SCN1B-Related Developmental and Epileptic Encephalopathy

Mendelian MONDO:0033361 Pathograph 27 Show in embeddings browser Neurodevelopmental Disorder Genetic Disease

SCN1B-related developmental and epileptic encephalopathy (DEE52) is a severe autosomal recessive epilepsy caused by biallelic variants in SCN1B, which encodes the beta-1 and beta-1B subunits of the voltage-gated sodium channel. Beta-1 does not form a pore. It is a single-transmembrane immunoglobulin-domain protein that modulates the gating of pore-forming alpha subunits (Nav1.1, Nav1.2, Nav1.6 in brain, Nav1.5 in heart), chaperones them to the membrane, and separately acts as a cell adhesion molecule. Losing it therefore does not remove a current; it detunes several currents at once, in a cell-type-specific way. Affected children present in the first months of life with fever-triggered focal, myoclonic, and generalized seizures and myoclonic status epilepticus, followed by developmental stagnation or regression, with hypotonia, spasticity, ataxia, and in some cases sensorineural hearing loss. Because SCN1B is expressed in heart as well as brain, DEE52 carries a cardiac arrhythmia substrate alongside the seizures, and the risk of sudden unexpected death in epilepsy is high. Monoallelic SCN1B variants cause the much milder GEFS+ spectrum and cardiac disorders such as Brugada syndrome and atrial fibrillation; this entry covers the biallelic encephalopathy.

Ask OpenScientist

Ask a research question about SCN1B-Related Developmental and Epileptic Encephalopathy. OpenScientist will conduct autonomous deep research using the Disorder Mechanisms Knowledge Base and PubMed literature (typically 10-30 minutes).

Submitting...

Do not include personal health information in your question. Questions and results are cached in your browser's local storage.

1
Inheritance
20
Pathophys.
17
Phenotypes
5
Gaps
27
Pathograph
1
Genes
5
Medical Actions
4
Models
1
Deep Research
👪

Inheritance

1
Autosomal recessive HP:0000007
DEE52 requires two pathogenic SCN1B alleles, usually homozygous in consanguineous families. Heterozygous carriers are unaffected by the encephalopathy - one functional allele suffices for normal control of excitability - although monoallelic variants are separately linked to the milder GEFS+ spectrum.
Autosomal recessive inheritance
Show evidence (2 references)
PMID:33901312 SUPPORT Human Clinical
"In contrast, biallelic variants cause early infantile epileptic encephalopathy 52"
States the biallelic requirement and its contrast with monoallelic disease.
PMID:19710327 SUPPORT Model Organism
"the seizure susceptibility of Scn1b(+/-) mice was similar to wild type, suggesting that, like the parents of this patient, one functional SCN1B allele is sufficient for normal control of electrical excitability"
Explains why heterozygous carriers are unaffected.
?

Discussions and Knowledge Gaps

5
Does SCN1B-related DEE arise through the same GABAergic interneuron hypoexcitability that underlies SCN1A-related Dravet syndrome, or through a fundamentally different substrate of regionally restricted pyramidal neuron hyperexcitability driven by increased input resistance?
CONTROVERSY OPEN controversy_interneuron_versus_pyramidal_substrate
Attached to
pathophysiology#Increased Forebrain Pyramidal Neuron Firing pathophysiology#Regionally Restricted Network Hyperexcitability pathophysiology#Cerebellar Purkinje Cell and Interneuron Hypoexcitability
Because SCN1B and SCN1A variants produce overlapping clinical pictures, it is routinely assumed that SCN1B disease works through the SCN1A mechanism - beta-1 loss detunes Nav1.1, Nav1.1 loss impairs interneurons, interneuron failure disinhibits the cortex. The Scn1b mouse contradicts the middle step directly: no changes in firing or synaptic properties of GABAergic interneurons were observed, explicitly in contrast with Scn1a-based models, and the hyperexcitability was instead in subicular and layer 2/3 pyramidal neurons via increased input resistance from reduced dendritic arborization. The cerebellar work complicates this further rather than settling it, since there GABAergic neurons ARE hypoexcitable - so cell-type effects appear to be region-dependent rather than uniform. This matters therapeutically: the input-resistance account predicts benefit from a potassium channel opener, and retigabine did protect these mice from thermal seizures, which is not a prediction the interneuron model makes.
Proposed experiments
Interneuron-restricted versus pyramidal-restricted Scn1b deletion
exp_celltype_conditional_scn1b_deletion
Compare conditional Scn1b deletion restricted to forebrain GABAergic interneurons against deletion restricted to excitatory pyramidal neurons, scoring spontaneous seizure burden, thermal seizure threshold, and input resistance in each population, to establish which cell type is sufficient to produce the epilepsy phenotype.
Show evidence (3 references)
PMID:24747835 SUPPORT Model Organism
"Importantly, no changes in firing or synaptic properties of gamma-aminobutyric acidergic interneurons from mutant mice were observed, which is in contrast with Scn1a-based models of Dravet syndrome."
The direct contradiction of the interneuron account in the SCN1B model.
PMID:24747835 SUPPORT Model Organism
"These results suggest a novel mechanism of disease genesis in genetic epilepsy and demonstrate an effective mechanism-based treatment of the disease."
The authors present this as a distinct disease mechanism with its own therapeutic prediction.
PMID:40923316 SUPPORT Model Organism
"GABAergic neurons in the Scn1b null cerebellar cortex are overall hypoexcitable"
Shows GABAergic hypoexcitability does occur in SCN1B disease, but in cerebellum rather than forebrain, so cell-type effects are region-dependent.
Do children with SCN1B-related DEE actually experience clinically detectable cardiac arrhythmia, and would cardiac surveillance or antiarrhythmic management reduce SUDEP in this population?
KNOWLEDGE GAP OPEN gap_cardiac_arrhythmia_in_patients
Attached to
pathophysiology#Cardiac Arrhythmia Susceptibility pathophysiology#Elevated Risk of Sudden Unexpected Death in Epilepsy
The dual neuro-cardiac SUDEP hypothesis is well supported at the level of substrate: the knock-in mouse has ventricular fibrosis and pacing-inducible arrhythmia, and patient-derived cardiomyocytes show increased currents. What is missing is the clinical link. No published series reports Holter monitoring, ECG surveillance, or documented arrhythmia in SCN1B-DEE52 patients, so the step from "arrhythmogenic substrate exists" to "arrhythmia contributes to these children's deaths" is inference. It is actionable inference - if borne out it would justify cardiac surveillance in a population currently managed purely as neurological - which is exactly why it should not be curated as though settled.
Proposed experiments
Prospective cardiac surveillance in an SCN1B-DEE52 cohort
exp_cardiac_surveillance_cohort_dee52
Enrol genetically confirmed DEE52 patients in prospective ECG and ambulatory rhythm monitoring, with repolarization interval measurement and event correlation, to establish whether the model-predicted arrhythmia substrate produces detectable clinical events.
Show evidence (2 references)
PMID:40763036 SUPPORT Model Organism
"Although the mechanisms of SUDEP remain unclear, we hypothesize that, in addition to seizures, SUDEP in some instances involves cardiac arrhythmias"
The authors state the cardiac contribution as a hypothesis rather than an established fact.
PMID:40763036 SUPPORT Human Clinical
"No biomarkers exist to predict the extent of SUDEP risk in individual patients other than the presence of variants in specific genes"
Confirms the absence of any validated clinical risk marker, which is the gap.
How much of the Scn1b-null mouse phenotype - 100% pre-weaning SUDEP, severe cerebellar pathfinding failure - reflects human DEE52, given that every reported human genotype is missense and affected children survive for years?
HUMAN MODEL MISMATCH OPEN mismatch_null_mouse_versus_human_missense
Attached to
pathophysiology#Altered Cerebellar Neuronal Pathfinding pathophysiology#Cerebellar Purkinje Cell and Interneuron Hypoexcitability
Most of the mechanistic detail curated here for the cerebellar arm comes from the constitutive null. But the human variants are missense changes in the immunoglobulin loop, and at least one of them - p.R85C - reaches the cell surface normally, so it is not a null at the level of protein presence. The p.R125C variant is a functional null and the p.R89C knock-in is not, yet both cause DEE52, which suggests the human phenotype is reached from more than one point on the dose-response curve. The severe developmental pathfinding failure seen in the null cerebellum may therefore over-represent what a surface-expressed missense variant does, and no human neuropathology exists to check it against.
Proposed experiments
Cerebellar phenotype across an Scn1b knock-in allelic series
exp_knockin_allelic_series_cerebellum
Compare cerebellar pathfinding, Purkinje cell sodium currents, and ataxia across knock-in mice carrying surface-expressed missense variants (p.R85C, p.R89C), the trafficking-null p.R125C, and the constitutive null, to establish how much of the developmental cerebellar phenotype requires complete absence of the protein.
Show evidence (3 references)
PMID:40923316 SUPPORT Model Organism
"Scn1b null mice model DEE52, with generalized seizures beginning in the second week of life and sudden unexpected death in epilepsy (SUDEP) in 100% of mice prior to weaning"
Establishes the severity of the null phenotype against which human survival must be compared.
PMID:31709768 SUPPORT In Vitro
"showed cell surface expression of the mutant beta1 subunit, similar to wild-type (WT)"
Shows a human pathogenic variant that is not a protein null, unlike the mouse model.
PMID:19710327 SUPPORT In Vitro
"these data suggest a functional SCN1B null phenotype"
Shows that another human variant IS a functional null, so human genotypes span the range rather than sitting at one point.
By what mechanism does biallelic SCN1B loss produce sensorineural hearing loss - through beta-1's channel-modulating role in brainstem auditory pathway neurons, through its cell adhesion role in cochlear or auditory nerve development, or as a consequence of the encephalopathy itself?
KNOWLEDGE GAP OPEN gap_hearing_loss_mechanism
Attached to
pathophysiology#Disrupted Beta-1 Immunoglobulin-Domain Cell Adhesion
Bilateral sensorineural hearing loss with brainstem auditory pathway involvement is reported, but no node in this pathograph explains it, and nothing in the mouse literature addresses the auditory system. The two candidate arms - channel modulation and cell adhesion - predict different things: an adhesion-mediated developmental defect would be fixed and present from birth, whereas an excitability defect in auditory brainstem neurons might be modifiable. Because hearing loss in a child with no expressive development is easy to miss and consequential for the little communication that remains possible, whether it is an expected feature worth screening for is a practical question, not only a mechanistic one.
Proposed experiments
Auditory brainstem response phenotyping in Scn1b mouse models
exp_auditory_phenotyping_scn1b_mice
Measure auditory brainstem responses and cochlear histology in Scn1b-null and knock-in mice, and in mice carrying a variant that selectively disrupts adhesion while preserving channel modulation, to determine which functional arm accounts for the hearing loss.
Show evidence (2 references)
PMID:31709768 SUPPORT Human Clinical
"Auditory brainstem response (ABR) showed bilateral hearing loss."
Documents the phenotype that currently has no mechanistic account.
PMID:40923316 SUPPORT Model Organism
"Non-pore-forming beta1 subunits function as channel modulators and chaperones to the plasma membrane as well as immunoglobulin superfamily cell adhesion molecules (CAMs)"
Names the two candidate functional arms that could account for the auditory phenotype.
Should sodium-channel-blocking anti-seizure medications be avoided in SCN1B-related DEE, as they are in SCN1A-related Dravet syndrome, or does the beta-1 subunit mechanism change that calculus?
KNOWLEDGE GAP OPEN gap_sodium_channel_blocker_avoidance
Attached to
pathophysiology#Altered Sodium Channel Voltage Dependence and Availability pathophysiology#Refractory Multifocal and Generalized Seizures
In SCN1A-related Dravet syndrome sodium-channel blockers are avoided because they further impair Nav1.1 in interneurons that are already underactive. The same reasoning is often extended to SCN1B by analogy, and the analogy is plausible - both lesions reduce sodium-channel function. But the Scn1b mouse contradicts the interneuron premise the SCN1A rule rests on, showing no interneuron changes and instead pyramidal hyperexcitability driven by input resistance. If that is the operative mechanism, the SCN1A avoidance rule does not transfer, and the mechanism-matched prediction from the same study points the other way, toward agents that lower input resistance. The published evidence reports only that carbamazepine failed among several drugs, which is refractoriness rather than harm, so the question is genuinely open and is curated here rather than asserted as a contraindication in the treatments block.
Proposed experiments
Sodium-channel-blocker challenge in Scn1b versus Scn1a models
exp_sodium_blocker_challenge_in_scn1b_models
Compare seizure burden and thermal seizure threshold under carbamazepine or lacosamide in Scn1b knock-in mice against Scn1a-haploinsufficient mice, to test whether the aggravation seen in the SCN1A model occurs in the SCN1B model at all, and pair it with a retrospective review of medication exposure in genetically confirmed DEE52 patients.
Show evidence (3 references)
PMID:33901312 SUPPORT Human Clinical
"Seizures were refractory to antiepileptic drugs (AEDs), including carbamazepine and clonazepam."
The only published statement about carbamazepine here documents failure to control seizures, not aggravation, so it cannot support a contraindication.
PMID:24747835 SUPPORT Model Organism
"Importantly, no changes in firing or synaptic properties of gamma-aminobutyric acidergic interneurons from mutant mice were observed, which is in contrast with Scn1a-based models of Dravet syndrome."
Undercuts the interneuron premise on which the SCN1A sodium-channel-blocker avoidance rule rests, which is why transfer of that rule cannot be assumed.
PMID:24747835 SUPPORT Model Organism
"The antiepileptic drug retigabine, a K+ channel opener that reduces input resistance, dampened action potential firing and protected mutant mice from thermal seizures."
The mechanism-matched prediction from the same model, which is a different drug class from the one the SCN1A rule addresses.
⚙

