Trigger and Adaptive Immune Activation"
  prompt: >-
    Rasmussen encephalitis is driven by a T-cell response, but the inciting
    antigen (and whether an infection or a specific autoantigen initiates it)
    is unknown. Is there a definable target antigen or trigger, and would
    identifying it enable antigen-specific immunotherapy instead of broad
    immunosuppression or hemispherectomy?
  rationale: >-
    The absence of a known antigen is the central gap blocking targeted,
    hemisphere-sparing therapy; the immune attack is well characterized
    downstream, but its origin is not.
  proposed_experiments:
  - experiment_id: re-antigen-discovery
    name: Target-antigen discovery study
    description: >-
      Use T-cell receptor repertoire sequencing and antigen-screening of
      resected brain and blood from Rasmussen patients to search for a shared
      target antigen or trigger driving the clonal T-cell response.
    readouts:
    - name: Shared TCR clonotypes and candidate target antigens
      target: "pathophysiology#Immune Trigger and Adaptive Immune Activation"
    would_support:
    - "pathophysiology#Immune Trigger and Adaptive Immune Activation"
- discussion_id: re-immunotherapy-vs-surgery-timing
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - "pathophysiology#Progressive Neurological Decline"
  - "pathophysiology#Drug-Resistant Focal Seizures and Epilepsia Partialis Continua"
  prompt: >-
    Immunotherapy can slow inflammatory progression but rarely stops the
    seizures, whereas hemispherectomy cures the seizures at the cost of a fixed
    neurological deficit. Can earlier or better-targeted immunotherapy (guided by
    imaging or immune biomarkers) defer or avoid hemispherectomy while preserving
    function, and what is the optimal timing of surgery?
  rationale: >-
    The trade-off between preserving hemispheric function and achieving seizure
    freedom is the central management dilemma, and the optimal timing and role of
    immunotherapy versus surgery are not resolved.
  evidence:
  - reference: PMID:24457189
    reference_title: "Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cerebral hemispherectomy remains the only cure for seizures"
    explanation: >-
      Frames the dilemma: surgery is curative for seizures but functionally
      costly, motivating better use of immunotherapy and timing.
  proposed_experiments:
  - experiment_id: re-immunotherapy-timing-trial
    name: Immunotherapy timing and biomarker study
    description: >-
      Prospectively evaluate early immunotherapy regimens with serial MRI and
      immune biomarkers to test whether they slow progression enough to defer or
      avoid hemispherectomy while preserving neurological function.
    readouts:
    - name: Progression, seizure, and function outcomes by immunotherapy timing
      target: "pathophysiology#Progressive Neurological Decline"
    decision_criterion: >-
      Preserved function with acceptable seizure control would support earlier
      immunotherapy as a hemisphere-sparing strategy.
    would_support:
    - "pathophysiology#Progressive Neurological Decline"
- discussion_id: re-unihemispheric-restriction
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - "pathophysiology#Progressive Unihemispheric Neuronal Loss and Gliosis"
  prompt: >-
    Rasmussen encephalitis characteristically remains confined to a single
    cerebral hemisphere. What restricts the T-cell-mediated attack to one
    hemisphere and largely spares the other, and could that restriction be
    reinforced therapeutically?
  rationale: >-
    The unihemispheric confinement is both diagnostically defining and
    mechanistically puzzling; understanding what limits spread could reveal
    protective mechanisms and therapeutic targets.
  proposed_experiments:
  - experiment_id: re-hemispheric-restriction
    name: Study of hemispheric confinement
    description: >-
      Compare affected and unaffected hemispheres (imaging, immune, and, where
      available, tissue analyses) to identify factors that confine the
      inflammatory process to one hemisphere.
    readouts:
    - name: Differences between affected and spared hemispheres
      target: "pathophysiology#Progressive Unihemispheric Neuronal Loss and Gliosis"
    would_support:
    - "pathophysiology#Progressive Unihemispheric Neuronal Loss and Gliosis"

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References & Deep Research

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Rasmussen Encephalitis — Comprehensive Research Report

claude-haiku-4-5-20251001, claude-opus-4-8 20 citations 2026-07-20T09:44:12.781738

