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Mappings

MONDO

MONDO:0030856 developmental and epileptic encephalopathy 89

MONDO:0030856 is the DEE 89 concept, xrefed to OMIM:619124 and carrying the RO:0004003 causal-gene relationship to HGNC:4092 (GAD1).

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Inheritance

1

Autosomal recessive inheritance HP:0000007

DEE 89 is autosomal recessive. Affected individuals carry biallelic loss-of-function GAD1 variants; the founding cohort was drawn from six independent consanguineous families, and subsequent reports have been homozygous or compound heterozygous.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:32282878 SUPPORT Human Clinical

"Here we describe a new syndromic developmental and epileptic encephalopathy caused by bi-allelic loss-of-function variants in GAD1, as presented by 11 patients from six independent consanguineous families."

Establishes biallelic (recessive) GAD1 loss of function as the cause, in consanguineous pedigrees.

PMID:32705143 SUPPORT Human Clinical

"Here we present six affected individuals from six unrelated families, carrying bi-allelic GAD1 variants"

Independent replication of biallelic GAD1 inheritance in six further families.

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Discussions and Knowledge Gaps

10

Do GAD1 missense variants genuinely spare palatal and ventral wall development, and if so is that because they retain residual decarboxylase activity above a developmental threshold that truncating alleles fall below?

KNOWLEDGE GAP OPEN gap_dee89_missense_sparing_of_malformations

Attached to

pathophysiology#Failure of Palatal Shelf Elevation pathophysiology#Impaired GABA-Dependent Fetal Motor Signaling pathophysiology#Impaired Retraction of Physiological Umbilical Hernia

The 2023 published-case comparison reported no cleft palate or omphalocele among missense cases, but the sample was small and enzyme activity was not quantified for the alleles. A residual-activity threshold is a testable explanation, not an established allelic subtype or prognosis.

Proposed experiments

Residual decarboxylase activity of patient GAD1 missense alleles

exp_dee89_gad1_missense_residual_activity

Express the reported missense alleles alongside truncating alleles and wild type, and measure glutamate decarboxylase activity and GABA production, to test whether the missense alleles retain measurable residual activity.

Show evidence (1 reference)

PMID:37029735 SUPPORT Other

"the comparison of clinical symptoms between patients with missense and truncating mutations did not show any significant clinical difference, except that patients with missense mutations did not show cleft palates or omphaloceles."

This is a small published-case comparison, not a systematic genotype-stratified cohort or enzyme assay.

Can any Gad1-loss animal model inform the neurological arm of DEE 89, given that the mouse null dies of cleft palate before an epilepsy phenotype can emerge and the surviving rat null has a mechanistically different seizure type?

HUMAN MODEL MISMATCH OPEN mismatch_dee89_gad1_null_mouse_neonatal_lethality

Attached to

pathophysiology#Early-Onset Epileptic Seizures pathophysiology#Neuronal Hyperexcitability and Hypersynchrony

Gad1-null mice die neonatally, limiting postnatal epilepsy assessment. Surviving null rats provide a neurological model with frequent spike-wave discharges from about two months, but no overt convulsive seizures in the study. Their EEG pattern, retained stimulus responsiveness and paradoxical valproate response differ from human neonatal spasms and suppression-burst. They inform GAD1 network biology without directly reproducing the human seizure syndrome.

Proposed experiments

Palate-rescued conditional Gad1 mouse with neonatal EEG

exp_dee89_palate_rescued_gad1_mouse_eeg

Generate a Gad1 null with palatal development rescued (for example by tissue-restricted expression), so that homozygotes survive the neonatal period, and record EEG through the neonatal and infantile period to establish whether a suppression-burst and spasm phenotype develops.

Show evidence (2 references)

PMID:32705143 SUPPORT Other

"as Gad1-/- mice die neonatally of severe cleft palate, it has not been possible to determine any potential neurological dysfunction"

States the inaccessibility of the neurological phenotype in the mouse null.

PMID:37830095 SUPPORT Model Organism

"VPA treatment alleviated SWD symptoms in control rats, however, counterintuitively exacerbated the symptoms in Gad1 (-/-) rats."

The rat null's paradoxical drug response illustrates why its pharmacology cannot be transferred to patients.

Does starting vigabatrin plus a ketogenic diet in the first weeks after genetic diagnosis change developmental outcome in DEE 89, or only seizure frequency?

KNOWLEDGE GAP OPEN gap_dee89_early_combination_therapy_and_developmental_outcome

Attached to

pathophysiology#Developmental Encephalopathy pathophysiology#GABA Depletion

One infant started on the combination in the second month of life had seizures stop within two days and normal growth and psychomotor development at 7 months, which is remarkable against a cohort in which every patient with a neonatal burst-suppression EEG had profound delay. But a second patient on the same combination, with unreported treatment-start age, remained refractory with severe delay, and the commentary authors explicitly caution against generalizing from a single case. Because the disorder is ultra-rare and a critical treatment window has not been established, the question is unlikely to be settled by a conventional trial and needs a prospective registry with a pre-specified developmental endpoint. There is also a mechanistic objection that any such registry would have to stratify for. Vigabatrin works by blocking GABA catabolism, so it can only spare GABA that is being made; where the variant abolishes GAD67 activity there is little to spare, and the 2023 review argues on that basis that vigabatrin is not a suitable solution for severe-reduction or complete-loss alleles. That makes residual enzyme activity - the same quantity the allelic knowledge gap in this entry asks about - the plausible determinant of who responds, and it is not measured in any reported patient. The same review notes that oral GABA does not cross the blood-brain barrier but that brain-penetrant GABA derivatives might, which is the alternative route if the catabolism-blocking rationale really does fail at low residual activity.

Proposed experiments

Prospective treat-on-diagnosis registry with developmental endpoints

exp_dee89_treat_on_diagnosis_registry

Enrol newly genetically diagnosed infants, record time from diagnosis to start of combination therapy, and follow standardized developmental assessments, so that outcome can be related to treatment latency rather than compared across ad hoc case reports.

Vigabatrin response stratified by residual GAD67 activity

exp_dee89_vigabatrin_response_by_residual_activity

For each reported allele, measure residual glutamate decarboxylase activity and relate it to that patient's vigabatrin response, to test the review's prediction that the drug fails where activity is abolished and works only where some synthesis remains.

Show evidence (3 references)

PMID:33169137 SUPPORT Human Clinical

"The presence of a neonatal burst-suppression pattern on EEG generally has a dire prognosis, and all families reported in our study indeed had a profound developmental delay."

Establishes the baseline against which the single favourable outcome stands out, and hence why the question is open rather than answered.

PMID:37029735 SUPPORT Other

"it seems that prescribing vigabatrin for patients with GAD1 deficiency is not a suitable solution, at least for mutations that result in severe reduction or complete loss of the enzyme function."

The review proposes a genotype-dependent limitation of vigabatrin; this mechanistic objection does not itself resolve the developmental-outcome question.

PMID:37029735 SUPPORT Other

"However, the production of GABA derivatives with the ability to cross the blood–brain barrier may be useful for controlling epilepsy in these patients."

Names the alternative therapeutic route the same authors propose if the catabolism-blocking rationale fails - brain-penetrant GABA derivatives, since oral GABA does not cross the blood-brain barrier. Evidence source is OTHER because this is the paper's proposal rather than data.

Which imaging changes are primary developmental lesions and which reflect secondary injury or fluid-space changes?

KNOWLEDGE GAP OPEN gap_dee89_neuroimaging

Attached to

phenotypes#Cerebral Atrophy phenotypes#Ventriculomegaly phenotypes#Cerebellar Atrophy phenotypes#Hypoplastic Corpus Callosum phenotypes#Hydrocephalus phenotypes#Microcephaly

Most initial MRI scans were normal. Some patients later developed atrophy, whereas others had callosal hypoplasia or hydrocephalus with craniocervical anomalies. The reviewed sources do not resolve primary GABA-dependent development, seizure-related injury and coincident structural causes. MRI volume loss does not by itself establish the regional cellular mechanism. The 2023 microcephaly report also raises cerebral palsy as an alternative attribution.

Show evidence (3 references)

PMID:32282878 SUPPORT Human Clinical

"showing hypoplastic corpus callosum, mainly body and to a lesser degree its genu, progressive cerebellar and cerebral atrophy and a cervical notch."

Serial MRI in case 3 showed cerebellar as well as cerebral atrophy; most other reported scans were normal.

PMID:32282878 SUPPORT Human Clinical

"Another had an atlanto-axial anomaly with minimal hydrocephalus at 2 months of age (Case 9, Patient E-III:2)."

Minimal hydrocephalus with an atlantoaxial anomaly was reported in case 9, whose prenatal imaging had also suggested hydrocephalus.

PMID:37029735 SUPPORT Human Clinical

"Also, he showed microcephaly, which may be due to cerebral palsy."

Microcephaly was reported in the 2023 patient, whose authors considered cerebral palsy as an alternative attribution. Chatron case 8 also had head circumference below the third centile.

How do bulbar dysfunction, structural abnormalities and other clinical factors contribute to feeding and growth findings?

KNOWLEDGE GAP OPEN gap_dee89_swallowing_growth

Attached to

phenotypes#Dysphagia phenotypes#Poor Feeding phenotypes#Failure to Thrive phenotypes#Constipation

Swallowing impairment and aspiration are documented, and the supported aspiration-to-pneumonia sequela is modeled. The source reports oropharyngeal dysfunction, a floppy epiglottis and cleft palate in different patients; their relative contribution is unresolved. Failure to thrive in the multiply malformed siblings cannot be assigned solely to the dysphagia in other cases. Constipation and neonatal poor feeding are observed without an established GAD1-specific route.

Show evidence (3 references)

PMID:32705143 SUPPORT Human Clinical

"The third key feature we observed was a reduced muscle strength (five of six individuals) of varying severity ranging from slight muscle tone (one of five) to limited head control, inability to sit or crawl (four of six) and nasogastric tube dependence, due to dysphagia (two of six)."

Dysphagia required nasogastric feeding in two of six patients. Table 1 documents dysphagia in three, including oropharyngeal dysphagia and one patient with a floppy epiglottis.

PMID:32282878 SUPPORT Human Clinical

"He also had failure to thrive, seizures, arthrogryposis and global developmental delay."

Failure to thrive affected both siblings in Family B, who died with severe growth failure and pulmonary infections.

PMID:37029735 SUPPORT Human Clinical

"Moreover, the patient manifested arthrogryposis in his hands, open mouth, high arched palate, large ear, constipation, and dysphasia."

Constipation was reported in the 2023 patient; its cause was not established.

Which sensory findings belong to the GAD1 disorder and which have independent structural causes?

KNOWLEDGE GAP OPEN gap_dee89_sensory_findings

Attached to

phenotypes#High Myopia phenotypes#Horizontal Nystagmus phenotypes#Strabismus phenotypes#Hearing Impairment phenotypes#Conductive Hearing Loss

The sources document these findings but do not establish a GAD1-specific ocular or auditory lesion. Nystagmus and strabismus may involve central control or ocular disease; high myopia is a separate refractive phenotype. Conductive hearing loss co-occurs with cleft palate in one patient, without middle-ear findings that establish that causal route, while another hearing deficit is untyped.

Show evidence (3 references)

PMID:32705143 SUPPORT Human Clinical

High myopia was recorded in patients A and F in the six-patient cohort.

PMID:37029735 SUPPORT Human Clinical

"Ophthalmology assessment revealed horizontal nystagmus and the right eye suffered from strabismus."

Horizontal nystagmus was documented in the 2023 patient.

PMID:32282878 SUPPORT Human Clinical

"She has a palatine cleft, a talipes on the left side and a conductive hearing loss."

Conductive hearing loss was documented in case 5, who also had cleft palate.

Are additional skeletal and dysmorphic findings prenatal consequences of impaired movement or secondary and coincidental findings?

KNOWLEDGE GAP OPEN gap_dee89_additional_structural_findings

Attached to

phenotypes#Scoliosis phenotypes#Plagiocephaly phenotypes#High Arched Palate phenotypes#Large Ears phenotypes#Hypertelorism phenotypes#Microretrognathia phenotypes#Diastasis Recti phenotypes#Congenital Hip Dislocation phenotypes#Pes Planus phenotypes#Thick Eyebrows phenotypes#Finger Clinodactyly phenotypes#Wide Mouth phenotypes#Depressed Nasal Bridge

The source-established fetal movement explanation for contractures, clubfoot and major palatal/ventral defects is represented. The additional findings have less secure attribution: scoliosis sometimes emerged later, plagiocephaly was explicitly positional in one child, and hip dislocation, flat feet and facial features do not establish a single fetal motor route. Extending the modeled mechanism to every malformation would obscure these differences. Thick eyebrows, wide mouth, depressed nasal bridge and finger clinodactyly are patient-level dysmorphic observations without evidence distinguishing a primary developmental GAD1 effect from secondary or coincidental anatomy; none establishes a fetal akinesia mechanism.

Show evidence (6 references)

PMID:32282878 SUPPORT Human Clinical

"He initially showed reduced muscle tone and developed spasticity and dystonia as well as scoliosis later during the disease course."

Dystonia emerged during follow-up in case 7; it was also recorded in cases 8 and 11.

PMID:32705143 SUPPORT Human Clinical

"the same patient also showed congenital bilateral hip dislocation with shallow acetabulum, talipes equinovarus and hearing impairment."

Congenital bilateral hip dislocation with shallow acetabula occurred in patient E.

PMID:32705143 SUPPORT Human Clinical

"In addition, significant diastasis recti can be observed."

Diastasis recti was observed in patient D; Chatron case 9 also had rectus diastasis. It is distinct from omphalocele.

+ 3 more references

Are the renal and enteric findings directly attributable to GAD1 deficiency?

KNOWLEDGE GAP OPEN gap_dee89_renal_enteric_findings

Attached to

phenotypes#Hirschsprung Disease phenotypes#Nephrocalcinosis phenotypes#Nephrolithiasis phenotypes#Hydronephrosis

Hirschsprung disease was confirmed in one genotyped Chatron patient; a differently affected sibling in Neuray et al. is not a second confirmed DEE89 case. Renal calcification occurs in two reports, with stones and hydronephrosis in one patient. Developmental GABA signaling is biologically relevant but the reviewed studies do not demonstrate enteric neuronal loss or a renal mechanism due to GAD1. Nor do they establish stones as the cause of hydronephrosis.

Show evidence (3 references)

PMID:32282878 SUPPORT Human Clinical

"The diagnosis of Hirschsprung was confirmed by rectal biopsy."

Biopsy-confirmed Hirschsprung disease occurred in Chatron case 9. The ungenotyped sibling mentioned in Neuray et al. is not included as additional DEE89 evidence.

PMID:32282878 SUPPORT Human Clinical

"and urinary ultrasonography revealed grade 1 nephrocalcinosis."

Grade 1 nephrocalcinosis was reported in Chatron case 9; Neuray patient A also had nephrocalcinosis with stones and hydronephrosis.

PMID:32705143 SUPPORT Human Clinical

"| Other features | Hydronephrosis, nephrocalcinosis, bilateral kidney stones |"

Bilateral kidney stones occurred in patient A of the six-patient cohort.

Which features determine antiseizure medication resistance?

KNOWLEDGE GAP OPEN gap_dee89_drug_response

Attached to

phenotypes#Refractory Drug Response

Both control and resistance occur. The represented GABA-deficiency seizure pathway explains epilepsy but does not establish why one patient responds and another does not. Seizure type, residual GAD67 activity, treatment timing and drug choice remain competing explanations.

Show evidence (1 reference)

PMID:32705143 SUPPORT Human Clinical

"Seizures were pharmacologically controlled in three of six affected individuals, with three reported as drug-resistant."

Three of six patients had drug-resistant epilepsy; this phenotype describes antiseizure treatment response, not a distinct seizure type.

Which inhibitory motor circuits account for increased tone and brisk reflexes, which generate dystonia or choreoathetosis, and why does one patient instead have hyporeflexia?

KNOWLEDGE GAP OPEN gap_dee89_motor_sign_localization

Attached to

phenotypes#Spasticity phenotypes#Hyperreflexia phenotypes#Clonus phenotypes#Dystonia phenotypes#Choreoathetosis phenotypes#Hyporeflexia

The authors explicitly propose a developmental explanation for axial hypotonia and genetically attribute weakness; those qualified causal relations are represented. For increased tone, the paper compares DEE89 with stiff-person syndrome, whose spinal and supraspinal disinhibition is an analogy rather than a demonstrated DEE89 mechanism. The case descriptions of spasticity and brisk reflexes establish the signs but do not localize their causal lesion. Clonus in the 2023 patient, dystonia emerging during follow-up, choreoathetotic arm movements and hyporeflexia in patient E likewise lack a source-established circuit explanation. These are unresolved phenotype-specific localization and attribution questions, not missing steps in an otherwise established central motor pathway.

Show evidence (5 references)

PMID:32282878 SUPPORT INDIRECT Other

"This autoimmune disorder is thought to result in an impairment of spinal and supra-spinal inhibitory neurons, leading to excessive excitatory drive upon the motor neurons."

The antecedent is stiff-person syndrome, not DEE89. This comparison supplies a hypothesis for increased tone but does not demonstrate the circuit responsible for DEE89 spasticity or reflex findings.

PMID:32282878 SUPPORT Human Clinical

"He initially showed reduced muscle tone and developed spasticity and dystonia as well as scoliosis later during the disease course."

Case 7 documents evolution of tone and dystonia without identifying the causal circuit.

PMID:32282878 SUPPORT Human Clinical

"She kept her hands fisted with flexion of wrists and her arms movements were uncoordinated and choreathetotic."

Case 11 documents choreoathetotic arm movements; this observation is not evidence that the axial-hypotonia mechanism causes them.

+ 2 more references

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Pathophysiology

12

Biallelic GAD1 Loss of Function

Biallelic loss-of-function variants in GAD1 (missense, nonsense, splice-site and deletion alleles distributed across the gene) are the initiating lesion. This node captures the single concept of the genetic lesion.

GAD1 hgnc:4092

Downstream

GAD67 Enzyme Deficiency Loss-of-function alleles reduce or abolish the activity of the GAD67 enzyme that GAD1 encodes.

Muscle Weakness The clinical series attributes weakness to biallelic GAD1 variants; the intervening mechanism and central versus peripheral localization are unresolved.

Show evidence (1 reference)

PMID:32282878 SUPPORT Human Clinical

"Here we describe a new syndromic developmental and epileptic encephalopathy caused by bi-allelic loss-of-function variants in GAD1, as presented by 11 patients from six independent consanguineous families."

Identifies biallelic GAD1 loss-of-function variants as the causal lesion of the syndrome.

GAD67 Enzyme Deficiency

GAD67 converts glutamate to GABA. Biallelic GAD1 variants are predicted or demonstrated to impair the protein; activity has not been measured for every allele, and missense or in-frame variants need not abolish all function.

glutamate decarboxylase activity GO:0004351 ↓ DECREASED

Downstream

GABA Depletion Reduced GAD67 function decreases basal GABA synthesis. GAD65 supplies residual and compartment-specific GABA but does not restore the normal cortical pool in null mice.

Show evidence (2 references)

PMID:32282878 SUPPORT Other

"GAD1 encodes the glutamate decarboxylase enzyme GAD67"

Establishes that the affected gene product is the GAD67 decarboxylase enzyme.

PMID:37029735 SUPPORT Other

"GAD67 is the rate-limiting enzyme in GABA synthesis, and its deficiency leads to developmental and epileptic encephalopathy 89 (DEE 89)."

Names GAD67 deficiency as the proximate biochemical defect in DEE 89 and identifies it as rate-limiting for GABA synthesis.

GABA Depletion

GAD67 loss markedly reduces basal CNS GABA in mouse models. GAD65-dependent synthesis persists and can preserve axonal GABA in Gad1-null rats. The magnitude and compartmental distribution of depletion in human DEE89 remain unmeasured in the reviewed cohorts.

GABAergic neuron CL:0000617

GABA biosynthetic process GO:0009449 ↓ DECREASED

Animal models

Gad1-null mouse (GAD67 knockout) Mouse recapitulates Direct biochemical measurement of the depletion: cortical GAD activity under 20% and GABA content 7% of wild type in newborn nulls.

Downstream

Excitation-Inhibition Imbalance Reduced GABA availability disrupts network excitation-inhibition balance. GABA also has developmental signaling roles, so this does not imply that every fetal or neonatal action is inhibitory.

Impaired GABA-Dependent Fetal Motor Signaling Loss of GABA signaling in the developing CNS impairs the fetal motor activity required for normal extra-neural morphogenesis.

Developmental Encephalopathy GABA-dependent neural development is proposed to be impaired independently of ongoing seizures. Developmental deficits persisted after seizure freedom in several patients, although earlier seizure injury and direct developmental effects cannot be quantitatively separated.

Impaired GABA-Dependent Axial Motor Development Constitutive GABA deficiency is proposed to impair axial motor development; the authors make this interpretation specifically for axial hypotonia.

Show evidence (2 references)

PMID:32705143 SUPPORT Other

"Its predominant isoform GAD67, contributes up to ∼90% of base-level GABA in the CNS, and is encoded by the GAD1 gene."

Background physiology summarized by the clinical paper, not a human GABA measurement.