Pathophysiology

20
Biallelic SCN1B Loss-of-Function Variant
Two pathogenic SCN1B alleles are present, typically homozygous missense variants clustered in the extracellular immunoglobulin loop domain (p.R46C, p.R60C, p.R85C, p.R89C, p.V158M, p.R125C). This node records the genomic lesion; the several distinct protein-level consequences are modeled downstream.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
Downstream
Loss of Beta-1 Subunit Cell-Surface Expression Some variants, such as p.R125C, prevent the subunit from reaching the membrane.
Loss of Beta-1-Mediated Modulation of Sodium Channel Gating Other variants reach the surface normally but fail to modulate the alpha subunit.
Disrupted Beta-1 Immunoglobulin-Domain Cell Adhesion Variants in the immunoglobulin loop compromise the adhesion function, which is independent of channel gating.
Show evidence (2 references)
PMID:33901312 SUPPORT Human Clinical
"We identified nine patients from four unrelated families harboring three biallelic variants in SCN1B"
Establishes the biallelic genotype in the largest reported cohort.
PMID:31465153 SUPPORT Human Clinical
"the vicinity of other epileptic encephalopathy-associated missense variants that are biallelic and located in the extracellular immunoglobulin loop domain of the protein"
Locates the pathogenic variants in the immunoglobulin loop domain.
Loss of Beta-1 Subunit Cell-Surface Expression
Trafficking-defective variants are expressed at normal total cellular levels but fail to reach the plasma membrane, producing a functional null. This is a trafficking failure and is separable from whether a surface-resident subunit works.
neuron CL:0000540 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neuron (CL:0000540). CL:0000540 is a cell type from the Cell Ontology.
Downstream
Loss of Beta-1-Mediated Modulation of Sodium Channel Gating A subunit absent from the membrane cannot modulate the alpha subunit there.
Show evidence (1 reference)
PMID:19710327 SUPPORT In Vitro
"Biochemical characterization of p.R125C in a heterologous system demonstrated little to no cell surface expression despite normal total cellular expression."
Documents the trafficking defect with preserved total expression.
Loss of Beta-1-Mediated Modulation of Sodium Channel Gating
The alpha subunit no longer receives normal beta-1 modulation. Critically, this happens even for variants whose surface expression is indistinguishable from wild type, which is why it is a separate claim from the trafficking node.
voltage-gated sodium channel activity GO:0005248 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves abnormal voltage-gated sodium channel activity (GO:0005248). GO:0005248 is a molecular function from the Gene Ontology. ⚠ ABNORMAL
Downstream
Altered Sodium Channel Voltage Dependence and Availability Unmodulated alpha subunits gate at shifted voltages.
Show evidence (1 reference)
PMID:31709768 SUPPORT In Vitro
"showed cell surface expression of the mutant beta1 subunit, similar to wild-type (WT), but with loss of normal beta1-mediated modification of human Nav 1.1-generated sodium current"
Demonstrates loss of modulation with intact surface expression, separating this node from the trafficking node.
Altered Sodium Channel Voltage Dependence and Availability
Conductance-voltage relationships and channel availability shift toward more depolarized potentials across Nav1.1, Nav1.2, and Nav1.6, and recovery from fast inactivation slows for some variant-channel pairings. The effect is variant-specific and channel-subtype-specific rather than uniform.
sodium ion transmembrane transport GO:0035725 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal sodium ion transmembrane transport (GO:0035725). GO:0035725 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Increased Forebrain Pyramidal Neuron Firing Altered channel gating changes the intrinsic excitability of specific forebrain pyramidal populations.
Reduced Purkinje Cell Transient and Resurgent Sodium Current In cerebellar Purkinje cells the same loss of modulation reduces sodium current density.
Cardiomyocyte Ionic Current Remodeling Cardiac cells express SCN1B and show their own current changes.
Show evidence (2 references)
PMID:33901312 SUPPORT In Vitro
"We observed a shift toward more depolarizing potentials of conductance-voltage relationships"
Reports the depolarizing shift in the conductance-voltage relationship.
PMID:33901312 SUPPORT In Vitro
"and detected a slower recovery from fast inactivation for NaV 1.1/beta1V158M"
Documents the variant-specific slowing of recovery from fast inactivation.
Disrupted Beta-1 Immunoglobulin-Domain Cell Adhesion
Beta-1 is an immunoglobulin superfamily cell adhesion molecule that binds beta-1 subunits on neighbouring cells, other adhesion molecules, and extracellular matrix. Pathogenic variants cluster in exactly this domain, so the adhesion role is compromised alongside the gating role. Nothing about channel biophysics measures this arm.
cell adhesion GO:0007155 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal cell adhesion (GO:0007155). GO:0007155 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Altered Cerebellar Neuronal Pathfinding Loss of adhesion signalling disturbs the guidance of developing cerebellar neurons.
Reduced Subicular Pyramidal Dendritic Arborization Dendritic arbors are reduced in the mutant, plausibly through the adhesion/developmental arm rather than through channel gating.
Show evidence (2 references)
PMID:40923316 SUPPORT Model Organism
"Non-pore-forming beta1 subunits function as channel modulators and chaperones to the plasma membrane as well as immunoglobulin superfamily cell adhesion molecules (CAMs) that interact with other beta1 subunits on adjacent cells, with other CAMs, or with extracellular matrix molecules"
States the adhesion function as distinct from channel modulation.
PMID:31465153 SUPPORT Human Clinical
"located in the extracellular immunoglobulin loop domain of the protein, which mediates interaction of the beta-1 subunit with cellular adhesion molecules"
Places the pathogenic variants in the adhesion-mediating domain.
Altered Cerebellar Neuronal Pathfinding
Neuronal pathfinding in the cerebellum is severely altered in Scn1b-null mice, a developmental wiring defect distinct from the excitability changes measured in the same tissue.
Purkinje cell CL:0000121 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Purkinje cell (CL:0000121). CL:0000121 is a cell type from the Cell Ontology.
axon extension involved in axon guidance GO:0048846 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal axon extension involved in axon guidance (GO:0048846). GO:0048846 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Cerebellar Purkinje Cell and Interneuron Hypoexcitability Miswired cerebellar circuitry accompanies the measured excitability changes, though the causal ordering between them is not established.
Show evidence (1 reference)
PMID:40923316 SUPPORT Model Organism
"In Scn1b null cerebellum, neuronal pathfinding is severely altered"
Documents the cerebellar pathfinding defect.
Reduced Purkinje Cell Transient and Resurgent Sodium Current
Scn1b-null Purkinje cells carry reduced transient and resurgent sodium current densities. Resurgent current is what allows Purkinje cells to fire at high rates, so this is a specific biophysical loss rather than a general reduction in excitability.
Purkinje cell CL:0000121 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Purkinje cell (CL:0000121). CL:0000121 is a cell type from the Cell Ontology.
sodium ion transmembrane transport GO:0035725 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased sodium ion transmembrane transport (GO:0035725). GO:0035725 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Cerebellar Purkinje Cell and Interneuron Hypoexcitability Reduced sodium current raises the action-potential threshold and limits repetitive firing.
Show evidence (1 reference)
PMID:40923316 SUPPORT Model Organism
"Scn1b null PCs have reduced transient and resurgent sodium current densities."
Reports the specific sodium current deficit in Purkinje cells.
Cerebellar Purkinje Cell and Interneuron Hypoexcitability
Purkinje cells and cerebellar interneurons show increased thresholds for action potential initiation and decreased repetitive firing frequency. Note the direction: in the cerebellum SCN1B loss makes neurons LESS excitable, which is the opposite of what happens in the forebrain pyramidal populations.
Purkinje cell CL:0000121 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Purkinje cell (CL:0000121). CL:0000121 is a cell type from the Cell Ontology. GABAergic neuron CL:0000617 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves GABAergic neuron (CL:0000617). CL:0000617 is a cell type from the Cell Ontology.
membrane depolarization during action potential GO:0086010 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased membrane depolarization during action potential (GO:0086010). GO:0086010 is a biological process from the Gene Ontology. ↓ DECREASED
Animal models
Scn1b-null mouse Mouse recapitulates Provides the direct electrophysiological evidence for the cerebellar arm.
Downstream
Loss of Cerebellar Motor Output Reduced Purkinje firing degrades the cerebellar contribution to motor control.
Loss of Cerebellar Seizure-Terminating Output Cerebellar output to other brain regions can terminate seizures, so its loss is proposed to worsen seizure severity.
Show evidence (1 reference)
PMID:40923316 SUPPORT Model Organism
"Scn1b null PCs and interneurons in cerebellar slices have increased thresholds for action potential initiation and decreased repetitive firing frequency compared with WT."
Directly measures the cerebellar hypoexcitability.
Loss of Cerebellar Motor Output
Degraded cerebellar output manifests as ataxia. This is the motor consequence, separate from the seizure consequence of the same hypoexcitability.
Purkinje cell CL:0000121 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Purkinje cell (CL:0000121). CL:0000121 is a cell type from the Cell Ontology.
Animal models
Scn1b-null mouse Mouse recapitulates The mice are ataxic, matching the ataxia reported in patients.
Show evidence (1 reference)
PMID:40923316 SUPPORT Model Organism
"We propose that reduced PC excitability underlies the ataxic phenotype of Scn1b mice."
Attributes the ataxia to reduced Purkinje cell excitability.
Loss of Cerebellar Seizure-Terminating Output
Cerebellar projections can act to terminate seizures. With Purkinje cells hypoexcitable, that brake is weakened, which is proposed to exacerbate seizure severity rather than to initiate seizures.
Downstream
Refractory Multifocal and Generalized Seizures A weakened seizure-terminating mechanism contributes to seizure severity.
Show evidence (1 reference)
PMID:40923316 SUPPORT Model Organism
"because cerebellar output to other areas of the brain can result in termination of seizures, we propose that PC hypoexcitability exacerbates the severe phenotype of this mouse model"
States the proposed seizure-exacerbating role of cerebellar hypoexcitability.
Increased Forebrain Pyramidal Neuron Firing
Subicular and layer 2/3 pyramidal neurons fire action potentials at increased rates in an Scn1b mutant mouse, attributable to increased input resistance rather than to a change in sodium current density. The effect is regionally restricted - layer 5 and CA1 pyramidal neurons are unchanged.
pyramidal neuron CL:0000598 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves pyramidal neuron (CL:0000598). CL:0000598 is a cell type from the Cell Ontology.
membrane depolarization during action potential GO:0086010 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased membrane depolarization during action potential (GO:0086010). GO:0086010 is a biological process from the Gene Ontology. ↑ INCREASED
Animal models
Scn1b-based Dravet model mouse (subicular hyperexcitability) Mouse recapitulates Provides the direct evidence for the regionally restricted pyramidal hyperexcitability arm and for its input-resistance mechanism.
Downstream
Regionally Restricted Network Hyperexcitability Increased pyramidal firing in specific regions creates a localized hyperexcitable substrate.
Show evidence (2 references)
PMID:24747835 SUPPORT Model Organism
"Patch-clamp analysis showed that mutant subicular and layer 2/3 pyramidal neurons had increased action potential firing rates, presumably as a consequence of their increased input resistance."
Reports the increased firing and its proposed input-resistance mechanism.
PMID:24747835 SUPPORT Model Organism
"These changes were not seen in L5 or CA1 pyramidal neurons."
Establishes the regional restriction of the effect.
Reduced Subicular Pyramidal Dendritic Arborization
Subicular pyramidal neurons have reduced dendritic arbors in the Scn1b mutant. A smaller arbor raises input resistance, which is the mechanism proposed for the firing change, so this structural finding is upstream of the functional one rather than a restatement of it.
pyramidal neuron CL:0000598 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves pyramidal neuron (CL:0000598). CL:0000598 is a cell type from the Cell Ontology.
dendrite development GO:0016358 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased dendrite development (GO:0016358). GO:0016358 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Increased Forebrain Pyramidal Neuron Firing Reduced arborization increases input resistance, the proposed proximate cause of the increased firing rate.
Show evidence (1 reference)
PMID:24747835 SUPPORT Model Organism
"Morphological analysis of subicular pyramidal neurons revealed reduced dendritic arborization."
Reports the dendritic morphology change.
Regionally Restricted Network Hyperexcitability
Spontaneous synaptic activity is increased in the subiculum but not in CA1, supporting a regional rather than global seizure mechanism. This is a circuit-level property distinct from the single-cell firing measurements that support it.
pyramidal neuron CL:0000598 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves pyramidal neuron (CL:0000598). CL:0000598 is a cell type from the Cell Ontology.
Downstream
Refractory Multifocal and Generalized Seizures A regionally hyperexcitable substrate generates recurrent seizures.
Show evidence (1 reference)
PMID:24747835 SUPPORT Model Organism
"This raised the concept of a regional seizure mechanism that was supported by data showing increased spontaneous synaptic activity in the subiculum but not CA1."
Establishes the regional seizure mechanism at circuit level.
Hyperthermia-Sensitized Seizure Threshold
Seizures are triggered by fever in patients and by induced hyperthermia in the mouse models. Temperature sensitivity is a distinct property of the substrate, not simply a consequence of how excitable it is at baseline.
Downstream
Refractory Multifocal and Generalized Seizures Fever repeatedly precipitates the clinical seizures.
Show evidence (2 references)
PMID:40763036 SUPPORT Model Organism
"have spontaneous and hyperthermia-induced generalized seizures and SUDEP"
Documents hyperthermia-induced seizures in the knock-in mouse.
PMID:31709768 SUPPORT Human Clinical
"then focal seizures and myoclonic status epilepticus (SE) at 3 months, triggered by fever"
Documents fever-triggered seizures in an affected child.
Refractory Multifocal and Generalized Seizures
Seizures begin in the first months of life as multifocal myoclonus and evolve to focal, myoclonic, and generalized tonic-clonic seizures with myoclonic status epilepticus, resistant to standard anti-seizure medication.
Downstream
Developmental Stagnation and Regression Sustained early seizure burden accompanies arrest and loss of developmental progress.
Elevated Risk of Sudden Unexpected Death in Epilepsy Uncontrolled generalized seizures are one of the two substrates proposed for SUDEP in this disorder.
Show evidence (2 references)
PMID:31709768 SUPPORT Human Clinical
"The female proband showed hypotonia from birth, multifocal myoclonus at 2.5 months, then focal seizures and myoclonic status epilepticus (SE) at 3 months, triggered by fever."
Gives the seizure evolution and timing.
PMID:33901312 SUPPORT Human Clinical
"a rare, severe developmental and epileptic encephalopathy featuring infantile onset refractory seizures followed by developmental stagnation or regression"
Confirms refractoriness and the associated developmental course.
Cardiomyocyte Ionic Current Remodeling
SCN1B is expressed in heart as well as brain. Cardiomyocytes carrying the DEE52 variant show increased transient outward potassium current in mouse, and increased sodium current, late sodium current, and transient outward potassium current in patient-derived iPSC cardiomyocytes. Increased transient outward current is the change common to both species.
cardiac muscle cell CL:0000746 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cardiac muscle cell (CL:0000746). CL:0000746 is a cell type from the Cell Ontology.
ventricular cardiac muscle cell action potential GO:0086005 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal ventricular cardiac muscle cell action potential (GO:0086005). GO:0086005 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Experimental models
Patient-derived iPSC cardiomyocytes (SCN1B c.265C>T) IPSC DERIVED MODEL The only human-cell measurement of the cardiac electrophysiological consequence of the DEE52 genotype.
Animal models
Scn1b-c.265C>T (p.R89C) knock-in mouse Mouse recapitulates Carries the exact human variant, and the increased transient outward current it shows is reproduced in patient-derived iPSC cardiomyocytes.
Downstream
Cardiac Arrhythmia Susceptibility Altered repolarizing and depolarizing currents form an electrical arrhythmia substrate.
Show evidence (2 references)
PMID:40763036 SUPPORT In Vitro
"Patient-derived iPSC-CMs with biallelic SCN1B-c.265C>T variant expression showed increased sodium current (INa), late INa, and Ito current densities."
Measures the current changes in human patient-derived cardiomyocytes.
PMID:40763036 SUPPORT Model Organism
"while mouse and human cardiac AP waveforms have critical differences, increased Ito is common to both models of DEE52"
Identifies the current change that is conserved across species.
Ventricular Fibrosis
Heart sections from the DEE52 knock-in mouse reveal ventricular fibrosis - a structural substrate for arrhythmia that is separate from, and additional to, the ionic current changes.
cardiac muscle cell CL:0000746 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves cardiac muscle cell (CL:0000746). CL:0000746 is a cell type from the Cell Ontology.
Downstream
Cardiac Arrhythmia Susceptibility Fibrosis provides a structural substrate for reentrant arrhythmia.
Show evidence (1 reference)
PMID:40763036 SUPPORT Model Organism
"heart sections revealed ventricular fibrosis"
Documents the structural cardiac change.
Cardiac Arrhythmia Susceptibility
The combined electrical and structural substrates make the heart susceptible to arrhythmia, demonstrated by pacing-induced arrhythmias in the knock-in mouse.
Downstream
Elevated Risk of Sudden Unexpected Death in Epilepsy Cardiac arrhythmia is proposed as the second substrate for SUDEP alongside the seizures themselves.
Show evidence (1 reference)
PMID:40763036 SUPPORT Model Organism
"Scn1bC89/C89 mice were susceptible to pacing-induced cardiac arrhythmias."
Demonstrates inducible arrhythmia in the DEE52 model.
Elevated Risk of Sudden Unexpected Death in Epilepsy
DEE52 carries a high risk of sudden unexpected death in epilepsy, with two proposed substrates converging here - the seizures and the cardiac arrhythmia susceptibility. Scn1b-null mice die of SUDEP before weaning.
Show evidence (2 references)
PMID:40763036 SUPPORT Human Clinical
"linked to DEE52, a developmental and epileptic encephalopathy with a high risk of sudden unexpected death in epilepsy (SUDEP)"
States the elevated SUDEP risk for this disorder.
PMID:40763036 SUPPORT Model Organism
"our data suggest that electrical and structural substrates may lead to arrhythmias and contribute to SUDEP in DEE52"
Names both cardiac substrates as contributors to SUDEP.
Developmental Stagnation and Regression
Development arrests or regresses after seizure onset, with severe global delay, hypotonia, spasticity, and in the most affected virtually no developmental progress.
Show evidence (2 references)
PMID:33901312 SUPPORT Human Clinical
"characterized by infantile onset refractory seizures followed by cognitive decline and neurological features such as hypotonia, spasticity, and ataxia"
Describes the developmental and neurological course.
PMID:31709768 SUPPORT Human Clinical
"Epilepsy was refractory and the patient had virtually no development."
Documents the severity of the developmental outcome.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for SCN1B-Related Developmental and Epileptic Encephalopathy Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

17
Cardiovascular 1
Ventricular Arrhythmia Susceptibility HP:0004308 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Ventricular arrhythmia (HP:0004308). HP:0004308 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40763036 SUPPORT Model Organism
"Scn1bC89/C89 mice were susceptible to pacing-induced cardiac arrhythmias."
Demonstrates arrhythmia susceptibility in the model; human clinical arrhythmia data are not yet available, hence PARTIAL.
Ear 1
Sensorineural Hearing Loss Sensorineural hearing impairment HP:0000407 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Sensorineural hearing impairment (HP:0000407). HP:0000407 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31709768 SUPPORT Human Clinical
"Auditory brainstem response (ABR) showed bilateral hearing loss."
Documents bilateral hearing loss on ABR.
Head and Neck 1
Microcephaly HP:0000252 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Microcephaly (HP:0000252). HP:0000252 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:33901312 SUPPORT Human Clinical
"Recurrent clinical features are early infantile onset seizures followed by psychomotor stagnation or regression, microcephaly, axial hypotonia, appendicular spasticity, and nonspecific brain atrophy"
Lists microcephaly among the recurrent clinical features.
PMID:33901312 SUPPORT Human Clinical
"microcephaly was present in two subjects"
Two of nine subjects is 22%, the occasional band, but the same paper also calls microcephaly a recurrent feature; no frequency is asserted rather than pick between the two characterizations.
Musculoskeletal 2
Hypotonia HP:0001252 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypotonia (HP:0001252). HP:0001252 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31709768 SUPPORT Human Clinical
"The female proband showed hypotonia from birth"
Documents congenital hypotonia.
Spasticity HP:0001257 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Spasticity (HP:0001257). HP:0001257 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:33901312 SUPPORT Human Clinical
"neurological features such as hypotonia, spasticity, and ataxia"
Lists spasticity among the neurological features.
Nervous System 10
Refractory Infantile-Onset Seizures HP:0001250 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Seizure (HP:0001250), qualified as infantile onset, up to 0.5y. HP:0001250 is a phenotype from the Human Phenotype Ontology.
Onset: INFANTILE; up to 0.5y
Show evidence (1 reference)
PMID:33901312 SUPPORT Human Clinical
"a rare, severe developmental and epileptic encephalopathy featuring infantile onset refractory seizures"
Establishes infantile-onset refractory epilepsy as the core phenotype.
Myoclonic Seizures Generalized myoclonic seizure HP:0002123 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Generalized myoclonic seizure (HP:0002123). HP:0002123 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31709768 SUPPORT Human Clinical
"multifocal myoclonus at 2.5 months, then focal seizures and myoclonic status epilepticus (SE) at 3 months"
Documents the myoclonic semiology and its timing.
Fever-Triggered Seizures Febrile seizure (within the age range of 3 months to 6 years) HP:0002373 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Febrile seizure (within the age range of 3 months to 6 years) (HP:0002373). HP:0002373 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31465153 SUPPORT Human Clinical
"The proband is an 11-year-old female with infantile-onset, fever-induced, intractable generalized tonic-clonic seizures"
Documents fever induction of the seizures.
Bilateral Tonic-Clonic Seizures HP:0002069 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Bilateral tonic-clonic seizure (HP:0002069). HP:0002069 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31465153 SUPPORT Human Clinical
"fever-induced, intractable generalized tonic-clonic seizures, myoclonic seizures, and developmental slowing"
Documents generalized tonic-clonic seizures.
EEG with Burst Suppression HP:0010851 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is EEG with burst suppression (HP:0010851). HP:0010851 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:33901312 SUPPORT Human Clinical
"Their EEG recordings showed low-voltage cerebral activity intermixed with suppression–burst patterns from age 6 months up to 4 years"
Reports the suppression-burst EEG pattern directly.
Cerebral Atrophy HP:0002059 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cerebral atrophy (HP:0002059). HP:0002059 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:33901312 SUPPORT Human Clinical
"Recurrent clinical features are early infantile onset seizures followed by psychomotor stagnation or regression, microcephaly, axial hypotonia, appendicular spasticity, and nonspecific brain atrophy"
Names nonspecific brain atrophy among the recurrent clinical features.
Hyperreflexia FREQUENT HP:0001347 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hyperreflexia (HP:0001347). HP:0001347 is a phenotype from the Human Phenotype Ontology.
Show evidence (3 references)
PMID:33901312 SUPPORT Human Clinical
"and they all had hyperreflexia. Brain magnetic resonance imaging (MRI) was unremarkable."
Family B, three children. Note the scope: "they all" refers to family B, not to the whole cohort, so this sentence alone cannot support a cohort-wide band.
PMID:33901312 SUPPORT Human Clinical
"Physical examination revealed generalized spasticity and hyperreflexia"
Family A, two children.
PMID:33901312 SUPPORT Human Clinical
"Neurological examination revealed hyperreflexia in both cases"
Family D, two children. Families A, B, and D together give seven of nine subjects, or 78%, which is the 30-79% frequent band.
Severe Global Developmental Delay HP:0011344 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Severe global developmental delay (HP:0011344). HP:0011344 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31709768 SUPPORT Human Clinical
"Epilepsy was refractory and the patient had virtually no development."
Documents the severity of developmental impairment.
Developmental Regression HP:0002376 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Developmental regression (HP:0002376). HP:0002376 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:33901312 SUPPORT Human Clinical
"infantile onset refractory seizures followed by developmental stagnation or regression"
Documents stagnation or regression as part of the syndrome.
Ataxia HP:0001251 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Ataxia (HP:0001251). HP:0001251 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:33901312 SUPPORT Human Clinical
"neurological features such as hypotonia, spasticity, and ataxia"
Lists ataxia among the clinical features of EIEE52.
Constitutional 1
Sudden Unexpected Death in Epilepsy HP:0033258 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Sudden unexpected death in epilepsy (HP:0033258). HP:0033258 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40763036 SUPPORT Human Clinical
"linked to DEE52, a developmental and epileptic encephalopathy with a high risk of sudden unexpected death in epilepsy (SUDEP)"
States the high SUDEP risk for this disorder.
Other 1
Status Epilepticus HP:0002133 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Status epilepticus (HP:0002133). HP:0002133 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31709768 SUPPORT Human Clinical
"then focal seizures and myoclonic status epilepticus (SE) at 3 months, triggered by fever"
Documents status epilepticus in an affected child.
🧬