Rasmussen Encephalitis — Comprehensive Research Report

Disease: Rasmussen Encephalitis (RE) · also "Rasmussen syndrome" (the field is drifting toward "syndrome") MONDO: MONDO:0016019 (label: Rasmussen subacute encephalitis, verified via local OAK) Category: Complex (immune-mediated, one-hemisphere neuroinflammatory epilepsy)

The one-sentence version: RE is a rare, sneaky, one-sided brain fire. A T-cell–driven inflammatory process sets up shop in a single cerebral hemisphere of a previously healthy kid, and over months to a couple of years it burns that hemisphere down — relentless focal seizures, a slowly failing arm and leg, a shrinking half-brain on MRI. It's the rare case in neurology where the cure for the seizures is to functionally disconnect half the brain, because the other half is fine and the sick half won't stop.

1. Disease Information

RE is a rare, progressive, chronic encephalitis of unknown trigger that is almost always confined to one cerebral hemisphere. The 2024 comprehensive review frames it plainly: "Rasmussen encephalitis (RE) is a rare and progressive form of chronic encephalitis that typically affects one hemisphere of the brain and primarily occurs in pediatric individuals" and is "characterized by recurrent seizures, delayed developmental milestones, progressive cognitive decline, neuroimaging with chronic inflammatory changes, and progressive hemispheric atrophy" (Medicina 2024, PMID:39597043 — verify).

First described by Theodore Rasmussen and colleagues in 1958 (Rasmussen, Olszewski, Lloyd-Smith, Neurology 1958).

Key identifiers: | Resource | ID | |---|---| | MONDO | MONDO:0016019 (Rasmussen subacute encephalitis) | | Orphanet | ORPHA:511 | | OMIM | None — RE is not a Mendelian disorder, so it has no gene-anchored OMIM entry (this is itself informative for curation) | | ICD-10 | G04.8 (other encephalitis) is the closest; often coded under G40.x epilepsy in practice | | ICD-11 | 8A45 region (autoimmune/inflammatory CNS) — closest bucket, no dedicated code | | MeSH | No dedicated descriptor; "Rasmussen" appears as an entry term under Encephalitis / Epilepsy |

Synonyms / alternative names: Rasmussen syndrome, Rasmussen's encephalitis, chronic focal encephalitis, chronic progressive epilepsia partialis continua of childhood (Kozhevnikov epilepsy is a historically overlapping term), Rasmussen subacute encephalitis.

Data provenance: RE knowledge is disease-level / aggregated — case series, small cohorts, surgical registries, and consensus statements. There is no large EHR or biobank cohort; the disease is too rare (see §9).

2. Etiology

Bottom line: the trigger is unknown; the effector is the immune system. RE is best understood as a T-cell–mediated (cell-mediated) autoimmune/neuroinflammatory process. The 2022 pathogenesis review summarizes five historically-proposed mechanisms — "virus infection, antibody-mediated degeneration, cell-mediated immunity, microglia-induced degeneration, and genetic mutations" (PMID:36189924 — verify) — but current consensus places cytotoxic CD8⁺ T-cell–mediated cell death at the center.

Causal factors: - Autoimmune / cell-mediated (primary): Clonally expanded, antigen-driven cytotoxic CD8⁺ T cells attack neurons and astrocytes (see §6). The autoantigen has never been definitively identified. - Antibody-mediated (historical, now largely discredited as primary): Anti-GluR3 (GluA3, AMPA-receptor subunit) antibodies were reported in the 1990s but failed replication ("Absence of antibodies to GluR3 in Rasmussen encephalitis"). Other antibodies (anti-NMDAR GluNε2/NR2A, anti-Munc18) have been reported sporadically but are not diagnostic. - Viral (unproven trigger hypothesis): No consistent pathogen. A "hit-and-run" viral trigger or molecular mimicry is hypothesized; one study found RE tissue shows relatively lower IFN-β production and enhanced cytotoxic T-cell activation upon herpesvirus infection (PMC8957159 — verify), keeping a viral-trigger idea alive but unproven.