PMID:9177246 SUPPORT Model Organism

"GAD activities and GABA contents were reduced to 20% and 7%, respectively, in the cerebral cortex of the newborn GAD67 -/- mice."

Direct measurement of the depletion in the Gad1-null mouse: cortical GABA falls to 7% of wild type. This is model-organism evidence for the magnitude of the depletion; the human biochemical measurement has not been reported.

Excitation-Inhibition Imbalance

Depletion of the principal inhibitory neurotransmitter shifts the balance between glutamatergic excitation and GABAergic inhibition toward net excitation. This node captures the single concept of the excitation-inhibition imbalance and conforms to the shared epilepsy final common pathway.

GABAergic neuron CL:0000617

gamma-aminobutyric acid signaling pathway GO:0007214 ↓ DECREASED

Downstream

Neuronal Hyperexcitability and Hypersynchrony Reduced GABAergic restraint promotes network hyperexcitability; the exact developmental and regional intermediates in human DEE89 are unresolved.

Show evidence (1 reference)

PMID:32705143 SUPPORT Other

"Disruption of GAD1 results in an imbalance of inhibitory and excitatory neurotransmitters"

States the excitation-inhibition imbalance as the direct consequence of GAD1 disruption.

Neuronal Hyperexcitability and Hypersynchrony

Impaired GABAergic signaling permits excessive, synchronized network activity. Human EEG shows epileptiform abnormalities, often on a severely disorganized background; suppression-burst is a readout of broader network dysfunction rather than a unique measurement of GABA depletion.

neuron CL:0000540

action potential GO:0001508 ↑ INCREASED

Animal models

Gad1-null rat Rat partially recapitulates GAD1 loss in the rat produces a hypersynchronous electrographic phenotype, supporting the general link from GABA synthesis failure to network hypersynchrony.

Downstream

Early-Onset Epileptic Seizures Abnormal synchronized network discharge produces the clinical seizures, which begin neonatally or later in infancy.

Show evidence (1 reference)

PMID:32282878 SUPPORT Human Clinical

"Early EEG showed suppression-burst or pattern of burst attenuation or hypsarrhythmia if only recorded in the post-neonatal period."

The suppression-burst and hypsarrhythmic EEG patterns are the electrophysiological signature of the hypersynchronous, poorly restrained neonatal network.

Early-Onset Epileptic Seizures

Published DEE89 cohorts have early epilepsy, with neonatal onset in the evaluable histories of Chatron et al. and onset at two to six months in Neuray et al. Epileptic spasms, myoclonic, tonic, tonic-clonic and focal seizures occur; some patients achieve control while others remain drug-resistant.

neuron CL:0000540

Animal models

Gad1-null mouse (GAD67 knockout) Mouse fails to recapitulate The defining human phenotype - neonatal epilepsy - cannot be observed in this model. Homozygotes die within a day of birth from the cleft palate, and their brains show no discernible structural defect, so the model gives no information about the seizure phenotype.

Downstream

Developmental Encephalopathy Frequent early epileptic activity may add to the developmental deficit. The authors distinguish this potentially modifiable component from the prenatal developmental role of GABA; their relative contributions remain unresolved.

Seizures This is a documented timing or semiological manifestation of the early epilepsy endpoint.

Neonatal-Onset Seizures This is a documented timing or semiological manifestation of the early epilepsy endpoint.

Epileptic Spasms This is a documented timing or semiological manifestation of the early epilepsy endpoint.

Myoclonic Seizures This is a documented timing or semiological manifestation of the early epilepsy endpoint.

Focal Motor Seizures This is a documented timing or semiological manifestation of the early epilepsy endpoint.

Bilateral Tonic-Clonic Seizures This is a documented timing or semiological manifestation of the early epilepsy endpoint.

Tonic Seizures This is a documented timing or semiological manifestation of the early epilepsy endpoint.

Show evidence (5 references)

PMID:32282878 SUPPORT Human Clinical

"All 10 patients, from whom early disease history was available, presented with seizure onset in the first month of life, mainly consisting of epileptic spasms or myoclonic seizures."

Documents first-month seizure onset and the predominant spasm/myoclonic semiology in the founding cohort.

PMID:37029735 SUPPORT Other

"All of the reported patients manifested seizures."

Establishes that seizures occur in every reported patient. Evidence source is OTHER because this is the paper's literature summary rather than its own case observation.

PMID:37029735 SUPPORT Other

"and the patients showed heterogeneous types of seizures such as tonic–clonic, epileptic spasm, myoclonic, and focal motor seizures."

Names the full range of reported semiologies, which is wider than the spasms and myoclonic seizures of the founding cohort. Evidence source is OTHER because this is the paper's literature summary.

+ 2 more references

Impaired GABA-Dependent Fetal Motor Signaling

Mechanism confidence: Provisional

Developing CNS GABA signaling supports fetal motor activity. Mouse CNS-specific deletion disrupts palatal development even when palatal Gad1 expression is retained; normal mutant palate fusion in explants argues against a required palate-intrinsic lesion. Translation of this motor mechanism to human malformations is provisional.

Downstream

Reduced Fetal Movement Impaired fetal CNS signaling reduces movements needed for normal morphogenesis.

Show evidence (1 reference)

PMID:20333300 SUPPORT INDIRECT Model Organism

"Our work strongly supports the idea that the cleft palate phenotype in Gad1 and Viaat knockout mice is due to a loss of GABA signaling in the CNS rather than in craniofacial tissues."

CNS-specific deletion, pharmacological rescue and oral explants support the mouse mechanism.

Failure of Palatal Shelf Elevation

Mechanism confidence: Provisional

Failed elevation of the palatal shelves prevents their normal apposition and fusion. Mouse histology and oral-explant experiments support a CNS-dependent fetal oral-movement mechanism; the equivalent prenatal sequence has not been demonstrated in humans.

roof of mouth development GO:0060021 ⚠ ABNORMAL

Animal models

Gad1-null mouse (GAD67 knockout) Mouse partially recapitulates Gad1-null mouse histology demonstrates failed palatal shelf elevation and cleft palate. CNS-specific deletion and oral explants support a neural movement-dependent mechanism, but the corresponding fetal intermediate has not been measured in human patients.

Downstream

Cleft Palate Failure of palatal shelf elevation prevents normal palate closure. The causal sequence is supported in mice and provisionally transferred to human GAD1 deficiency.

Show evidence (2 references)

PMID:20333300 SUPPORT INDIRECT Model Organism

"In both genotypes, palate shelf elevation fails to occur at E14.5 and all Gad1 and Viaat mutants were born with cleft secondary palates (Fig. 3A-H and data not shown)."

Mouse histology identifies failed shelf elevation preceding cleft palate; the human developmental intermediate is inferred from the model.

PMID:32282878 SUPPORT INDIRECT Other

"Further studies demonstrated that the presence of cleft palate is due to a defect of foetal oral movement of the tongue during palatal development and Gad1 is specifically required in the CNS for normal palatal formation"

The clinical authors interpret prior mouse experiments as a CNS-dependent fetal oral-movement mechanism. This is a proposed explanation for human cleft palate, not a measured prenatal human event.

Reduced Fetal Movement

Mechanism confidence: Provisional

Reduced fetal movement is the human authors' proposed intermediate linking GABA-related CNS dysfunction to congenital joint and palatal abnormalities. It was not measured prenatally in the clinical cohorts.

Downstream

Congenital Joint Contractures Reduced movement in utero can fix joints in abnormal positions, producing the congenital contracture phenotype.

Talipes Equinovarus Reduced fetal movement is the authors' proposed cause of the congenital clubfoot.

Failure of Palatal Shelf Elevation Abnormal fetal tongue movement can obstruct palatal shelf elevation; the clinical authors propose this mouse-supported explanation for the human cleft.

Impaired Retraction of Physiological Umbilical Hernia Reduced fetal movement is proposed to alter fetal posture and pressure, preventing normal hernia retraction.

Show evidence (1 reference)

PMID:32282878 SUPPORT INDIRECT Other

"Also the pes equinovarus, joint contractures and arthrogryposis, seen in several of the patients in our study, are known to reflect a reduction of foetal movements"

The authors propose fetal movement reduction as the causal explanation for these human structural findings.

Developmental Encephalopathy

Impaired neurodevelopment generally causes major cognitive, language and motor limitations, sometimes with regression. Severity varies: one older child had moderate intellectual disability and some speech and ambulation, and an early-treated infant had unremarkable development at seven months. Deaths in the original cohort had heterogeneous causes and are not treated as a single developmental endpoint.

Downstream

Global Developmental Delay This is a cognitive, language or acquired developmental manifestation of the encephalopathy.

Intellectual Disability This is a cognitive, language or acquired developmental manifestation of the encephalopathy.

Absent Speech This is a cognitive, language or acquired developmental manifestation of the encephalopathy.

Developmental Regression This is a cognitive, language or acquired developmental manifestation of the encephalopathy.

Show evidence (2 references)

PMID:32705143 SUPPORT Human Clinical

"Most patients did not achieve any speech or non-verbal communication, only one was reported to have developed simple speech and basic perceptive language skills."

The six-patient cohort documents a range of developmental outcomes.

PMID:32705143 SUPPORT Human Clinical

"Of the more severely affected individuals, despite remaining seizure-free following pharmacological intervention, they still failed to accelerate in their intellectual development."

Developmental impairment persisted in some seizure-free patients.

Impaired GABA-Dependent Axial Motor Development

Mechanism confidence: Provisional

The clinical authors propose that constitutive GABA deficiency impairs axial motor development, explaining axial hypotonia. This interpretation is not a demonstrated circuit lesion or an explanation for every abnormal motor sign.

Downstream

Hypotonia Impaired axial motor development is the authors' proposed cause of axial hypotonia; the responsible circuitry and developmental intermediates remain unresolved.

Show evidence (1 reference)

PMID:32282878 SUPPORT INDIRECT Other

"This most likely reflects the detrimental impact of a constitutive GABA deficiency on neurodevelopment."

The authors specifically propose a developmental effect of constitutive GABA deficiency to explain axial hypotonia. Their comparison with stiff-person syndrome does not establish the cause of other motor signs in DEE89.

Impaired Retraction of Physiological Umbilical Hernia

Mechanism confidence: Provisional

The authors propose that impaired fetal movement alters posture and intra-abdominal pressure, interfering with retraction of the physiological umbilical hernia. Gad1-null mice have persistent umbilical hernia rather than histologically identical human omphalocele; transfer of this mechanism to human omphalocele is provisional.

Downstream

Omphalocele Failure of normal visceral retraction is proposed as a contributor to human omphalocele. This human extrapolation is less secure than the demonstrated mouse umbilical-hernia phenotype.

Show evidence (2 references)

PMID:20333300 SUPPORT INDIRECT Model Organism

"These phenotypes suggest that Gad1 and Viaat functions are not necessary for body wall formation per se but are instead required for the retraction of the umbilical hernia during development."

Mouse histology supports a retraction defect rather than failed body-wall formation; it does not demonstrate human omphalocele.

PMID:32282878 SUPPORT INDIRECT Other

"movement reduction leads to a hunched posture in the foetus and increased intra-abdominal pressure, resulting in failure of retracting umbilical hernia and omphalocele"

The clinical authors propose this movement/posture/retraction route. Mouse histology establishes umbilical hernia, so extension to human omphalocele remains a hypothesis.

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Pathograph

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Phenotypes

60

Digestive 6

Omphalocele HP:0001539

Show evidence (1 reference)

PMID:32282878 SUPPORT Human Clinical

"At birth, omphalocele and bilateral talipes equinovarus were observed."

Case 4 had omphalocele; the clinical table records no cleft palate in this sibling.

Dysphagia HP:0002015

Sequelae: Aspiration

Show evidence (1 reference)

PMID:32705143 SUPPORT Human Clinical

"The third key feature we observed was a reduced muscle strength (five of six individuals) of varying severity ranging from slight muscle tone (one of five) to limited head control, inability to sit or crawl (four of six) and nasogastric tube dependence, due to dysphagia (two of six)."

Dysphagia required nasogastric feeding in two of six patients. Table 1 documents dysphagia in three, including oropharyngeal dysphagia and one patient with a floppy epiglottis.

Constipation HP:0002019

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PMID:37029735 SUPPORT Human Clinical

"Moreover, the patient manifested arthrogryposis in his hands, open mouth, high arched palate, large ear, constipation, and dysphasia."

Constipation was reported in the 2023 patient; its cause was not established.

Hirschsprung Disease Aganglionic megacolon HP:0002251

Show evidence (1 reference)

PMID:32282878 SUPPORT Human Clinical

"The diagnosis of Hirschsprung was confirmed by rectal biopsy."

Biopsy-confirmed Hirschsprung disease occurred in Chatron case 9. The ungenotyped sibling mentioned in Neuray et al. is not included as additional DEE89 evidence.

Diastasis Recti HP:0001540

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PMID:32705143 SUPPORT Human Clinical

"In addition, significant diastasis recti can be observed."

Diastasis recti was observed in patient D; Chatron case 9 also had rectus diastasis. It is distinct from omphalocele.

Poor Feeding Feeding difficulties HP:0011968

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PMID:37029735 SUPPORT Human Clinical

"After birth due to poor feeding and seizure admitted to neonatal intensive care unit for 20 days."

Poor feeding required neonatal admission in the 2023 case.

Ear 3

Hearing Impairment HP:0000365

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PMID:32705143 SUPPORT Human Clinical

Moderate hearing impairment of unspecified type was recorded in patient E; this is separate from the conductive loss in Chatron case 5.

Conductive Hearing Loss Conductive hearing impairment HP:0000405

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PMID:32282878 SUPPORT Human Clinical

"She has a palatine cleft, a talipes on the left side and a conductive hearing loss."

Conductive hearing loss was documented in case 5, who also had cleft palate.

Large Ears Macrotia HP:0000400

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PMID:37029735 SUPPORT Human Clinical

"Moreover, the patient manifested arthrogryposis in his hands, open mouth, high arched palate, large ear, constipation, and dysphasia."

Large ears were recorded in the 2023 patient.

Eye 4

High Myopia HP:0011003

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PMID:32705143 SUPPORT Human Clinical

High myopia was recorded in patients A and F in the six-patient cohort.

Horizontal Nystagmus HP:0000666

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PMID:37029735 SUPPORT Human Clinical

"Ophthalmology assessment revealed horizontal nystagmus and the right eye suffered from strabismus."

Horizontal nystagmus was documented in the 2023 patient.

Strabismus HP:0000486

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PMID:37029735 SUPPORT Human Clinical

"Ophthalmology assessment revealed horizontal nystagmus and the right eye suffered from strabismus."

Right-eye strabismus was documented in the 2023 patient; earlier cases also included squint and alternating esotropia.

Hypertelorism HP:0000316

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PMID:32282878 SUPPORT Human Clinical

"Note hypertelorism, downslanting palpebral fissure, broad nasal bridge with anteverted nares, smooth philtrum and thin upper lip vermilion."

Hypertelorism occurred among the variable facial findings in the 11-patient cohort.

Genitourinary 3

Nephrocalcinosis HP:0000121

Show evidence (1 reference)

PMID:32282878 SUPPORT Human Clinical

"and urinary ultrasonography revealed grade 1 nephrocalcinosis."

Grade 1 nephrocalcinosis was reported in Chatron case 9; Neuray patient A also had nephrocalcinosis with stones and hydronephrosis.

Nephrolithiasis HP:0000787

Show evidence (1 reference)

PMID:32705143 SUPPORT Human Clinical

"| Other features | Hydronephrosis, nephrocalcinosis, bilateral kidney stones |"

Bilateral kidney stones occurred in patient A of the six-patient cohort.

Hydronephrosis HP:0000126

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PMID:32705143 SUPPORT Human Clinical

"| Other features | Hydronephrosis, nephrocalcinosis, bilateral kidney stones |"

Hydronephrosis accompanied renal calcifications in patient A; the source does not establish an obstructive cause.

Head and Neck 8

Cleft Palate HP:0000175

Show evidence (1 reference)

PMID:32282878 SUPPORT Human Clinical

"Seven patients presented a cleft palate and two also had an omphalocele, reproducing the phenotype of the knockout Gad1-/- mouse model."

The human cohort establishes cleft palate. The abstract's claim of complete mouse correspondence is qualified by the primary mouse study distinguishing umbilical hernia from omphalocele.

Plagiocephaly HP:0001357

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PMID:32282878 SUPPORT Human Clinical

"At last examination, at 6 years of age, her weight was 17 kg, occipital frontal circumference 50 cm with positional plagiocephaly, inverted nipples, hirsutism and severe scoliosis."

Case 11 had positional plagiocephaly; other cases also had cranial asymmetry.

Microcephaly HP:0000252

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PMID:37029735 SUPPORT Human Clinical

"Also, he showed microcephaly, which may be due to cerebral palsy."

Microcephaly was reported in the 2023 patient, whose authors considered cerebral palsy as an alternative attribution. Chatron case 8 also had head circumference below the third centile.

High Arched Palate High palate HP:0000218

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PMID:37029735 SUPPORT Human Clinical

"Moreover, the patient manifested arthrogryposis in his hands, open mouth, high arched palate, large ear, constipation, and dysphasia."

A high arched palate without cleft was reported in the 2023 patient; Chatron case 3 also had a high arched palate.

Microretrognathia HP:0000308

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PMID:32282878 SUPPORT Human Clinical

"Note flat facies, microretrognathia and abnormal asymmetric shaped ears."

Microretrognathia was documented in the multiply malformed proband of Family B and in case 9.

Thick Eyebrows HP:0000574

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PMID:32705143 SUPPORT Human Clinical

"The female patient from Family A (Patient II-2) carries the homozygous c.1691A>G p.(Asn564Ser) variant and shows dysmorphic features with thick eyebrows, protruding ears, scoliosis, and long fingers with clinodactyly."

Thick eyebrows were documented in patient A of Neuray et al.; this single-case observation does not establish a general frequency.

Wide Mouth HP:0000154

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PMID:32705143 SUPPORT Human Clinical

"He has slight dysmorphic features (wide mouth, thin upper lips, bitemporal narrowing and retrognathia)."

Wide mouth was described in patient B of Neuray et al. This differs from an open-mouth posture.

Depressed Nasal Bridge HP:0005280

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PMID:32705143 SUPPORT Human Clinical

"He is severely hypotonic and shows severe dysmorphic features (infra-orbital creases, severely depressed nasal bridge, anteverted nares, prominent nasolabial folds)."

A severely depressed nasal bridge was described in patient D of Neuray et al.; Chatron et al. also documented this finding in dysmorphic cases.

Immune 1

Recurrent Aspiration Pneumonia HP:0002100

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PMID:32282878 SUPPORT Human Clinical

"In the follow-up, the patient had severe recurrent aspiration pneumonia requiring hospitalization and oxygen treatment."

Case 9 had recurrent aspiration pneumonia requiring hospitalization.

Limbs 4

Talipes Equinovarus HP:0001762

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PMID:32282878 SUPPORT Human Clinical

"Interestingly, in addition to neurological features, seven patients presented a cleft palate, six joint contractures and five pes equinovarus."

Five patients had clubfoot; the combined eight-person abstract count is not a clubfoot frequency.

Congenital Hip Dislocation HP:0001374

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PMID:32705143 SUPPORT Human Clinical

"the same patient also showed congenital bilateral hip dislocation with shallow acetabulum, talipes equinovarus and hearing impairment."

Congenital bilateral hip dislocation with shallow acetabula occurred in patient E.

Pes Planus HP:0001763

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PMID:32705143 SUPPORT Human Clinical

"| Skeletal abnormalities | Clindodactyly, pes planus, scoliosis |"

Pes planus was recorded in patient A, distinct from the clubfoot in other patients.

Finger Clinodactyly HP:0040019

Show evidence (1 reference)

PMID:32705143 SUPPORT Human Clinical

"The female patient from Family A (Patient II-2) carries the homozygous c.1691A>G p.(Asn564Ser) variant and shows dysmorphic features with thick eyebrows, protruding ears, scoliosis, and long fingers with clinodactyly."

Finger clinodactyly was documented in patient A. The affected digits were not specified, so a fifth-finger-specific term is not justified.

Metabolism 1

Refractory Drug Response HP:0020174

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PMID:32705143 SUPPORT Human Clinical

"Seizures were pharmacologically controlled in three of six affected individuals, with three reported as drug-resistant."

Three of six patients had drug-resistant epilepsy; this phenotype describes antiseizure treatment response, not a distinct seizure type.

Musculoskeletal 5

Hypotonia HP:0001252

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PMID:32282878 SUPPORT Human Clinical

"Whereas in stiff person syndrome axial muscles are predominantly affected, patients reported in our manuscript often had axial hypotonia."

The primary cohort distinguishes axial hypotonia from increased limb tone.

Spasticity HP:0001257

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PMID:37029735 SUPPORT Human Clinical

"he manifested severe neurodevelopmental delay with bed confinement, spasticity in limbs, speech absence, and incontinency."

Documents limb spasticity in the index patient. No frequency band is asserted because this is a single-patient observation.

Congenital Joint Contractures Congenital contracture HP:0002803

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PMID:32282878 SUPPORT Human Clinical

"Interestingly, in addition to neurological features, seven patients presented a cleft palate, six joint contractures and five pes equinovarus."