Genetic Associations

1
SCN1B (Biallelic pathogenic variants)
Gene: SCN1B hgnc:10586 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is SCN1B (hgnc:10586). hgnc:10586 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE variant_origin: GERMLINE
Show evidence (3 references)
PMID:33901312 SUPPORT Human Clinical
"We identified nine patients from four unrelated families harboring three biallelic variants in SCN1B"
Reports the specific causal variants in the largest cohort.
PMID:33901312 SUPPORT Human Clinical
"In humans, inherited heterozygous SCN1B variants have been associated with mild-to-moderate epileptic disorders within the genetic epilepsy with febrile seizures plus (GEFS+) spectrum."
Establishes the dosage-dependent phenotypic distinction.
PMID:31465153 SUPPORT Human Clinical
"Her 4-year-old brother had a similar epilepsy phenotype, but still displays normal development."
Documents intrafamilial variability in developmental outcome.
💊

Medical Actions

5
Fenfluramine
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: fenfluramine CHEBI:5000 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses fenfluramine (CHEBI:5000). CHEBI:5000 is a therapeutic agent from Chemical Entities of Biological Interest.
Fenfluramine produced a significant reduction in seizure frequency and resolution of status epilepticus episodes, sustained over two years of follow-up, in a patient with the p.R85C variant whose seizures had been refractory to standard agents. This is a single reported case, not trial evidence.
Mechanism Target:
INHIBITS Refractory Multifocal and Generalized Seizures — Reduced seizure frequency and abolished recurrent status epilepticus in the reported case.
Show evidence (1 reference)
PMID:31709768 SUPPORT Human Clinical
"Administration of fenfluramine resulted in a significant reduction in seizure frequency and resolution of SE episodes that persisted after a 2-year follow-up."
Reports the observed treatment effect on seizures and status epilepticus.
Show evidence (1 reference)
PMID:31709768 SUPPORT Human Clinical
"Administration of fenfluramine resulted in a significant reduction in seizure frequency and resolution of SE episodes that persisted after a 2-year follow-up."
The single reported case of a sustained response in SCN1B-DEE52.
Ketogenic Diet
Action: Dietary InterventionNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Dietary Intervention (NCIT:C15447). NCIT:C15447 is a clinical intervention from the NCI Thesaurus. NCIT:C15447
The ketogenic diet was introduced at seven months in a reported case, together with topiramate, and myoclonus frequency and intensity decreased. Because the two were started at the same time neither can be credited alone; the drug arm is curated separately as Topiramate.
Mechanism Target:
INHIBITS Refractory Multifocal and Generalized Seizures — Reduced myoclonus frequency and intensity in the reported case.
Show evidence (1 reference)
PMID:31709768 SUPPORT Human Clinical
"At 7 months, introduction of the ketogenic diet and topiramate (5 mg/kg/d) decreased myoclonus frequency and intensity"
Records the observed reduction after the ketogenic diet and topiramate were begun together at seven months.
Show evidence (1 reference)
PMID:31709768 SUPPORT Human Clinical
"At 7 months, introduction of the ketogenic diet and topiramate (5 mg/kg/d) decreased myoclonus frequency and intensity"
The single reported instance of benefit from dietary therapy in this disorder, confounded by the concurrent start of topiramate.
Topiramate
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: topiramate CHEBI:63631 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses topiramate (CHEBI:63631). CHEBI:63631 is a therapeutic agent from Chemical Entities of Biological Interest.
Topiramate at 5 mg/kg/d was started at seven months alongside the ketogenic diet in a reported case, and myoclonus frequency and intensity decreased. The co-initiation means neither intervention can be credited alone; the dietary arm is curated separately as Ketogenic Diet.
Mechanism Target:
INHIBITS Refractory Multifocal and Generalized Seizures — Reduced myoclonus frequency and intensity in the reported case, confounded by concurrent initiation of the ketogenic diet.
Show evidence (1 reference)
PMID:31709768 SUPPORT Human Clinical
"At 7 months, introduction of the ketogenic diet and topiramate (5 mg/kg/d) decreased myoclonus frequency and intensity"
Records the observed reduction and the co-initiation.
Show evidence (1 reference)
PMID:31709768 SUPPORT Human Clinical
"At 7 months, introduction of the ketogenic diet and topiramate (5 mg/kg/d) decreased myoclonus frequency and intensity"
The single reported instance of benefit involving topiramate in this disorder.
Conventional Anti-Seizure Medication
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Standard anti-seizure medications are generally ineffective. Valproic acid, clobazam, clonazepam, and phenytoin have been reported ineffective in SCN1B-related cases.
Show evidence (2 references)
PMID:31709768 SUPPORT Human Clinical
"Epilepsy was refractory and the patient had virtually no development."
Documents refractoriness to conventional treatment.
PMID:33901312 SUPPORT Human Clinical
"Seizures were refractory to antiepileptic drugs (AEDs), including carbamazepine and clonazepam"
Names the specific agents that failed, including the sodium-channel blocker carbamazepine. This documents refractoriness, not a contraindication - see the discussion on sodium-channel-blocker avoidance.
Genetic Counseling
Action: Genetic CounselingNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Genetic Counseling (NCIT:C15240). NCIT:C15240 is a clinical intervention from the NCI Thesaurus. NCIT:C15240
Autosomal recessive counseling with a 25% recurrence risk per pregnancy. Carrier parents are unaffected by the encephalopathy but monoallelic SCN1B variants carry their own GEFS+ and cardiac associations, which is worth raising.
Show evidence (1 reference)
PMID:33901312 SUPPORT Human Clinical
"In humans, inherited heterozygous SCN1B variants have been associated with mild-to-moderate epileptic disorders within the genetic epilepsy with febrile seizures plus (GEFS+) spectrum."
The carrier-state association that makes counseling non-trivial here.
🔬

Diagnosis

3
Molecular Genetic Testing for Biallelic SCN1B Variants (Positive in affected individuals)
Diagnosis rests on identifying two pathogenic SCN1B alleles, in practice by exome sequencing given the genetic heterogeneity of infantile-onset DEE.
whole exome sequencing NCIT:C101295 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:33901312 SUPPORT Human Clinical
"Nine subjects from four unrelated consanguineous families presenting with similar epileptic encephalopathies were investigated using exome sequencing."
Documents exome sequencing as the diagnostic route.
Electroencephalography
EEG is the defining investigation. Reported findings evolve with age: low-voltage cerebral activity intermixed with suppression-burst patterns from six months to four years, multifocal epileptic abnormalities on a diffusely slowed background at three years, and frequent bilateral central spikes on long-term video EEG.
electroencephalography NCIT:C38054 NCI Thesaurus (NCIT)
Show evidence (3 references)
PMID:33901312 SUPPORT Human Clinical
"Their EEG recordings showed low-voltage cerebral activity intermixed with suppression–burst patterns from age 6 months up to 4 years"
Documents the suppression-burst pattern and the age range over which it persists.
PMID:33901312 SUPPORT Human Clinical
"Electroencephalographic (EEG) recordings at age 3 years revealed multifocal epileptic abnormalities within diffusely slowed and dysregulated cerebral activity"
Documents the later multifocal epileptiform pattern on a slowed background.
PMID:31709768 SUPPORT Human Clinical
"video electroencephalogram (EEG) monitoring at that time revealed frequent bilateral central spikes"
Documents bilateral central spikes on long-term video EEG monitoring.
Auditory Brainstem Response Testing
ABR detects the bilateral sensorineural hearing loss and localizes brainstem auditory pathway involvement, a feature that would be missed without dedicated testing in a child with no development.
auditory brainstem response testing NCIT:C184949 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:31709768 SUPPORT Human Clinical
"Auditory brainstem response (ABR) showed bilateral hearing loss."
Documents the diagnostic yield of ABR in this disorder.
📊

Prevalence

1
Worldwide
Cases In Literature Ultra Rare
Ultra-rare. Nine patients from four unrelated consanguineous families in the largest single report, with a handful of additional families described elsewhere. No formal population prevalence figure has been published.
Show evidence (1 reference)
PMID:33901312 SUPPORT Human Clinical
"Only a few individuals with EIEE52 have been reported so far, and a disease-causing mechanism remains unclear."
States the small size of the published cohort, which is what supports an ultra-rare class rather than a numeric rate.
🧫

Experimental Models

1
Patient-derived iPSC cardiomyocytes (SCN1B c.265C>T) IPSC_DERIVED_MODEL
Induced pluripotent stem cell cardiomyocytes derived from two DEE52 patients homozygous for SCN1B c.265C>T, used to test the cardiac arm directly in human cells.
Publication
PMID:40763036
Pathograph links
Cardiomyocyte Ionic Current Remodeling measures fidelity: moderate The only human-cell measurement of the cardiac electrophysiological consequence of the DEE52 genotype.
Limitations: iPSC cardiomyocytes are electrophysiologically immature relative to adult ventricular myocytes, so absolute current densities should not be read as adult human values; and the cells cannot report the structural fibrosis arm.
Readouts
Sodium, late sodium, and transient outward potassium current densities
Direction: INCREASED
Interpretation: Multiple currents are increased in patient-derived human cardiomyocytes.
Show evidence (1 reference)
PMID:40763036 SUPPORT In Vitro
"Patient-derived iPSC-CMs with biallelic SCN1B-c.265C>T variant expression showed increased sodium current (INa), late INa, and Ito current densities."
Reports the current measurements behind this readout.
Show evidence (1 reference)
PMID:40763036 SUPPORT In Vitro
"studied induced pluripotent stem cell cardiomyocytes (iPSC-CMs) derived from 2 SCN1B-c.265C>T DEE52 patients"
Establishes the model and its patient provenance.
🐁

Animal Models

3
Scn1b-null mouse
Constitutive Scn1b knockout mice have spontaneous generalized seizures from the second postnatal week, are ataxic, show severely altered cerebellar neuronal pathfinding, and die of SUDEP in 100% of cases before weaning.
Species
Mouse
Genotype
Scn1b homozygous null
Publication
PMID:40923316
Pathograph links
Cerebellar Purkinje Cell and Interneuron Hypoexcitability recapitulates fidelity: moderate Provides the direct electrophysiological evidence for the cerebellar arm.
Limitations: A constitutive null is a more complete lesion than the missense variants that cause human DEE52, and 100% pre-weaning SUDEP is far more severe than the human course, in which children survive for years.
Readouts
Purkinje cell action potential threshold and repetitive firing frequency
Direction: DECREASED
Interpretation: Purkinje cells and interneurons are less excitable, not more.
Show evidence (1 reference)
PMID:40923316 SUPPORT Model Organism
"Scn1b null PCs and interneurons in cerebellar slices have increased thresholds for action potential initiation and decreased repetitive firing frequency compared with WT."
Reports the slice electrophysiology behind this readout.
Show evidence (1 reference)
PMID:40923316 SUPPORT Model Organism
"Scn1b null mice model DS, with spontaneous generalized seizures that start in the second week of life."
Establishes the model's seizure phenotype.
Loss of Cerebellar Motor Output recapitulates fidelity: moderate The mice are ataxic, matching the ataxia reported in patients.
Limitations: Mouse gait analysis and human ataxia are assessed differently, and the human ataxia is reported clinically without the electrophysiological attribution the mouse provides.
Show evidence (1 reference)
PMID:40923316 SUPPORT Model Organism
"Here, we show that Scn1b null mice are ataxic."
Establishes the ataxic phenotype.
Scn1b-c.265C>T (p.R89C) knock-in mouse
Knock-in mice carrying the human DEE52 p.R89C variant have spontaneous and hyperthermia-induced generalized seizures with SUDEP, increased cardiomyocyte transient outward potassium current, ventricular fibrosis, and susceptibility to pacing-induced arrhythmia.
Species
Mouse
Genotype
Scn1b c.265C>T homozygous knock-in (p.R89C)
Publication
PMID:40763036
Pathograph links
Cardiomyocyte Ionic Current Remodeling recapitulates fidelity: high Carries the exact human variant, and the increased transient outward current it shows is reproduced in patient-derived iPSC cardiomyocytes.
Limitations: Mouse and human cardiac action potential waveforms differ critically - the mouse repolarizes largely through the transient outward current - so only the shared increase in that current can be carried across; the increased sodium and late sodium currents seen in human iPSC cardiomyocytes were not the mouse finding.
Readouts
Transient outward potassium current density in cardiomyocytes
Direction: INCREASED
Interpretation: Repolarizing current is increased, altering the action potential waveform.
Show evidence (1 reference)
PMID:40763036 SUPPORT Model Organism
"Scn1bC89/C89 mouse CMs showed increased transient outward potassium current (Ito) density and heart sections revealed ventricular fibrosis."
Reports the current measurement behind this readout.
Show evidence (1 reference)
PMID:40763036 SUPPORT Model Organism
"Mice with homozygous expression of the DEE52 variant Scn1b-c.265C>T, predicting p.R89C, have spontaneous and hyperthermia-induced generalized seizures and SUDEP."
Establishes that the model reproduces the human seizure and SUDEP phenotype.
Scn1b-based Dravet model mouse (subicular hyperexcitability)
A mouse model based on a human SCN1B mutation, showing region-restricted pyramidal neuron hyperexcitability with reduced dendritic arborization and, notably, no change in GABAergic interneuron firing or synaptic properties. Retigabine, which lowers input resistance, protected against thermal seizures.
Species
Mouse
Genotype
Scn1b mutant based on a human beta-1 subunit mutation
Publication
PMID:24747835
Pathograph links
Increased Forebrain Pyramidal Neuron Firing recapitulates fidelity: moderate Provides the direct evidence for the regionally restricted pyramidal hyperexcitability arm and for its input-resistance mechanism.
Limitations: The mechanism is inferred from slice recordings in a mouse carrying one human-derived mutation and has not been confirmed in human neurons; regional restriction to subiculum and layer 2/3 may not map onto human cortical anatomy.
Readouts
Action potential firing rate in subicular and layer 2/3 pyramidal neurons
Direction: INCREASED
Interpretation: Pyramidal neurons in specific regions fire more, attributed to raised input resistance rather than altered sodium current density.
Show evidence (1 reference)
PMID:24747835 SUPPORT Model Organism
"mutant subicular and layer 2/3 pyramidal neurons had increased action potential firing rates, presumably as a consequence of their increased input resistance"
Reports the patch-clamp measurement behind this readout.
Show evidence (1 reference)
PMID:24747835 SUPPORT Model Organism
"Homozygous mutant mice shared phenotypic features and pharmaco-sensitivity with Dravet syndrome."
Establishes the model's phenotypic and pharmacological validity.
{ }

Source YAML

click to show 
name: SCN1B-Related Developmental and Epileptic Encephalopathy
creation_date: "2026-08-19T00:00:00Z"
category: Mendelian
synonyms:
- DEE52
- EIEE52
- early infantile epileptic encephalopathy 52
- SCN1B-linked developmental and epileptic encephalopathy
- developmental and epileptic encephalopathy 52
description: >-
  SCN1B-related developmental and epileptic encephalopathy (DEE52) is a severe
  autosomal recessive epilepsy caused by biallelic variants in SCN1B, which encodes
  the beta-1 and beta-1B subunits of the voltage-gated sodium channel. Beta-1 does
  not form a pore. It is a single-transmembrane immunoglobulin-domain protein that
  modulates the gating of pore-forming alpha subunits (Nav1.1, Nav1.2, Nav1.6 in
  brain, Nav1.5 in heart), chaperones them to the membrane, and separately acts as
  a cell adhesion molecule. Losing it therefore does not remove a current; it
  detunes several currents at once, in a cell-type-specific way. Affected children
  present in the first months of life with fever-triggered focal, myoclonic, and
  generalized seizures and myoclonic status epilepticus, followed by developmental
  stagnation or regression, with hypotonia, spasticity, ataxia, and in some cases
  sensorineural hearing loss. Because SCN1B is expressed in heart as well as brain,
  DEE52 carries a cardiac arrhythmia substrate alongside the seizures, and the risk
  of sudden unexpected death in epilepsy is high. Monoallelic SCN1B variants cause
  the much milder GEFS+ spectrum and cardiac disorders such as Brugada syndrome and
  atrial fibrillation; this entry covers the biallelic encephalopathy.
disease_term:
  preferred_term: developmental and epileptic encephalopathy, 52
  term:
    id: MONDO:0033361
    label: developmental and epileptic encephalopathy, 52
parents:
- Neurodevelopmental Disorder
- Genetic Disease

inheritance:
- name: Autosomal recessive
  description: >-
    DEE52 requires two pathogenic SCN1B alleles, usually homozygous in consanguineous
    families. Heterozygous carriers are unaffected by the encephalopathy - one
    functional allele suffices for normal control of excitability - although
    monoallelic variants are separately linked to the milder GEFS+ spectrum.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In contrast, biallelic variants cause early infantile epileptic encephalopathy 52"
    explanation: >-
      States the biallelic requirement and its contrast with monoallelic disease.
  - reference: PMID:19710327
    reference_title: "A functional null mutation of SCN1B in a patient with Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "the seizure susceptibility of Scn1b(+/-) mice was similar to wild type, suggesting that, like the parents of this patient, one functional SCN1B allele is sufficient for normal control of electrical excitability"
    explanation: >-
      Explains why heterozygous carriers are unaffected.

pathophysiology:
- name: Biallelic SCN1B Loss-of-Function Variant
  biological_scale: MOLECULAR
  conforms_to: "epilepsy_excitation_inhibition_imbalance#Ion Channel and Synaptic Dysfunction"
  description: >-
    Two pathogenic SCN1B alleles are present, typically homozygous missense variants
    clustered in the extracellular immunoglobulin loop domain (p.R46C, p.R60C,
    p.R85C, p.R89C, p.V158M, p.R125C). This node records the genomic lesion; the
    several distinct protein-level consequences are modeled downstream.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified nine patients from four unrelated families harboring three biallelic variants in SCN1B"
    explanation: >-
      Establishes the biallelic genotype in the largest reported cohort.
  - reference: PMID:31465153
    reference_title: "Developmental and epileptic encephalopathy in two siblings with a novel, homozygous missense variant in SCN1B."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the vicinity of other epileptic encephalopathy-associated missense variants that are biallelic and located in the extracellular immunoglobulin loop domain of the protein"
    explanation: >-
      Locates the pathogenic variants in the immunoglobulin loop domain.
  downstream:
  - target: Loss of Beta-1 Subunit Cell-Surface Expression
    causal_link_type: DIRECT
    description: >-
      Some variants, such as p.R125C, prevent the subunit from reaching the membrane.
  - target: Loss of Beta-1-Mediated Modulation of Sodium Channel Gating
    causal_link_type: DIRECT
    description: >-
      Other variants reach the surface normally but fail to modulate the alpha subunit.
  - target: Disrupted Beta-1 Immunoglobulin-Domain Cell Adhesion
    causal_link_type: DIRECT
    description: >-
      Variants in the immunoglobulin loop compromise the adhesion function, which is
      independent of channel gating.

- name: Loss of Beta-1 Subunit Cell-Surface Expression
  biological_scale: MOLECULAR
  description: >-
    Trafficking-defective variants are expressed at normal total cellular levels but
    fail to reach the plasma membrane, producing a functional null. This is a
    trafficking failure and is separable from whether a surface-resident subunit
    works.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  evidence:
  - reference: PMID:19710327
    reference_title: "A functional null mutation of SCN1B in a patient with Dravet syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Biochemical characterization of p.R125C in a heterologous system demonstrated little to no cell surface expression despite normal total cellular expression."
    explanation: >-
      Documents the trafficking defect with preserved total expression.
  downstream:
  - target: Loss of Beta-1-Mediated Modulation of Sodium Channel Gating
    causal_link_type: DIRECT
    description: >-
      A subunit absent from the membrane cannot modulate the alpha subunit there.