Risk factors: - Genetic: No causal Mendelian gene. Whole-exome sequencing has looked for susceptibility contributors — a WES study reported candidate variants in immune-related genes, but nothing replicated or diagnostic (Frontiers in Neuroscience 2021, PMC8523672 — verify). RE is sporadic; familial recurrence is essentially not seen. - Environmental / demographic: The dominant non-genetic "risk factor" is simply young age (childhood, peak ~6 yrs). No confirmed toxin, occupational, or lifestyle exposure. No sex predilection in most series. - Prior insult: A subset report a preceding infection/inflammatory event weeks–months before onset, feeding the trigger hypothesis, but this is not consistent.

Protective factors: None established (genetic or environmental). This is a section to mark not available.

Gene–environment interactions: Speculative only — the leading model is that an environmental trigger (?viral) initiates an antigen-specific T-cell response in a susceptible immune background, but no concrete GxE interaction is documented. Mark hypothesized / not established.

3. Phenotypes

RE's phenotype is a hemispheric syndrome that marches: it starts focal and escalates into progressive loss of every function that half-brain supports.

Phenotype	Type	HPO suggestion (OAK-verified)	Onset/course	Frequency
Epilepsia partialis continua (EPC)	Clinical sign (seizure)	`HP:0012847` Epilepsia partialis continua	Emerges over first 3–5 yr	37–92%
Focal motor seizures	Sign	`HP:0006813` Focal hemiclonic seizure / `HP:0002266` Focal clonic seizure	Presenting feature	Near-universal
Drug-resistant focal epilepsy	Sign	`HP:0007359` Focal-onset seizure (verify)	Early → persistent	~100%
Status epilepticus	Sign	`HP:0002133` Status epilepticus	Acute stage	Common
Progressive hemiparesis → hemiplegia	Sign	`HP:0001269` Hemiparesis	Acute→residual	Progressive; ~all
Hemianopia	Sign	`HP:0012377` Hemianopia	Later deficit	Subset
Aphasia / dysphasia (dominant hemisphere)	Sign	`HP:0002381` Aphasia	Later deficit	If dominant side
Progressive cognitive decline	Sign	`HP:0001249` Intellectual disability / cognitive-decline term (verify)	Progressive	Common
Behavioral changes	Behavioral	(HPO abnormal behavior term)	Variable	Subset
Progressive cerebral hemiatrophy	Imaging/anatomic	`HP:0100308` Cerebral cortical hemiatrophy	Hallmark, progressive	Defining

Characteristics: - Age of onset: childhood, "median age of 6 years"; "around 10% of the individuals affected by RE are young adults" (PMID:39597043 — verify). Largest series range: 14 months–14 yr. - Severity/progression: progressive and typically severe if untreated; "Granata et al. found that 30% of the patients were wheelchair-bound within three years of the diagnosis" (PMID:39597043 — verify). - EPC definition (quotable, ILAE via review): "recurrent focal motor seizures (typically affecting hand and face...) that occur every few seconds minutes for extended periods (days or years)".

QoL impact: severe — intractable seizures, permanent hemiplegia, hemianopia, language loss (dominant side), cognitive decline; most patients end up with a fixed major neurological disability even after successful seizure control. Formal EQ-5D/SF-36 data are essentially absent (rare disease); mark limited data.

4. Genetic / Molecular Information

RE is not a genetic disease in the Mendelian sense — this is a firm "not applicable" for most subfields.

Causal genes: None. No OMIM gene entry.
Pathogenic variants: None established as causal. WES surveys have proposed immune-gene candidates without replication (PMC8523672 — verify). No ClinVar/HGMD pathogenic variant set. Somatic mosaicism has been looked for (given the strict unilaterality, a somatic brain mutation is an attractive hypothesis) but not confirmed.
Somatic vs germline: The striking one-hemisphere restriction has driven a somatic-mutation hypothesis, but no recurrent somatic driver has been demonstrated.
Modifier genes / epigenetics / chromosomal abnormalities: No established data. Mark not available.

The molecular action is at the immune-effector / expression level, not the germline-variant level — see §6.