Separates the joint-contracture and clubfoot counts in the 11-patient cohort.

Scoliosis HP:0002650

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PMID:32282878 SUPPORT Human Clinical

"Scoliosis was reported in four patients."

The primary 11-patient cohort documents four cases without establishing a congenital or uniformly progressive course.

Muscle Weakness HP:0001324

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PMID:32705143 SUPPORT Human Clinical

"The reduced muscle tone and weakness, causing severe disability in four of six affected individuals was a surprising finding."

Four of six refers to the combined tone/weakness-related disability; the results describe reduced strength in five of six.

PMID:32705143 SUPPORT Human Clinical

"The third key feature we observed was a reduced muscle strength (five of six individuals) of varying severity ranging from slight muscle tone (one of five) to limited head control, inability to sit or crawl (four of six) and nasogastric tube dependence, due to dysphagia (two of six)."

The results give five of six for reduced strength, while the severity descriptions mix strength, tone, motor milestones and dysphagia. These subgroup counts are not interchangeable.

Nervous System 23

Seizures HP:0001250

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PMID:32705143 SUPPORT Human Clinical

"A key clinical feature common to all affected individuals was early onset seizures (from 2 to 6 months), predominantly focal motor seizures with and without impaired awareness (two with additional epileptic spasms, four with focal non-motor seizures, and five with bilateral motor seizures)."

All six patients in this cohort had epilepsy; this is a cohort observation rather than a penetrance estimate.

Neonatal-Onset Seizures Neonatal seizure HP:0032807

Show evidence (2 references)

PMID:32282878 SUPPORT Human Clinical

"All 10 patients, from whom early disease history was available, presented with seizure onset in the first month of life, mainly consisting of epileptic spasms or myoclonic seizures."

The ten-person denominator refers only to evaluable early histories in this 11-patient cohort, not to all published patients.

PMID:37029735 SUPPORT Other

"In reported patients, the age‐onset of seizures was from the birth to 6 months old"

The 2023 review summarizes the wider birth-to-six-month onset range, which includes non-neonatal onset. No pooled frequency band is inferred.

Epileptic Spasms HP:0011097

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PMID:32282878 SUPPORT Human Clinical

"mainly consisting of epileptic spasms or myoclonic seizures"

Names epileptic spasms as a predominant early semiology.

Myoclonic Seizures HP:0032794

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PMID:32282878 SUPPORT Human Clinical

"mainly consisting of epileptic spasms or myoclonic seizures"

Names myoclonic seizures as a predominant early semiology.

Focal Motor Seizures HP:0011153

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PMID:32705143 SUPPORT Human Clinical

"predominantly focal motor seizures with and without impaired awareness (two with additional epileptic spasms, four with focal non-motor seizures, and five with bilateral motor seizures)."

The six-patient primary cohort documents focal motor semiology without assigning it to every patient.

Bilateral Tonic-Clonic Seizures HP:0002069

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PMID:32282878 SUPPORT Human Clinical

"At the age of 5 months, she developed generalized tonic-clonic seizures."

Case 5 developed generalized tonic-clonic seizures; the broader bilateral tonic-clonic binding also covers other reports without established onset classification.

Suppression-Burst EEG EEG with burst suppression HP:0010851

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PMID:32282878 SUPPORT Human Clinical

"Early EEG showed suppression-burst or pattern of burst attenuation or hypsarrhythmia if only recorded in the post-neonatal period."

Documents the suppression-burst / burst-attenuation neonatal EEG.

Hypsarrhythmia HP:0002521

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PMID:32282878 SUPPORT Human Clinical

"Early EEG showed suppression-burst or pattern of burst attenuation or hypsarrhythmia if only recorded in the post-neonatal period."

Documents hypsarrhythmia on post-neonatal recordings.

Global Developmental Delay HP:0001263

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PMID:32705143 SUPPORT Human Clinical

"Most patients did not achieve any speech or non-verbal communication, only one was reported to have developed simple speech and basic perceptive language skills."

The six-patient cohort documents a range of developmental outcomes.

PMID:33169137 SUPPORT Human Clinical

"This combination treatment not only resulted in clinical cessation of seizures within 2 days, but at 7 months of age, growth and psychomotor development were unremarkable."

The reply summarizes another group's infant; short follow-up does not establish a normal long-term outcome.

Absent Speech HP:0001344

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PMID:37029735 SUPPORT Human Clinical

"he manifested severe neurodevelopmental delay with bed confinement, spasticity in limbs, speech absence, and incontinency."

Documents absent speech in the index patient. No frequency band is asserted because this is a single-patient observation.

Cerebral Atrophy HP:0002059

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PMID:37029735 SUPPORT Human Clinical

"MRI showed diffuse cerebral atrophy and severe ventriculomegaly."

Documents cerebral atrophy on MRI in the index patient. No frequency band is asserted because the same paper reports MRI as normal in the majority.

Ventriculomegaly HP:0002119

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PMID:37029735 SUPPORT Human Clinical

"MRI showed diffuse cerebral atrophy and severe ventriculomegaly."

Documents ventriculomegaly on MRI in the index patient. No frequency band is asserted because this is a single-patient observation.

Intellectual Disability HP:0001249

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PMID:32705143 SUPPORT Human Clinical

"However, despite seizure control (seizure freedom achieved in three of six individuals), all patients described here still showed severe intellectual disability."

Intellectual disability persisted after seizure control. The source narrative calls all cases severe, but Table 1 records moderate disability in patient A and severe disability in the other five.

Hyperreflexia HP:0001347

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PMID:37029735 SUPPORT Human Clinical

"The deep tendon reflex (DTR) test showed hyperreflexia and manifested frequent tremors in the toes of both feet."

Hyperreflexia was observed in the 2023 case and in several patients in the earlier cohorts.

Clonus HP:0002169

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PMID:37029735 SUPPORT Human Clinical

"showed microcephaly and clonus in the toe, which were novel clinical findings."

Toe clonus was reported in the 2023 patient; this does not specify ankle clonus.

Dystonia HP:0001332

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PMID:32282878 SUPPORT Human Clinical

"He initially showed reduced muscle tone and developed spasticity and dystonia as well as scoliosis later during the disease course."

Dystonia emerged during follow-up in case 7; it was also recorded in cases 8 and 11.

Choreoathetosis HP:0001266

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PMID:32282878 SUPPORT Human Clinical

"She kept her hands fisted with flexion of wrists and her arms movements were uncoordinated and choreathetotic."

Choreoathetotic arm movements were documented in case 11.

Developmental Regression HP:0002376

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PMID:32282878 SUPPORT Human Clinical

"At the age of 2 years there was a regression evolving to a complete tetraparesis, with generalized increased muscle tonus without clear pyramidal signs, and pes equinus."

Case 5 lost motor function; case 1 also lost visual contact in infancy. Regression is not asserted for every patient.

Cerebellar Atrophy HP:0001272

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PMID:32282878 SUPPORT Human Clinical

"showing hypoplastic corpus callosum, mainly body and to a lesser degree its genu, progressive cerebellar and cerebral atrophy and a cervical notch."

Serial MRI in case 3 showed cerebellar as well as cerebral atrophy; most other reported scans were normal.

Hypoplastic Corpus Callosum Hypoplasia of the corpus callosum HP:0002079

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PMID:32282878 SUPPORT Human Clinical

"One patient presented with hypoplastic corpus callosum and mild-to-moderate dilated subarachnoid spaces, predominating on left hemisphere and mild enlarged lateral ventricles (Case 3, Patient B-IV:4)."

Corpus callosum hypoplasia was documented in case 3.

Hydrocephalus HP:0000238

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PMID:32282878 SUPPORT Human Clinical

"Another had an atlanto-axial anomaly with minimal hydrocephalus at 2 months of age (Case 9, Patient E-III:2)."

Minimal hydrocephalus with an atlantoaxial anomaly was reported in case 9, whose prenatal imaging had also suggested hydrocephalus.

Tonic Seizures HP:0032792

Show evidence (2 references)

PMID:32282878 SUPPORT Human Clinical

"He showed a similar phenotype as his older sister (Patient C-III:1), with refractory epilepsy with myoclonic, tonic and tonic-clonic seizures, from the first day of life."

The prose documents tonic seizures from the first day of life in case 6.

PMID:32282878 SUPPORT Human Clinical

The final column of Table 1 is case 11; its evolution-of-seizures cell records tonic seizures, epileptic spasms (ES) and focal seizures.

Hyporeflexia HP:0001265

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PMID:32705143 SUPPORT Human Clinical

Hyporeflexia was recorded in patient E in Table 1 of Neuray et al., contrasting with brisk reflexes in other patients. The source does not localize the reflex impairment.

Respiratory 1

Aspiration HP:0002835

Sequelae: Recurrent Aspiration Pneumonia

Show evidence (1 reference)

PMID:32282878 SUPPORT Human Clinical

"Barium oesophagogram showed nasal regurgitation and laryngotracheal aspiration, requiring nasogastric tube feeding."

Laryngotracheal aspiration was demonstrated by contrast study in case 9.

Growth 1

Failure to Thrive HP:0001508

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PMID:32282878 SUPPORT Human Clinical

"He also had failure to thrive, seizures, arthrogryposis and global developmental delay."

Failure to thrive affected both siblings in Family B, who died with severe growth failure and pulmonary infections.

🧬

Genetic Associations

1

GAD1

Gene: GAD1 hgnc:4092 gene page relationship_type: CAUSATIVE

Show evidence (2 references)

PMID:37029735 SUPPORT Other

"The recurrent c.1591C>T, p.(Arg531*) variant has been reported three times (20% of all reported variants) in different populations, indicating it may be a probable hotspot mutation."

The 2023 literature review reports recurrence of p.(Arg531*) across three published occurrences; the percentage is a publication-based variant count, not a population allele frequency or established mutational hotspot.

PMID:37029735 SUPPORT Computational

"The mutation is located in the PLP‐binding domain, which is important for the activity of the protein"

Locates a reported missense allele in the pyridoxal-phosphate-binding domain, the structural basis on which missense alleles are argued to impair catalysis. Evidence source is COMPUTATIONAL because the functional inference rests on docking and molecular-dynamics simulation, not an enzyme assay.

💊

Medical Actions

4

Vigabatrin

Action: Pharmacotherapy NCIT:C15986

Agent: vigabatrin CHEBI:63638

Platform: Small molecule

Vigabatrin irreversibly inhibits GABA transaminase, the enzyme that degrades GABA, and is therefore a mechanistically rational attempt to raise whatever GABA the residual synthetic capacity produces. Five of seven patients in the founding cohort who tried it had a good seizure response, but the authors themselves cautioned that the responders were particularly those with epileptic spasms, so the effect may be semiology-driven rather than GAD1-specific. The rationale has a published objection, and it is a mechanistic one rather than a null trial result: sparing GABA from degradation cannot help much when synthesis is the step that has failed, since GAD67 supplies over 90% of basal GABA. The 2023 review states that vigabatrin is therefore not a suitable solution "at least for mutations that result in severe reduction or complete loss of the enzyme function" - a genotype-stratified claim, which is the same residual-activity axis this entry records as an open gap. Two treated patients, including one on the vigabatrin-plus-ketogenic-diet combination, continued to have seizures. Both sides are curated as evidence below rather than resolved here, because the objection is an inference from the mechanism and the response is an observation, and neither refutes the other.

Mechanism Target:

RESTORES GABA Depletion — Blocking GABA catabolism is intended to raise the available GABA pool and partially offset the synthetic deficit. The link is mechanistic rationale plus an observed clinical seizure response, not a measured rise in human brain GABA.

Show evidence (2 references)

PMID:33169137 SUPPORT Other

"Both treatment strategies are thought to increase the available pool of GABA, and combined they might compensate for the severely impaired GABA synthesis."

States the intended mechanism - raising the available GABA pool to compensate for impaired synthesis - for vigabatrin and the ketogenic diet.

PMID:37029735 REFUTE Other

"it seems that prescribing vigabatrin for patients with GAD1 deficiency is not a suitable solution, at least for mutations that result in severe reduction or complete loss of the enzyme function."

The direct argument against this link. Because GAD67 supplies most basal GABA, blocking catabolism has little left to spare where the variant abolishes synthesis, so the restorative effect is expected to fail for null and severe-reduction alleles. `treatment_effect` remains RESTORES because that is the intended mechanism the drug is chosen for; this item records that the intent is disputed on mechanistic grounds. Evidence source is OTHER because this is the paper's reasoning over the literature rather than a measurement.

Show evidence (2 references)

PMID:33169137 SUPPORT Human Clinical

"In our report, five of seven patients who tried vigabatrin showed a remarkably good seizure response."

Five of seven treated patients in the authors' original cohort improved, particularly those with spasms. This may be a semiology-related response rather than a genotype-specific effect.

PMID:37029735 REFUTE Human Clinical

"He suffers from refractory tonic–clonic seizures despite treatment with a combination of vigabatrin and a ketogenic diet."

The 2023 index patient remained refractory on the combination. A separate patient in Neuray et al. also remained refractory, as summarized in the reply.

Ketogenic Diet

Action: Ketogenic Diet NCIT:C173168

Platform: Behavioral / lifestyle

The ketogenic diet is used alongside vigabatrin on the same rationale of increasing the available GABA pool. Its disease-specific evidence is a single treated infant with an excellent outcome set against at least two patients on the same combination who remained refractory.

Mechanism Target:

RESTORES GABA Depletion — The diet is proposed to increase the available GABA pool; this is a hypothesized mechanism carried over from ketogenic-diet pharmacology generally, not a measurement made in GAD1-deficient patients.

Show evidence (1 reference)

PMID:33169137 SUPPORT Other

"Both treatment strategies are thought to increase the available pool of GABA, and combined they might compensate for the severely impaired GABA synthesis."

States the intended GABA-raising mechanism shared by the ketogenic diet and vigabatrin.

Show evidence (1 reference)

PMID:33169137 REFUTE Human Clinical

"One patient (Patient C) also appears to take a combination of ketogenic diet and vigabatrin at the age of 28 months, and still has refractory seizures and severe delay."

The reply summarizes a patient from the independent cohort who remained refractory on the combination; the treatment-start age was not reported. This argues against uniform benefit.

Early Combined Vigabatrin and Ketogenic Diet

Action: Pharmacotherapy NCIT:C15986

Agent: vigabatrin CHEBI:63638

Platform: Other

Combination therapy started in the second month of life, immediately after genetic diagnosis, was reported in one infant to stop seizures within two days and leave growth and psychomotor development unremarkable at 7 months - a striking exception in a disorder where a neonatal burst-suppression EEG has otherwise predicted profound delay. It is one observation, and another patient on the same combination with unreported treatment-start age remained refractory.

Mechanism Target:

RESTORES GABA Depletion — Both components are proposed to raise the available GABA pool - vigabatrin by blocking GABA catabolism, the ketogenic diet by shifting substrate availability - so the combination is directed at the same depletion node each single agent targets. The effect is an inferred mechanism, not a measured rise in human brain GABA.

Show evidence (1 reference)

PMID:33169137 SUPPORT Other

"Both treatment strategies are thought to increase the available pool of GABA, and combined they might compensate for the severely impaired GABA synthesis."

The authors propose increasing the available GABA pool; GABA restoration was not measured in treated patients.

Show evidence (2 references)

PMID:33169137 SUPPORT Human Clinical

"This combination treatment not only resulted in clinical cessation of seizures within 2 days, but at 7 months of age, growth and psychomotor development were unremarkable."

The reply summarizes a single infant treated by another group; seven-month follow-up does not establish sustained developmental benefit.

PMID:33169137 SUPPORT Other

"While this is certainly a reasonable hypothesis, one should be cautious drawing conclusions from one single observation."

The authors' own caution about the strength of the single-patient developmental-outcome claim.

Individualized Antiseizure Medication

Action: Pharmacotherapy NCIT:C15986

Platform: Small molecule

No single antiseizure medication has emerged as the treatment of choice. Across the patients whose epilepsy was controlled there was no drug in common, so regimen choice remains empirical.

Show evidence (1 reference)

PMID:37029735 SUPPORT Other

"we found that there was no common drug therapy among patients whose epilepsy was controlled"

Documents the absence of a shared effective drug across controlled cases, supporting individualized rather than protocolized therapy.

🔬

Diagnosis

2

Molecular Genetic Testing

The diagnosis rests on identification of biallelic pathogenic GAD1 variants, typically by exome sequencing, in an infant with neonatal-onset epileptic encephalopathy. There is no specific biochemical marker in routine use; metabolic screening was normal in the reported case where it was performed.

Genetic Testing NCIT:C15709

Show evidence (1 reference)

PMID:32705143 SUPPORT Human Clinical

"Our findings highlight an important role for GAD1 in seizure induction, neuronal and extraneuronal development, and introduce GAD1 as a new gene associated with developmental and epileptic encephalopathy."

Establishes GAD1 as the gene to be tested in this presentation; the diagnosis is molecular.

Neuroimaging

Brain MRI is normal in most patients early on; later imaging at older ages can show atrophic change, so a normal early MRI does not argue against the diagnosis.

Magnetic Resonance Imaging NCIT:C16809

Show evidence (1 reference)

PMID:37029735 SUPPORT Other

"The majority of the patients had normal MRI, although, in some patients, later MRI at older ages revealed defects."

Records that MRI is usually normal initially with later abnormalities in some. Evidence source is OTHER because this is the paper's literature summary.

📊

Prevalence

1

Worldwide

Cases In Literature Ultra Rare

The two 2020 cohorts comprised eleven and six patients, followed by isolated reports including the early-treated infant and the 2023 case. These publication counts do not establish a population prevalence or a current worldwide case total.

Show evidence (2 references)

PMID:32282878 SUPPORT Human Clinical

"Here we describe a new syndromic developmental and epileptic encephalopathy caused by bi-allelic loss-of-function variants in GAD1, as presented by 11 patients from six independent consanguineous families."

Provides the founding literature case count; no normalized population rate is asserted.

PMID:32705143 SUPPORT Human Clinical

"Here we present six affected individuals from six unrelated families, carrying bi-allelic GAD1 variants"

Adds six further reported patients to the literature count.

🐁

Animal Models

2

Gad1-null mouse (GAD67 knockout)

Targeted disruption of exon 1 of mouse Gad1 abolishes GAD67. Homozygotes are born at Mendelian frequency but die on the first morning after birth with severe cleft palate, and cortical GABA is reduced to 7% of wild type. Because death is neonatal, the model cannot be used to study the epilepsy that defines the human disorder.

Species

Mouse

Genotype

Gad1 (GAD67) homozygous null

Publication

PMID:9177246

Pathograph links

GABA Depletion recapitulates fidelity: high Direct biochemical measurement of the depletion: cortical GAD activity under 20% and GABA content 7% of wild type in newborn nulls.

Limitations: Measured in newborn mouse cerebral cortex; the equivalent measurement has not been made in human patients, so the magnitude is transferred by inference.

Readouts

Cerebral cortical GABA content

HPLC measurement of GABA in cerebral cortex homogenate of P0.5 nulls against wild-type littermates.

Direction: DECREASED

Interpretation: GABA at 7% of wild type is the quantitative correlate of the depletion node.

Show evidence (1 reference)

PMID:9177246 SUPPORT Model Organism

"GAD activities and GABA contents were reduced to 20% and 7%, respectively, in the cerebral cortex of the newborn GAD67 -/- mice."

Reports the cortical GAD activity and GABA measurements.

Show evidence (1 reference)

PMID:9177246 SUPPORT Model Organism

"GAD activities and GABA contents were reduced to 20% and 7%, respectively, in the cerebral cortex of the newborn GAD67 -/- mice."

Supports treating the null mouse as informative for the GABA-depletion node.

Failure of Palatal Shelf Elevation partially recapitulates fidelity: low Gad1-null mouse histology demonstrates failed palatal shelf elevation and cleft palate. CNS-specific deletion and oral explants support a neural movement-dependent mechanism, but the corresponding fetal intermediate has not been measured in human patients.

Limitations: Mouse cleft palate is highly penetrant and lethal, whereas the human malformation is variable and survivable. Human shelf elevation is not directly observed. The separate mouse umbilical-hernia finding does not establish identical human omphalocele.

Readouts

Secondary palate fusion

Gross and histological examination of the upper jaw and coronal facial sections in newborn and E17.5 animals.

Direction: ABOLISHED

Interpretation: Complete failure of secondary palate formation in every homozygote is the structural readout for this node.

Show evidence (1 reference)

PMID:9177246 SUPPORT Model Organism

"Severe cleft palate was found in all homozygous mutants"

Reports full penetrance of the cleft palate readout.

Show evidence (2 references)

PMID:20333300 SUPPORT INDIRECT Model Organism

"In both genotypes, palate shelf elevation fails to occur at E14.5 and all Gad1 and Viaat mutants were born with cleft secondary palates (Fig. 3A-H and data not shown)."

Mouse histology identifies failed shelf elevation preceding cleft palate; the human developmental intermediate is inferred from the model.

+ 1 more reference

Early-Onset Epileptic Seizures fails to recapitulate fidelity: low The defining human phenotype - neonatal epilepsy - cannot be observed in this model. Homozygotes die within a day of birth from the cleft palate, and their brains show no discernible structural defect, so the model gives no information about the seizure phenotype.