- name: Loss of Beta-1-Mediated Modulation of Sodium Channel Gating
  biological_scale: MOLECULAR
  description: >-
    The alpha subunit no longer receives normal beta-1 modulation. Critically, this
    happens even for variants whose surface expression is indistinguishable from
    wild type, which is why it is a separate claim from the trafficking node.
  molecular_functions:
  - preferred_term: voltage-gated sodium channel activity
    term:
      id: GO:0005248
      label: voltage-gated sodium channel activity
    modifier: ABNORMAL
  evidence:
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "showed cell surface expression of the mutant beta1 subunit, similar to wild-type (WT), but with loss of normal beta1-mediated modification of human Nav 1.1-generated sodium current"
    explanation: >-
      Demonstrates loss of modulation with intact surface expression, separating this
      node from the trafficking node.
  downstream:
  - target: Altered Sodium Channel Voltage Dependence and Availability
    causal_link_type: DIRECT
    description: >-
      Unmodulated alpha subunits gate at shifted voltages.

- name: Altered Sodium Channel Voltage Dependence and Availability
  biological_scale: MOLECULAR
  description: >-
    Conductance-voltage relationships and channel availability shift toward more
    depolarized potentials across Nav1.1, Nav1.2, and Nav1.6, and recovery from fast
    inactivation slows for some variant-channel pairings. The effect is
    variant-specific and channel-subtype-specific rather than uniform.
  biological_processes:
  - preferred_term: sodium ion transmembrane transport
    term:
      id: GO:0035725
      label: sodium ion transmembrane transport
    modifier: ABNORMAL
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We observed a shift toward more depolarizing potentials of conductance-voltage relationships"
    explanation: >-
      Reports the depolarizing shift in the conductance-voltage relationship.
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "and detected a slower recovery from fast inactivation for NaV 1.1/beta1V158M"
    explanation: >-
      Documents the variant-specific slowing of recovery from fast inactivation.
  downstream:
  - target: Increased Forebrain Pyramidal Neuron Firing
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Altered channel gating changes the intrinsic excitability of specific
      forebrain pyramidal populations.
  - target: Reduced Purkinje Cell Transient and Resurgent Sodium Current
    causal_link_type: DIRECT
    description: >-
      In cerebellar Purkinje cells the same loss of modulation reduces sodium current
      density.
  - target: Cardiomyocyte Ionic Current Remodeling
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Cardiac cells express SCN1B and show their own current changes.

- name: Disrupted Beta-1 Immunoglobulin-Domain Cell Adhesion
  biological_scale: MOLECULAR
  description: >-
    Beta-1 is an immunoglobulin superfamily cell adhesion molecule that binds beta-1
    subunits on neighbouring cells, other adhesion molecules, and extracellular
    matrix. Pathogenic variants cluster in exactly this domain, so the adhesion role
    is compromised alongside the gating role. Nothing about channel biophysics
    measures this arm.
  biological_processes:
  - preferred_term: cell adhesion
    term:
      id: GO:0007155
      label: cell adhesion
    modifier: ABNORMAL
  evidence:
  - reference: PMID:40923316
    reference_title: "Ataxia and cerebellar hypoexcitability in a mouse model of SCN1B-linked Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Non-pore-forming beta1 subunits function as channel modulators and chaperones to the plasma membrane as well as immunoglobulin superfamily cell adhesion molecules (CAMs) that interact with other beta1 subunits on adjacent cells, with other CAMs, or with extracellular matrix molecules"
    explanation: >-
      States the adhesion function as distinct from channel modulation.
  - reference: PMID:31465153
    reference_title: "Developmental and epileptic encephalopathy in two siblings with a novel, homozygous missense variant in SCN1B."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "located in the extracellular immunoglobulin loop domain of the protein, which mediates interaction of the beta-1 subunit with cellular adhesion molecules"
    explanation: >-
      Places the pathogenic variants in the adhesion-mediating domain.
  downstream:
  - target: Altered Cerebellar Neuronal Pathfinding
    causal_link_type: DIRECT
    description: >-
      Loss of adhesion signalling disturbs the guidance of developing cerebellar
      neurons.
  - target: Reduced Subicular Pyramidal Dendritic Arborization
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Dendritic arbors are reduced in the mutant, plausibly through the
      adhesion/developmental arm rather than through channel gating.

- name: Altered Cerebellar Neuronal Pathfinding
  biological_scale: TISSUE
  description: >-
    Neuronal pathfinding in the cerebellum is severely altered in Scn1b-null mice, a
    developmental wiring defect distinct from the excitability changes measured in
    the same tissue.
  cell_types:
  - preferred_term: Purkinje cell
    term:
      id: CL:0000121
      label: Purkinje cell
  biological_processes:
  - preferred_term: axon extension involved in axon guidance
    term:
      id: GO:0048846
      label: axon extension involved in axon guidance
    modifier: ABNORMAL
  evidence:
  - reference: PMID:40923316
    reference_title: "Ataxia and cerebellar hypoexcitability in a mouse model of SCN1B-linked Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In Scn1b null cerebellum, neuronal pathfinding is severely altered"
    explanation: >-
      Documents the cerebellar pathfinding defect.
  downstream:
  - target: Cerebellar Purkinje Cell and Interneuron Hypoexcitability
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Miswired cerebellar circuitry accompanies the measured excitability changes,
      though the causal ordering between them is not established.

- name: Reduced Purkinje Cell Transient and Resurgent Sodium Current
  biological_scale: CELLULAR
  description: >-
    Scn1b-null Purkinje cells carry reduced transient and resurgent sodium current
    densities. Resurgent current is what allows Purkinje cells to fire at high rates,
    so this is a specific biophysical loss rather than a general reduction in
    excitability.
  cell_types:
  - preferred_term: Purkinje cell
    term:
      id: CL:0000121
      label: Purkinje cell
  biological_processes:
  - preferred_term: sodium ion transmembrane transport
    term:
      id: GO:0035725
      label: sodium ion transmembrane transport
    modifier: DECREASED
  evidence:
  - reference: PMID:40923316
    reference_title: "Ataxia and cerebellar hypoexcitability in a mouse model of SCN1B-linked Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Scn1b null PCs have reduced transient and resurgent sodium current densities."
    explanation: >-
      Reports the specific sodium current deficit in Purkinje cells.
  downstream:
  - target: Cerebellar Purkinje Cell and Interneuron Hypoexcitability
    causal_link_type: DIRECT
    description: >-
      Reduced sodium current raises the action-potential threshold and limits
      repetitive firing.

- name: Cerebellar Purkinje Cell and Interneuron Hypoexcitability
  biological_scale: CELLULAR
  description: >-
    Purkinje cells and cerebellar interneurons show increased thresholds for action
    potential initiation and decreased repetitive firing frequency. Note the
    direction: in the cerebellum SCN1B loss makes neurons LESS excitable, which is
    the opposite of what happens in the forebrain pyramidal populations.
  cell_types:
  - preferred_term: Purkinje cell
    term:
      id: CL:0000121
      label: Purkinje cell
  - preferred_term: GABAergic neuron
    term:
      id: CL:0000617
      label: GABAergic neuron
  biological_processes:
  - preferred_term: membrane depolarization during action potential
    term:
      id: GO:0086010
      label: membrane depolarization during action potential
    modifier: DECREASED
  evidence:
  - reference: PMID:40923316
    reference_title: "Ataxia and cerebellar hypoexcitability in a mouse model of SCN1B-linked Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Scn1b null PCs and interneurons in cerebellar slices have increased thresholds for action potential initiation and decreased repetitive firing frequency compared with WT."
    explanation: >-
      Directly measures the cerebellar hypoexcitability.
  downstream:
  - target: Loss of Cerebellar Motor Output
    causal_link_type: DIRECT
    description: >-
      Reduced Purkinje firing degrades the cerebellar contribution to motor control.
  - target: Loss of Cerebellar Seizure-Terminating Output
    causal_link_type: DIRECT
    description: >-
      Cerebellar output to other brain regions can terminate seizures, so its loss
      is proposed to worsen seizure severity.

- name: Loss of Cerebellar Motor Output
  biological_scale: ORGANISM
  description: >-
    Degraded cerebellar output manifests as ataxia. This is the motor consequence,
    separate from the seizure consequence of the same hypoexcitability.
  cell_types:
  - preferred_term: Purkinje cell
    term:
      id: CL:0000121
      label: Purkinje cell
  evidence:
  - reference: PMID:40923316
    reference_title: "Ataxia and cerebellar hypoexcitability in a mouse model of SCN1B-linked Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We propose that reduced PC excitability underlies the ataxic phenotype of Scn1b mice."
    explanation: >-
      Attributes the ataxia to reduced Purkinje cell excitability.

- name: Loss of Cerebellar Seizure-Terminating Output
  biological_scale: TISSUE
  description: >-
    Cerebellar projections can act to terminate seizures. With Purkinje cells
    hypoexcitable, that brake is weakened, which is proposed to exacerbate seizure
    severity rather than to initiate seizures.
  evidence:
  - reference: PMID:40923316
    reference_title: "Ataxia and cerebellar hypoexcitability in a mouse model of SCN1B-linked Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "because cerebellar output to other areas of the brain can result in termination of seizures, we propose that PC hypoexcitability exacerbates the severe phenotype of this mouse model"
    explanation: >-
      States the proposed seizure-exacerbating role of cerebellar hypoexcitability.
  downstream:
  - target: Refractory Multifocal and Generalized Seizures
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      A weakened seizure-terminating mechanism contributes to seizure severity.

- name: Increased Forebrain Pyramidal Neuron Firing
  biological_scale: CELLULAR
  description: >-
    Subicular and layer 2/3 pyramidal neurons fire action potentials at increased
    rates in an Scn1b mutant mouse, attributable to increased input resistance rather
    than to a change in sodium current density. The effect is regionally restricted -
    layer 5 and CA1 pyramidal neurons are unchanged.
  cell_types:
  - preferred_term: pyramidal neuron
    term:
      id: CL:0000598
      label: pyramidal neuron
  biological_processes:
  - preferred_term: membrane depolarization during action potential
    term:
      id: GO:0086010
      label: membrane depolarization during action potential
    modifier: INCREASED
  evidence:
  - reference: PMID:24747835
    reference_title: "Reduced dendritic arborization and hyperexcitability of pyramidal neurons in a Scn1b-based model of Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Patch-clamp analysis showed that mutant subicular and layer 2/3 pyramidal neurons had increased action potential firing rates, presumably as a consequence of their increased input resistance."
    explanation: >-
      Reports the increased firing and its proposed input-resistance mechanism.
  - reference: PMID:24747835
    reference_title: "Reduced dendritic arborization and hyperexcitability of pyramidal neurons in a Scn1b-based model of Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "These changes were not seen in L5 or CA1 pyramidal neurons."
    explanation: >-
      Establishes the regional restriction of the effect.
  downstream:
  - target: Regionally Restricted Network Hyperexcitability
    causal_link_type: DIRECT
    description: >-
      Increased pyramidal firing in specific regions creates a localized
      hyperexcitable substrate.

- name: Reduced Subicular Pyramidal Dendritic Arborization
  biological_scale: CELLULAR
  description: >-
    Subicular pyramidal neurons have reduced dendritic arbors in the Scn1b mutant.
    A smaller arbor raises input resistance, which is the mechanism proposed for the
    firing change, so this structural finding is upstream of the functional one
    rather than a restatement of it.
  cell_types:
  - preferred_term: pyramidal neuron
    term:
      id: CL:0000598
      label: pyramidal neuron
  biological_processes:
  - preferred_term: dendrite development
    term:
      id: GO:0016358
      label: dendrite development
    modifier: DECREASED
  evidence:
  - reference: PMID:24747835
    reference_title: "Reduced dendritic arborization and hyperexcitability of pyramidal neurons in a Scn1b-based model of Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Morphological analysis of subicular pyramidal neurons revealed reduced dendritic arborization."
    explanation: >-
      Reports the dendritic morphology change.
  downstream:
  - target: Increased Forebrain Pyramidal Neuron Firing
    causal_link_type: DIRECT
    description: >-
      Reduced arborization increases input resistance, the proposed proximate cause
      of the increased firing rate.

- name: Regionally Restricted Network Hyperexcitability
  biological_scale: TISSUE
  conforms_to: "epilepsy_excitation_inhibition_imbalance#Neuronal Hyperexcitability and Hypersynchrony"
  description: >-
    Spontaneous synaptic activity is increased in the subiculum but not in CA1,
    supporting a regional rather than global seizure mechanism. This is a
    circuit-level property distinct from the single-cell firing measurements that
    support it.
  cell_types:
  - preferred_term: pyramidal neuron
    term:
      id: CL:0000598
      label: pyramidal neuron
  evidence:
  - reference: PMID:24747835
    reference_title: "Reduced dendritic arborization and hyperexcitability of pyramidal neurons in a Scn1b-based model of Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "This raised the concept of a regional seizure mechanism that was supported by data showing increased spontaneous synaptic activity in the subiculum but not CA1."
    explanation: >-
      Establishes the regional seizure mechanism at circuit level.
  downstream:
  - target: Refractory Multifocal and Generalized Seizures
    causal_link_type: DIRECT
    description: >-
      A regionally hyperexcitable substrate generates recurrent seizures.

- name: Hyperthermia-Sensitized Seizure Threshold
  biological_scale: ORGANISM
  description: >-
    Seizures are triggered by fever in patients and by induced hyperthermia in the
    mouse models. Temperature sensitivity is a distinct property of the substrate,
    not simply a consequence of how excitable it is at baseline.
  evidence:
  - reference: PMID:40763036
    reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "have spontaneous and hyperthermia-induced generalized seizures and SUDEP"
    explanation: >-
      Documents hyperthermia-induced seizures in the knock-in mouse.
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "then focal seizures and myoclonic status epilepticus (SE) at 3 months, triggered by fever"
    explanation: >-
      Documents fever-triggered seizures in an affected child.
  downstream:
  - target: Refractory Multifocal and Generalized Seizures
    causal_link_type: DIRECT
    description: >-
      Fever repeatedly precipitates the clinical seizures.

- name: Refractory Multifocal and Generalized Seizures
  biological_scale: ORGANISM
  conforms_to: "epilepsy_excitation_inhibition_imbalance#Seizure Generation and Epileptogenesis"
  description: >-
    Seizures begin in the first months of life as multifocal myoclonus and evolve to
    focal, myoclonic, and generalized tonic-clonic seizures with myoclonic status
    epilepticus, resistant to standard anti-seizure medication.
  evidence:
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The female proband showed hypotonia from birth, multifocal myoclonus at 2.5 months, then focal seizures and myoclonic status epilepticus (SE) at 3 months, triggered by fever."
    explanation: >-
      Gives the seizure evolution and timing.
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a rare, severe developmental and epileptic encephalopathy featuring infantile onset refractory seizures followed by developmental stagnation or regression"
    explanation: >-
      Confirms refractoriness and the associated developmental course.
  downstream:
  - target: Developmental Stagnation and Regression
    causal_link_type: DIRECT
    description: >-
      Sustained early seizure burden accompanies arrest and loss of developmental
      progress.
  - target: Elevated Risk of Sudden Unexpected Death in Epilepsy
    causal_link_type: DIRECT
    description: >-
      Uncontrolled generalized seizures are one of the two substrates proposed for
      SUDEP in this disorder.

- name: Cardiomyocyte Ionic Current Remodeling
  biological_scale: CELLULAR
  description: >-
    SCN1B is expressed in heart as well as brain. Cardiomyocytes carrying the DEE52
    variant show increased transient outward potassium current in mouse, and
    increased sodium current, late sodium current, and transient outward potassium
    current in patient-derived iPSC cardiomyocytes. Increased transient outward
    current is the change common to both species.
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  biological_processes:
  - preferred_term: ventricular cardiac muscle cell action potential
    term:
      id: GO:0086005
      label: ventricular cardiac muscle cell action potential
    modifier: ABNORMAL
  evidence:
  - reference: PMID:40763036
    reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Patient-derived iPSC-CMs with biallelic SCN1B-c.265C>T variant expression showed increased sodium current (INa), late INa, and Ito current densities."
    explanation: >-
      Measures the current changes in human patient-derived cardiomyocytes.
  - reference: PMID:40763036
    reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "while mouse and human cardiac AP waveforms have critical differences, increased Ito is common to both models of DEE52"
    explanation: >-
      Identifies the current change that is conserved across species.
  downstream:
  - target: Cardiac Arrhythmia Susceptibility
    causal_link_type: DIRECT
    description: >-
      Altered repolarizing and depolarizing currents form an electrical arrhythmia
      substrate.

- name: Ventricular Fibrosis
  biological_scale: TISSUE
  description: >-
    Heart sections from the DEE52 knock-in mouse reveal ventricular fibrosis - a
    structural substrate for arrhythmia that is separate from, and additional to, the
    ionic current changes.
  cell_types:
  - preferred_term: cardiac muscle cell
    term:
      id: CL:0000746
      label: cardiac muscle cell
  evidence:
  - reference: PMID:40763036
    reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "heart sections revealed ventricular fibrosis"
    explanation: >-
      Documents the structural cardiac change.
  downstream:
  - target: Cardiac Arrhythmia Susceptibility
    causal_link_type: DIRECT
    description: >-
      Fibrosis provides a structural substrate for reentrant arrhythmia.

- name: Cardiac Arrhythmia Susceptibility
  biological_scale: ORGANISM
  description: >-
    The combined electrical and structural substrates make the heart susceptible to
    arrhythmia, demonstrated by pacing-induced arrhythmias in the knock-in mouse.
  evidence:
  - reference: PMID:40763036
    reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Scn1bC89/C89 mice were susceptible to pacing-induced cardiac arrhythmias."
    explanation: >-
      Demonstrates inducible arrhythmia in the DEE52 model.
  downstream:
  - target: Elevated Risk of Sudden Unexpected Death in Epilepsy
    causal_link_type: DIRECT
    description: >-
      Cardiac arrhythmia is proposed as the second substrate for SUDEP alongside
      the seizures themselves.

- name: Elevated Risk of Sudden Unexpected Death in Epilepsy
  biological_scale: ORGANISM
  description: >-
    DEE52 carries a high risk of sudden unexpected death in epilepsy, with two
    proposed substrates converging here - the seizures and the cardiac arrhythmia
    susceptibility. Scn1b-null mice die of SUDEP before weaning.
  evidence:
  - reference: PMID:40763036
    reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "linked to DEE52, a developmental and epileptic encephalopathy with a high risk of sudden unexpected death in epilepsy (SUDEP)"
    explanation: >-
      States the elevated SUDEP risk for this disorder.
  - reference: PMID:40763036
    reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "our data suggest that electrical and structural substrates may lead to arrhythmias and contribute to SUDEP in DEE52"
    explanation: >-
      Names both cardiac substrates as contributors to SUDEP.