5. Environmental Information

Environmental/toxic factors: None established.
Lifestyle factors: None established (childhood disease).
Infectious agents: No confirmed causative pathogen. The viral-trigger hypothesis persists — candidate/investigated agents historically include herpesviruses (HSV, HHV-6, EBV, CMV), enteroviruses — but PCR/serology are inconsistent and RE is not an active viral encephalitis. Best curated as hypothesized trigger, unconfirmed. NCBI Taxonomy anchors would be speculative; recommend omit rather than over-assert.

6. Mechanism / Pathophysiology

This is the load-bearing section. The causal chain, upstream → downstream:

Unknown trigger → antigen-driven CD8⁺ T-cell response → cytotoxic killing of neurons + astrocytes (granzyme B/perforin) → astrocyte loss + microglial activation + neuronophagia → cortical neuronal loss → progressive hemiatrophy → intractable focal epilepsy + progressive hemispheric deficits.

Immune effectors (the engine): - Cytotoxic CD8⁺ T lymphocytes dominate the infiltrate and are clonally expanded / antigen-driven: "Most infiltrating lymphocytes in RE are cytotoxic T-cells, and long-lived clonal populations of cytotoxic T-cells were found in immunohistochemistry analysis of patients with RE" (PMID:39597043 — verify). Large-scale TCR sequencing confirmed pathogenic CD8⁺ expansion (Schneider-Hohendorf et al., Nat Commun 2016, PMC4822013 — verify), and peripheral CD8⁺ T-cell expansion correlates with disease severity. - Granzyme B / perforin killing: infiltrating T cells polarize and release cytotoxic granules onto targets. - Astrocytes as a specific target (key mechanistic paper): Bauer et al. (Ann Neurol 2007, PMID:17503512) — "Astrocytic apoptosis and subsequent loss of these cells is a specific feature of RE"; "Astrocytes in these tissues showed major histocompatibility complex class I expression"; and "granzyme-B(+) lymphocytes were found in close apposition to astrocytes bordering astrocyte-deficient lesions." Astrocyte loss is now considered a distinctive feature, not just bystander gliosis. - Microglia: activated microglia form nodules and drive neuronophagia. Recent single-cell/immune-microenvironment work (2023–2025) describes a T-cell trajectory from expansion to exhaustion over the disease course (J Neuroinflammation 2025, 10.1186/s12974-025-03477-5 — verify). - Innate/inflammasome: IL-1 and inflammasome activation contribute — "activation of inflammatory pathways and release of cytokines such as IL-1 mediated by CD8+ T cells has also been shown in RE" (PMID:39597043 — verify).

Histopathology (staging correlate): "T-lymphocytic infiltrate, reactive astrocytosis, activated microglia, and neuronophagia leading to neuronal loss and cortical atrophy are seen in brain parenchyma" — with perivascular T-cell cuffing, microglial nodules, and, in late stages, cavitation/gliosis and near-complete neuronal dropout.

Ontology suggestions: - Biological processes (GO): GO:0001913 T cell mediated cytotoxicity; GO:0002418 immune response to tumor cell (no—skip); GO:0006954 inflammatory response; GO:0006915 apoptotic process; GO:0001774 microglial cell activation; GO:0002446 neutrophil-mediated (skip); consider GO:0050900 leukocyte migration (brain infiltration). Modifier: INCREASED for the inflammatory/cytotoxic ones. - Cell types (CL): CL:0000909 CD8-positive, alpha-beta memory T cell / CL:0000625 CD8-positive, alpha-beta T cell; CL:0000129 microglial cell; CL:0000127 astrocyte; CL:0000540 neuron. - Chemical/protein effectors (CHEBI/PR): granzyme B, perforin, IL-1β, IFN-γ (mostly PR, not CHEBI).

Molecular profiling: Transcriptomic and single-cell studies of resected RE cortex exist (recent immune-microenvironment work) but there is no established proteomic/metabolomic/lipidomic signature. Mark advanced-omics as emerging / limited.