Limitations: This is a negative result by inaccessibility rather than by measurement: the animals do not survive long enough for an epilepsy phenotype to develop or be recorded, and no EEG was obtained. It should not be read as evidence that GAD67 loss fails to cause seizures.

Show evidence (2 references)

PMID:32705143 SUPPORT Other

"as Gad1-/- mice die neonatally of severe cleft palate, it has not been possible to determine any potential neurological dysfunction"

States explicitly that neonatal lethality prevents the mouse from informing the neurological phenotype.

+ 1 more reference

Show evidence (1 reference)

PMID:9177246 SUPPORT Model Organism

"These mice were born at the expected frequency but died of severe cleft palate during the first morning after birth."

Establishes the model and its neonatal lethal cleft-palate phenotype, which is what makes it informative for the malformation arm and uninformative for the epilepsy arm.

Gad1-null rat

Unlike the mouse, Gad1-null rats survive to adulthood and can be recorded by chronic EEG. They show abundant spike-wave discharges from two months of age and reduced GABA immunoreactivity in reticular thalamic neuronal somata. The seizure phenotype is absence-type spike-wave discharge, not the neonatal spasms and suppression-burst pattern of the human disorder.

Species

Rat

Genotype

Gad1 homozygous knockout

Publication

PMID:37830095

Pathograph links

Neuronal Hyperexcitability and Hypersynchrony partially recapitulates fidelity: low GAD1 loss in the rat produces a hypersynchronous electrographic phenotype, supporting the general link from GABA synthesis failure to network hypersynchrony.

Limitations: The discharge type is absence-like spike-wave activity in adolescent and adult animals, mechanistically a thalamocortical oscillation, rather than the neonatal epileptic spasms and suppression-burst background that define the human disease. Common laboratory rat strains also show spike-wave discharges spontaneously, so the phenotype is a shift in severity against a noisy background rather than an all-or-none disease model. Valproate, which suppressed discharges in controls, made them worse in the nulls, so drug responses in this model should not be transferred to patients.

Readouts

Reticular thalamic somatic GABA immunoreactivity

Immunohistochemistry for GABA in reticular thalamic nucleus neurons of null versus control rats.

Direction: DECREASED

Interpretation: Confirms that the electrographic phenotype is accompanied by the expected loss of GABA in the implicated inhibitory nucleus.

Show evidence (1 reference)

PMID:37830095 SUPPORT Model Organism

"GABA immunoreactivity was significantly reduced in the somata of RTN neurons in Gad1 (-/-) rats but not in their axons targeting the thalamus."

Reports the immunohistochemical GABA measurement.

Show evidence (1 reference)

PMID:37830095 SUPPORT Model Organism

"VPA treatment alleviated SWD symptoms in control rats, however, counterintuitively exacerbated the symptoms in Gad1 (-/-) rats."

The paradoxical valproate response is why this model is treated as only partially informative and its pharmacology is not transferred to patients.

Show evidence (1 reference)

PMID:37830095 SUPPORT Model Organism

"SWDs were abundant in EEG from Gad1 (-/-) rats as young as 2 months old."

Establishes that this model, unlike the mouse, survives to yield an electrographic seizure phenotype.

{ }

Source YAML

click to show

name: Developmental and Epileptic Encephalopathy 89
creation_date: "2026-08-27T00:00:00Z"
category: Mendelian
disease_term:
  preferred_term: developmental and epileptic encephalopathy 89
  term:
    id: MONDO:0030856
    label: developmental and epileptic encephalopathy 89
synonyms:
- DEE89
- DEE 89
- GAD1 deficiency
- GAD67 deficiency
description: >-
  Developmental and epileptic encephalopathy 89 (DEE 89) is an autosomal
  recessive disorder associated with biallelic GAD1 variants that impair GAD67,
  an enzyme converting glutamate to GABA. Mouse experiments demonstrate marked
  depletion of cortical GABA; residual synthesis and compartment-specific
  compensation by GAD2/GAD65 vary, and human brain GABA has not been measured in
  the reviewed clinical studies.

  Epilepsy was reported in the published DEE89 cohorts, with onset from birth
  to six months. Chatron et al. reported first-month onset in ten patients with
  an available early history, whereas Neuray et al.'s six patients had onset at
  two to six months. Seizure types and medication response vary. EEG may show
  suppression-burst, hypsarrhythmia or other epileptiform abnormalities.
  Developmental impairment is usually severe, but one older patient had moderate
  intellectual disability and an early-treated infant had unremarkable
  psychomotor development at seven months, a short follow-up exception.

  GABA deficiency can affect neural development as well as inhibitory network
  function. Developmental deficits persisted despite seizure control in several
  patients. Structural findings include cleft palate, omphalocele, contractures
  and clubfoot. CNS-specific Gad1 deletion and palate explant experiments in
  mice support a fetal motor mechanism for palatal abnormalities, rather than
  requiring a primary defect within the palate. The human authors likewise
  propose reduced fetal movement as a cause of contractures and malformations;
  that extrapolation remains provisional, and mouse umbilical hernia is not
  identical to human omphalocele.

  Additional motor, swallowing, ocular, auditory, renal and dysmorphic findings
  are variably reported, often in single patients. A small published-case
  comparison found fewer major malformations with missense alleles, without
  measuring residual GAD67 activity. Neither that observation nor the single
  favourable early combination-treatment outcome establishes a genotype-specific
  prognosis or a developmental treatment effect.

parents:
- Epilepsy
- Neurodevelopmental Disorder
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0030856
      label: developmental and epileptic encephalopathy 89
    mapping_predicate: skos:exactMatch
    mapping_source: MONDO
    mapping_justification: >-
      MONDO:0030856 is the DEE 89 concept, xrefed to OMIM:619124 and carrying the
      RO:0004003 causal-gene relationship to HGNC:4092 (GAD1).
inheritance:
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    DEE 89 is autosomal recessive. Affected individuals carry biallelic
    loss-of-function GAD1 variants; the founding cohort was drawn from six
    independent consanguineous families, and subsequent reports have been
    homozygous or compound heterozygous.
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we describe a new syndromic developmental and epileptic
      encephalopathy caused by bi-allelic loss-of-function variants in GAD1, as
      presented by 11 patients from six independent consanguineous families.
    explanation: >-
      Establishes biallelic (recessive) GAD1 loss of function as the cause, in
      consanguineous pedigrees.
  - reference: PMID:32705143
    reference_title: "Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we present six affected individuals from six unrelated families,
      carrying bi-allelic GAD1 variants
    explanation: >-
      Independent replication of biallelic GAD1 inheritance in six further
      families.
pathophysiology:
- name: Biallelic GAD1 Loss of Function
  description: >-
    Biallelic loss-of-function variants in GAD1 (missense, nonsense, splice-site
    and deletion alleles distributed across the gene) are the initiating lesion.
    This node captures the single concept of the genetic lesion.
  role: trigger
  biological_scale: MOLECULAR
  gene:
    preferred_term: GAD1
    term:
      id: hgnc:4092
      label: GAD1
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we describe a new syndromic developmental and epileptic
      encephalopathy caused by bi-allelic loss-of-function variants in GAD1, as
      presented by 11 patients from six independent consanguineous families.
    explanation: >-
      Identifies biallelic GAD1 loss-of-function variants as the causal lesion of
      the syndrome.
  downstream:
  - target: GAD67 Enzyme Deficiency
    causal_link_type: DIRECT
    description: >-
      Loss-of-function alleles reduce or abolish the activity of the GAD67
      enzyme that GAD1 encodes.
  - target: Muscle Weakness
    description: The clinical series attributes weakness to biallelic GAD1 variants; the intervening
      mechanism and central versus peripheral localization are unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:32705143
      reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic
        GAD1 variants.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: In conclusion, this case series reports distinct phenotypical features caused by GAD1
        variants, including early-infantile onset epilepsy, severe developmental delay and muscle
        weakness.
      explanation: The clinical genetic series explicitly attributes muscle weakness to GAD1 variants.
        This supports a qualified causal relation with unknown intermediates, but does not localize
        weakness to central motor development, peripheral nerves or muscle.
      directness: INDIRECT

- name: GAD67 Enzyme Deficiency
  description: GAD67 converts glutamate to GABA. Biallelic GAD1 variants are predicted or demonstrated
    to impair the protein; activity has not been measured for every allele, and missense or in-frame
    variants need not abolish all function.
  role: mediator
  biological_scale: MOLECULAR
  molecular_functions:
  - preferred_term: glutamate decarboxylase activity
    term:
      id: GO:0004351
      label: glutamate decarboxylase activity
    modifier: DECREASED
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      GAD1 encodes the glutamate decarboxylase enzyme GAD67
    explanation: >-
      Establishes that the affected gene product is the GAD67 decarboxylase
      enzyme.
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      GAD67 is the rate-limiting enzyme in GABA synthesis, and its deficiency
      leads to developmental and epileptic encephalopathy 89 (DEE 89).
    explanation: >-
      Names GAD67 deficiency as the proximate biochemical defect in DEE 89 and
      identifies it as rate-limiting for GABA synthesis.
  downstream:
  - target: GABA Depletion
    causal_link_type: DIRECT
    description: Reduced GAD67 function decreases basal GABA synthesis. GAD65 supplies residual and
      compartment-specific GABA but does not restore the normal cortical pool in null mice.

- name: GABA Depletion
  description: GAD67 loss markedly reduces basal CNS GABA in mouse models. GAD65-dependent synthesis
    persists and can preserve axonal GABA in Gad1-null rats. The magnitude and compartmental distribution
    of depletion in human DEE89 remain unmeasured in the reviewed cohorts.
  role: mediator
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: GABAergic neuron
    term:
      id: CL:0000617
      label: GABAergic neuron
  biological_processes:
  - preferred_term: GABA biosynthetic process
    term:
      id: GO:0009449
      label: GABA biosynthetic process
    modifier: DECREASED
  evidence:
  - reference: PMID:32705143
    reference_title: "Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1 variants."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Its predominant isoform GAD67, contributes up to ∼90% of base-level GABA
      in the CNS, and is encoded by the GAD1 gene.
    explanation: Background physiology summarized by the clinical paper, not a human GABA measurement.
  - reference: PMID:9177246
    reference_title: "Cleft palate and decreased brain gamma-aminobutyric acid in mice lacking the 67-kDa isoform of glutamic acid decarboxylase."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      GAD activities and GABA contents were reduced to 20% and 7%,
      respectively, in the cerebral cortex of the newborn GAD67 -/- mice.
    explanation: >-
      Direct measurement of the depletion in the Gad1-null mouse: cortical GABA
      falls to 7% of wild type. This is model-organism evidence for the
      magnitude of the depletion; the human biochemical measurement has not been
      reported.
  downstream:
  - target: Excitation-Inhibition Imbalance
    causal_link_type: DIRECT
    description: Reduced GABA availability disrupts network excitation-inhibition balance. GABA also
      has developmental signaling roles, so this does not imply that every fetal or neonatal action
      is inhibitory.
  - target: Impaired GABA-Dependent Fetal Motor Signaling
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Loss of GABA signaling in the developing CNS impairs the fetal motor activity required
      for normal extra-neural morphogenesis.
    evidence:
    - reference: PMID:20333300
      reference_title: Cleft palate is caused by CNS dysfunction in Gad1 and Viaat knockout mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: In addition, we showed that CNS-specific inactivation of Gad1 was sufficient to disrupt
        palate development.
      explanation: CNS-specific mouse deletion supports a neural developmental route to structural
        defects.
      directness: INDIRECT
  - target: Developmental Encephalopathy
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: GABA-dependent neural development is proposed to be impaired independently of ongoing
      seizures. Developmental deficits persisted after seizure freedom in several patients, although
      earlier seizure injury and direct developmental effects cannot be quantitatively separated.
    evidence:
    - reference: PMID:32705143
      reference_title: "Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1 variants."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: However, despite seizure control (seizure freedom achieved in three of six individuals),
        all patients described here still showed severe intellectual disability.
      explanation: Persistence after seizure control supports a developmental component, without excluding
        earlier seizure injury.
    - reference: PMID:32705143
      reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic
        GAD1 variants.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: leading to the assumption that genetic defects themselves are influencing development
        and cognition, independently from seizure control.
      explanation: The authors interpret the clinical dissociation as a direct developmental contribution;
        this remains a causal inference.
      directness: INDIRECT
  - target: Impaired GABA-Dependent Axial Motor Development
    description: Constitutive GABA deficiency is proposed to impair axial motor development; the authors
      make this interpretation specifically for axial hypotonia.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:32282878
      reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and
        epileptic encephalopathy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: This most likely reflects the detrimental impact of a constitutive GABA deficiency
        on neurodevelopment.
      explanation: The authors specifically propose a developmental effect of constitutive GABA deficiency
        to explain axial hypotonia. Their comparison with stiff-person syndrome does not establish
        the cause of other motor signs in DEE89.
      directness: INDIRECT

- name: Excitation-Inhibition Imbalance
  description: >-
    Depletion of the principal inhibitory neurotransmitter shifts the balance
    between glutamatergic excitation and GABAergic inhibition toward net
    excitation. This node captures the single concept of the excitation-inhibition
    imbalance and conforms to the shared epilepsy final common pathway.
  role: mediator
  biological_scale: CELLULAR
  conforms_to: "epilepsy_excitation_inhibition_imbalance#Excitation-Inhibition Imbalance"
  cell_types:
  - preferred_term: GABAergic neuron
    term:
      id: CL:0000617
      label: GABAergic neuron
  biological_processes:
  - preferred_term: gamma-aminobutyric acid signaling pathway
    term:
      id: GO:0007214
      label: gamma-aminobutyric acid signaling pathway
    modifier: DECREASED
  evidence:
  - reference: PMID:32705143
    reference_title: "Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1 variants."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Disruption of GAD1 results in an imbalance of inhibitory and excitatory
      neurotransmitters
    explanation: >-
      States the excitation-inhibition imbalance as the direct consequence of
      GAD1 disruption.
  downstream:
  - target: Neuronal Hyperexcitability and Hypersynchrony
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Reduced GABAergic restraint promotes network hyperexcitability; the exact developmental
      and regional intermediates in human DEE89 are unresolved.

- name: Neuronal Hyperexcitability and Hypersynchrony
  description: Impaired GABAergic signaling permits excessive, synchronized network activity. Human
    EEG shows epileptiform abnormalities, often on a severely disorganized background; suppression-burst
    is a readout of broader network dysfunction rather than a unique measurement of GABA depletion.
  role: central_effector
  biological_scale: CELLULAR
  conforms_to: "epilepsy_excitation_inhibition_imbalance#Neuronal Hyperexcitability and Hypersynchrony"
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: action potential
    term:
      id: GO:0001508
      label: action potential
    modifier: INCREASED
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Early EEG showed suppression-burst or pattern of burst attenuation or
      hypsarrhythmia if only recorded in the post-neonatal period.
    explanation: >-
      The suppression-burst and hypsarrhythmic EEG patterns are the
      electrophysiological signature of the hypersynchronous, poorly restrained
      neonatal network.
  downstream:
  - target: Early-Onset Epileptic Seizures
    causal_link_type: DIRECT
    description: Abnormal synchronized network discharge produces the clinical seizures, which begin
      neonatally or later in infancy.

- name: Early-Onset Epileptic Seizures
  description: Published DEE89 cohorts have early epilepsy, with neonatal onset in the evaluable histories
    of Chatron et al. and onset at two to six months in Neuray et al. Epileptic spasms, myoclonic,
    tonic, tonic-clonic and focal seizures occur; some patients achieve control while others remain
    drug-resistant.
  role: effector
  biological_scale: ORGANISM
  conforms_to: "epilepsy_excitation_inhibition_imbalance#Recurrent Unprovoked Seizures"
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All 10 patients, from whom early disease history was available, presented
      with seizure onset in the first month of life, mainly consisting of
      epileptic spasms or myoclonic seizures.
    explanation: >-
      Documents first-month seizure onset and the predominant spasm/myoclonic
      semiology in the founding cohort.
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "All of the reported patients manifested seizures."
    explanation: >-
      Establishes that seizures occur in every reported patient. Evidence source
      is OTHER because this is the paper's literature summary rather than its own
      case observation.
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "and the patients showed heterogeneous types of seizures such as tonic–clonic, epileptic spasm, myoclonic, and focal motor seizures."
    explanation: >-
      Names the full range of reported semiologies, which is wider than the spasms
      and myoclonic seizures of the founding cohort. Evidence source is OTHER
      because this is the paper's literature summary.
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "In reported patients, the age‐onset of seizures was from the birth to 6 months old"
    explanation: >-
      States the onset window this node's description asserts - birth to six
      months across the published literature, wider than the first-month onset of
      the founding cohort. Evidence source is OTHER because this is the paper's
      literature summary.
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "In some patients, the administration of antiseizure medications led to the control of epilepsy, but in others, epilepsy remained uncontrolled."
    explanation: Medication response varies; refractoriness is represented separately as a drug-response
      phenotype.
  downstream:
  - target: Developmental Encephalopathy
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Frequent early epileptic activity may add to the developmental deficit. The authors
      distinguish this potentially modifiable component from the prenatal developmental role of GABA;
      their relative contributions remain unresolved.
    evidence:
    - reference: PMID:32282878
      reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and
        epileptic encephalopathy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: whether this exceeds the expected beneficial effect of a reduction of seizure burden
        on neurodevelopment.
      explanation: The clinical authors recognize a seizure-burden contribution while leaving any
        additional developmental treatment effect unresolved.
      directness: INDIRECT
  - target: Seizures
    description: This is a documented timing or semiological manifestation of the early epilepsy endpoint.
    causal_link_type: DIRECT
  - target: Neonatal-Onset Seizures
    description: This is a documented timing or semiological manifestation of the early epilepsy endpoint.
    causal_link_type: DIRECT
  - target: Epileptic Spasms
    description: This is a documented timing or semiological manifestation of the early epilepsy endpoint.
    causal_link_type: DIRECT
  - target: Myoclonic Seizures
    description: This is a documented timing or semiological manifestation of the early epilepsy endpoint.
    causal_link_type: DIRECT
  - target: Focal Motor Seizures
    description: This is a documented timing or semiological manifestation of the early epilepsy endpoint.
    causal_link_type: DIRECT
  - target: Bilateral Tonic-Clonic Seizures
    description: This is a documented timing or semiological manifestation of the early epilepsy endpoint.
    causal_link_type: DIRECT
  - target: Tonic Seizures
    description: This is a documented timing or semiological manifestation of the early epilepsy endpoint.
    causal_link_type: DIRECT

- name: Impaired GABA-Dependent Fetal Motor Signaling
  description: Developing CNS GABA signaling supports fetal motor activity. Mouse CNS-specific deletion
    disrupts palatal development even when palatal Gad1 expression is retained; normal mutant palate
    fusion in explants argues against a required palate-intrinsic lesion. Translation of this motor
    mechanism to human malformations is provisional.
  role: mediator
  biological_scale: TISSUE
  evidence:
  - reference: PMID:20333300
    reference_title: Cleft palate is caused by CNS dysfunction in Gad1 and Viaat knockout mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Our work strongly supports the idea that the cleft palate phenotype in Gad1 and Viaat
      knockout mice is due to a loss of GABA signaling in the CNS rather than in craniofacial tissues.
    explanation: CNS-specific deletion, pharmacological rescue and oral explants support the mouse
      mechanism.
    directness: INDIRECT
  downstream:
  - target: Reduced Fetal Movement
    description: Impaired fetal CNS signaling reduces movements needed for normal morphogenesis.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:20333300
      reference_title: Cleft palate is caused by CNS dysfunction in Gad1 and Viaat knockout mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: Our work strongly supports the idea that the cleft palate phenotype in Gad1 and Viaat
        knockout mice is due to a loss of GABA signaling in the CNS rather than in craniofacial tissues.
      explanation: CNS-specific deletion, pharmacological rescue and oral explants support the mouse
        mechanism.
      directness: INDIRECT
    - reference: PMID:32282878
      reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and
        epileptic encephalopathy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Also the pes equinovarus, joint contractures and arthrogryposis, seen in several of
        the patients in our study, are known to reflect a reduction of foetal movements
      explanation: The authors propose fetal movement reduction as the causal explanation for these
        human structural findings.
      directness: INDIRECT
  mechanism_confidence: PROVISIONAL