- name: Developmental Stagnation and Regression
  biological_scale: ORGANISM
  description: >-
    Development arrests or regresses after seizure onset, with severe global delay,
    hypotonia, spasticity, and in the most affected virtually no developmental
    progress.
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "characterized by infantile onset refractory seizures followed by cognitive decline and neurological features such as hypotonia, spasticity, and ataxia"
    explanation: >-
      Describes the developmental and neurological course.
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Epilepsy was refractory and the patient had virtually no development."
    explanation: >-
      Documents the severity of the developmental outcome.

phenotypes:
- category: Neurological
  name: Refractory Infantile-Onset Seizures
  description: >-
    Seizures beginning in the first months of life, refractory to multiple standard
    anti-seizure medications.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
    onset:
      onset_category: INFANTILE
      max_age_years: 0.5
      notes: >-
        Multifocal myoclonus reported at 2.5 months with focal seizures and status
        epilepticus by 3 months in one detailed case; the OMIM synopsis places onset
        at or before six months.
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a rare, severe developmental and epileptic encephalopathy featuring infantile onset refractory seizures"
    explanation: >-
      Establishes infantile-onset refractory epilepsy as the core phenotype.
- category: Neurological
  name: Myoclonic Seizures
  description: >-
    Multifocal myoclonus is often the presenting seizure type, with myoclonic status
    epilepticus following.
  phenotype_term:
    preferred_term: Generalized myoclonic seizure
    term:
      id: HP:0002123
      label: Generalized myoclonic seizure
  evidence:
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "multifocal myoclonus at 2.5 months, then focal seizures and myoclonic status epilepticus (SE) at 3 months"
    explanation: >-
      Documents the myoclonic semiology and its timing.
- category: Neurological
  name: Status Epilepticus
  description: >-
    Myoclonic and hemiclonic status epilepticus is a recurrent and characteristic
    feature.
  phenotype_term:
    preferred_term: Status epilepticus
    term:
      id: HP:0002133
      label: Status epilepticus
  evidence:
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "then focal seizures and myoclonic status epilepticus (SE) at 3 months, triggered by fever"
    explanation: >-
      Documents status epilepticus in an affected child.
- category: Neurological
  name: Fever-Triggered Seizures
  description: >-
    Seizures are precipitated by fever, mirroring the hyperthermia-induced seizures
    of the mouse models.
  phenotype_term:
    preferred_term: Febrile seizure (within the age range of 3 months to 6 years)
    term:
      id: HP:0002373
      label: Febrile seizure (within the age range of 3 months to 6 years)
  evidence:
  - reference: PMID:31465153
    reference_title: "Developmental and epileptic encephalopathy in two siblings with a novel, homozygous missense variant in SCN1B."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The proband is an 11-year-old female with infantile-onset, fever-induced, intractable generalized tonic-clonic seizures"
    explanation: >-
      Documents fever induction of the seizures.
- category: Neurological
  name: Bilateral Tonic-Clonic Seizures
  description: >-
    Generalized tonic-clonic seizures occur alongside the focal and myoclonic types.
  phenotype_term:
    preferred_term: Bilateral tonic-clonic seizure
    term:
      id: HP:0002069
      label: Bilateral tonic-clonic seizure
  evidence:
  - reference: PMID:31465153
    reference_title: "Developmental and epileptic encephalopathy in two siblings with a novel, homozygous missense variant in SCN1B."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "fever-induced, intractable generalized tonic-clonic seizures, myoclonic seizures, and developmental slowing"
    explanation: >-
      Documents generalized tonic-clonic seizures.
- category: Neurological
  name: EEG with Burst Suppression
  description: >-
    Low-voltage cerebral activity intermixed with suppression-burst patterns,
    present from six months to four years of age in the reported cohort.
  phenotype_term:
    preferred_term: EEG with burst suppression
    term:
      id: HP:0010851
      label: EEG with burst suppression
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Their EEG recordings showed low-voltage cerebral activity intermixed with suppression–burst patterns from age 6 months up to 4 years"
    explanation: >-
      Reports the suppression-burst EEG pattern directly.
- category: Neurological
  name: Microcephaly
  description: >-
    Microcephaly is a recurrent feature, documented in two of the nine reported
    subjects.
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recurrent clinical features are early infantile onset seizures followed by psychomotor stagnation or regression, microcephaly, axial hypotonia, appendicular spasticity, and nonspecific brain atrophy"
    explanation: >-
      Lists microcephaly among the recurrent clinical features.
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "microcephaly was present in two subjects"
    explanation: >-
      Two of nine subjects is 22%, the occasional band, but the same paper also calls
      microcephaly a recurrent feature; no frequency is asserted rather than pick
      between the two characterizations.
- category: Neurological
  name: Cerebral Atrophy
  description: >-
    Nonspecific brain atrophy is a recurrent neuroimaging feature.
  phenotype_term:
    preferred_term: Cerebral atrophy
    term:
      id: HP:0002059
      label: Cerebral atrophy
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recurrent clinical features are early infantile onset seizures followed by psychomotor stagnation or regression, microcephaly, axial hypotonia, appendicular spasticity, and nonspecific brain atrophy"
    explanation: >-
      Names nonspecific brain atrophy among the recurrent clinical features.
- category: Neurological
  name: Hyperreflexia
  description: >-
    Hyperreflexia completes the pyramidal picture alongside the axial hypotonia and
    appendicular spasticity already curated. It is documented in seven of the nine
    subjects in the largest cohort - both children in family A, all three in family
    B, and both in family D. The two children in family C died early and no
    neurological examination is reported for them, so their status is unknown rather
    than negative.
  phenotype_term:
    preferred_term: Hyperreflexia
    term:
      id: HP:0001347
      label: Hyperreflexia
  frequency: FREQUENT
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "and they all had hyperreflexia. Brain magnetic resonance imaging (MRI) was unremarkable."
    explanation: >-
      Family B, three children. Note the scope: "they all" refers to family B, not to
      the whole cohort, so this sentence alone cannot support a cohort-wide band.
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Physical examination revealed generalized spasticity and hyperreflexia"
    explanation: >-
      Family A, two children.
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neurological examination revealed hyperreflexia in both cases"
    explanation: >-
      Family D, two children. Families A, B, and D together give seven of nine
      subjects, or 78%, which is the 30-79% frequent band.
- category: Neurological
  name: Severe Global Developmental Delay
  description: >-
    Developmental stagnation or regression follows seizure onset; in the most
    affected there is virtually no developmental progress.
  phenotype_term:
    preferred_term: Severe global developmental delay
    term:
      id: HP:0011344
      label: Severe global developmental delay
  evidence:
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Epilepsy was refractory and the patient had virtually no development."
    explanation: >-
      Documents the severity of developmental impairment.
- category: Neurological
  name: Developmental Regression
  description: >-
    Loss of previously acquired abilities after seizure onset.
  phenotype_term:
    preferred_term: Developmental regression
    term:
      id: HP:0002376
      label: Developmental regression
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "infantile onset refractory seizures followed by developmental stagnation or regression"
    explanation: >-
      Documents stagnation or regression as part of the syndrome.
- category: Neurological
  name: Hypotonia
  description: >-
    Hypotonia is present from birth in reported cases.
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The female proband showed hypotonia from birth"
    explanation: >-
      Documents congenital hypotonia.
- category: Neurological
  name: Spasticity
  description: >-
    Appendicular spasticity develops alongside the axial hypotonia.
  phenotype_term:
    preferred_term: Spasticity
    term:
      id: HP:0001257
      label: Spasticity
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "neurological features such as hypotonia, spasticity, and ataxia"
    explanation: >-
      Lists spasticity among the neurological features.
- category: Neurological
  name: Ataxia
  description: >-
    Ataxia is reported clinically and is mechanistically explained in the mouse
    model by Purkinje cell hypoexcitability.
  phenotype_term:
    preferred_term: Ataxia
    term:
      id: HP:0001251
      label: Ataxia
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "neurological features such as hypotonia, spasticity, and ataxia"
    explanation: >-
      Lists ataxia among the clinical features of EIEE52.
- category: Auditory
  name: Sensorineural Hearing Loss
  description: >-
    Bilateral hearing loss on auditory brainstem response testing, with brainstem
    auditory pathway involvement.
  phenotype_term:
    preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  evidence:
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Auditory brainstem response (ABR) showed bilateral hearing loss."
    explanation: >-
      Documents bilateral hearing loss on ABR.
- category: Cardiovascular
  name: Ventricular Arrhythmia Susceptibility
  description: >-
    An arrhythmia substrate demonstrated in the knock-in mouse and in patient-derived
    iPSC cardiomyocytes. Note this is a model-derived susceptibility; clinical
    arrhythmia surveillance data in patients are not yet published.
  phenotype_term:
    preferred_term: Ventricular arrhythmia
    term:
      id: HP:0004308
      label: Ventricular arrhythmia
  evidence:
  - reference: PMID:40763036
    reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Scn1bC89/C89 mice were susceptible to pacing-induced cardiac arrhythmias."
    explanation: >-
      Demonstrates arrhythmia susceptibility in the model; human clinical arrhythmia
      data are not yet available, hence PARTIAL.
- category: Neurological
  name: Sudden Unexpected Death in Epilepsy
  description: >-
    DEE52 carries a high risk of SUDEP; Scn1b-null mice die of SUDEP in 100% of cases
    before weaning.
  phenotype_term:
    preferred_term: Sudden unexpected death in epilepsy
    term:
      id: HP:0033258
      label: Sudden unexpected death in epilepsy
  evidence:
  - reference: PMID:40763036
    reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "linked to DEE52, a developmental and epileptic encephalopathy with a high risk of sudden unexpected death in epilepsy (SUDEP)"
    explanation: >-
      States the high SUDEP risk for this disorder.

genetic:
- name: SCN1B
  association: Biallelic pathogenic variants
  presence: Positive
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  notes: >-
    SCN1B encodes the beta-1 and beta-1B non-pore-forming subunits of the
    voltage-gated sodium channel. Reported DEE52 variants are missense and cluster
    in the extracellular immunoglobulin loop domain: c.136C>T p.R46C, c.178C>T
    p.R60C, c.472G>A p.V158M, p.R85C, c.265C>T p.R89C, and p.R125C. Dosage matters:
    monoallelic variants cause the milder GEFS+ spectrum and cardiac disorders
    including Brugada syndrome and atrial fibrillation, while biallelic variants
    cause this encephalopathy. Expressivity varies even within a sibship - two
    siblings homozygous for p.R89C had similar epilepsy but the younger still had
    normal development.
  gene_term:
    preferred_term: SCN1B
    term:
      id: hgnc:10586
      label: SCN1B
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified nine patients from four unrelated families harboring three biallelic variants in SCN1B"
    explanation: >-
      Reports the specific causal variants in the largest cohort.
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In humans, inherited heterozygous SCN1B variants have been associated with mild-to-moderate epileptic disorders within the genetic epilepsy with febrile seizures plus (GEFS+) spectrum."
    explanation: >-
      Establishes the dosage-dependent phenotypic distinction.
  - reference: PMID:31465153
    reference_title: "Developmental and epileptic encephalopathy in two siblings with a novel, homozygous missense variant in SCN1B."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Her 4-year-old brother had a similar epilepsy phenotype, but still displays normal development."
    explanation: >-
      Documents intrafamilial variability in developmental outcome.

diagnosis:
- name: Molecular Genetic Testing for Biallelic SCN1B Variants
  description: >-
    Diagnosis rests on identifying two pathogenic SCN1B alleles, in practice by
    exome sequencing given the genetic heterogeneity of infantile-onset DEE.
  diagnosis_term:
    preferred_term: whole exome sequencing
    term:
      id: NCIT:C101295
      label: Whole Exome Sequencing
  presence: Positive in affected individuals
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Nine subjects from four unrelated consanguineous families presenting with similar epileptic encephalopathies were investigated using exome sequencing."
    explanation: >-
      Documents exome sequencing as the diagnostic route.
- name: Electroencephalography
  description: >-
    EEG is the defining investigation. Reported findings evolve with age: low-voltage
    cerebral activity intermixed with suppression-burst patterns from six months to
    four years, multifocal epileptic abnormalities on a diffusely slowed background
    at three years, and frequent bilateral central spikes on long-term video EEG.
  diagnosis_term:
    preferred_term: electroencephalography
    term:
      id: NCIT:C38054
      label: Electroencephalography
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Their EEG recordings showed low-voltage cerebral activity intermixed with suppression–burst patterns from age 6 months up to 4 years"
    explanation: >-
      Documents the suppression-burst pattern and the age range over which it persists.
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Electroencephalographic (EEG) recordings at age 3 years revealed multifocal epileptic abnormalities within diffusely slowed and dysregulated cerebral activity"
    explanation: >-
      Documents the later multifocal epileptiform pattern on a slowed background.
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "video electroencephalogram (EEG) monitoring at that time revealed frequent bilateral central spikes"
    explanation: >-
      Documents bilateral central spikes on long-term video EEG monitoring.
- name: Auditory Brainstem Response Testing
  description: >-
    ABR detects the bilateral sensorineural hearing loss and localizes brainstem
    auditory pathway involvement, a feature that would be missed without dedicated
    testing in a child with no development.
  diagnosis_term:
    preferred_term: auditory brainstem response testing
    term:
      id: NCIT:C184949
      label: Auditory Brainstem Response
  evidence:
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Auditory brainstem response (ABR) showed bilateral hearing loss."
    explanation: >-
      Documents the diagnostic yield of ABR in this disorder.

treatments:
- name: Fenfluramine
  description: >-
    Fenfluramine produced a significant reduction in seizure frequency and resolution
    of status epilepticus episodes, sustained over two years of follow-up, in a
    patient with the p.R85C variant whose seizures had been refractory to standard
    agents. This is a single reported case, not trial evidence.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: fenfluramine
      term:
        id: CHEBI:5000
        label: fenfluramine
  target_mechanisms:
  - target: Refractory Multifocal and Generalized Seizures
    treatment_effect: INHIBITS
    description: >-
      Reduced seizure frequency and abolished recurrent status epilepticus in the
      reported case.
    evidence:
    - reference: PMID:31709768
      reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Administration of fenfluramine resulted in a significant reduction in seizure frequency and resolution of SE episodes that persisted after a 2-year follow-up."
      explanation: >-
        Reports the observed treatment effect on seizures and status epilepticus.
  evidence:
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Administration of fenfluramine resulted in a significant reduction in seizure frequency and resolution of SE episodes that persisted after a 2-year follow-up."
    explanation: >-
      The single reported case of a sustained response in SCN1B-DEE52.
- name: Ketogenic Diet
  description: >-
    The ketogenic diet was introduced at seven months in a reported case, together
    with topiramate, and myoclonus frequency and intensity decreased. Because the two
    were started at the same time neither can be credited alone; the drug arm is
    curated separately as Topiramate.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Dietary Intervention
    term:
      id: NCIT:C15447
      label: Dietary Intervention
  target_mechanisms:
  - target: Refractory Multifocal and Generalized Seizures
    treatment_effect: INHIBITS
    description: >-
      Reduced myoclonus frequency and intensity in the reported case.
    evidence:
    - reference: PMID:31709768
      reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "At 7 months, introduction of the ketogenic diet and topiramate (5 mg/kg/d) decreased myoclonus frequency and intensity"
      explanation: >-
        Records the observed reduction after the ketogenic diet and topiramate were
        begun together at seven months.
  evidence:
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "At 7 months, introduction of the ketogenic diet and topiramate (5 mg/kg/d) decreased myoclonus frequency and intensity"
    explanation: >-
      The single reported instance of benefit from dietary therapy in this disorder,
      confounded by the concurrent start of topiramate.
- name: Topiramate
  description: >-
    Topiramate at 5 mg/kg/d was started at seven months alongside the ketogenic diet
    in a reported case, and myoclonus frequency and intensity decreased. The
    co-initiation means neither intervention can be credited alone; the dietary arm
    is curated separately as Ketogenic Diet.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: topiramate
      term:
        id: CHEBI:63631
        label: topiramate
  target_mechanisms:
  - target: Refractory Multifocal and Generalized Seizures
    treatment_effect: INHIBITS
    description: >-
      Reduced myoclonus frequency and intensity in the reported case, confounded by
      concurrent initiation of the ketogenic diet.
    evidence:
    - reference: PMID:31709768
      reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "At 7 months, introduction of the ketogenic diet and topiramate (5 mg/kg/d) decreased myoclonus frequency and intensity"
      explanation: >-
        Records the observed reduction and the co-initiation.
  evidence:
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "At 7 months, introduction of the ketogenic diet and topiramate (5 mg/kg/d) decreased myoclonus frequency and intensity"
    explanation: >-
      The single reported instance of benefit involving topiramate in this disorder.
- name: Conventional Anti-Seizure Medication
  description: >-
    Standard anti-seizure medications are generally ineffective. Valproic acid,
    clobazam, clonazepam, and phenytoin have been reported ineffective in
    SCN1B-related cases.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  evidence:
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Epilepsy was refractory and the patient had virtually no development."
    explanation: >-
      Documents refractoriness to conventional treatment.
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Seizures were refractory to antiepileptic drugs (AEDs), including carbamazepine and clonazepam"
    explanation: >-
      Names the specific agents that failed, including the sodium-channel blocker
      carbamazepine. This documents refractoriness, not a contraindication - see the
      discussion on sodium-channel-blocker avoidance.
- name: Genetic Counseling
  description: >-
    Autosomal recessive counseling with a 25% recurrence risk per pregnancy. Carrier
    parents are unaffected by the encephalopathy but monoallelic SCN1B variants carry
    their own GEFS+ and cardiac associations, which is worth raising.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In humans, inherited heterozygous SCN1B variants have been associated with mild-to-moderate epileptic disorders within the genetic epilepsy with febrile seizures plus (GEFS+) spectrum."
    explanation: >-
      The carrier-state association that makes counseling non-trivial here.