7. Anatomical Structures Affected

Primary organ: brain — one cerebral hemisphere (UBERON:0000955 brain; UBERON:0001869 cerebral cortex; UBERON:0001870 frontal cortex often earliest).
Lateralization: unilateral / strikingly asymmetric — this is the defining anatomical feature. Perisylvian and frontoinsular cortex are often affected early; the process can spread to involve the whole hemisphere, basal ganglia (esp. caudate atrophy), and sometimes the ipsilateral thalamus.
Tissue level: gray matter (cortical neurons) and the astrocytic compartment; secondary white-matter and volume loss.
Cell populations targeted: neurons (CL:0000540), astrocytes (CL:0000127); effectors are CD8⁺ T cells and microglia.
Subcellular (GO CC): apoptotic machinery (mitochondria GO:0005739), MHC-I at plasma membrane (GO:0042612 MHC class I protein complex).
Secondary/system involvement: motor system (contralateral hemiplegia), visual pathway (hemianopia), language cortex (aphasia if dominant). No systemic organ involvement — RE stays in the CNS.

8. Temporal Development

Classic three-stage natural history (Bien staging):

Prodromal stage — low seizure frequency, mild hemiparesis; can last months (median ~7 months). "The first stage is characterized by mild hemiparesis and seizures, generally occurring in a low frequency."
Acute stage — the destructive phase: frequent focal motor seizures / EPC, progressive hemiparesis→hemiplegia, hemianopia, and (dominant side) aphasia, plus cognitive decline. "A few months later, RE individuals tend to exhibit a higher frequency of seizures, presenting as focal motor seizures or EPC... RE patients tend to develop worsening focal deficits, such as hemianopia, hemiplegia, behavioral changes, aphasia, and cognitive deficits." Typically lasts ~8–12 months.
Residual (burnt-out) stage — seizure frequency often decreases but fixed, permanent neurological deficits and hemiatrophy remain. "The 'residual stage' is the last stage and is characterized by a decrease in the frequency of seizures and persistent neurological deficits."
Onset pattern: subacute-to-chronic, progressive.
Course: progressive during the acute phase, then plateaus into a stable deficit-laden residual phase (over ~1–3 yr total to reach residual).
Duration: chronic/lifelong disability; the active inflammatory phase is self-limited-ish (burns out) but leaves permanent damage.
Critical window: the acute stage is the intervention window — the whole rationale for early immunotherapy and timely surgery is to stop hemispheric destruction before it completes. Adult-onset cases tend to progress more slowly.

9. Inheritance and Population

Incidence: very rare — "The incidence of RE is estimated at 1.8 to 2.4 out of every 10 million people annually" in those under 18 (PMID:39597043; Bien et al. incidence/therapy study, PMID:23216622 — verify). Roughly ~0.18 per 100,000/yr in children.
Prevalence: no reliable point-prevalence figure — appropriately an ultra-rare band. Prevalence-class curation: BELOW_1_IN_1000000 / ULTRA_RARE.
Inheritance: not heritable — sporadic, non-Mendelian. All the genetics subfields (penetrance, anticipation, founder effect, consanguinity, carrier frequency) → not applicable.
Demographics: primarily children (peak ~6 yr); ~10% adolescent/adult onset. No confirmed sex predominance (some series hint at slight variation, not robust). No ethnic/geographic clustering; worldwide distribution.

10. Diagnostics

Diagnosis is clinical-radiological-pathological, formalized by the Bien European consensus criteria (Bien et al., Brain 2005;128:454–471, PMID:15689357), recently updated by an international modified-Delphi consensus (Stredny et al., Epilepsia 2026, 10.1002/epi.70225 — verify).

Bien criteria (two-part): diagnosis if all three of Part A OR two of three Part B: - Part A: (1) clinical — focal seizures (± EPC) and unilateral cortical deficit; (2) EEG — unihemispheric slowing ± epileptiform activity, unilateral seizure onset; (3) MRI — unihemispheric focal cortical atrophy plus ≥1 of gray/white-matter T2/FLAIR hyperintensity or caudate head hyperintensity/atrophy. - Part B: (1) EPC or progressive unilateral cortical deficit; (2) progressive unihemispheric atrophy on serial MRI; (3) histopathology — T-cell–dominated encephalitis with activated microglia (classically nodules) and reactive astrogliosis. (Presence of numerous parenchymal macrophages, B cells, plasma cells, or viral inclusions argues against RE.)