- name: Failure of Palatal Shelf Elevation
  description: Failed elevation of the palatal shelves prevents their normal apposition and fusion.
    Mouse histology and oral-explant experiments support a CNS-dependent fetal oral-movement mechanism;
    the equivalent prenatal sequence has not been demonstrated in humans.
  role: mediator
  biological_scale: TISSUE
  biological_processes:
  - preferred_term: roof of mouth development
    term:
      id: GO:0060021
      label: roof of mouth development
    modifier: ABNORMAL
  evidence:
  - reference: PMID:20333300
    reference_title: Cleft palate is caused by CNS dysfunction in Gad1 and Viaat knockout mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: In both genotypes, palate shelf elevation fails to occur at E14.5 and all Gad1 and Viaat
      mutants were born with cleft secondary palates (Fig. 3A-H and data not shown).
    explanation: Mouse histology identifies failed shelf elevation preceding cleft palate; the human
      developmental intermediate is inferred from the model.
    directness: INDIRECT
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Further studies demonstrated that the presence of cleft palate is due to a defect of
      foetal oral movement of the tongue during palatal development and Gad1 is specifically required
      in the CNS for normal palatal formation
    explanation: The clinical authors interpret prior mouse experiments as a CNS-dependent fetal oral-movement
      mechanism. This is a proposed explanation for human cleft palate, not a measured prenatal human
      event.
    directness: INDIRECT
  mechanism_confidence: PROVISIONAL
  downstream:
  - target: Cleft Palate
    description: Failure of palatal shelf elevation prevents normal palate closure. The causal sequence
      is supported in mice and provisionally transferred to human GAD1 deficiency.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:20333300
      reference_title: Cleft palate is caused by CNS dysfunction in Gad1 and Viaat knockout mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: In both genotypes, palate shelf elevation fails to occur at E14.5 and all Gad1 and
        Viaat mutants were born with cleft secondary palates (Fig. 3A-H and data not shown).
      explanation: Mouse histology identifies failed shelf elevation preceding cleft palate; the human
        developmental intermediate is inferred from the model.
      directness: INDIRECT

- name: Reduced Fetal Movement
  description: Reduced fetal movement is the human authors' proposed intermediate linking GABA-related
    CNS dysfunction to congenital joint and palatal abnormalities. It was not measured prenatally
    in the clinical cohorts.
  role: mediator
  biological_scale: ORGANISM
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Also the pes equinovarus, joint contractures and arthrogryposis, seen in several of the
      patients in our study, are known to reflect a reduction of foetal movements
    explanation: The authors propose fetal movement reduction as the causal explanation for these
      human structural findings.
    directness: INDIRECT
  mechanism_confidence: PROVISIONAL
  downstream:
  - target: Congenital Joint Contractures
    description: Reduced movement in utero can fix joints in abnormal positions, producing the congenital
      contracture phenotype.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:32282878
      reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and
        epileptic encephalopathy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Also the pes equinovarus, joint contractures and arthrogryposis, seen in several of
        the patients in our study, are known to reflect a reduction of foetal movements
      explanation: The authors propose fetal movement reduction as the causal explanation for these
        human structural findings.
      directness: INDIRECT
  - target: Talipes Equinovarus
    description: Reduced fetal movement is the authors' proposed cause of the congenital clubfoot.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:32282878
      reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and
        epileptic encephalopathy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Also the pes equinovarus, joint contractures and arthrogryposis, seen in several of
        the patients in our study, are known to reflect a reduction of foetal movements
      explanation: The authors propose fetal movement reduction as the causal explanation for these
        human structural findings.
      directness: INDIRECT
  - target: Failure of Palatal Shelf Elevation
    description: Abnormal fetal tongue movement can obstruct palatal shelf elevation; the clinical
      authors propose this mouse-supported explanation for the human cleft.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:32282878
      reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and
        epileptic encephalopathy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Further studies demonstrated that the presence of cleft palate is due to a defect of
        foetal oral movement of the tongue during palatal development and Gad1 is specifically required
        in the CNS for normal palatal formation
      explanation: The clinical authors interpret prior mouse experiments as a CNS-dependent fetal
        oral-movement mechanism. This is a proposed explanation for human cleft palate, not a measured
        prenatal human event.
      directness: INDIRECT
  - target: Impaired Retraction of Physiological Umbilical Hernia
    description: Reduced fetal movement is proposed to alter fetal posture and pressure, preventing
      normal hernia retraction.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:32282878
      reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and
        epileptic encephalopathy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: movement reduction leads to a hunched posture in the foetus and increased intra-abdominal
        pressure, resulting in failure of retracting umbilical hernia and omphalocele
      explanation: The clinical authors propose this movement/posture/retraction route. Mouse histology
        establishes umbilical hernia, so extension to human omphalocele remains a hypothesis.
      directness: INDIRECT

- name: Developmental Encephalopathy
  description: 'Impaired neurodevelopment generally causes major cognitive, language and motor limitations,
    sometimes with regression. Severity varies: one older child had moderate intellectual disability
    and some speech and ambulation, and an early-treated infant had unremarkable development at seven
    months. Deaths in the original cohort had heterogeneous causes and are not treated as a single
    developmental endpoint.'
  role: consequence
  biological_scale: ORGANISM
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Most patients did not achieve any speech or non-verbal communication, only one was reported
      to have developed simple speech and basic perceptive language skills.
    explanation: The six-patient cohort documents a range of developmental outcomes.
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Of the more severely affected individuals, despite remaining seizure-free following pharmacological
      intervention, they still failed to accelerate in their intellectual development.
    explanation: Developmental impairment persisted in some seizure-free patients.
  downstream:
  - target: Global Developmental Delay
    description: This is a cognitive, language or acquired developmental manifestation of the encephalopathy.
    causal_link_type: DIRECT
  - target: Intellectual Disability
    description: This is a cognitive, language or acquired developmental manifestation of the encephalopathy.
    causal_link_type: DIRECT
  - target: Absent Speech
    description: This is a cognitive, language or acquired developmental manifestation of the encephalopathy.
    causal_link_type: DIRECT
  - target: Developmental Regression
    description: This is a cognitive, language or acquired developmental manifestation of the encephalopathy.
    causal_link_type: DIRECT

- name: Impaired GABA-Dependent Axial Motor Development
  biological_scale: TISSUE
  mechanism_confidence: PROVISIONAL
  description: The clinical authors propose that constitutive GABA deficiency impairs axial motor
    development, explaining axial hypotonia. This interpretation is not a demonstrated circuit lesion
    or an explanation for every abnormal motor sign.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: This most likely reflects the detrimental impact of a constitutive GABA deficiency on
      neurodevelopment.
    explanation: The authors specifically propose a developmental effect of constitutive GABA deficiency
      to explain axial hypotonia. Their comparison with stiff-person syndrome does not establish the
      cause of other motor signs in DEE89.
    directness: INDIRECT
  downstream:
  - target: Hypotonia
    description: Impaired axial motor development is the authors' proposed cause of axial hypotonia;
      the responsible circuitry and developmental intermediates remain unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:32282878
      reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and
        epileptic encephalopathy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: This most likely reflects the detrimental impact of a constitutive GABA deficiency
        on neurodevelopment.
      explanation: The authors specifically propose a developmental effect of constitutive GABA deficiency
        to explain axial hypotonia. Their comparison with stiff-person syndrome does not establish
        the cause of other motor signs in DEE89.
      directness: INDIRECT

- name: Impaired Retraction of Physiological Umbilical Hernia
  description: The authors propose that impaired fetal movement alters posture and intra-abdominal
    pressure, interfering with retraction of the physiological umbilical hernia. Gad1-null mice have
    persistent umbilical hernia rather than histologically identical human omphalocele; transfer of
    this mechanism to human omphalocele is provisional.
  role: mediator
  biological_scale: TISSUE
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:20333300
    reference_title: Cleft palate is caused by CNS dysfunction in Gad1 and Viaat knockout mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: These phenotypes suggest that Gad1 and Viaat functions are not necessary for body wall
      formation per se but are instead required for the retraction of the umbilical hernia during
      development.
    explanation: Mouse histology supports a retraction defect rather than failed body-wall formation;
      it does not demonstrate human omphalocele.
    directness: INDIRECT
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: movement reduction leads to a hunched posture in the foetus and increased intra-abdominal
      pressure, resulting in failure of retracting umbilical hernia and omphalocele
    explanation: The clinical authors propose this movement/posture/retraction route. Mouse histology
      establishes umbilical hernia, so extension to human omphalocele remains a hypothesis.
    directness: INDIRECT
  downstream:
  - target: Omphalocele
    description: Failure of normal visceral retraction is proposed as a contributor to human omphalocele.
      This human extrapolation is less secure than the demonstrated mouse umbilical-hernia phenotype.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:32282878
      reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and
        epileptic encephalopathy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: movement reduction leads to a hunched posture in the foetus and increased intra-abdominal
        pressure, resulting in failure of retracting umbilical hernia and omphalocele
      explanation: The clinical authors propose this movement/posture/retraction route. Mouse histology
        establishes umbilical hernia, so extension to human omphalocele remains a hypothesis.
      directness: INDIRECT

phenotypes:
- name: Seizures
  description: Epilepsy was present in the published DEE89 cohorts and case reports reviewed through
    2023. These epilepsy-ascertained cases do not establish complete penetrance of all biallelic GAD1
    variants.
  category: Neurological
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A key clinical feature common to all affected individuals was early onset seizures (from
      2 to 6 months), predominantly focal motor seizures with and without impaired awareness (two
      with additional epileptic spasms, four with focal non-motor seizures, and five with bilateral
      motor seizures).
    explanation: All six patients in this cohort had epilepsy; this is a cohort observation rather
      than a penetrance estimate.

- name: Neonatal-Onset Seizures
  description: Chatron et al. reported first-month seizure onset in ten patients with an available
    early history. Their other patient was first evaluated later, with onset incompletely defined.
    Neuray et al. instead reported onset at two to six months in six patients.
  category: Neurological
  phenotype_term:
    preferred_term: Neonatal seizure
    term:
      id: HP:0032807
      label: Neonatal seizure
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All 10 patients, from whom early disease history was available, presented
      with seizure onset in the first month of life, mainly consisting of
      epileptic spasms or myoclonic seizures.
    explanation: The ten-person denominator refers only to evaluable early histories in this 11-patient
      cohort, not to all published patients.
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "In reported patients, the age‐onset of seizures was from the birth to 6 months old"
    explanation: The 2023 review summarizes the wider birth-to-six-month onset range, which includes
      non-neonatal onset. No pooled frequency band is inferred.

- name: Epileptic Spasms
  description: >-
    Epileptic (infantile) spasms are one of the two predominant early seizure
    semiologies.
  category: Neurological
  phenotype_term:
    preferred_term: Epileptic spasm
    term:
      id: HP:0011097
      label: Epileptic spasm
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      mainly consisting of epileptic spasms or myoclonic seizures
    explanation: Names epileptic spasms as a predominant early semiology.
- name: Myoclonic Seizures
  description: >-
    Myoclonic seizures are the other predominant early seizure semiology.
  category: Neurological
  phenotype_term:
    preferred_term: Myoclonic seizure
    term:
      id: HP:0032794
      label: Myoclonic seizure
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      mainly consisting of epileptic spasms or myoclonic seizures
    explanation: Names myoclonic seizures as a predominant early semiology.
- name: Focal Motor Seizures
  description: Focal motor seizures are among the reported semiologies.
  category: Neurological
  phenotype_term:
    preferred_term: Focal motor seizure
    term:
      id: HP:0011153
      label: Focal motor seizure
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: predominantly focal motor seizures with and without impaired awareness (two with additional
      epileptic spasms, four with focal non-motor seizures, and five with bilateral motor seizures).
    explanation: The six-patient primary cohort documents focal motor semiology without assigning
      it to every patient.

- name: Bilateral Tonic-Clonic Seizures
  description: Tonic-clonic seizures are among the reported semiologies.
  category: Neurological
  phenotype_term:
    preferred_term: Bilateral tonic-clonic seizure
    term:
      id: HP:0002069
      label: Bilateral tonic-clonic seizure
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: At the age of 5 months, she developed generalized tonic-clonic seizures.
    explanation: Case 5 developed generalized tonic-clonic seizures; the broader bilateral tonic-clonic
      binding also covers other reports without established onset classification.

- name: Suppression-Burst EEG
  description: >-
    Neonatal EEG shows a suppression-burst pattern or burst attenuation.
  category: Neurological
  phenotype_term:
    preferred_term: EEG with burst suppression
    term:
      id: HP:0010851
      label: EEG with burst suppression
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Early EEG showed suppression-burst or pattern of burst attenuation or
      hypsarrhythmia if only recorded in the post-neonatal period.
    explanation: Documents the suppression-burst / burst-attenuation neonatal EEG.
  reports_on:
  - target: Neuronal Hyperexcitability and Hypersynchrony
    relationship: CORRELATES_WITH
    direction: POSITIVE
    interpretation: This EEG pattern accompanies disordered epileptic network activity. It does not
      quantify GABA depletion or require continuing clinical seizures.
    evidence:
    - reference: PMID:32282878
      reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and
        epileptic encephalopathy.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Early EEG showed suppression-burst or pattern of burst attenuation or hypsarrhythmia
        if only recorded in the post-neonatal period.
      explanation: Documents the suppression-burst / burst-attenuation neonatal EEG.

- name: Hypsarrhythmia
  description: >-
    Hypsarrhythmia is seen when EEG is first recorded after the neonatal period.
  category: Neurological
  phenotype_term:
    preferred_term: Hypsarrhythmia
    term:
      id: HP:0002521
      label: Hypsarrhythmia
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Early EEG showed suppression-burst or pattern of burst attenuation or
      hypsarrhythmia if only recorded in the post-neonatal period.
    explanation: Documents hypsarrhythmia on post-neonatal recordings.
  reports_on:
  - target: Neuronal Hyperexcitability and Hypersynchrony
    relationship: CORRELATES_WITH
    direction: POSITIVE
    interpretation: This EEG pattern accompanies disordered epileptic network activity. It does not
      quantify GABA depletion or require continuing clinical seizures.
    evidence:
    - reference: PMID:32282878
      reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and
        epileptic encephalopathy.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Early EEG showed suppression-burst or pattern of burst attenuation or hypsarrhythmia
        if only recorded in the post-neonatal period.
      explanation: Documents hypsarrhythmia on post-neonatal recordings.

- name: Global Developmental Delay
  description: Global developmental delay is generally severe, with absent motor and language milestones.
    One older patient had moderate intellectual disability and achieved simple speech and ambulation;
    one early-treated infant had unremarkable development at seven months, with longer-term outcome
    unresolved.
  category: Neurological
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Most patients did not achieve any speech or non-verbal communication, only one was reported
      to have developed simple speech and basic perceptive language skills.
    explanation: The six-patient cohort documents a range of developmental outcomes.
  - reference: PMID:33169137
    reference_title: 'Reply: Rational therapy with vigabatrin and a ketogenic diet in a patient with
      GAD1 deficiency.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: This combination treatment not only resulted in clinical cessation of seizures within
      2 days, but at 7 months of age, growth and psychomotor development were unremarkable.
    explanation: The reply summarizes another group's infant; short follow-up does not establish a
      normal long-term outcome.

- name: Hypotonia
  description: Axial hypotonia frequently coexists with increased limb tone; generalized hypotonia
    of variable severity also occurs.
  category: Neurological
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Whereas in stiff person syndrome axial muscles are predominantly affected, patients reported
      in our manuscript often had axial hypotonia.
    explanation: The primary cohort distinguishes axial hypotonia from increased limb tone.

- name: Absent Speech
  description: >-
    Speech was absent in the index patient of the 2023 report, consistent with the
    bed-confined, severely impaired functional status of most reported patients.
  category: Neurological
  phenotype_term:
    preferred_term: Absent speech
    term:
      id: HP:0001344
      label: Absent speech
  evidence:
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "he manifested severe neurodevelopmental delay with bed confinement, spasticity in limbs, speech absence, and incontinency."
    explanation: >-
      Documents absent speech in the index patient. No frequency band is asserted
      because this is a single-patient observation.
- name: Spasticity
  description: >-
    Limb spasticity was present in the index patient of the 2023 report.
  category: Neurological
  phenotype_term:
    preferred_term: Spasticity
    term:
      id: HP:0001257
      label: Spasticity
  evidence:
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "he manifested severe neurodevelopmental delay with bed confinement, spasticity in limbs, speech absence, and incontinency."
    explanation: >-
      Documents limb spasticity in the index patient. No frequency band is
      asserted because this is a single-patient observation.
- name: Cerebral Atrophy
  description: >-
    Brain MRI is normal in most patients, but diffuse cerebral atrophy was present
    in the index patient of the 2023 report and later imaging at older ages shows
    abnormalities in some.
  category: Neurological
  phenotype_term:
    preferred_term: Cerebral atrophy
    term:
      id: HP:0002059
      label: Cerebral atrophy
  evidence:
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "MRI showed diffuse cerebral atrophy and severe ventriculomegaly."
    explanation: >-
      Documents cerebral atrophy on MRI in the index patient. No frequency band is
      asserted because the same paper reports MRI as normal in the majority.
- name: Ventriculomegaly
  description: >-
    Severe ventriculomegaly accompanied the cerebral atrophy in the index patient
    of the 2023 report.
  category: Neurological
  phenotype_term:
    preferred_term: Ventriculomegaly
    term:
      id: HP:0002119
      label: Ventriculomegaly
  evidence:
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "MRI showed diffuse cerebral atrophy and severe ventriculomegaly."
    explanation: >-
      Documents ventriculomegaly on MRI in the index patient. No frequency band is
      asserted because this is a single-patient observation.
- name: Cleft Palate
  description: Cleft palate occurred in seven of eleven patients in Chatron et al. and one of six
    in Neuray et al. It is a variable malformation, not a majority finding across all cohorts.
  category: Craniofacial
  phenotype_term:
    preferred_term: Cleft palate
    term:
      id: HP:0000175
      label: Cleft palate
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Seven patients presented a cleft palate and two also had an omphalocele,
      reproducing the phenotype of the knockout Gad1-/- mouse model.
    explanation: The human cohort establishes cleft palate. The abstract's claim of complete mouse
      correspondence is qualified by the primary mouse study distinguishing umbilical hernia from
      omphalocele.

- name: Omphalocele
  description: Omphalocele was present in two siblings in the 11-patient cohort. The sister also had
    cleft palate, but the brother did not; co-occurrence with cleft palate is therefore not obligatory.
  category: Gastrointestinal
  phenotype_term:
    preferred_term: Omphalocele
    term:
      id: HP:0001539
      label: Omphalocele
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: At birth, omphalocele and bilateral talipes equinovarus were observed.
    explanation: Case 4 had omphalocele; the clinical table records no cleft palate in this sibling.

- name: Congenital Joint Contractures
  description: Congenital contractures and arthrogryposis occur in some patients. Six of eleven patients
    had joint contractures in Chatron et al.; the abstract's eight-person count combines contractures
    and/or clubfoot, and does not give eight congenital-contracture cases.
  category: Musculoskeletal
  phenotype_term:
    preferred_term: Congenital contracture
    term:
      id: HP:0002803
      label: Congenital contracture
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Interestingly, in addition to neurological features, seven patients presented a cleft
      palate, six joint contractures and five pes equinovarus.
    explanation: Separates the joint-contracture and clubfoot counts in the 11-patient cohort.

- name: Talipes Equinovarus
  description: Clubfoot was recorded in five of eleven patients in Chatron et al., including patients
    without documented joint contractures.
  category: Musculoskeletal
  phenotype_term:
    preferred_term: Talipes equinovarus
    term:
      id: HP:0001762
      label: Talipes equinovarus
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Interestingly, in addition to neurological features, seven patients presented a cleft
      palate, six joint contractures and five pes equinovarus.
    explanation: Five patients had clubfoot; the combined eight-person abstract count is not a clubfoot
      frequency.

- name: Scoliosis
  description: Scoliosis was reported in four patients in Chatron et al. and in an ambulant patient
    in Neuray et al.; in at least one patient it developed later.
  category: Musculoskeletal
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Scoliosis was reported in four patients.
    explanation: The primary 11-patient cohort documents four cases without establishing a congenital
      or uniformly progressive course.

- name: Plagiocephaly
  description: Plagiocephaly occurred in several patients; case 11 was explicitly described as positional
    rather than as a primary cranial malformation.
  category: Craniofacial
  phenotype_term:
    preferred_term: Plagiocephaly
    term:
      id: HP:0001357
      label: Plagiocephaly
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: At last examination, at 6 years of age, her weight was 17 kg, occipital frontal circumference
      50 cm with positional plagiocephaly, inverted nipples, hirsutism and severe scoliosis.
    explanation: Case 11 had positional plagiocephaly; other cases also had cranial asymmetry.

- name: Refractory Drug Response
  category: Neurological
  phenotype_term:
    preferred_term: Refractory Drug Response
    term:
      id: HP:0020174
      label: Refractory drug response
  description: Three of six patients had drug-resistant epilepsy; this phenotype describes antiseizure
    treatment response, not a distinct seizure type.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Seizures were pharmacologically controlled in three of six affected individuals, with
      three reported as drug-resistant.
    explanation: Three of six patients had drug-resistant epilepsy; this phenotype describes antiseizure
      treatment response, not a distinct seizure type.

- name: Intellectual Disability
  category: Neurological
  phenotype_term:
    preferred_term: Intellectual Disability
    term:
      id: HP:0001249
      label: Intellectual disability
  description: Intellectual disability persisted after seizure control. The source narrative calls
    all cases severe, but Table 1 records moderate disability in patient A and severe disability in
    the other five.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: However, despite seizure control (seizure freedom achieved in three of six individuals),
      all patients described here still showed severe intellectual disability.
    explanation: Intellectual disability persisted after seizure control. The source narrative calls
      all cases severe, but Table 1 records moderate disability in patient A and severe disability
      in the other five.