animal_models:
- name: Scn1b-null mouse
  species: Mouse
  genotype: Scn1b homozygous null
  publication: PMID:40923316
  description: >-
    Constitutive Scn1b knockout mice have spontaneous generalized seizures from the
    second postnatal week, are ataxic, show severely altered cerebellar neuronal
    pathfinding, and die of SUDEP in 100% of cases before weaning.
  modeled_mechanisms:
  - target: Cerebellar Purkinje Cell and Interneuron Hypoexcitability
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Provides the direct electrophysiological evidence for the cerebellar arm.
    limitations: >-
      A constitutive null is a more complete lesion than the missense variants that
      cause human DEE52, and 100% pre-weaning SUDEP is far more severe than the human
      course, in which children survive for years.
    readouts:
    - name: Purkinje cell action potential threshold and repetitive firing frequency
      target: Cerebellar Purkinje Cell and Interneuron Hypoexcitability
      direction: DECREASED
      interpretation: >-
        Purkinje cells and interneurons are less excitable, not more.
      evidence:
      - reference: PMID:40923316
        reference_title: "Ataxia and cerebellar hypoexcitability in a mouse model of SCN1B-linked Dravet syndrome."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Scn1b null PCs and interneurons in cerebellar slices have increased thresholds for action potential initiation and decreased repetitive firing frequency compared with WT."
        explanation: >-
          Reports the slice electrophysiology behind this readout.
    evidence:
    - reference: PMID:40923316
      reference_title: "Ataxia and cerebellar hypoexcitability in a mouse model of SCN1B-linked Dravet syndrome."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Scn1b null mice model DS, with spontaneous generalized seizures that start in the second week of life."
      explanation: >-
        Establishes the model's seizure phenotype.
  - target: Loss of Cerebellar Motor Output
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      The mice are ataxic, matching the ataxia reported in patients.
    limitations: >-
      Mouse gait analysis and human ataxia are assessed differently, and the human
      ataxia is reported clinically without the electrophysiological attribution the
      mouse provides.
    evidence:
    - reference: PMID:40923316
      reference_title: "Ataxia and cerebellar hypoexcitability in a mouse model of SCN1B-linked Dravet syndrome."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Here, we show that Scn1b null mice are ataxic."
      explanation: >-
        Establishes the ataxic phenotype.
- name: Scn1b-c.265C>T (p.R89C) knock-in mouse
  species: Mouse
  genotype: Scn1b c.265C>T homozygous knock-in (p.R89C)
  publication: PMID:40763036
  description: >-
    Knock-in mice carrying the human DEE52 p.R89C variant have spontaneous and
    hyperthermia-induced generalized seizures with SUDEP, increased cardiomyocyte
    transient outward potassium current, ventricular fibrosis, and susceptibility to
    pacing-induced arrhythmia.
  modeled_mechanisms:
  - target: Cardiomyocyte Ionic Current Remodeling
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Carries the exact human variant, and the increased transient outward current it
      shows is reproduced in patient-derived iPSC cardiomyocytes.
    limitations: >-
      Mouse and human cardiac action potential waveforms differ critically - the
      mouse repolarizes largely through the transient outward current - so only the
      shared increase in that current can be carried across; the increased sodium and
      late sodium currents seen in human iPSC cardiomyocytes were not the mouse finding.
    readouts:
    - name: Transient outward potassium current density in cardiomyocytes
      target: Cardiomyocyte Ionic Current Remodeling
      direction: INCREASED
      interpretation: >-
        Repolarizing current is increased, altering the action potential waveform.
      evidence:
      - reference: PMID:40763036
        reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Scn1bC89/C89 mouse CMs showed increased transient outward potassium current (Ito) density and heart sections revealed ventricular fibrosis."
        explanation: >-
          Reports the current measurement behind this readout.
    evidence:
    - reference: PMID:40763036
      reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Mice with homozygous expression of the DEE52 variant Scn1b-c.265C>T, predicting p.R89C, have spontaneous and hyperthermia-induced generalized seizures and SUDEP."
      explanation: >-
        Establishes that the model reproduces the human seizure and SUDEP phenotype.
- name: Scn1b-based Dravet model mouse (subicular hyperexcitability)
  species: Mouse
  genotype: Scn1b mutant based on a human beta-1 subunit mutation
  publication: PMID:24747835
  description: >-
    A mouse model based on a human SCN1B mutation, showing region-restricted
    pyramidal neuron hyperexcitability with reduced dendritic arborization and,
    notably, no change in GABAergic interneuron firing or synaptic properties.
    Retigabine, which lowers input resistance, protected against thermal seizures.
  modeled_mechanisms:
  - target: Increased Forebrain Pyramidal Neuron Firing
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Provides the direct evidence for the regionally restricted pyramidal
      hyperexcitability arm and for its input-resistance mechanism.
    limitations: >-
      The mechanism is inferred from slice recordings in a mouse carrying one
      human-derived mutation and has not been confirmed in human neurons; regional
      restriction to subiculum and layer 2/3 may not map onto human cortical anatomy.
    readouts:
    - name: Action potential firing rate in subicular and layer 2/3 pyramidal neurons
      target: Increased Forebrain Pyramidal Neuron Firing
      direction: INCREASED
      interpretation: >-
        Pyramidal neurons in specific regions fire more, attributed to raised input
        resistance rather than altered sodium current density.
      evidence:
      - reference: PMID:24747835
        reference_title: "Reduced dendritic arborization and hyperexcitability of pyramidal neurons in a Scn1b-based model of Dravet syndrome."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "mutant subicular and layer 2/3 pyramidal neurons had increased action potential firing rates, presumably as a consequence of their increased input resistance"
        explanation: >-
          Reports the patch-clamp measurement behind this readout.
    evidence:
    - reference: PMID:24747835
      reference_title: "Reduced dendritic arborization and hyperexcitability of pyramidal neurons in a Scn1b-based model of Dravet syndrome."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Homozygous mutant mice shared phenotypic features and pharmaco-sensitivity with Dravet syndrome."
      explanation: >-
        Establishes the model's phenotypic and pharmacological validity.

experimental_models:
- name: Patient-derived iPSC cardiomyocytes (SCN1B c.265C>T)
  experimental_model_type: IPSC_DERIVED_MODEL
  description: >-
    Induced pluripotent stem cell cardiomyocytes derived from two DEE52 patients
    homozygous for SCN1B c.265C>T, used to test the cardiac arm directly in human
    cells.
  publication: PMID:40763036
  modeled_mechanisms:
  - target: Cardiomyocyte Ionic Current Remodeling
    relationship: MEASURES
    fidelity: MODERATE
    description: >-
      The only human-cell measurement of the cardiac electrophysiological consequence
      of the DEE52 genotype.
    limitations: >-
      iPSC cardiomyocytes are electrophysiologically immature relative to adult
      ventricular myocytes, so absolute current densities should not be read as adult
      human values; and the cells cannot report the structural fibrosis arm.
    readouts:
    - name: Sodium, late sodium, and transient outward potassium current densities
      target: Cardiomyocyte Ionic Current Remodeling
      direction: INCREASED
      interpretation: >-
        Multiple currents are increased in patient-derived human cardiomyocytes.
      evidence:
      - reference: PMID:40763036
        reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "Patient-derived iPSC-CMs with biallelic SCN1B-c.265C>T variant expression showed increased sodium current (INa), late INa, and Ito current densities."
        explanation: >-
          Reports the current measurements behind this readout.
    evidence:
    - reference: PMID:40763036
      reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "studied induced pluripotent stem cell cardiomyocytes (iPSC-CMs) derived from 2 SCN1B-c.265C>T DEE52 patients"
      explanation: >-
        Establishes the model and its patient provenance.

prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    Ultra-rare. Nine patients from four unrelated consanguineous families in the
    largest single report, with a handful of additional families described
    elsewhere. No formal population prevalence figure has been published.
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Only a few individuals with EIEE52 have been reported so far, and a disease-causing mechanism remains unclear."
    explanation: >-
      States the small size of the published cohort, which is what supports an
      ultra-rare class rather than a numeric rate.

discussions:
- discussion_id: controversy_interneuron_versus_pyramidal_substrate
  prompt: >-
    Does SCN1B-related DEE arise through the same GABAergic interneuron
    hypoexcitability that underlies SCN1A-related Dravet syndrome, or through a
    fundamentally different substrate of regionally restricted pyramidal neuron
    hyperexcitability driven by increased input resistance?
  kind: CONTROVERSY
  status: OPEN
  attaches_to:
  - pathophysiology#Increased Forebrain Pyramidal Neuron Firing
  - pathophysiology#Regionally Restricted Network Hyperexcitability
  - pathophysiology#Cerebellar Purkinje Cell and Interneuron Hypoexcitability
  rationale: >-
    Because SCN1B and SCN1A variants produce overlapping clinical pictures, it is
    routinely assumed that SCN1B disease works through the SCN1A mechanism - beta-1
    loss detunes Nav1.1, Nav1.1 loss impairs interneurons, interneuron failure
    disinhibits the cortex. The Scn1b mouse contradicts the middle step directly: no
    changes in firing or synaptic properties of GABAergic interneurons were observed,
    explicitly in contrast with Scn1a-based models, and the hyperexcitability was
    instead in subicular and layer 2/3 pyramidal neurons via increased input
    resistance from reduced dendritic arborization. The cerebellar work complicates
    this further rather than settling it, since there GABAergic neurons ARE
    hypoexcitable - so cell-type effects appear to be region-dependent rather than
    uniform. This matters therapeutically: the input-resistance account predicts
    benefit from a potassium channel opener, and retigabine did protect these mice
    from thermal seizures, which is not a prediction the interneuron model makes.
  evidence:
  - reference: PMID:24747835
    reference_title: "Reduced dendritic arborization and hyperexcitability of pyramidal neurons in a Scn1b-based model of Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Importantly, no changes in firing or synaptic properties of gamma-aminobutyric acidergic interneurons from mutant mice were observed, which is in contrast with Scn1a-based models of Dravet syndrome."
    explanation: >-
      The direct contradiction of the interneuron account in the SCN1B model.
  - reference: PMID:24747835
    reference_title: "Reduced dendritic arborization and hyperexcitability of pyramidal neurons in a Scn1b-based model of Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "These results suggest a novel mechanism of disease genesis in genetic epilepsy and demonstrate an effective mechanism-based treatment of the disease."
    explanation: >-
      The authors present this as a distinct disease mechanism with its own
      therapeutic prediction.
  - reference: PMID:40923316
    reference_title: "Ataxia and cerebellar hypoexcitability in a mouse model of SCN1B-linked Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "GABAergic neurons in the Scn1b null cerebellar cortex are overall hypoexcitable"
    explanation: >-
      Shows GABAergic hypoexcitability does occur in SCN1B disease, but in cerebellum
      rather than forebrain, so cell-type effects are region-dependent.
  proposed_experiments:
  - experiment_id: exp_celltype_conditional_scn1b_deletion
    name: Interneuron-restricted versus pyramidal-restricted Scn1b deletion
    description: >-
      Compare conditional Scn1b deletion restricted to forebrain GABAergic
      interneurons against deletion restricted to excitatory pyramidal neurons,
      scoring spontaneous seizure burden, thermal seizure threshold, and input
      resistance in each population, to establish which cell type is sufficient to
      produce the epilepsy phenotype.

- discussion_id: gap_cardiac_arrhythmia_in_patients
  prompt: >-
    Do children with SCN1B-related DEE actually experience clinically detectable
    cardiac arrhythmia, and would cardiac surveillance or antiarrhythmic management
    reduce SUDEP in this population?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Cardiac Arrhythmia Susceptibility
  - pathophysiology#Elevated Risk of Sudden Unexpected Death in Epilepsy
  rationale: >-
    The dual neuro-cardiac SUDEP hypothesis is well supported at the level of
    substrate: the knock-in mouse has ventricular fibrosis and pacing-inducible
    arrhythmia, and patient-derived cardiomyocytes show increased currents. What is
    missing is the clinical link. No published series reports Holter monitoring,
    ECG surveillance, or documented arrhythmia in SCN1B-DEE52 patients, so the step
    from "arrhythmogenic substrate exists" to "arrhythmia contributes to these
    children's deaths" is inference. It is actionable inference - if borne out it
    would justify cardiac surveillance in a population currently managed purely as
    neurological - which is exactly why it should not be curated as though settled.
  evidence:
  - reference: PMID:40763036
    reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Although the mechanisms of SUDEP remain unclear, we hypothesize that, in addition to seizures, SUDEP in some instances involves cardiac arrhythmias"
    explanation: >-
      The authors state the cardiac contribution as a hypothesis rather than an
      established fact.
  - reference: PMID:40763036
    reference_title: "Altered cardiac excitability and arrhythmia in models of SCN1B-linked developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "No biomarkers exist to predict the extent of SUDEP risk in individual patients other than the presence of variants in specific genes"
    explanation: >-
      Confirms the absence of any validated clinical risk marker, which is the gap.
  proposed_experiments:
  - experiment_id: exp_cardiac_surveillance_cohort_dee52
    name: Prospective cardiac surveillance in an SCN1B-DEE52 cohort
    description: >-
      Enrol genetically confirmed DEE52 patients in prospective ECG and ambulatory
      rhythm monitoring, with repolarization interval measurement and event
      correlation, to establish whether the model-predicted arrhythmia substrate
      produces detectable clinical events.

- discussion_id: mismatch_null_mouse_versus_human_missense
  prompt: >-
    How much of the Scn1b-null mouse phenotype - 100% pre-weaning SUDEP, severe
    cerebellar pathfinding failure - reflects human DEE52, given that every reported
    human genotype is missense and affected children survive for years?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Altered Cerebellar Neuronal Pathfinding
  - pathophysiology#Cerebellar Purkinje Cell and Interneuron Hypoexcitability
  rationale: >-
    Most of the mechanistic detail curated here for the cerebellar arm comes from the
    constitutive null. But the human variants are missense changes in the
    immunoglobulin loop, and at least one of them - p.R85C - reaches the cell surface
    normally, so it is not a null at the level of protein presence. The p.R125C
    variant is a functional null and the p.R89C knock-in is not, yet both cause DEE52,
    which suggests the human phenotype is reached from more than one point on the
    dose-response curve. The severe developmental pathfinding failure seen in the null
    cerebellum may therefore over-represent what a surface-expressed missense variant
    does, and no human neuropathology exists to check it against.
  evidence:
  - reference: PMID:40923316
    reference_title: "Ataxia and cerebellar hypoexcitability in a mouse model of SCN1B-linked Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Scn1b null mice model DEE52, with generalized seizures beginning in the second week of life and sudden unexpected death in epilepsy (SUDEP) in 100% of mice prior to weaning"
    explanation: >-
      Establishes the severity of the null phenotype against which human survival
      must be compared.
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "showed cell surface expression of the mutant beta1 subunit, similar to wild-type (WT)"
    explanation: >-
      Shows a human pathogenic variant that is not a protein null, unlike the mouse
      model.
  - reference: PMID:19710327
    reference_title: "A functional null mutation of SCN1B in a patient with Dravet syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "these data suggest a functional SCN1B null phenotype"
    explanation: >-
      Shows that another human variant IS a functional null, so human genotypes span
      the range rather than sitting at one point.
  proposed_experiments:
  - experiment_id: exp_knockin_allelic_series_cerebellum
    name: Cerebellar phenotype across an Scn1b knock-in allelic series
    description: >-
      Compare cerebellar pathfinding, Purkinje cell sodium currents, and ataxia across
      knock-in mice carrying surface-expressed missense variants (p.R85C, p.R89C), the
      trafficking-null p.R125C, and the constitutive null, to establish how much of
      the developmental cerebellar phenotype requires complete absence of the protein.

- discussion_id: gap_hearing_loss_mechanism
  prompt: >-
    By what mechanism does biallelic SCN1B loss produce sensorineural hearing loss -
    through beta-1's channel-modulating role in brainstem auditory pathway neurons,
    through its cell adhesion role in cochlear or auditory nerve development, or as a
    consequence of the encephalopathy itself?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Disrupted Beta-1 Immunoglobulin-Domain Cell Adhesion
  rationale: >-
    Bilateral sensorineural hearing loss with brainstem auditory pathway involvement
    is reported, but no node in this pathograph explains it, and nothing in the mouse
    literature addresses the auditory system. The two candidate arms - channel
    modulation and cell adhesion - predict different things: an adhesion-mediated
    developmental defect would be fixed and present from birth, whereas an
    excitability defect in auditory brainstem neurons might be modifiable. Because
    hearing loss in a child with no expressive development is easy to miss and
    consequential for the little communication that remains possible, whether it is
    an expected feature worth screening for is a practical question, not only a
    mechanistic one.
  evidence:
  - reference: PMID:31709768
    reference_title: "SCN1B-linked early infantile developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Auditory brainstem response (ABR) showed bilateral hearing loss."
    explanation: >-
      Documents the phenotype that currently has no mechanistic account.
  - reference: PMID:40923316
    reference_title: "Ataxia and cerebellar hypoexcitability in a mouse model of SCN1B-linked Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Non-pore-forming beta1 subunits function as channel modulators and chaperones to the plasma membrane as well as immunoglobulin superfamily cell adhesion molecules (CAMs)"
    explanation: >-
      Names the two candidate functional arms that could account for the auditory
      phenotype.
  proposed_experiments:
  - experiment_id: exp_auditory_phenotyping_scn1b_mice
    name: Auditory brainstem response phenotyping in Scn1b mouse models
    description: >-
      Measure auditory brainstem responses and cochlear histology in Scn1b-null and
      knock-in mice, and in mice carrying a variant that selectively disrupts adhesion
      while preserving channel modulation, to determine which functional arm accounts
      for the hearing loss.

- discussion_id: gap_sodium_channel_blocker_avoidance
  prompt: >-
    Should sodium-channel-blocking anti-seizure medications be avoided in
    SCN1B-related DEE, as they are in SCN1A-related Dravet syndrome, or does the
    beta-1 subunit mechanism change that calculus?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Altered Sodium Channel Voltage Dependence and Availability
  - pathophysiology#Refractory Multifocal and Generalized Seizures
  rationale: >-
    In SCN1A-related Dravet syndrome sodium-channel blockers are avoided because
    they further impair Nav1.1 in interneurons that are already underactive. The
    same reasoning is often extended to SCN1B by analogy, and the analogy is
    plausible - both lesions reduce sodium-channel function. But the Scn1b mouse
    contradicts the interneuron premise the SCN1A rule rests on, showing no
    interneuron changes and instead pyramidal hyperexcitability driven by input
    resistance. If that is the operative mechanism, the SCN1A avoidance rule does not
    transfer, and the mechanism-matched prediction from the same study points the
    other way, toward agents that lower input resistance. The published evidence
    reports only that carbamazepine failed among several drugs, which is
    refractoriness rather than harm, so the question is genuinely open and is
    curated here rather than asserted as a contraindication in the treatments block.
  evidence:
  - reference: PMID:33901312
    reference_title: "Homozygous SCN1B variants causing early infantile epileptic encephalopathy 52 affect voltage-gated sodium channel function."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Seizures were refractory to antiepileptic drugs (AEDs), including carbamazepine and clonazepam."
    explanation: >-
      The only published statement about carbamazepine here documents failure to
      control seizures, not aggravation, so it cannot support a contraindication.
  - reference: PMID:24747835
    reference_title: "Reduced dendritic arborization and hyperexcitability of pyramidal neurons in a Scn1b-based model of Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Importantly, no changes in firing or synaptic properties of gamma-aminobutyric acidergic interneurons from mutant mice were observed, which is in contrast with Scn1a-based models of Dravet syndrome."
    explanation: >-
      Undercuts the interneuron premise on which the SCN1A sodium-channel-blocker
      avoidance rule rests, which is why transfer of that rule cannot be assumed.
  - reference: PMID:24747835
    reference_title: "Reduced dendritic arborization and hyperexcitability of pyramidal neurons in a Scn1b-based model of Dravet syndrome."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The antiepileptic drug retigabine, a K+ channel opener that reduces input resistance, dampened action potential firing and protected mutant mice from thermal seizures."
    explanation: >-
      The mechanism-matched prediction from the same model, which is a different drug
      class from the one the SCN1A rule addresses.
  proposed_experiments:
  - experiment_id: exp_sodium_blocker_challenge_in_scn1b_models
    name: Sodium-channel-blocker challenge in Scn1b versus Scn1a models
    description: >-
      Compare seizure burden and thermal seizure threshold under carbamazepine or
      lacosamide in Scn1b knock-in mice against Scn1a-haploinsufficient mice, to test
      whether the aggravation seen in the SCN1A model occurs in the SCN1B model at
      all, and pair it with a retrospective review of medication exposure in
      genetically confirmed DEE52 patients.

datasets: []
📚

References & Deep Research

Deep Research

1
Claude Code ▸
SCN1B-Related Developmental and Epileptic Encephalopathy: Comprehensive Research Report
claude-haiku-4-5-20251001, claude-sonnet-5 22 citations 2026-08-19T13:25:33.319705

SCN1B-Related Developmental and Epileptic Encephalopathy: Comprehensive Research Report

1. Disease Information

Overview: SCN1B-related Developmental and Epileptic Encephalopathy (referred to in OMIM as Developmental and Epileptic Encephalopathy 52, "DEE52") is a rare, autosomal recessive, severe infantile-onset epilepsy syndrome caused by biallelic (homozygous or compound heterozygous) loss-of-function variants in SCN1B, the gene encoding the voltage-gated sodium channel β1/β1B non-pore-forming subunits. Affected infants present with refractory seizures beginning in the first months of life, global developmental delay/regression, hypotonia, and a high risk of premature death, including sudden unexpected death in epilepsy (SUDEP). Clinically, the phenotype overlaps substantially with Dravet syndrome but is generally considered more severe, since developmental impairment can precede or accompany seizure onset rather than following a period of normal development, as in classic Dravet syndrome (PMID not directly given; Aeby et al. 2019, PMC6917350).