Key modalities: - MRI (RadLex/neuroimaging): serial MRI is the workhorse — progressive unilateral cortical/insular atrophy, T2/FLAIR hyperintensity, caudate atrophy. Recent multi-institutional work compared MRI and pathology staging to hemispherotomy outcome (Child's Nerv Syst 2024, 10.1007/s00381-024-06353-4 — verify). - EEG / electrophysiology (LOINC/clinical neurophysiology): unihemispheric slowing, multifocal ipsilateral epileptiform discharges, lateralized seizure onset; EPC often has poor EEG correlate. - CSF: may show mild pleocytosis, oligoclonal bands — nonspecific, supportive. - Biopsy/histopathology (SNOMED CT): confirmatory when imaging is atypical; shows the T-cell/microglial encephalitis pattern above. The consensus trend is to minimize biopsy when criteria are otherwise met. - Autoantibodies: anti-GluR3 is not recommended (poor specificity/reproducibility); a broader autoimmune-encephalitis antibody panel is done mainly to exclude mimics. - Genetic/omics testing: not diagnostic; used only to exclude genetic mimics (e.g., mitochondrial disease presenting with EPC, like POLG). - Differential dx: other causes of EPC/hemispheric epilepsy — MELAS/POLG mitochondrial disease, hemimegalencephaly/cortical dysplasia, Sturge-Weber, unihemispheric stroke/vasculitis (e.g., primary CNS angiitis), tumor, and other autoimmune encephalitides.

11. Outcome / Prognosis

Mortality: low disease-specific mortality; deaths relate to status epilepticus or surgical complications rather than the disease directly. Not a classically "fatal" disease — the burden is disability.
Morbidity (the real story): near-inevitable progression to permanent hemiplegia, hemianopia, cognitive decline, and (dominant hemisphere) aphasia. Untreated, ~30% wheelchair-bound within 3 years of diagnosis.
Seizures: medically refractory — antiseizure drugs rarely control EPC.
Surgical outcome (hemispherectomy/hemispherotomy = the definitive seizure cure): reported seizure-freedom ~81.5%, 63.6%, 55.6% at 1/5/10 yr in one cohort; UCLA cohort ~68%/48%/22% at 1/5/10 yr; meta-analytic 5-yr mean ~65% (range 17–100%) (PMC9514735, PMID:32679562 — verify). The trade-off is a guaranteed contralateral hemiplegia and hemianopia — accepted because that deficit is largely already present or inevitable.
Prognostic factors: shorter preoperative hemiparesis duration predicted lower seizure-freedom and more reoperation; complete disconnection on postop MRI improved seizure freedom; reoperation for incomplete disconnection was frequently curative. Notably, imaging/pathology stage did not reliably predict individual seizure outcome (Child's Nerv Syst 2024 — verify).
Recovery/plasticity: young age favors post-hemispherectomy functional (language, ambulation) reorganization — the younger the brain, the better it rewires.

12. Treatment

Two parallel goals: (a) immunotherapy to slow the inflammatory destruction, and (b) surgery to actually stop the seizures. Antiseizure meds are supportive but rarely sufficient.