- name: Muscle Weakness
  category: Neurological
  phenotype_term:
    preferred_term: Muscle Weakness
    term:
      id: HP:0001324
      label: Muscle weakness
  description: Reduced muscle strength was reported in five of six patients in Neuray et al. The separate
    four-of-six statement combines reduced tone and weakness with severe functional limitation; it
    is not an isolated weakness frequency.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The reduced muscle tone and weakness, causing severe disability in four of six affected
      individuals was a surprising finding.
    explanation: Four of six refers to the combined tone/weakness-related disability; the results
      describe reduced strength in five of six.
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The third key feature we observed was a reduced muscle strength (five of six individuals)
      of varying severity ranging from slight muscle tone (one of five) to limited head control, inability
      to sit or crawl (four of six) and nasogastric tube dependence, due to dysphagia (two of six).
    explanation: The results give five of six for reduced strength, while the severity descriptions
      mix strength, tone, motor milestones and dysphagia. These subgroup counts are not interchangeable.

- name: Hyperreflexia
  category: Neurological
  phenotype_term:
    preferred_term: Hyperreflexia
    term:
      id: HP:0001347
      label: Hyperreflexia
  description: Hyperreflexia was observed in the 2023 case and in several patients in the earlier
    cohorts.
  evidence:
  - reference: PMID:37029735
    reference_title: 'Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular
      dynamics simulation, and a comprehensive clinical and molecular profile.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The deep tendon reflex (DTR) test showed hyperreflexia and manifested frequent tremors
      in the toes of both feet.
    explanation: Hyperreflexia was observed in the 2023 case and in several patients in the earlier
      cohorts.

- name: Clonus
  category: Neurological
  phenotype_term:
    preferred_term: Clonus
    term:
      id: HP:0002169
      label: Clonus
  description: Toe clonus was reported in the 2023 patient; this does not specify ankle clonus.
  evidence:
  - reference: PMID:37029735
    reference_title: 'Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular
      dynamics simulation, and a comprehensive clinical and molecular profile.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: showed microcephaly and clonus in the toe, which were novel clinical findings.
    explanation: Toe clonus was reported in the 2023 patient; this does not specify ankle clonus.

- name: Dystonia
  category: Neurological
  phenotype_term:
    preferred_term: Dystonia
    term:
      id: HP:0001332
      label: Dystonia
  description: Dystonia emerged during follow-up in case 7; it was also recorded in cases 8 and 11.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: He initially showed reduced muscle tone and developed spasticity and dystonia as well
      as scoliosis later during the disease course.
    explanation: Dystonia emerged during follow-up in case 7; it was also recorded in cases 8 and
      11.

- name: Choreoathetosis
  category: Neurological
  phenotype_term:
    preferred_term: Choreoathetosis
    term:
      id: HP:0001266
      label: Choreoathetosis
  description: Choreoathetotic arm movements were documented in case 11.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: She kept her hands fisted with flexion of wrists and her arms movements were uncoordinated
      and choreathetotic.
    explanation: Choreoathetotic arm movements were documented in case 11.

- name: Developmental Regression
  category: Neurological
  phenotype_term:
    preferred_term: Developmental Regression
    term:
      id: HP:0002376
      label: Developmental regression
  description: Case 5 lost motor function; case 1 also lost visual contact in infancy. Regression
    is not asserted for every patient.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: At the age of 2 years there was a regression evolving to a complete tetraparesis, with
      generalized increased muscle tonus without clear pyramidal signs, and pes equinus.
    explanation: Case 5 lost motor function; case 1 also lost visual contact in infancy. Regression
      is not asserted for every patient.

- name: Dysphagia
  category: Gastrointestinal
  phenotype_term:
    preferred_term: Dysphagia
    term:
      id: HP:0002015
      label: Dysphagia
  description: Dysphagia required nasogastric feeding in two of six patients. Table 1 documents dysphagia
    in three, including oropharyngeal dysphagia and one patient with a floppy epiglottis.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The third key feature we observed was a reduced muscle strength (five of six individuals)
      of varying severity ranging from slight muscle tone (one of five) to limited head control, inability
      to sit or crawl (four of six) and nasogastric tube dependence, due to dysphagia (two of six).
    explanation: Dysphagia required nasogastric feeding in two of six patients. Table 1 documents
      dysphagia in three, including oropharyngeal dysphagia and one patient with a floppy epiglottis.
  sequelae:
  - target: Aspiration
    description: Impaired swallowing can allow food or liquid to enter the airway, as demonstrated
      in case 9.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32282878
      reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and
        epileptic encephalopathy.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Barium oesophagogram showed nasal regurgitation and laryngotracheal aspiration, requiring
        nasogastric tube feeding.
      explanation: Contrast swallowing assessment demonstrated airway entry, supporting the swallowing-to-aspiration
        relation.

- name: Aspiration
  category: Respiratory
  phenotype_term:
    preferred_term: Aspiration
    term:
      id: HP:0002835
      label: Aspiration
  description: Laryngotracheal aspiration was demonstrated by contrast study in case 9.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Barium oesophagogram showed nasal regurgitation and laryngotracheal aspiration, requiring
      nasogastric tube feeding.
    explanation: Laryngotracheal aspiration was demonstrated by contrast study in case 9.
  sequelae:
  - target: Recurrent Aspiration Pneumonia
    description: Repeated airway aspiration causes the recurrent aspiration pneumonia documented in
      the same case.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32282878
      reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and
        epileptic encephalopathy.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: In the follow-up, the patient had severe recurrent aspiration pneumonia requiring hospitalization
        and oxygen treatment.
      explanation: Case 9 had recurrent aspiration pneumonia requiring hospitalization.

- name: Recurrent Aspiration Pneumonia
  category: Respiratory
  phenotype_term:
    preferred_term: Recurrent Aspiration Pneumonia
    term:
      id: HP:0002100
      label: Recurrent aspiration pneumonia
  description: Case 9 had recurrent aspiration pneumonia requiring hospitalization.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In the follow-up, the patient had severe recurrent aspiration pneumonia requiring hospitalization
      and oxygen treatment.
    explanation: Case 9 had recurrent aspiration pneumonia requiring hospitalization.

- name: Failure to Thrive
  category: Growth
  phenotype_term:
    preferred_term: Failure to Thrive
    term:
      id: HP:0001508
      label: Failure to thrive
  description: Failure to thrive affected both siblings in Family B, who died with severe growth failure
    and pulmonary infections.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: He also had failure to thrive, seizures, arthrogryposis and global developmental delay.
    explanation: Failure to thrive affected both siblings in Family B, who died with severe growth
      failure and pulmonary infections.

- name: Microcephaly
  category: Craniofacial
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  description: Microcephaly was reported in the 2023 patient, whose authors considered cerebral palsy
    as an alternative attribution. Chatron case 8 also had head circumference below the third centile.
  evidence:
  - reference: PMID:37029735
    reference_title: 'Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular
      dynamics simulation, and a comprehensive clinical and molecular profile.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Also, he showed microcephaly, which may be due to cerebral palsy.
    explanation: Microcephaly was reported in the 2023 patient, whose authors considered cerebral
      palsy as an alternative attribution. Chatron case 8 also had head circumference below the third
      centile.

- name: Cerebellar Atrophy
  category: Neurological
  phenotype_term:
    preferred_term: Cerebellar Atrophy
    term:
      id: HP:0001272
      label: Cerebellar atrophy
  description: Serial MRI in case 3 showed cerebellar as well as cerebral atrophy; most other reported
    scans were normal.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: showing hypoplastic corpus callosum, mainly body and to a lesser degree its genu, progressive
      cerebellar and cerebral atrophy and a cervical notch.
    explanation: Serial MRI in case 3 showed cerebellar as well as cerebral atrophy; most other reported
      scans were normal.

- name: Hypoplastic Corpus Callosum
  category: Neurological
  phenotype_term:
    preferred_term: Hypoplastic Corpus Callosum
    term:
      id: HP:0002079
      label: Hypoplasia of the corpus callosum
  description: Corpus callosum hypoplasia was documented in case 3.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: One patient presented with hypoplastic corpus callosum and mild-to-moderate dilated subarachnoid
      spaces, predominating on left hemisphere and mild enlarged lateral ventricles (Case 3, Patient
      B-IV:4).
    explanation: Corpus callosum hypoplasia was documented in case 3.

- name: Hydrocephalus
  category: Neurological
  phenotype_term:
    preferred_term: Hydrocephalus
    term:
      id: HP:0000238
      label: Hydrocephalus
  description: Minimal hydrocephalus with an atlantoaxial anomaly was reported in case 9, whose prenatal
    imaging had also suggested hydrocephalus.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Another had an atlanto-axial anomaly with minimal hydrocephalus at 2 months of age (Case
      9, Patient E-III:2).
    explanation: Minimal hydrocephalus with an atlantoaxial anomaly was reported in case 9, whose
      prenatal imaging had also suggested hydrocephalus.

- name: High Myopia
  category: Ophthalmologic
  phenotype_term:
    preferred_term: High Myopia
    term:
      id: HP:0011003
      label: High myopia
  description: High myopia was recorded in patients A and F in the six-patient cohort.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: '| Vision/hearing | High myopia | Normal | NA | Normal | Moderate hearing impairment
      | High myopia |'
    explanation: High myopia was recorded in patients A and F in the six-patient cohort.

- name: Horizontal Nystagmus
  category: Ophthalmologic
  phenotype_term:
    preferred_term: Horizontal Nystagmus
    term:
      id: HP:0000666
      label: Horizontal nystagmus
  description: Horizontal nystagmus was documented in the 2023 patient.
  evidence:
  - reference: PMID:37029735
    reference_title: 'Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular
      dynamics simulation, and a comprehensive clinical and molecular profile.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Ophthalmology assessment revealed horizontal nystagmus and the right eye suffered from
      strabismus.
    explanation: Horizontal nystagmus was documented in the 2023 patient.

- name: Strabismus
  category: Ophthalmologic
  phenotype_term:
    preferred_term: Strabismus
    term:
      id: HP:0000486
      label: Strabismus
  description: Right-eye strabismus was documented in the 2023 patient; earlier cases also included
    squint and alternating esotropia.
  evidence:
  - reference: PMID:37029735
    reference_title: 'Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular
      dynamics simulation, and a comprehensive clinical and molecular profile.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Ophthalmology assessment revealed horizontal nystagmus and the right eye suffered from
      strabismus.
    explanation: Right-eye strabismus was documented in the 2023 patient; earlier cases also included
      squint and alternating esotropia.

- name: Hearing Impairment
  category: Auditory
  phenotype_term:
    preferred_term: Hearing Impairment
    term:
      id: HP:0000365
      label: Hearing impairment
  description: Moderate hearing impairment of unspecified type was recorded in patient E; this is
    separate from the conductive loss in Chatron case 5.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: '| Vision/hearing | High myopia | Normal | NA | Normal | Moderate hearing impairment
      | High myopia |'
    explanation: Moderate hearing impairment of unspecified type was recorded in patient E; this is
      separate from the conductive loss in Chatron case 5.

- name: Conductive Hearing Loss
  category: Auditory
  phenotype_term:
    preferred_term: Conductive Hearing Loss
    term:
      id: HP:0000405
      label: Conductive hearing impairment
  description: Conductive hearing loss was documented in case 5, who also had cleft palate.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: She has a palatine cleft, a talipes on the left side and a conductive hearing loss.
    explanation: Conductive hearing loss was documented in case 5, who also had cleft palate.

- name: Constipation
  category: Gastrointestinal
  phenotype_term:
    preferred_term: Constipation
    term:
      id: HP:0002019
      label: Constipation
  description: Constipation was reported in the 2023 patient; its cause was not established.
  evidence:
  - reference: PMID:37029735
    reference_title: 'Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular
      dynamics simulation, and a comprehensive clinical and molecular profile.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Moreover, the patient manifested arthrogryposis in his hands, open mouth, high arched
      palate, large ear, constipation, and dysphasia.
    explanation: Constipation was reported in the 2023 patient; its cause was not established.

- name: Hirschsprung Disease
  category: Gastrointestinal
  phenotype_term:
    preferred_term: Hirschsprung Disease
    term:
      id: HP:0002251
      label: Aganglionic megacolon
  description: Biopsy-confirmed Hirschsprung disease occurred in Chatron case 9. The ungenotyped sibling
    mentioned in Neuray et al. is not included as additional DEE89 evidence.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The diagnosis of Hirschsprung was confirmed by rectal biopsy.
    explanation: Biopsy-confirmed Hirschsprung disease occurred in Chatron case 9. The ungenotyped
      sibling mentioned in Neuray et al. is not included as additional DEE89 evidence.

- name: Nephrocalcinosis
  category: Genitourinary
  phenotype_term:
    preferred_term: Nephrocalcinosis
    term:
      id: HP:0000121
      label: Nephrocalcinosis
  description: Grade 1 nephrocalcinosis was reported in Chatron case 9; Neuray patient A also had
    nephrocalcinosis with stones and hydronephrosis.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: and urinary ultrasonography revealed grade 1 nephrocalcinosis.
    explanation: Grade 1 nephrocalcinosis was reported in Chatron case 9; Neuray patient A also had
      nephrocalcinosis with stones and hydronephrosis.

- name: Nephrolithiasis
  category: Genitourinary
  phenotype_term:
    preferred_term: Nephrolithiasis
    term:
      id: HP:0000787
      label: Nephrolithiasis
  description: Bilateral kidney stones occurred in patient A of the six-patient cohort.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: '| Other features | Hydronephrosis, nephrocalcinosis, bilateral kidney stones |'
    explanation: Bilateral kidney stones occurred in patient A of the six-patient cohort.

- name: Hydronephrosis
  category: Genitourinary
  phenotype_term:
    preferred_term: Hydronephrosis
    term:
      id: HP:0000126
      label: Hydronephrosis
  description: Hydronephrosis accompanied renal calcifications in patient A; the source does not establish
    an obstructive cause.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: '| Other features | Hydronephrosis, nephrocalcinosis, bilateral kidney stones |'
    explanation: Hydronephrosis accompanied renal calcifications in patient A; the source does not
      establish an obstructive cause.

- name: High Arched Palate
  category: Craniofacial
  phenotype_term:
    preferred_term: High Arched Palate
    term:
      id: HP:0000218
      label: High palate
  description: A high arched palate without cleft was reported in the 2023 patient; Chatron case 3
    also had a high arched palate.
  evidence:
  - reference: PMID:37029735
    reference_title: 'Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular
      dynamics simulation, and a comprehensive clinical and molecular profile.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Moreover, the patient manifested arthrogryposis in his hands, open mouth, high arched
      palate, large ear, constipation, and dysphasia.
    explanation: A high arched palate without cleft was reported in the 2023 patient; Chatron case
      3 also had a high arched palate.

- name: Large Ears
  category: Craniofacial
  phenotype_term:
    preferred_term: Large Ears
    term:
      id: HP:0000400
      label: Macrotia
  description: Large ears were recorded in the 2023 patient.
  evidence:
  - reference: PMID:37029735
    reference_title: 'Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular
      dynamics simulation, and a comprehensive clinical and molecular profile.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Moreover, the patient manifested arthrogryposis in his hands, open mouth, high arched
      palate, large ear, constipation, and dysphasia.
    explanation: Large ears were recorded in the 2023 patient.

- name: Hypertelorism
  category: Craniofacial
  phenotype_term:
    preferred_term: Hypertelorism
    term:
      id: HP:0000316
      label: Hypertelorism
  description: Hypertelorism occurred among the variable facial findings in the 11-patient cohort.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Note hypertelorism, downslanting palpebral fissure, broad nasal bridge with anteverted
      nares, smooth philtrum and thin upper lip vermilion.
    explanation: Hypertelorism occurred among the variable facial findings in the 11-patient cohort.

- name: Microretrognathia
  category: Craniofacial
  phenotype_term:
    preferred_term: Microretrognathia
    term:
      id: HP:0000308
      label: Microretrognathia
  description: Microretrognathia was documented in the multiply malformed proband of Family B and
    in case 9.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Note flat facies, microretrognathia and abnormal asymmetric shaped ears.
    explanation: Microretrognathia was documented in the multiply malformed proband of Family B and
      in case 9.

- name: Diastasis Recti
  category: Abdominal
  phenotype_term:
    preferred_term: Diastasis Recti
    term:
      id: HP:0001540
      label: Diastasis recti
  description: Diastasis recti was observed in patient D; Chatron case 9 also had rectus diastasis.
    It is distinct from omphalocele.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In addition, significant diastasis recti can be observed.
    explanation: Diastasis recti was observed in patient D; Chatron case 9 also had rectus diastasis.
      It is distinct from omphalocele.

- name: Congenital Hip Dislocation
  category: Musculoskeletal
  phenotype_term:
    preferred_term: Congenital Hip Dislocation
    term:
      id: HP:0001374
      label: Congenital hip dislocation
  description: Congenital bilateral hip dislocation with shallow acetabula occurred in patient E.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the same patient also showed congenital bilateral hip dislocation with shallow acetabulum,
      talipes equinovarus and hearing impairment.
    explanation: Congenital bilateral hip dislocation with shallow acetabula occurred in patient E.

- name: Pes Planus
  category: Musculoskeletal
  phenotype_term:
    preferred_term: Pes Planus
    term:
      id: HP:0001763
      label: Pes planus
  description: Pes planus was recorded in patient A, distinct from the clubfoot in other patients.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: '| Skeletal abnormalities | Clindodactyly, pes planus, scoliosis |'
    explanation: Pes planus was recorded in patient A, distinct from the clubfoot in other patients.

- name: Poor Feeding
  category: Gastrointestinal
  phenotype_term:
    preferred_term: Poor Feeding
    term:
      id: HP:0011968
      label: Feeding difficulties
  description: Poor feeding required neonatal admission in the 2023 case.
  evidence:
  - reference: PMID:37029735
    reference_title: 'Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular
      dynamics simulation, and a comprehensive clinical and molecular profile.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: After birth due to poor feeding and seizure admitted to neonatal intensive care unit
      for 20 days.
    explanation: Poor feeding required neonatal admission in the 2023 case.

- name: Tonic Seizures
  category: Neurological
  phenotype_term:
    preferred_term: Tonic Seizures
    term:
      id: HP:0032792
      label: Tonic seizure
  description: Tonic seizures were documented in case 6 and later in case 11.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: He showed a similar phenotype as his older sister (Patient C-III:1), with refractory
      epilepsy with myoclonic, tonic and tonic-clonic seizures, from the first day of life.
    explanation: The prose documents tonic seizures from the first day of life in case 6.
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: '| Evolution of seizures | GTCS after the age of 3 y | Seizure-free from age 3m | Seizure-free
      from age 9m | Seizure-free from age 2 y | GTCS from the age of 5 m | Increasing seizure frequency
      (type unknown) | Last seizure at age 10 y | No seizures reported for 2 m | Siezure-free from
      age 2 m | Deceased at 9th day of life | Tonic, ES, and focal |'
    explanation: The final column of Table 1 is case 11; its evolution-of-seizures cell records tonic
      seizures, epileptic spasms (ES) and focal seizures.

- name: Thick Eyebrows
  category: Craniofacial
  phenotype_term:
    preferred_term: Thick Eyebrows
    term:
      id: HP:0000574
      label: Thick eyebrow
  description: Thick eyebrows were documented in patient A of Neuray et al.; this single-case observation
    does not establish a general frequency.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The female patient from Family A (Patient II-2) carries the homozygous c.1691A>G p.(Asn564Ser)
      variant and shows dysmorphic features with thick eyebrows, protruding ears, scoliosis, and long
      fingers with clinodactyly.
    explanation: Thick eyebrows were documented in patient A of Neuray et al.; this single-case observation
      does not establish a general frequency.

- name: Finger Clinodactyly
  category: Musculoskeletal
  phenotype_term:
    preferred_term: Finger Clinodactyly
    term:
      id: HP:0040019
      label: Finger clinodactyly
  description: Finger clinodactyly was documented in patient A. The affected digits were not specified,
    so a fifth-finger-specific term is not justified.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The female patient from Family A (Patient II-2) carries the homozygous c.1691A>G p.(Asn564Ser)
      variant and shows dysmorphic features with thick eyebrows, protruding ears, scoliosis, and long
      fingers with clinodactyly.
    explanation: Finger clinodactyly was documented in patient A. The affected digits were not specified,
      so a fifth-finger-specific term is not justified.

- name: Wide Mouth
  category: Craniofacial
  phenotype_term:
    preferred_term: Wide Mouth
    term:
      id: HP:0000154
      label: Wide mouth
  description: Wide mouth was described in patient B of Neuray et al. This differs from an open-mouth
    posture.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: He has slight dysmorphic features (wide mouth, thin upper lips, bitemporal narrowing
      and retrognathia).
    explanation: Wide mouth was described in patient B of Neuray et al. This differs from an open-mouth
      posture.

- name: Depressed Nasal Bridge
  category: Craniofacial
  phenotype_term:
    preferred_term: Depressed Nasal Bridge
    term:
      id: HP:0005280
      label: Depressed nasal bridge
  description: A severely depressed nasal bridge was described in patient D of Neuray et al.; Chatron
    et al. also documented this finding in dysmorphic cases.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: He is severely hypotonic and shows severe dysmorphic features (infra-orbital creases,
      severely depressed nasal bridge, anteverted nares, prominent nasolabial folds).
    explanation: A severely depressed nasal bridge was described in patient D of Neuray et al.; Chatron
      et al. also documented this finding in dysmorphic cases.