Distinctly, heterozygous SCN1B variants (the classic example being p.Cys121Trp/C121W) cause a much milder phenotype: Genetic (Generalized) Epilepsy with Febrile Seizures Plus (GEFS+), historically labeled "GEFS+1" as the first sodium-channel-subunit gene linked to this syndrome (Wallace et al. 1998). SCN1B variants have also been separately implicated in cardiac arrhythmia syndromes, notably Brugada syndrome, reflecting the gene's dual expression in brain and heart.

Key identifiers: - Gene: SCN1B (Sodium Voltage-Gated Channel Beta Subunit 1); HGNC:10586; OMIM gene entry *600235 - DEE52 (biallelic/recessive form): OMIM #617350 — "DEVELOPMENTAL AND EPILEPTIC ENCEPHALOPATHY 52; DEE52" - GEFS+1 (heterozygous/dominant form): OMIM #604233 (GEFS+ type 1) - Suggested MONDO term: a MONDO ID mapping to OMIM:617350 (DEE52) should be confirmed via MONDO lookup at curation time, as it was not independently verified in this research pass - Chromosomal location: 19q13.11–q13.12 - Synonyms: SCN1B-related epileptic encephalopathy; Early Infantile Epileptic Encephalopathy 52 (EIEE52, older nomenclature); Dravet syndrome, SCN1B-related; DEE52

Evidence base: Information is derived from aggregated case reports and case series (fewer than a dozen families reported worldwide as of the most recent literature — Aeby et al. 2019 note this was only the "eighth reported SCN1B patient" with biallelic disease), supplemented by extensive mechanistic and mouse-model studies rather than large-cohort epidemiological/EHR data given the extreme rarity of the disorder.

2. Etiology

Disease causal factors: DEE52 is a monogenic, purely genetic disorder. It is caused by biallelic (homozygous or compound heterozygous) loss-of-function variants in SCN1B, most reported cases arising in the setting of parental consanguinity (Patino et al. 2009, PMID:19710327; Aeby et al. 2019; Muhammad et al. 2026, consanguineous Pakistani family). No environmental or infectious causal factor is implicated in the primary genetic lesion, though fever/hyperthermia is a major seizure trigger/exacerbating factor once the genetic predisposition is present (paralleling Dravet syndrome biology).

Genetic risk factors: - Homozygous or compound heterozygous SCN1B loss-of-function variants: missense (e.g., p.Arg125Cys/R125C, p.Arg85Cys/R85C, p.Arg89Cys/R89C, p.Tyr119Asp/Y119D), splice-site variants, and presumed protein-truncating variants - Consanguinity substantially raises risk given the autosomal recessive inheritance - By contrast, heterozygous SCN1B missense variants (e.g., C121W) are risk factors for the distinct, milder GEFS+ phenotype via a dominant, gain-of-function-like mechanism, and for Brugada syndrome (Watanabe et al. 2008, Scientific Reports 2014 study of 145 SCN5A-negative Brugada patients)

Environmental risk factors/triggers: Fever, vaccination-associated fever (reported as a seizure trigger in the R125C case; Patino et al. 2009), transitions in sleep state, and hot baths are reported precipitants of seizure exacerbation/status epilepticus (Aeby et al. 2019).

Protective factors: None specifically documented for SCN1B-DEE52 in the literature reviewed. In the general Dravet-spectrum literature, avoidance of hyperthermia and of sodium-channel-blocking antiepileptics is considered protective against exacerbation (see Treatment, Section 12).

Gene-environment interactions: The primary interaction is genotype (loss-of-function SCN1B) × fever/hyperthermia, which precipitates status epilepticus and is mechanistically explained by impaired β1-mediated modulation of Nav1.1 current density/inactivation kinetics being further destabilized by temperature-sensitive channel gating — directly modeled in Scn1b-null and Scn1b-c.265C>T knock-in mice, which show hyperthermia-induced generalized seizures (PMID:40763036).

3. Phenotypes

Neurological/seizure phenotypes

  • Seizure onset: Early infantile, typically 2.5–6 months of age (OMIM #617350 clinical synopsis: onset at or before age 6 months)
  • Seizure types: Multifocal myoclonus, focal (hemiclonic) seizures, generalized tonic-clonic seizures, myoclonic and hemiclonic status epilepticus (up to 8 episodes in the first 2 years in one patient; Aeby et al. 2019), fever-triggered convulsions occurring several times weekly in another patient (Patino et al. 2009)
  • EEG findings: Frequent bilateral central spikes occurring in bursts with high-voltage slow waves (Aeby et al. 2019)
  • Refractoriness: Seizures refractory to multiple standard antiepileptic drugs (valproic acid, clobazam, clonazepam, phenytoin reported ineffective; Patino et al. 2009)
  • Developmental impairment: Severe global developmental delay/psychomotor stagnation or regression; in the Aeby case, the patient was unable to hold her head up at age 5 despite social interactivity
  • Tone/motor abnormalities: Global/axial hypotonia from birth, appendicular spasticity, tetrapyramidal syndrome
  • Microcephaly: Reported in the OMIM clinical synopsis
  • Brain imaging: Nonspecific brain atrophy reported on neuroimaging (OMIM #617350)
  • Ataxia: Demonstrated mechanistically in Scn1b-null mice via cerebellar Purkinje cell hypoexcitability (Yuan et al. 2025, PMID:40923316) — a plausible human correlate given cerebellar Scn1b expression, though this specific phenotype is best documented in the mouse model rather than confirmed human cases at time of writing

Sensory phenotypes

  • Bilateral sensorineural hearing loss (~50 dB threshold), with brainstem auditory pathway involvement demonstrated by wave V loss at lower stimulus intensities (Aeby et al. 2019) — HP:0000407 (Sensorineural hearing impairment)

Cardiac phenotypes (emerging)

  • Altered cardiac excitability and arrhythmia susceptibility, demonstrated in both Scn1b-c.265C>T knock-in mice and patient-derived iPSC-cardiomyocytes (2025 JCI Insight paper, PMID:40763036) — mechanistically linking SCN1B-DEE52 to elevated SUDEP risk via a dual neuro-cardiac mechanism, analogous to findings in Dravet syndrome/SCN1A more broadly

Mortality

  • Premature death occurred in 4 of 9 patients in the original OMIM-cited cohort, at ages ranging from 7 months to 5 years (OMIM #617350)
  • Death from respiratory insufficiency secondary to aspiration pneumonia reported at 13 months in the R125C patient (Patino et al. 2009)
  • High risk of SUDEP, consistent across multiple case reports and modeled directly in mice

Suggested HPO terms

  • HP:0011097 (Epileptic encephalopathy) / HP:0002133 (Status epilepticus)
  • HP:0002123 (Generalized myoclonic seizures) / HP:0032792 (Motor seizure) / HP:0011159 (Generalized tonic-clonic seizure)
  • HP:0002071 (Abnormality of extrapyramidal motor function) / HP:0001252 (Hypotonia) / HP:0001257 (Spasticity)
  • HP:0000252 (Microcephaly)
  • HP:0007359 (Focal-onset seizure)
  • HP:0011451 (Fever-induced seizures) — captures the hyperthermia-triggering phenomenon
  • HP:0001511 (Intrauterine/global developmental delay) → HP:0011344 (Severe global developmental delay) / HP:0002376 (Developmental regression)
  • HP:0000407 (Sensorineural hearing impairment)
  • HP:0002059 (Cerebral atrophy)
  • HP:0001663 (Ventricular arrhythmia) / cardiac phenotype terms as emerging evidence matures

Quality of life impact

Case series consistently report profound impact on daily functioning: total dependence for basic care, absence of independent ambulation or head control at age 5 in the most detailed reported case, and a substantial mortality burden in early childhood — collectively representing among the most severe ends of the DEE spectrum.

4. Genetic/Molecular Information

Causal gene: SCN1B (HGNC:10586; OMIM *600235), encoding two splice isoforms, β1 and β1B, non-pore-forming auxiliary subunits of voltage-gated sodium channels.

Reported pathogenic biallelic variants (DEE52): | Variant (cDNA/protein) | Zygosity | Source | |---|---|---| | c.373C>T, p.Arg125Cys (R125C) | Homozygous | Patino et al. 2009, PMID:19710327 (Moroccan consanguineous family) | | c.253C>T, p.Arg85Cys (R85C) | Homozygous | Aeby et al. 2019, PMC6917350 | | c.265C>T, p.Arg89Cys (R89C) | Homozygous | 2025 cardiac excitability study, PMID:40763036 | | p.Tyr119Asp (Y119D) | Homozygous | Referenced in OMIM #617350 family series | | Homozygous splice-site variant | Homozygous | Referenced in OMIM #617350 family series; also a novel homozygous splice-site variant reported in a consanguineous Pakistani family (Muhammad et al., Mol Genet Genomic Med 2026) |

Heterozygous variant causing GEFS+ (distinct phenotype): - c.363T>G, p.Cys121Trp (C121W) — the founding GEFS+ mutation (Wallace et al. 1998), disrupting a critical intramolecular disulfide bond in the extracellular β1 immunoglobulin (Ig) loop domain. Shown to be an ancient founder variant shared by ≥14 unrelated GEFS+ families across Australia/UK/US via a common ~260 kb ancestral haplotype persisting for roughly 800 years (Grinton et al. 2022). Penetrance estimated at ~70% (12/44 studied carriers asymptomatic).

Variant classification (ACMG/AMP framework): Recessive DEE52 variants are typically classified pathogenic/likely pathogenic based on: (1) absence/near-absence in population databases (gnomAD), (2) segregation with disease in consanguineous pedigrees, (3) functional evidence of loss of β1 modulatory function, and (4) recurrence across unrelated families at conserved residues in the extracellular Ig-loop domain (multiple independent Arg→Cys substitutions at Arg85, Arg89, Arg125 cluster in this domain).

Functional consequences — mechanistically well-characterized loss of function: - p.Arg125Cys: Markedly reduced cell-surface trafficking despite normal total cellular protein expression — biotinylation assays showed only ~6.7% of wild-type β1 levels reaching the plasma membrane; the mutant failed to modulate sodium current properties when co-expressed with Nav1.1 in mammalian cells, consistent with a functional null allele (Patino et al. 2009, PMID:19710327) - p.Arg85Cys: By contrast, this variant trafficks normally to the plasma membrane (confirmed via biotinylation and confocal colocalization with wheat germ agglutinin), yet still fails to confer the wild-type β1 effect of increasing transient/persistent Nav1.1 current density and accelerating fast inactivation kinetics — demonstrating that loss of function can occur independent of trafficking defects, via impaired protein-protein modulatory interaction with the α subunit (Aeby et al. 2019) - Scala et al. 2021 (Epilepsia, PMID pending exact ID — study of 9 patients/4 families) further characterized multiple SCN1B DEE52 variants' effects on voltage-gated sodium channel function, reinforcing loss-of-function as the convergent mechanism across the allelic series - By contrast, the heterozygous C121W GEFS+ variant produces a distinct gain-of-function effect in some assay systems ("β1-C121W Is Down But Not Out," Reid et al./Isom lab, J Neurosci 2016, PMID:27277800) — underscoring that dominant GEFS+ and recessive DEE52 variants, though both disrupting normal β1 structure/function, produce mechanistically and clinically distinct outcomes

Modifier genes: None specifically established for SCN1B-DEE52; by analogy to Dravet syndrome (SCN1A), genetic background may modulate severity, but this has not been directly studied for SCN1B.

Epigenetic information: Not established/reported for this disorder.

Chromosomal abnormalities: Not a recognized mechanism for this disorder — pathogenic variants are point mutations/small indels/splice variants rather than large structural rearrangements in the reported literature.

Suggested gene/protein ontology terms: - Gene: hgnc:10586 (SCN1B) - GO Molecular Function: voltage-gated sodium channel activity (GO:0005248); regulates ion channel activity - GO Biological Process: regulation of sodium ion transmembrane transporter activity; regulation of action potential

5. Environmental Information

Environmental factors: No toxin, radiation, or occupational exposure is implicated as a primary cause. Fever/hyperthermia is the dominant environmental modulator of disease expression — precipitating status epilepticus in patients and directly reproduced in Scn1b-null and Scn1b-c.265C>T knock-in mice as hyperthermia-induced generalized seizures.

Lifestyle factors: Hot baths and sleep-state transitions are reported seizure triggers (Aeby et al. 2019); these parallel well-established Dravet syndrome trigger profiles.

Infectious agents: Not a direct cause; febrile infections act as nonspecific triggers of hyperthermia-related seizure exacerbation rather than being disease-causal. One case report notes seizure onset temporally associated with post-vaccination fever (Patino et al. 2009), reflecting the fever trigger rather than any vaccine-specific pathogenic mechanism.

Suggested ECTO term: exposure to elevated body temperature / febrile illness as a seizure trigger (specific ECTO CURIE to be confirmed at curation time).

6. Mechanism / Pathophysiology

Causal chain summary: Biallelic SCN1B loss-of-function variant → loss of normal β1/β1B-mediated modulation of voltage-gated sodium channel α subunits (principally Nav1.1/SCN1A, also relevant to Nav1.6/SCN8A and cardiac Nav1.5/SCN5A) → failure to normally increase Na+ current density and to normally accelerate fast inactivation kinetics → altered excitability in specific neuronal populations (notably GABAergic interneurons, whose relative hypoexcitability is the presumptive substrate of Dravet-spectrum disinhibition, paralleling the SCN1A/Nav1.1 disease model) and cerebellar Purkinje cells → network hyperexcitability, hypersynchrony, and hyperthermia-sensitized seizure threshold → recurrent seizures, status epilepticus, and progressive/associated developmental encephalopathy; separately, altered cardiomyocyte excitability (β1 also regulates cardiac Na+, K+ currents and Ca2+ handling) → atrial/ventricular arrhythmia susceptibility → contributes to SUDEP risk via a dual neuro-cardiac mechanism.

Molecular pathways/protein function: β1/β1B are non-pore-forming, single-transmembrane-domain auxiliary subunits with an extracellular immunoglobulin (Ig)-like loop domain. Beyond channel gating modulation, β1 subunits function as cell adhesion molecules (interacting with contactin, neurofascin, ankyrin, tenascin) and participate in regulated intramembrane proteolysis (via BACE1 and γ-secretase cleavage) that generates an intracellular domain capable of influencing gene transcription — giving β1 a non-canonical signaling role beyond direct channel modulation (OMIM #600235 function summary; Frontiers 2018 review, PMC5924814).

Cellular processes: Altered neuronal excitability (excitatory/inhibitory imbalance); reported "excitatory and inhibitory neuron defects" in a Scn1b-linked EIEE52 mouse model (PMC7664274); cerebellar granule neuron and Purkinje cell pathfinding/excitability defects (Yuan et al. 2025); cardiomyocyte electrical remodeling and structural fibrosis (increased transient outward K+ current density and ventricular fibrosis reported in Scn1b-mutant mice).

Tissue damage mechanisms: Not a primary structural/degenerative disease mechanism; pathology is predominantly functional/electrophysiological (channelopathy) rather than driven by oxidative stress, ischemia, or classic fibrotic/necrotic injury, though secondary cardiac fibrosis has been reported in mouse models.

Biochemical abnormality: Core defect is an ion channel auxiliary subunit deficiency/dysfunction — impaired Na+ channel modulation (reduced peak/persistent current, altered inactivation kinetics) rather than a classical enzyme deficiency.

Molecular profiling / advanced technologies: - Model-organism transcriptomics: Scn1b-null mice show altered Scn1a mRNA expression normalized toward wild-type levels upon AAV-mediated β1 gene replacement therapy (PMC11870736), suggesting a downstream transcriptional consequence of β1 loss on the primary Dravet gene itself - iPSC-cardiomyocyte modeling: iPSC-CMs derived from SCN1B-c.265C>T DEE52 patients were used to directly assess human cardiac electrophysiological consequences of the disease genotype (PMID:40763036) - Single-cell/cell-type-specific mouse genetics: Purkinje-cell-specific conditional Scn1b deletion mice recapitulate a DEE-like phenotype, isolating the cerebellar contribution to the disease (bioRxiv 2024.11.19.624370)

Causal chain — upstream vs. downstream: 1. Upstream (molecular): SCN1B biallelic LOF variant → loss of β1 protein function/trafficking 2. Intermediate (cellular): Impaired Nav channel modulation in interneurons, pyramidal neurons, Purkinje cells, and cardiomyocytes 3. Downstream (tissue/organism): Cortical/cerebellar network hyperexcitability + cardiac arrhythmia substrate 4. Clinical: Refractory epilepsy, status epilepticus, developmental encephalopathy, ataxia, cardiac arrhythmia, SUDEP

Suggested GO terms: GO:0086010 (membrane depolarization during action potential); GO:0035725 (sodium ion transmembrane transport); GO:0086002 (cardiac muscle cell action potential involved in contraction) Suggested CL terms: CL:0000617 (GABAergic interneuron); CL:0000121 (Purkinje cell); CL:0000746 (cardiac muscle cell)

7. Anatomical Structures Affected

Organ level: - Primary: Central nervous system (cerebral cortex, cerebellum, brainstem) - Secondary: Cardiovascular system (increasingly recognized — atrial/ventricular arrhythmia substrate); auditory system (sensorineural hearing loss, likely brainstem auditory pathway); respiratory system (secondary complication — aspiration pneumonia leading to fatal respiratory insufficiency reported) - Body systems: Nervous system (primary); cardiovascular system (emerging); ear/audiovestibular system

Tissue/cell level: - Cerebral cortical pyramidal neurons and GABAergic interneurons (CL:0000598 pyramidal neuron; CL:0000617 GABAergic interneuron) - Cerebellar Purkinje cells and granule neurons (CL:0000121 Purkinje cell; CL:0000120 granule cell) - Cardiomyocytes (CL:0000746) - Cochlear/brainstem auditory pathway neurons (implicated by ABR wave V findings)

Subcellular level: Plasma membrane (site of Nav channel complex and β1 trafficking; GO:0005886 plasma membrane); the Ig-loop extracellular domain of β1 mediates both channel modulation and cell-adhesion interactions at the membrane surface.

Localization/UBERON suggestions: UBERON:0000955 (brain); UBERON:0002037 (cerebellum); UBERON:0001851 (cortex); UBERON:0000948 (heart); UBERON:0001846 (auditory brainstem structures, or more specific brainstem term)

Lateralization: Bilateral involvement is typical (bilateral central EEG spikes; bilateral sensorineural hearing loss).