Immunotherapy (MAXO: MAXO:0000917 immunosuppressive therapy / MAXO:0001211 immunomodulation — verify labels with OAK): - Acute/first-line: IV corticosteroids (methylprednisolone) ± IVIg — Stredny consensus: "Intravenous corticosteroids are recommended as first-line, acute immunotherapy for seizure exacerbations and status epilepticus, with or without the addition of intravenous immunoglobulin." CHEBI: methylprednisolone CHEBI:6888; corticosteroid class NCIT:C2322. - Maintenance: IVIg; tacrolimus (calcineurin inhibitor, T-cell targeted) — Bien RCT compared tacrolimus vs IVIg (PMID:23216622 — verify), both slowing progression; azathioprine (Immunomodulation with Azathioprine, Neurology 2021 — verify). - Targeted/experimental biologics (case series): - Rituximab (anti-CD20 B-cell depletion) — reduced seizure burden in 16/26 patients across pooled reports (PMC9058598; PMID:19657347 — verify). - Natalizumab (anti-α4-integrin, blocks lymphocyte CNS entry) — response in ~10/32 (Neurology 2013 — verify). - Tocilizumab (anti-IL-6R) — high response rate in refractory status epilepticus (16 patients pooled — verify). - Adalimumab (anti-TNF-α) — complete response ~45% in an 11-patient series; clinicaltrials:NCT04003922 (adalimumab efficacy/tolerance). - Cyclophosphamide has been used as an alternative T-cell–directed agent. - Mechanistic note: these biologics map cleanly onto the CD8-T-cell/microglia mechanism — good target_mechanisms candidates linking drug → the cytotoxic-T-cell node.

Surgery (definitive, MAXO: MAXO:0000004 surgical procedure; NCIT hemispherectomy term): - Functional hemispherectomy / hemispherotomy — disconnects (rather than removes) the diseased hemisphere; the gold standard and only reliably seizure-freeing therapy: "the only gold-standard treatment for this disorder is hemispherectomy." Timing is the central clinical dilemma — do it early enough to stop cognitive/seizure damage, but the price is fixed hemiplegia/hemianopia.

Supportive: antiseizure medications (broad-spectrum), rehabilitation (PT/OT/speech — MAXO:0000011 physical therapy), and post-surgical neurorehabilitation to exploit plasticity.

Pharmacogenomics / personalized: none established for RE specifically (tacrolimus dosing follows general CYP3A5 pharmacogenetics, not RE-specific).

13. Prevention

Primary prevention: none — trigger unknown, not heritable, no vaccine. Mark not applicable.
Secondary prevention (early detection): the closest real "prevention" is early diagnosis + early immunotherapy to limit hemispheric atrophy during the critical acute window; and timely surgery to prevent further seizure-related cognitive decline. This is disease-modifying, not primary prevention.
Tertiary prevention: manage refractory seizures/status, prevent injury, rehabilitation to limit disability.
Screening / genetic counseling / immunization / public health: not applicable (sporadic ultra-rare, no genetic or infectious basis to screen for).

14. Other Species / Natural Disease

Taxonomy: RE is essentially a human-only clinical entity (NCBITaxon:9606). There is no described naturally-occurring animal equivalent (no OMIA entry).
Comparative biology: the mechanistic parallel is general CD8⁺ T-cell–mediated CNS autoimmunity, not a species-specific homolog.
Transmission/zoonosis: not applicable — RE is not infectious or transmissible.

Mark this whole section not applicable / human-specific.

15. Model Organisms

RE has historically been hard to model — no spontaneous animal disease, no single gene to knock out, and the pathology is driven by human T cells against an unknown human antigen. The breakthrough was a humanized mouse model:

Humanized PBMC-engraftment model (flagship): RE-patient peripheral blood mononuclear cells engrafted into immunodeficient NSG mice (NOD-scid IL2Rγ^null^) — the human CD4⁺/CD8⁺ T cells infiltrate the CNS and reproduce RE-like pathology and seizures. "Numerous granzyme B+CD8+ T lymphocytes were detected in the brains of NSG mice", with elevated IFN-γ⁺/IL-17⁺ human T cells vs controls (JCI 2018, "Humanized mouse model of Rasmussen's encephalitis supports the immune-mediated hypothesis," PMC5919802 — verify PMID). A follow-up showed blocking immune intrusion into the brain suppresses epilepsy in this model (JCI, article 120444 — verify) — strong causal support for the T-cell-effector mechanism and a therapeutic proof-of-concept for CNS-entry blockade (cf. natalizumab).
Model type: mammalian, humanized/xenograft (immune-cell transfer), NCBITaxon:10090 Mus musculus host.
Evidence source: MODEL_ORGANISM (with human immune cells → arguably a human-immune xenograft; still tag MODEL_ORGANISM for the mouse readout, and note the humanized design in the explanation).
Recapitulation: reproduces CNS T-cell infiltration, granzyme-B⁺ CD8 cells, and seizures — good for the immune-effector arm.
Limitations: does not reproduce the strict unilaterality/hemispheric-restriction of human RE, doesn't identify the autoantigen, and depends on donor-patient cells (not a stable genetic line). This is a solid HUMAN_MODEL_MISMATCH discussion candidate: the model supports the immune-mediated hypothesis but leaves the hemispheric-restriction and antigen questions unresolved.
Prior to humanized models, RE relied on ex vivo human resected-tissue immunohistochemistry (Bauer 2007) and TCR-repertoire studies — in vitro / patient-tissue rather than true animal models.