- name: Hyporeflexia
  category: Neurological
  phenotype_term:
    preferred_term: Hyporeflexia
    term:
      id: HP:0001265
      label: Hyporeflexia
  description: Hyporeflexia was recorded in patient E in Table 1 of Neuray et al., contrasting with
    brisk reflexes in other patients. The source does not localize the reflex impairment.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: '| Neurological examination | Mild hypotonia | Brisk DTR, stereotypic hand movements,
      oral automatisms | Mild hypotonia, spasticity in lower extremities, oropharyngeal dysphagia
      | Severe hypotonia, dysphagia (floppy epiglottis) | Severe hypotonia, hyporeflexia, dysphagia
      | Severe hypotonia |'
    explanation: Hyporeflexia was recorded in patient E in Table 1 of Neuray et al., contrasting with
      brisk reflexes in other patients. The source does not localize the reflex impairment.

genetic:
- name: GAD1
  gene_term:
    preferred_term: GAD1
    term:
      id: hgnc:4092
      label: GAD1
  relationship_type: CAUSATIVE
  notes: >-
    GAD1 (2q31.1, 21 exons) encodes GAD67. Reported pathogenic alleles include
    missense, nonsense, splice-site and in-frame deletion variants distributed
    across the protein, including the PLP-binding domain. A recurrent nonsense
    allele, c.1591C>T p.(Arg531*), has been seen in several unrelated
    populations.
  evidence:
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The recurrent c.1591C>T, p.(Arg531*) variant has been reported three times
      (20% of all reported variants) in different populations, indicating it may
      be a probable hotspot mutation.
    explanation: The 2023 literature review reports recurrence of p.(Arg531*) across three published
      occurrences; the percentage is a publication-based variant count, not a population allele frequency
      or established mutational hotspot.
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: "The mutation is located in the PLP‐binding domain, which is important for the activity of the protein"
    explanation: >-
      Locates a reported missense allele in the pyridoxal-phosphate-binding
      domain, the structural basis on which missense alleles are argued to impair
      catalysis. Evidence source is COMPUTATIONAL because the functional inference
      rests on docking and molecular-dynamics simulation, not an enzyme assay.

diagnosis:
- name: Molecular Genetic Testing
  description: >-
    The diagnosis rests on identification of biallelic pathogenic GAD1 variants,
    typically by exome sequencing, in an infant with neonatal-onset epileptic
    encephalopathy. There is no specific biochemical marker in routine use;
    metabolic screening was normal in the reported case where it was performed.
  evidence:
  - reference: PMID:32705143
    reference_title: "Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Our findings highlight an important role for GAD1 in seizure induction,
      neuronal and extraneuronal development, and introduce GAD1 as a new gene
      associated with developmental and epileptic encephalopathy.
    explanation: >-
      Establishes GAD1 as the gene to be tested in this presentation; the
      diagnosis is molecular.
  diagnosis_term:
    preferred_term: Genetic Testing
    term:
      id: NCIT:C15709
      label: Genetic Testing

- name: Neuroimaging
  description: >-
    Brain MRI is normal in most patients early on; later imaging at older ages can
    show atrophic change, so a normal early MRI does not argue against the
    diagnosis.
  evidence:
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The majority of the patients had normal MRI, although, in some patients,
      later MRI at older ages revealed defects.
    explanation: >-
      Records that MRI is usually normal initially with later abnormalities in
      some. Evidence source is OTHER because this is the paper's literature
      summary.
  diagnosis_term:
    preferred_term: Magnetic Resonance Imaging
    term:
      id: NCIT:C16809
      label: Magnetic Resonance Imaging

treatments:
- name: Vigabatrin
  description: >-
    Vigabatrin irreversibly inhibits GABA transaminase, the enzyme that degrades
    GABA, and is therefore a mechanistically rational attempt to raise whatever
    GABA the residual synthetic capacity produces. Five of seven patients in the
    founding cohort who tried it had a good seizure response, but the authors
    themselves cautioned that the responders were particularly those with
    epileptic spasms, so the effect may be semiology-driven rather than
    GAD1-specific.

    The rationale has a published objection, and it is a mechanistic one rather
    than a null trial result: sparing GABA from degradation cannot help much when
    synthesis is the step that has failed, since GAD67 supplies over 90% of basal
    GABA. The 2023 review states that vigabatrin is therefore not a suitable
    solution "at least for mutations that result in severe reduction or complete
    loss of the enzyme function" - a genotype-stratified claim, which is the same
    residual-activity axis this entry records as an open gap. Two treated
    patients, including one on the vigabatrin-plus-ketogenic-diet combination,
    continued to have seizures. Both sides are curated as evidence below rather
    than resolved here, because the objection is an inference from the mechanism
    and the response is an observation, and neither refutes the other.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: vigabatrin
      term:
        id: CHEBI:63638
        label: vigabatrin
  target_mechanisms:
  - target: GABA Depletion
    treatment_effect: RESTORES
    description: >-
      Blocking GABA catabolism is intended to raise the available GABA pool and
      partially offset the synthetic deficit. The link is mechanistic rationale
      plus an observed clinical seizure response, not a measured rise in human
      brain GABA.
    evidence:
    - reference: PMID:33169137
      reference_title: "Reply: Rational therapy with vigabatrin and a ketogenic diet in a patient with GAD1 deficiency."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        Both treatment strategies are thought to increase the available pool of
        GABA, and combined they might compensate for the severely impaired GABA
        synthesis.
      explanation: >-
        States the intended mechanism - raising the available GABA pool to
        compensate for impaired synthesis - for vigabatrin and the ketogenic diet.
    - reference: PMID:37029735
      reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
      supports: REFUTE
      evidence_source: OTHER
      snippet: "it seems that prescribing vigabatrin for patients with GAD1 deficiency is not a suitable solution, at least for mutations that result in severe reduction or complete loss of the enzyme function."
      explanation: >-
        The direct argument against this link. Because GAD67 supplies most basal
        GABA, blocking catabolism has little left to spare where the variant
        abolishes synthesis, so the restorative effect is expected to fail for
        null and severe-reduction alleles. `treatment_effect` remains RESTORES
        because that is the intended mechanism the drug is chosen for; this item
        records that the intent is disputed on mechanistic grounds. Evidence
        source is OTHER because this is the paper's reasoning over the literature
        rather than a measurement.
  evidence:
  - reference: PMID:33169137
    reference_title: "Reply: Rational therapy with vigabatrin and a ketogenic diet in a patient with GAD1 deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In our report, five of seven patients who tried vigabatrin showed a
      remarkably good seizure response.
    explanation: Five of seven treated patients in the authors' original cohort improved, particularly
      those with spasms. This may be a semiology-related response rather than a genotype-specific
      effect.
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: He suffers from refractory tonic–clonic seizures despite treatment with a combination
      of vigabatrin and a ketogenic diet.
    explanation: The 2023 index patient remained refractory on the combination. A separate patient
      in Neuray et al. also remained refractory, as summarized in the reply.

- name: Ketogenic Diet
  description: >-
    The ketogenic diet is used alongside vigabatrin on the same rationale of
    increasing the available GABA pool. Its disease-specific evidence is a single
    treated infant with an excellent outcome set against at least two patients on
    the same combination who remained refractory.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Ketogenic Diet
    term:
      id: NCIT:C173168
      label: Ketogenic Diet
  target_mechanisms:
  - target: GABA Depletion
    treatment_effect: RESTORES
    description: >-
      The diet is proposed to increase the available GABA pool; this is a
      hypothesized mechanism carried over from ketogenic-diet pharmacology
      generally, not a measurement made in GAD1-deficient patients.
    evidence:
    - reference: PMID:33169137
      reference_title: "Reply: Rational therapy with vigabatrin and a ketogenic diet in a patient with GAD1 deficiency."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        Both treatment strategies are thought to increase the available pool of
        GABA, and combined they might compensate for the severely impaired GABA
        synthesis.
      explanation: >-
        States the intended GABA-raising mechanism shared by the ketogenic diet
        and vigabatrin.
  evidence:
  - reference: PMID:33169137
    reference_title: "Reply: Rational therapy with vigabatrin and a ketogenic diet in a patient with GAD1 deficiency."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      One patient (Patient C) also appears to take a combination of ketogenic
      diet and vigabatrin at the age of 28 months, and still has refractory
      seizures and severe delay.
    explanation: The reply summarizes a patient from the independent cohort who remained refractory
      on the combination; the treatment-start age was not reported. This argues against uniform benefit.

- name: Early Combined Vigabatrin and Ketogenic Diet
  description: Combination therapy started in the second month of life, immediately after genetic
    diagnosis, was reported in one infant to stop seizures within two days and leave growth and psychomotor
    development unremarkable at 7 months - a striking exception in a disorder where a neonatal burst-suppression
    EEG has otherwise predicted profound delay. It is one observation, and another patient on the
    same combination with unreported treatment-start age remained refractory.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: vigabatrin
      term:
        id: CHEBI:63638
        label: vigabatrin
  evidence:
  - reference: PMID:33169137
    reference_title: "Reply: Rational therapy with vigabatrin and a ketogenic diet in a patient with GAD1 deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This combination treatment not only resulted in clinical cessation of
      seizures within 2 days, but at 7 months of age, growth and psychomotor
      development were unremarkable.
    explanation: The reply summarizes a single infant treated by another group; seven-month follow-up
      does not establish sustained developmental benefit.
  - reference: PMID:33169137
    reference_title: "Reply: Rational therapy with vigabatrin and a ketogenic diet in a patient with GAD1 deficiency."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      While this is certainly a reasonable hypothesis, one should be cautious
      drawing conclusions from one single observation.
    explanation: >-
      The authors' own caution about the strength of the single-patient
      developmental-outcome claim.
  target_mechanisms:
  - target: GABA Depletion
    treatment_effect: RESTORES
    description: >-
      Both components are proposed to raise the available GABA pool - vigabatrin
      by blocking GABA catabolism, the ketogenic diet by shifting substrate
      availability - so the combination is directed at the same depletion node
      each single agent targets. The effect is an inferred mechanism, not a
      measured rise in human brain GABA.
    evidence:
    - reference: PMID:33169137
      reference_title: "Reply: Rational therapy with vigabatrin and a ketogenic diet in a patient with GAD1 deficiency."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        Both treatment strategies are thought to increase the available pool of
        GABA, and combined they might compensate for the severely impaired GABA
        synthesis.
      explanation: The authors propose increasing the available GABA pool; GABA restoration was not
        measured in treated patients.

- name: Individualized Antiseizure Medication
  description: >-
    No single antiseizure medication has emerged as the treatment of choice.
    Across the patients whose epilepsy was controlled there was no drug in
    common, so regimen choice remains empirical.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  evidence:
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      we found that there was no common drug therapy among patients whose
      epilepsy was controlled
    explanation: >-
      Documents the absence of a shared effective drug across controlled cases,
      supporting individualized rather than protocolized therapy.

animal_models:
- name: Gad1-null mouse (GAD67 knockout)
  species: Mouse
  genotype: Gad1 (GAD67) homozygous null
  publication: PMID:9177246
  description: >-
    Targeted disruption of exon 1 of mouse Gad1 abolishes GAD67. Homozygotes are
    born at Mendelian frequency but die on the first morning after birth with
    severe cleft palate, and cortical GABA is reduced to 7% of wild type. Because
    death is neonatal, the model cannot be used to study the epilepsy that defines
    the human disorder.
  evidence:
  - reference: PMID:9177246
    reference_title: "Cleft palate and decreased brain gamma-aminobutyric acid in mice lacking the 67-kDa isoform of glutamic acid decarboxylase."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      These mice were born at the expected frequency but died of severe cleft
      palate during the first morning after birth.
    explanation: >-
      Establishes the model and its neonatal lethal cleft-palate phenotype, which
      is what makes it informative for the malformation arm and uninformative for
      the epilepsy arm.
  modeled_mechanisms:
  - target: GABA Depletion
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Direct biochemical measurement of the depletion: cortical GAD activity
      under 20% and GABA content 7% of wild type in newborn nulls.
    limitations: >-
      Measured in newborn mouse cerebral cortex; the equivalent measurement has
      not been made in human patients, so the magnitude is transferred by
      inference.
    readouts:
    - name: Cerebral cortical GABA content
      target: GABA Depletion
      description: >-
        HPLC measurement of GABA in cerebral cortex homogenate of P0.5 nulls
        against wild-type littermates.
      direction: DECREASED
      interpretation: >-
        GABA at 7% of wild type is the quantitative correlate of the depletion
        node.
      evidence:
      - reference: PMID:9177246
        reference_title: "Cleft palate and decreased brain gamma-aminobutyric acid in mice lacking the 67-kDa isoform of glutamic acid decarboxylase."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          GAD activities and GABA contents were reduced to 20% and 7%,
          respectively, in the cerebral cortex of the newborn GAD67 -/- mice.
        explanation: Reports the cortical GAD activity and GABA measurements.
    evidence:
    - reference: PMID:9177246
      reference_title: "Cleft palate and decreased brain gamma-aminobutyric acid in mice lacking the 67-kDa isoform of glutamic acid decarboxylase."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        GAD activities and GABA contents were reduced to 20% and 7%,
        respectively, in the cerebral cortex of the newborn GAD67 -/- mice.
      explanation: >-
        Supports treating the null mouse as informative for the GABA-depletion
        node.
  - target: Failure of Palatal Shelf Elevation
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    description: Gad1-null mouse histology demonstrates failed palatal shelf elevation and cleft palate.
      CNS-specific deletion and oral explants support a neural movement-dependent mechanism, but the
      corresponding fetal intermediate has not been measured in human patients.
    limitations: Mouse cleft palate is highly penetrant and lethal, whereas the human malformation
      is variable and survivable. Human shelf elevation is not directly observed. The separate mouse
      umbilical-hernia finding does not establish identical human omphalocele.
    readouts:
    - name: Secondary palate fusion
      target: Failure of Palatal Shelf Elevation
      description: >-
        Gross and histological examination of the upper jaw and coronal facial
        sections in newborn and E17.5 animals.
      direction: ABOLISHED
      interpretation: >-
        Complete failure of secondary palate formation in every homozygote is the
        structural readout for this node.
      evidence:
      - reference: PMID:9177246
        reference_title: "Cleft palate and decreased brain gamma-aminobutyric acid in mice lacking the 67-kDa isoform of glutamic acid decarboxylase."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Severe cleft palate was found in all homozygous mutants
        explanation: Reports full penetrance of the cleft palate readout.
    evidence:
    - reference: PMID:20333300
      reference_title: Cleft palate is caused by CNS dysfunction in Gad1 and Viaat knockout mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: In both genotypes, palate shelf elevation fails to occur at E14.5 and all Gad1 and
        Viaat mutants were born with cleft secondary palates (Fig. 3A-H and data not shown).
      explanation: Mouse histology identifies failed shelf elevation preceding cleft palate; the human
        developmental intermediate is inferred from the model.
      directness: INDIRECT
    - reference: PMID:20333300
      reference_title: Cleft palate is caused by CNS dysfunction in Gad1 and Viaat knockout mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: In all cases the ViaatlacZ and Gad1lacZ mutant explants underwent palatal shelf outgrowth
        and elevation in culture.
      explanation: Mutant shelves can elevate after removal from the embryonic context, supporting
        an indirect neural movement-dependent cause.
  - target: Early-Onset Epileptic Seizures
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >-
      The defining human phenotype - neonatal epilepsy - cannot be observed in
      this model. Homozygotes die within a day of birth from the cleft palate, and
      their brains show no discernible structural defect, so the model gives no
      information about the seizure phenotype.
    limitations: >-
      This is a negative result by inaccessibility rather than by measurement: the
      animals do not survive long enough for an epilepsy phenotype to develop or
      be recorded, and no EEG was obtained. It should not be read as evidence that
      GAD67 loss fails to cause seizures.
    evidence:
    - reference: PMID:32705143
      reference_title: "Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1 variants."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        as Gad1-/- mice die neonatally of severe cleft palate, it has not been
        possible to determine any potential neurological dysfunction
      explanation: >-
        States explicitly that neonatal lethality prevents the mouse from
        informing the neurological phenotype.
    - reference: PMID:9177246
      reference_title: "Cleft palate and decreased brain gamma-aminobutyric acid in mice lacking the 67-kDa isoform of glutamic acid decarboxylase."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Their brain, however, did not show any discernible defects.
      explanation: >-
        The original report found no brain abnormality in the nulls, consistent
        with the model being uninformative about the neurological phenotype.

- name: Gad1-null rat
  species: Rat
  genotype: Gad1 homozygous knockout
  publication: PMID:37830095
  description: >-
    Unlike the mouse, Gad1-null rats survive to adulthood and can be recorded by
    chronic EEG. They show abundant spike-wave discharges from two months of age
    and reduced GABA immunoreactivity in reticular thalamic neuronal somata. The
    seizure phenotype is absence-type spike-wave discharge, not the neonatal
    spasms and suppression-burst pattern of the human disorder.
  evidence:
  - reference: PMID:37830095
    reference_title: "Gad1 knock-out rats exhibit abundant spike-wave discharges in EEG, exacerbated with valproate treatment."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      SWDs were abundant in EEG from Gad1 (-/-) rats as young as 2 months old.
    explanation: >-
      Establishes that this model, unlike the mouse, survives to yield an
      electrographic seizure phenotype.
  modeled_mechanisms:
  - target: Neuronal Hyperexcitability and Hypersynchrony
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    description: >-
      GAD1 loss in the rat produces a hypersynchronous electrographic phenotype,
      supporting the general link from GABA synthesis failure to network
      hypersynchrony.
    limitations: >-
      The discharge type is absence-like spike-wave activity in adolescent and
      adult animals, mechanistically a thalamocortical oscillation, rather than
      the neonatal epileptic spasms and suppression-burst background that define
      the human disease. Common laboratory rat strains also show spike-wave
      discharges spontaneously, so the phenotype is a shift in severity against a
      noisy background rather than an all-or-none disease model. Valproate, which
      suppressed discharges in controls, made them worse in the nulls, so drug
      responses in this model should not be transferred to patients.
    readouts:
    - name: Reticular thalamic somatic GABA immunoreactivity
      target: Neuronal Hyperexcitability and Hypersynchrony
      description: >-
        Immunohistochemistry for GABA in reticular thalamic nucleus neurons of
        null versus control rats.
      direction: DECREASED
      interpretation: >-
        Confirms that the electrographic phenotype is accompanied by the expected
        loss of GABA in the implicated inhibitory nucleus.
      evidence:
      - reference: PMID:37830095
        reference_title: "Gad1 knock-out rats exhibit abundant spike-wave discharges in EEG, exacerbated with valproate treatment."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          GABA immunoreactivity was significantly reduced in the somata of RTN
          neurons in Gad1 (-/-) rats but not in their axons targeting the
          thalamus.
        explanation: Reports the immunohistochemical GABA measurement.
    evidence:
    - reference: PMID:37830095
      reference_title: "Gad1 knock-out rats exhibit abundant spike-wave discharges in EEG, exacerbated with valproate treatment."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        VPA treatment alleviated SWD symptoms in control rats, however,
        counterintuitively exacerbated the symptoms in Gad1 (-/-) rats.
      explanation: >-
        The paradoxical valproate response is why this model is treated as only
        partially informative and its pharmacology is not transferred to patients.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    The two 2020 cohorts comprised eleven and six patients, followed by
    isolated reports including the early-treated infant and the 2023 case.
    These publication counts do not establish a population prevalence or a
    current worldwide case total.
  evidence:
  - reference: PMID:32282878
    reference_title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we describe a new syndromic developmental and epileptic
      encephalopathy caused by bi-allelic loss-of-function variants in GAD1, as
      presented by 11 patients from six independent consanguineous families.
    explanation: >-
      Provides the founding literature case count; no normalized population rate
      is asserted.
  - reference: PMID:32705143
    reference_title: "Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here we present six affected individuals from six unrelated families,
      carrying bi-allelic GAD1 variants
    explanation: Adds six further reported patients to the literature count.
datasets: []
discussions:
- discussion_id: gap_dee89_missense_sparing_of_malformations
  prompt: >-
    Do GAD1 missense variants genuinely spare palatal and ventral wall
    development, and if so is that because they retain residual decarboxylase
    activity above a developmental threshold that truncating alleles fall below?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Failure of Palatal Shelf Elevation
  - pathophysiology#Impaired GABA-Dependent Fetal Motor Signaling
  - pathophysiology#Impaired Retraction of Physiological Umbilical Hernia
  rationale: The 2023 published-case comparison reported no cleft palate or omphalocele among missense
    cases, but the sample was small and enzyme activity was not quantified for the alleles. A residual-activity
    threshold is a testable explanation, not an established allelic subtype or prognosis.
  proposed_experiments:
  - experiment_id: exp_dee89_gad1_missense_residual_activity
    name: Residual decarboxylase activity of patient GAD1 missense alleles
    description: >-
      Express the reported missense alleles alongside truncating alleles and wild
      type, and measure glutamate decarboxylase activity and GABA production, to
      test whether the missense alleles retain measurable residual activity.
  evidence:
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      the comparison of clinical symptoms between patients with missense and
      truncating mutations did not show any significant clinical difference,
      except that patients with missense mutations did not show cleft palates or
      omphaloceles.
    explanation: This is a small published-case comparison, not a systematic genotype-stratified cohort
      or enzyme assay.