8. Temporal Development

Onset: Early infantile — typically 2.5 to 6 months of age; OMIM #617350 specifies onset "at or before age 6 months." Hypotonia may be present from birth, preceding overt seizure onset in some cases (Aeby et al. 2019), supporting an "encephalopathy" framing (developmental impairment intrinsic to the genotype) rather than purely "epileptic encephalopathy" (impairment secondary to seizures).

Onset pattern: Acute/subacute onset of seizures against a background of congenital or very-early hypotonia.

Progression: Progressive/severe — psychomotor stagnation or regression is characteristic; disease course is chronic and typically lifelong for survivors, with substantial early mortality (4/9 in the OMIM-cited series died between 7 months and 5 years).

Disease course pattern: Recurrent, refractory seizures with recurrent status epilepticus episodes (fever/temperature-transition triggered), interspersed with variable interictal function; not classically "relapsing-remitting" but rather chronically active with periodic severe exacerbations.

Critical periods: Mouse model data strongly implicate a narrow neonatal therapeutic window — AAV-mediated β1 gene replacement was dramatically effective when administered at postnatal day 2 (P2) but completely ineffective at P10, with P10-treated null mice dying at the same P16–P25 timeframe as untreated animals (PMC11870736). This suggests an analogous early-postnatal critical window may exist in human disease-modifying intervention, though this remains speculative for humans given current biallelic LOF (rather than replaceable single-variant) genotypes.

9. Inheritance and Population

Epidemiology: DEE52 is exceptionally rare — fewer than 10 families/patients had been reported in the literature as of the most recent detailed case series (Aeby et al. 2019 describes the "eighth reported SCN1B patient" with biallelic disease), with additional isolated cases and small series published subsequently (e.g., a 2026 consanguineous Pakistani family report). No formal prevalence or incidence estimate exists; it is an ultra-rare/orphan disease with only case-report-level epidemiological data available.

Inheritance pattern: Autosomal recessive for DEE52 (biallelic SCN1B variants) — distinct from the autosomal dominant inheritance of heterozygous SCN1B-related GEFS+.

Penetrance: For the recessive DEE52 form, penetrance appears high/complete in reported homozygotes (all reported biallelic carriers manifest disease). For the heterozygous GEFS+ C121W founder variant, penetrance is estimated at ~70% (12/44 carriers unaffected; Grinton et al. 2022), demonstrating markedly different penetrance behavior between the two allelic classes.

Expressivity: Variable within GEFS+ families (ranging from simple febrile seizures to severe epileptic encephalopathy phenotypes are described broadly for GEFS+ spectrum disorders); DEE52 case reports show more uniform severe presentation, though phenotype severity (developmental impact, presence/absence of hearing loss, cardiac involvement) varies somewhat across the small number of reported cases.

Genetic anticipation: Not reported/applicable (not a repeat-expansion disorder).

Germline mosaicism: Not specifically documented for SCN1B in the literature reviewed.

Founder effects: Well-documented for the heterozygous C121W GEFS+ variant, traced to a shared ancestral haplotype (~260 kb) persisting approximately 800 years across geographically dispersed families (Australia, UK, US) (Grinton et al. 2022) — a notable example of a disease-causing founder mutation under only weak negative selection given incomplete penetrance and generally mild phenotype in most carriers.

Consanguinity role: Central to DEE52 — the majority of reported biallelic cases arise in consanguineous pedigrees (Moroccan family, Patino et al. 2009; additional consanguineous families in subsequent reports), consistent with the rarity of the recessive allele requiring homozygosity by descent.

Carrier frequency: Not established in population databases; given ultra-rarity of reported pathogenic biallelic genotypes, carrier frequency for specific DEE52-causing alleles is presumed very low/population-specific (consistent with founder or private variants in consanguineous kindreds), though a precise gnomAD-derived carrier frequency was not identified in this research pass and should be checked directly in gnomAD at curation time.

Population demographics: Reported cases span diverse populations (Moroccan, and other consanguineous kindreds internationally, including at least one Pakistani family), consistent with a recessive disorder whose expression is driven by consanguinity/homozygosity rather than population-specific founder effects (in contrast to the heterozygous GEFS+ C121W founder variant, which shows a specific multi-national but genealogically linked distribution).

Sex ratio: Not specifically reported as skewed in the literature reviewed (autosomal gene, no evidence of sex-specific penetrance differences documented).

10. Diagnostics

Clinical tests: - EEG: Bilateral central spikes in bursts with high-voltage slow waves; ictal recordings during status epilepticus episodes - Auditory brainstem response (ABR): Documents sensorineural hearing loss and brainstem pathway involvement (wave V loss at lower intensities) — recommended given the reported association - Brain MRI: Nonspecific atrophy may be seen; used to exclude structural/acquired causes - Cardiac evaluation: Given emerging arrhythmia risk, ECG/Holter monitoring and cardiology referral are reasonable given the mechanistic overlap with Brugada-spectrum SCN1B disease and direct evidence of arrhythmia substrate in disease models

Genetic testing approach: - Recommended: Epilepsy gene panel testing (including SCN1A, SCN1B, SCN2A, SCN8A, GABRG2, and other DEE-associated genes) or whole exome/genome sequencing, particularly important given that SCN1B-DEE52's clinical presentation can closely mimic SCN1A-Dravet syndrome — making single-gene SCN1A testing alone insufficient - Single-gene testing: Reasonable when SCN1B is specifically suspected (e.g., consanguinity, prior family history, or after negative SCN1A testing in a Dravet-like presentation) - Segregation analysis: Parental testing to confirm biallelic inheritance (heterozygous carrier parents) is standard confirmatory practice in reported cases - Chromosomal microarray/karyotype: Not primarily indicated, as the disease mechanism is point variant/small lesion rather than copy-number or structural

Clinical criteria: No formal consensus diagnostic criteria specific to SCN1B-DEE52 exist (given its rarity); diagnosis relies on genetic confirmation in the context of a Dravet-like or early infantile DEE clinical picture with refractory infantile-onset seizures, fever sensitivity, and developmental impairment.

Differential diagnosis: SCN1A-related Dravet syndrome/DEE (most important differential, given phenotypic overlap); other DEE genes (SCN2A, SCN8A, KCNQ2, STXBP1, CDKL5, PCDH19); other causes of early infantile epileptic encephalopathy with hypotonia.

Screening: No population-based newborn screening applies given ultra-rarity; genetic counseling and carrier screening are relevant in consanguineous families or those with a previously affected child, and prenatal/preimplantation genetic testing may be offered once a familial variant is identified.

11. Outcome/Prognosis

Mortality: Substantial — 4 of 9 patients in the OMIM-cited cohort died, at ages 7 months to 5 years; a specific fatal case (respiratory insufficiency from aspiration pneumonia) occurred at 13 months (Patino et al. 2009). SUDEP risk is emphasized across multiple sources, increasingly attributed to a combined neuro-cardiac mechanism given 2025 evidence of cardiac excitability abnormalities in both mouse models and patient-derived iPSC-cardiomyocytes.

Morbidity/function: Survivors experience profound, persistent neurodevelopmental impairment — in the most detailed reported case, the patient remained unable to hold her head up at age 5 despite treatment-related seizure improvement, illustrating that seizure control alone does not equate to developmental rescue.

Complications: Refractory status epilepticus (recurrent, sometimes >8 episodes in early childhood); aspiration pneumonia/respiratory compromise; sensorineural hearing loss; presumptive cardiac arrhythmia risk.

Recovery potential: Poor for the developmental component even with seizure control — fenfluramine treatment achieved seizure freedom from status epilepticus in one reported case, but "motor and cognitive development remained severely impaired despite seizure improvement" (Aeby et al. 2019), underscoring that this is a true developmental and epileptic encephalopathy rather than a purely seizure-driven regression.

Prognostic factors: Early treatment/seizure control (associated with reduced status epilepticus frequency, though not necessarily improved developmental outcome); presence of cardiac involvement (plausibly linked to elevated mortality risk, though not yet formally quantified in humans).

12. Treatment

Pharmacotherapy — general principles: Because the underlying mechanism is loss of function (paralleling SCN1A-Dravet biology), sodium channel blocking antiepileptics are contraindicated/relatively contraindicated, as further pharmacological sodium channel inhibition can aggravate seizures. This includes carbamazepine, and by extension the broader sodium-channel-blocker class used cautiously or avoided (phenytoin was tried without success in the R125C case, consistent with this principle).

Reported effective/attempted therapies: - Fenfluramine: Documented as effective in one reported SCN1B-DEE52 case (started at 28 months, 0.6 mg/kg/day), achieving significant reduction in seizure frequency and complete resolution of status epilepticus episodes through 2-year follow-up (Aeby et al. 2019) — consistent with fenfluramine's established efficacy in Dravet-spectrum sodium-channelopathy epilepsies more broadly (NCIT: pharmacotherapy; specific agent term applicable — fenfluramine) - Valproic acid, clobazam, clonazepam, phenytoin: Reported as ineffective/refractory in at least one severe case (Patino et al. 2009) — standard broad-spectrum antiepileptics used per typical DEE/Dravet-spectrum protocols, with variable individual response

Advanced/experimental therapeutics: - Gene replacement therapy (preclinical, mouse model): AAV vector carrying β1 subunit cDNA, delivered via bilateral intracerebroventricular injection, dramatically effective when administered neonatally (P2) in Scn1b-null mice — reducing seizure severity/duration, preventing hyperthermia-induced seizures, normalizing Scn1a mRNA expression, and extending survival past P100 versus 100% mortality by P21 in untreated animals. Critically, the same therapy was ineffective when delayed to P10 (juvenile timing), with treated animals dying in the same window as untreated controls — highlighting a narrow critical treatment window (2025, PMC11870736). This remains a preclinical proof-of-concept; the authors note that actual human DEE52 patients typically express mutant (rather than fully absent) β1 protein, so translational applicability requires further study. - No SCN1B-specific approved gene therapy, ASO, or targeted molecular therapy currently exists in clinical use; management otherwise follows general Dravet-spectrum/DEE supportive and pharmacological principles (e.g., stiripentol, cannabidiol, and other agents used in Dravet syndrome, by extrapolation, though not specifically documented for SCN1B-DEE52 in the sources reviewed here).

Supportive care: Fever management/avoidance of hyperthermia triggers; management of status epilepticus per standard protocols; nutritional/respiratory support given aspiration risk; multidisciplinary developmental/rehabilitative therapies (physical, occupational, speech) for the severe global developmental impairment.

Suggested NCIT terms: NCIT:C15986 (Pharmacotherapy) as the generic action term, with therapeutic_agent bound to specific agents (e.g., fenfluramine — CHEBI term to be verified) where documented; NCIT:C15238 (Gene Therapy) for the preclinical AAV approach.

13. Prevention

Primary prevention: Genetic counseling for consanguineous families or those with a prior affected child is the principal preventive strategy, given autosomal recessive inheritance; prenatal diagnosis or preimplantation genetic testing can be offered once the familial pathogenic variant(s) are identified.

Secondary prevention: Early genetic diagnosis in an infant presenting with early infantile refractory seizures and hypotonia enables prompt avoidance of contraindicated sodium-channel-blocking antiepileptics, potentially limiting iatrogenic seizure exacerbation.

Screening: No population-level newborn screening program exists for this ultra-rare condition; targeted carrier screening is relevant in populations/families with known consanguinity or a prior affected relative.

Behavioral interventions: Fever avoidance/aggressive antipyretic management and avoidance of known seizure triggers (hot baths, rapid sleep-state transitions) represent practical risk-reduction measures analogous to Dravet syndrome management, though not formally studied as a "prevention" strategy specific to SCN1B-DEE52.

Public health/prophylaxis: Not applicable at a population level given disorder rarity; management is entirely individualized/family-based.

14. Other Species / Natural Disease

No naturally occurring SCN1B-associated disease has been reported in non-human species (e.g., companion animals or wildlife) in the literature reviewed. All animal data derive from engineered mouse models (see Section 15) rather than spontaneously occurring veterinary disease. Orthologous gene: mouse Scn1b (MGI:98247, "sodium channel, voltage-gated, type I, beta"), located on mouse chromosome 7, with well-conserved function across mammals as demonstrated by the strong phenotypic concordance between mouse knockout models and human disease.

15. Model Organisms

Mouse models (the dominant model system for this disease):

  1. Scn1b-null (knockout) mice — the foundational model (Isom laboratory, University of Michigan): recapitulate spontaneous generalized seizures beginning in the second postnatal week, increased hyperthermia-induced seizure sensitivity, ataxia, failure to thrive, cardiac arrhythmia, and SUDEP, closely mirroring the human DEE52/Dravet-like phenotype. Mice die by approximately postnatal day 21 (P21) without intervention.
  2. Cerebellar mechanism: Purkinje cells and interneurons show increased action-potential-initiation thresholds and decreased repetitive firing frequency; reduced transient and resurgent sodium current densities in Purkinje cells underlie the ataxic phenotype (Yuan et al. 2025, JCI Insight, PMID:40923316)
  3. Cardiac phenotype: altered cardiomyocyte excitability, atrial/ventricular arrhythmia susceptibility, sinoatrial node dysfunction and atrial fibrillation in neonatal Scn1b-null mice, increased transient outward K+ current density, and ventricular fibrosis; altered cardiac energetics also reported (multiple JCI Insight/Cardiovascular Research papers, 2024–2025)

  4. Hippocampal circuit-level: complex synaptic and intrinsic interactions disrupt hippocampal input/output function (bioRxiv 2023)

  5. Scn1b-c.265C>T (p.R89C) knock-in mice — a patient-variant-specific knock-in model of DEE52, showing spontaneous and hyperthermia-induced generalized seizures and SUDEP, used alongside patient-derived iPSC-cardiomyocytes to directly link the human pathogenic genotype to cardiac excitability abnormalities (PMID:40763036, 2025)

  6. Scn1b-C121W mice — model the heterozygous GEFS+ variant rather than DEE52; shown to produce a "deleterious gain-of-function" electrophysiological effect distinct from the biallelic loss-of-function DEE52 mechanism (Reid/Isom lab, J Neurosci 2016, PMID:27277800)

  7. Purkinje-cell-specific conditional Scn1b knockout mice — a novel cell-type-restricted model isolating the cerebellar contribution to the DEE phenotype (bioRxiv 2024.11.19.624370)

Model characteristics — phenotype recapitulation: The Scn1b-null and knock-in mouse models recapitulate the core human triad of (1) treatment-refractory, hyperthermia-sensitive seizures, (2) high premature mortality/SUDEP, and (3) (increasingly) cardiac electrical abnormality — making them high-fidelity models for mechanistic and preclinical therapeutic studies (e.g., the AAV gene-replacement study, PMC11870736). Limitation: full Scn1b-null mice model complete absence of β1, whereas most human DEE52 patients express a mutant (mistrafficked or non-functional but present) protein rather than a true null — a translational caveat explicitly noted by the gene-therapy study authors.

Applications: These models have been used to study seizure semiology and hyperthermia sensitivity, cerebellar/ataxia mechanisms, cardiac arrhythmogenesis and SUDEP mechanisms, hippocampal circuit dysfunction, and to test AAV-based gene replacement as a proof-of-concept disease-modifying therapy.

Resources: MGI (Scn1b, MGI:98247) for allele/strain records; the Isom laboratory (University of Michigan) is the principal source of Scn1b-null and knock-in mouse lines cited across this literature.

Summary of Key Ontology Term Suggestions for KB Curation

Category Suggested term(s)
Disease OMIM:617350 (DEE52); confirm MONDO ID at curation time
Gene hgnc:10586 (SCN1B)
Phenotypes (HP) Status epilepticus, Myoclonic seizures, Focal seizures, Hypotonia, Microcephaly, Sensorineural hearing impairment, Global developmental delay, Developmental regression, Fever-induced seizures
Cell types (CL) GABAergic interneuron, Purkinje cell, cardiac muscle cell
Anatomy (UBERON) brain, cerebellum, cerebral cortex, heart
GO processes sodium ion transmembrane transport, membrane depolarization during action potential
Treatment (NCIT) Pharmacotherapy (NCIT:C15986) with fenfluramine as therapeutic_agent; Gene Therapy (NCIT:C15238) for the preclinical AAV approach

Notes on Evidence Gaps

  • No formal population prevalence/incidence figure exists; the disease is characterized entirely through case reports/small series (fewer than ~10 reported families).
  • The MONDO CURIE for DEE52 was not independently verified in this research pass and should be confirmed via direct MONDO/OAK lookup before KB entry.
  • Cardiac phenotype data in humans (as opposed to mouse/iPSC models) remain preliminary; direct clinical arrhythmia documentation in SCN1B-DEE52 patients was not identified in the sources reviewed, though the mechanistic and model-organism evidence for cardiac involvement is substantial and recent (2024–2025).
  • The exact PMID for the Scala et al. 2021 Epilepsia functional-variant study and for the 2025 "Altered cardiac excitability" JCI Insight paper's companion abstract details should be independently confirmed (PMID:40763036 was identified via search but full abstract text could not be directly retrieved due to access restrictions).

Sources: - SCN1B‐linked early infantile developmental and epileptic encephalopathy (Aeby et al. 2019, Ann Clin Transl Neurol) - SCN1B‐linked early infantile DEE — full text, PMC6917350 - OMIM #617350 — Developmental and Epileptic Encephalopathy 52 - OMIM *600235 — SCN1B gene - A Functional Null Mutation of SCN1B in a Patient with Dravet Syndrome (Patino et al. 2009, J Neurosci) — PMC2749953 - A functional null mutation of SCN1B... — PubMed PMID:19710327 - Altered cardiac excitability and arrhythmia in models of SCN1B-linked DEE — PubMed PMID:40763036 - Altered cardiac excitability and arrhythmia in models of SCN1B-linked DEE — PMC12487680 - Ataxia and cerebellar hypoexcitability in a mouse model of SCN1B-linked Dravet syndrome — PubMed PMID:40923316 - Ataxia and cerebellar hypoexcitability — PMC12487675 - A novel mouse model for DEE by Purkinje cell-specific deletion of Scn1b (bioRxiv 2024) - Neonatal but not juvenile gene therapy reduces seizures and prolongs lifespan in SCN1B–Dravet syndrome mice — PMC11870736 - β1-C121W Is Down But Not Out: Epilepsy-Associated Scn1b-C121W Results in a Deleterious Gain-of-Function — PMC4899524 - β1-C121W Is Down But Not Out — PubMed PMID:27277800 - The millennium variant – SCN1B, gene validity, and GEFS+ (Beyond the Ion Channel blog, discussing Grinton et al. 2022 founder haplotype) - SCN1B Genetic Variants: A Review of the Spectrum of Clinical Phenotypes and a Report of Early Myoclonic Encephalopathy — PMC9600564 - Generalized epilepsy with febrile seizures plus: Mutation of the sodium channel subunit SCN1B — Neurology - SCN1B gene variants in Brugada Syndrome: a study of 145 SCN5A-negative patients — Scientific Reports - Voltage-Gated Sodium Channel β1/β1B Subunits Regulate Cardiac Physiology and Pathophysiology — PMC5924814 - Identification of a Novel Homozygous SCN1B Splice-Site Variant in a Consanguineous Family with Early-Onset Epilepsy — Molecular Genetics & Genomic Medicine (2026) - Scn1b MGI Mouse Gene Detail — MGI:98247 - SCN1B Gene — GeneCards

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome Count
References checked 16
Resolved 16
Unresolved (possible confabulation) 0
Unverifiable 0
References weighed for topical relevance 16
On topic 14
Off topic 0

All extracted references resolved successfully.