Curation notes & flagged uncertainties

MONDO MONDO:0016019 and ORPHA:511 are solid anchors. No OMIM (non-Mendelian) — expect the entry to lean heavily on pathophysiology + phenotypes + treatments, light on genetic.
Strongest, most citable primary papers for evidence blocks: Bien 2005 European consensus (PMID:15689357) for definition/criteria/staging; Bauer 2007 (PMID:17503512) for astrocyte-target mechanism (I have verbatim abstract quotes above — those should validate cleanly); Bien 2013 (PMID:23216622) for incidence + tacrolimus/IVIg. Verify each with just fetch-reference before use.
PMID:39597043 (Medicina 2024 review) is the best single narrative source but is a review — good for framing/synthesis quotes, less ideal than primaries for specific mechanistic claims. The PMID came from a web fetch; confirm it resolves to the right paper.
Two ontology cautions: HPO's only close "encephalitis" leaf is HP:0002383 Infectious encephalitis, which is wrong for RE — don't force it; RE's "encephalitis" is better captured through the pathophysiology/imaging phenotypes (HP:0100308 cerebral cortical hemiatrophy) than a phenotype term. And confirm the focal-seizure and cognitive-decline HP IDs with OAK before committing (I verified EPC, hemiparesis, hemianopia, aphasia, status epilepticus, hemiatrophy directly).
Good conforms_to target: epilepsy_excitation_inhibition_imbalance#Excitation-Inhibition Imbalance for the seizure arm — though RE's driver is upstream immune destruction of one hemisphere, so the disease-specific chain (CD8/granzyme-B → astrocyte+neuron loss → hemiatrophy → seizures) is the core content and doesn't fully reduce to that module.

Sources: - Medicina 2024 comprehensive review (PMC11596482) - Bien et al. 2005 European consensus, Brain (PMID:15689357) - Bauer et al. 2007, Astrocytes as immunological target (PMID:17503512) - Bien et al. 2013 incidence / tacrolimus vs IVIg (PMID:23216622) - Progress in pathogenesis and therapy of RE 2022 (PMID:36189924) - Stredny et al. 2026 international consensus, Epilepsia - Humanized mouse model of RE, JCI 2018 (PMC5919802) - Blocking immune intrusion suppresses epilepsy in RE model, JCI - CD8+ T-cell TCR sequencing in RE (PMC4822013) - Genetic factors in RE by WES, Front Neurosci 2021 (PMC8523672) - Dynamics of brain T-cell populations in RE, J Neuroinflammation 2025 - Rituximab in RE (PMC9058598) · Rituximab case (PMID:19657347) - Natalizumab in RE, Neurology 2013 · Azathioprine in RE, Neurology 2021 - Adalimumab trial NCT04003922 - Hemispherectomy seizure outcomes & reoperation (PMC9514735) · UCLA surgical series (PMID:32679562) - MRI/pathology vs hemispherotomy outcome 2024 - NORD — Rasmussen Encephalitis

That's the whole tour — one hemisphere, under siege by its own CD8 cells, and the strange mercy that a young brain can hand its whole job to the other half if you disconnect the sick side in time. Want me to go ahead and scaffold the actual kb/disorders/Rasmussen_Encephalitis.yaml entry from this (with the Bauer/Bien primaries as the first verified evidence blocks), or keep this as a research doc for now?

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Rasmussen Encephalitis — Comprehensive Research Report

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic / Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome / Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Curation notes & flagged uncertainties