- discussion_id: mismatch_dee89_gad1_null_mouse_neonatal_lethality
  prompt: >-
    Can any Gad1-loss animal model inform the neurological arm of DEE 89, given
    that the mouse null dies of cleft palate before an epilepsy phenotype can
    emerge and the surviving rat null has a mechanistically different seizure
    type?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Early-Onset Epileptic Seizures
  - pathophysiology#Neuronal Hyperexcitability and Hypersynchrony
  rationale: Gad1-null mice die neonatally, limiting postnatal epilepsy assessment. Surviving null
    rats provide a neurological model with frequent spike-wave discharges from about two months, but
    no overt convulsive seizures in the study. Their EEG pattern, retained stimulus responsiveness
    and paradoxical valproate response differ from human neonatal spasms and suppression-burst. They
    inform GAD1 network biology without directly reproducing the human seizure syndrome.
  proposed_experiments:
  - experiment_id: exp_dee89_palate_rescued_gad1_mouse_eeg
    name: Palate-rescued conditional Gad1 mouse with neonatal EEG
    description: >-
      Generate a Gad1 null with palatal development rescued (for example by
      tissue-restricted expression), so that homozygotes survive the neonatal
      period, and record EEG through the neonatal and infantile period to
      establish whether a suppression-burst and spasm phenotype develops.
  evidence:
  - reference: PMID:32705143
    reference_title: "Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1 variants."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      as Gad1-/- mice die neonatally of severe cleft palate, it has not been
      possible to determine any potential neurological dysfunction
    explanation: States the inaccessibility of the neurological phenotype in the mouse null.
  - reference: PMID:37830095
    reference_title: "Gad1 knock-out rats exhibit abundant spike-wave discharges in EEG, exacerbated with valproate treatment."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      VPA treatment alleviated SWD symptoms in control rats, however,
      counterintuitively exacerbated the symptoms in Gad1 (-/-) rats.
    explanation: >-
      The rat null's paradoxical drug response illustrates why its pharmacology
      cannot be transferred to patients.

- discussion_id: gap_dee89_early_combination_therapy_and_developmental_outcome
  prompt: >-
    Does starting vigabatrin plus a ketogenic diet in the first weeks after
    genetic diagnosis change developmental outcome in DEE 89, or only seizure
    frequency?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Developmental Encephalopathy
  - pathophysiology#GABA Depletion
  rationale: 'One infant started on the combination in the second month of life had seizures stop
    within two days and normal growth and psychomotor development at 7 months, which is remarkable
    against a cohort in which every patient with a neonatal burst-suppression EEG had profound delay.
    But a second patient on the same combination, with unreported treatment-start age, remained refractory
    with severe delay, and the commentary authors explicitly caution against generalizing from a single
    case. Because the disorder is ultra-rare and a critical treatment window has not been established,
    the question is unlikely to be settled by a conventional trial and needs a prospective registry
    with a pre-specified developmental endpoint.

    There is also a mechanistic objection that any such registry would have to stratify for. Vigabatrin
    works by blocking GABA catabolism, so it can only spare GABA that is being made; where the variant
    abolishes GAD67 activity there is little to spare, and the 2023 review argues on that basis that
    vigabatrin is not a suitable solution for severe-reduction or complete-loss alleles. That makes
    residual enzyme activity - the same quantity the allelic knowledge gap in this entry asks about
    - the plausible determinant of who responds, and it is not measured in any reported patient. The
    same review notes that oral GABA does not cross the blood-brain barrier but that brain-penetrant
    GABA derivatives might, which is the alternative route if the catabolism-blocking rationale really
    does fail at low residual activity.'
  proposed_experiments:
  - experiment_id: exp_dee89_treat_on_diagnosis_registry
    name: Prospective treat-on-diagnosis registry with developmental endpoints
    description: >-
      Enrol newly genetically diagnosed infants, record time from diagnosis to
      start of combination therapy, and follow standardized developmental
      assessments, so that outcome can be related to treatment latency rather
      than compared across ad hoc case reports.
  - experiment_id: exp_dee89_vigabatrin_response_by_residual_activity
    name: Vigabatrin response stratified by residual GAD67 activity
    description: >-
      For each reported allele, measure residual glutamate decarboxylase activity
      and relate it to that patient's vigabatrin response, to test the review's
      prediction that the drug fails where activity is abolished and works only
      where some synthesis remains.
  evidence:
  - reference: PMID:33169137
    reference_title: "Reply: Rational therapy with vigabatrin and a ketogenic diet in a patient with GAD1 deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The presence of a neonatal burst-suppression pattern on EEG generally has a
      dire prognosis, and all families reported in our study indeed had a
      profound developmental delay.
    explanation: >-
      Establishes the baseline against which the single favourable outcome stands
      out, and hence why the question is open rather than answered.
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "it seems that prescribing vigabatrin for patients with GAD1 deficiency is not a suitable solution, at least for mutations that result in severe reduction or complete loss of the enzyme function."
    explanation: The review proposes a genotype-dependent limitation of vigabatrin; this mechanistic
      objection does not itself resolve the developmental-outcome question.
  - reference: PMID:37029735
    reference_title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "However, the production of GABA derivatives with the ability to cross the blood–brain barrier may be useful for controlling epilepsy in these patients."
    explanation: >-
      Names the alternative therapeutic route the same authors propose if the
      catabolism-blocking rationale fails - brain-penetrant GABA derivatives,
      since oral GABA does not cross the blood-brain barrier. Evidence source is
      OTHER because this is the paper's proposal rather than data.

- discussion_id: gap_dee89_neuroimaging
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - phenotypes#Cerebral Atrophy
  - phenotypes#Ventriculomegaly
  - phenotypes#Cerebellar Atrophy
  - phenotypes#Hypoplastic Corpus Callosum
  - phenotypes#Hydrocephalus
  - phenotypes#Microcephaly
  prompt: Which imaging changes are primary developmental lesions and which reflect secondary injury
    or fluid-space changes?
  rationale: Most initial MRI scans were normal. Some patients later developed atrophy, whereas others
    had callosal hypoplasia or hydrocephalus with craniocervical anomalies. The reviewed sources do
    not resolve primary GABA-dependent development, seizure-related injury and coincident structural
    causes. MRI volume loss does not by itself establish the regional cellular mechanism. The 2023
    microcephaly report also raises cerebral palsy as an alternative attribution.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: showing hypoplastic corpus callosum, mainly body and to a lesser degree its genu, progressive
      cerebellar and cerebral atrophy and a cervical notch.
    explanation: Serial MRI in case 3 showed cerebellar as well as cerebral atrophy; most other reported
      scans were normal.
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Another had an atlanto-axial anomaly with minimal hydrocephalus at 2 months of age (Case
      9, Patient E-III:2).
    explanation: Minimal hydrocephalus with an atlantoaxial anomaly was reported in case 9, whose
      prenatal imaging had also suggested hydrocephalus.
  - reference: PMID:37029735
    reference_title: 'Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular
      dynamics simulation, and a comprehensive clinical and molecular profile.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Also, he showed microcephaly, which may be due to cerebral palsy.
    explanation: Microcephaly was reported in the 2023 patient, whose authors considered cerebral
      palsy as an alternative attribution. Chatron case 8 also had head circumference below the third
      centile.

- discussion_id: gap_dee89_swallowing_growth
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - phenotypes#Dysphagia
  - phenotypes#Poor Feeding
  - phenotypes#Failure to Thrive
  - phenotypes#Constipation
  prompt: How do bulbar dysfunction, structural abnormalities and other clinical factors contribute
    to feeding and growth findings?
  rationale: Swallowing impairment and aspiration are documented, and the supported aspiration-to-pneumonia
    sequela is modeled. The source reports oropharyngeal dysfunction, a floppy epiglottis and cleft
    palate in different patients; their relative contribution is unresolved. Failure to thrive in
    the multiply malformed siblings cannot be assigned solely to the dysphagia in other cases. Constipation
    and neonatal poor feeding are observed without an established GAD1-specific route.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The third key feature we observed was a reduced muscle strength (five of six individuals)
      of varying severity ranging from slight muscle tone (one of five) to limited head control, inability
      to sit or crawl (four of six) and nasogastric tube dependence, due to dysphagia (two of six).
    explanation: Dysphagia required nasogastric feeding in two of six patients. Table 1 documents
      dysphagia in three, including oropharyngeal dysphagia and one patient with a floppy epiglottis.
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: He also had failure to thrive, seizures, arthrogryposis and global developmental delay.
    explanation: Failure to thrive affected both siblings in Family B, who died with severe growth
      failure and pulmonary infections.
  - reference: PMID:37029735
    reference_title: 'Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular
      dynamics simulation, and a comprehensive clinical and molecular profile.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Moreover, the patient manifested arthrogryposis in his hands, open mouth, high arched
      palate, large ear, constipation, and dysphasia.
    explanation: Constipation was reported in the 2023 patient; its cause was not established.

- discussion_id: gap_dee89_sensory_findings
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - phenotypes#High Myopia
  - phenotypes#Horizontal Nystagmus
  - phenotypes#Strabismus
  - phenotypes#Hearing Impairment
  - phenotypes#Conductive Hearing Loss
  prompt: Which sensory findings belong to the GAD1 disorder and which have independent structural
    causes?
  rationale: The sources document these findings but do not establish a GAD1-specific ocular or auditory
    lesion. Nystagmus and strabismus may involve central control or ocular disease; high myopia is
    a separate refractive phenotype. Conductive hearing loss co-occurs with cleft palate in one patient,
    without middle-ear findings that establish that causal route, while another hearing deficit is
    untyped.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: '| Vision/hearing | High myopia | Normal | NA | Normal | Moderate hearing impairment
      | High myopia |'
    explanation: High myopia was recorded in patients A and F in the six-patient cohort.
  - reference: PMID:37029735
    reference_title: 'Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular
      dynamics simulation, and a comprehensive clinical and molecular profile.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Ophthalmology assessment revealed horizontal nystagmus and the right eye suffered from
      strabismus.
    explanation: Horizontal nystagmus was documented in the 2023 patient.
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: She has a palatine cleft, a talipes on the left side and a conductive hearing loss.
    explanation: Conductive hearing loss was documented in case 5, who also had cleft palate.

- discussion_id: gap_dee89_additional_structural_findings
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - phenotypes#Scoliosis
  - phenotypes#Plagiocephaly
  - phenotypes#High Arched Palate
  - phenotypes#Large Ears
  - phenotypes#Hypertelorism
  - phenotypes#Microretrognathia
  - phenotypes#Diastasis Recti
  - phenotypes#Congenital Hip Dislocation
  - phenotypes#Pes Planus
  - phenotypes#Thick Eyebrows
  - phenotypes#Finger Clinodactyly
  - phenotypes#Wide Mouth
  - phenotypes#Depressed Nasal Bridge
  prompt: Are additional skeletal and dysmorphic findings prenatal consequences of impaired movement
    or secondary and coincidental findings?
  rationale: 'The source-established fetal movement explanation for contractures, clubfoot and major
    palatal/ventral defects is represented. The additional findings have less secure attribution:
    scoliosis sometimes emerged later, plagiocephaly was explicitly positional in one child, and hip
    dislocation, flat feet and facial features do not establish a single fetal motor route. Extending
    the modeled mechanism to every malformation would obscure these differences. Thick eyebrows, wide
    mouth, depressed nasal bridge and finger clinodactyly are patient-level dysmorphic observations
    without evidence distinguishing a primary developmental GAD1 effect from secondary or coincidental
    anatomy; none establishes a fetal akinesia mechanism.'
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: He initially showed reduced muscle tone and developed spasticity and dystonia as well
      as scoliosis later during the disease course.
    explanation: Dystonia emerged during follow-up in case 7; it was also recorded in cases 8 and
      11.
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: the same patient also showed congenital bilateral hip dislocation with shallow acetabulum,
      talipes equinovarus and hearing impairment.
    explanation: Congenital bilateral hip dislocation with shallow acetabula occurred in patient E.
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In addition, significant diastasis recti can be observed.
    explanation: Diastasis recti was observed in patient D; Chatron case 9 also had rectus diastasis.
      It is distinct from omphalocele.
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The female patient from Family A (Patient II-2) carries the homozygous c.1691A>G p.(Asn564Ser)
      variant and shows dysmorphic features with thick eyebrows, protruding ears, scoliosis, and long
      fingers with clinodactyly.
    explanation: Figure 1 documents thick eyebrows and finger clinodactyly in patient A; no particular
      digit is specified.
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: He has slight dysmorphic features (wide mouth, thin upper lips, bitemporal narrowing
      and retrognathia).
    explanation: Wide mouth was described in patient B of Neuray et al. This differs from an open-mouth
      posture.
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: He is severely hypotonic and shows severe dysmorphic features (infra-orbital creases,
      severely depressed nasal bridge, anteverted nares, prominent nasolabial folds).
    explanation: A severely depressed nasal bridge was described in patient D of Neuray et al.; Chatron
      et al. also documented this finding in dysmorphic cases.

- discussion_id: gap_dee89_renal_enteric_findings
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - phenotypes#Hirschsprung Disease
  - phenotypes#Nephrocalcinosis
  - phenotypes#Nephrolithiasis
  - phenotypes#Hydronephrosis
  prompt: Are the renal and enteric findings directly attributable to GAD1 deficiency?
  rationale: Hirschsprung disease was confirmed in one genotyped Chatron patient; a differently affected
    sibling in Neuray et al. is not a second confirmed DEE89 case. Renal calcification occurs in two
    reports, with stones and hydronephrosis in one patient. Developmental GABA signaling is biologically
    relevant but the reviewed studies do not demonstrate enteric neuronal loss or a renal mechanism
    due to GAD1. Nor do they establish stones as the cause of hydronephrosis.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The diagnosis of Hirschsprung was confirmed by rectal biopsy.
    explanation: Biopsy-confirmed Hirschsprung disease occurred in Chatron case 9. The ungenotyped
      sibling mentioned in Neuray et al. is not included as additional DEE89 evidence.
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: and urinary ultrasonography revealed grade 1 nephrocalcinosis.
    explanation: Grade 1 nephrocalcinosis was reported in Chatron case 9; Neuray patient A also had
      nephrocalcinosis with stones and hydronephrosis.
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: '| Other features | Hydronephrosis, nephrocalcinosis, bilateral kidney stones |'
    explanation: Bilateral kidney stones occurred in patient A of the six-patient cohort.

- discussion_id: gap_dee89_drug_response
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - phenotypes#Refractory Drug Response
  prompt: Which features determine antiseizure medication resistance?
  rationale: Both control and resistance occur. The represented GABA-deficiency seizure pathway explains
    epilepsy but does not establish why one patient responds and another does not. Seizure type, residual
    GAD67 activity, treatment timing and drug choice remain competing explanations.
  evidence:
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Seizures were pharmacologically controlled in three of six affected individuals, with
      three reported as drug-resistant.
    explanation: Three of six patients had drug-resistant epilepsy; this phenotype describes antiseizure
      treatment response, not a distinct seizure type.

- discussion_id: gap_dee89_motor_sign_localization
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - phenotypes#Spasticity
  - phenotypes#Hyperreflexia
  - phenotypes#Clonus
  - phenotypes#Dystonia
  - phenotypes#Choreoathetosis
  - phenotypes#Hyporeflexia
  prompt: Which inhibitory motor circuits account for increased tone and brisk reflexes, which generate
    dystonia or choreoathetosis, and why does one patient instead have hyporeflexia?
  rationale: The authors explicitly propose a developmental explanation for axial hypotonia and genetically
    attribute weakness; those qualified causal relations are represented. For increased tone, the
    paper compares DEE89 with stiff-person syndrome, whose spinal and supraspinal disinhibition is
    an analogy rather than a demonstrated DEE89 mechanism. The case descriptions of spasticity and
    brisk reflexes establish the signs but do not localize their causal lesion. Clonus in the 2023
    patient, dystonia emerging during follow-up, choreoathetotic arm movements and hyporeflexia in
    patient E likewise lack a source-established circuit explanation. These are unresolved phenotype-specific
    localization and attribution questions, not missing steps in an otherwise established central
    motor pathway.
  evidence:
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: This autoimmune disorder is thought to result in an impairment of spinal and supra-spinal
      inhibitory neurons, leading to excessive excitatory drive upon the motor neurons.
    explanation: The antecedent is stiff-person syndrome, not DEE89. This comparison supplies a hypothesis
      for increased tone but does not demonstrate the circuit responsible for DEE89 spasticity or
      reflex findings.
    directness: INDIRECT
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: He initially showed reduced muscle tone and developed spasticity and dystonia as well
      as scoliosis later during the disease course.
    explanation: Case 7 documents evolution of tone and dystonia without identifying the causal circuit.
  - reference: PMID:32282878
    reference_title: Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic
      encephalopathy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: She kept her hands fisted with flexion of wrists and her arms movements were uncoordinated
      and choreathetotic.
    explanation: Case 11 documents choreoathetotic arm movements; this observation is not evidence
      that the axial-hypotonia mechanism causes them.
  - reference: PMID:32705143
    reference_title: Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1
      variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: '| Neurological examination | Mild hypotonia | Brisk DTR, stereotypic hand movements,
      oral automatisms | Mild hypotonia, spasticity in lower extremities, oropharyngeal dysphagia
      | Severe hypotonia, dysphagia (floppy epiglottis) | Severe hypotonia, hyporeflexia, dysphagia
      | Severe hypotonia |'
    explanation: Hyporeflexia was recorded in patient E in Table 1 of Neuray et al., contrasting with
      brisk reflexes in other patients. The source does not localize the reflex impairment.
  - reference: PMID:37029735
    reference_title: 'Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular
      dynamics simulation, and a comprehensive clinical and molecular profile.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: This study's patient, in addition to typical symptoms of the DEE89, showed microcephaly
      and clonus in the toe, which were novel clinical findings.
    explanation: The 2023 report calls the toe movement clonus; its proposed motor pathway was not
      studied.

references:
- reference: PMID:32282878
  title: "Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy."
- reference: PMID:32705143
  title: "Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1 variants."
- reference: PMID:37029735
  title: "Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile."
- reference: PMID:33169137
  title: "Reply: Rational therapy with vigabatrin and a ketogenic diet in a patient with GAD1 deficiency."
- reference: PMID:9177246
  title: "Cleft palate and decreased brain gamma-aminobutyric acid in mice lacking the 67-kDa isoform of glutamic acid decarboxylase."
- reference: PMID:37830095
  title: "Gad1 knock-out rats exhibit abundant spike-wave discharges in EEG, exacerbated with valproate treatment."
- reference: PMID:20333300
  title: "Cleft palate is caused by CNS dysfunction in Gad1 and Viaat knockout mice."

📚

References & Deep Research

References

7

PMID:32282878

Bi-allelic GAD1 variants cause a neonatal onset syndromic developmental and epileptic encephalopathy.

No top-level findings curated for this source.

PMID:32705143

Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1 variants.

No top-level findings curated for this source.

PMID:37029735

Developmental and epileptic encephalopathy 89: A novel bi-allelic variant, molecular dynamics simulation, and a comprehensive clinical and molecular profile.

No top-level findings curated for this source.

PMID:33169137

Reply: Rational therapy with vigabatrin and a ketogenic diet in a patient with GAD1 deficiency.

No top-level findings curated for this source.

PMID:9177246

Cleft palate and decreased brain gamma-aminobutyric acid in mice lacking the 67-kDa isoform of glutamic acid decarboxylase.

No top-level findings curated for this source.

PMID:37830095

Gad1 knock-out rats exhibit abundant spike-wave discharges in EEG, exacerbated with valproate treatment.

No top-level findings curated for this source.

PMID:20333300

Cleft palate is caused by CNS dysfunction in Gad1 and Viaat knockout mice.

No top-level findings curated for this source.

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Falcon ▸

Developmental and Epileptic Encephalopathy 89 (DEE89): Disease Characteristics Report

Edison Scientific Literature 10 citations 2026-08-27T02:40:44.230110

Developmental and Epileptic Encephalopathy 89 (DEE89): Disease Characteristics Report

Executive summary and evidence limits

Developmental and epileptic encephalopathy 89 (DEE89) is an ultra-rare, autosomal-recessive neurodevelopmental disorder caused by biallelic loss-of-function variants in GAD1, which encodes glutamate decarboxylase 67 (GAD67), the principal enzyme supporting basal γ-aminobutyric acid (GABA) production in the central nervous system. The defining phenotype is early-infantile epilepsy followed by—or accompanied by—severe developmental impairment, hypotonia or weakness, and occasional craniofacial or skeletal abnormalities. The disease was established from only six unrelated affected individuals, so most percentages below describe that ascertainment cohort rather than population-level frequencies. (neuray2020earlyinfantileonsetepilepsy pages 3-3, neuray2020earlyinfantileonsetepilepsy pages 1-1, OpenTargets Search: developmental and epileptic encephalopathy 89-GAD1)

The foundational primary report is Neuray et al., “Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1 variants,” published online 10 July 2020 in Brain, volume 143, pages 2388–2397; PMID 32282878; DOI/URL: https://doi.org/10.1093/brain/awaa178. Its abstract states: “Mice lacking GAD1 show neonatal mortality, but the human phenotype associated with GAD1 disruption is poorly characterized. Neuray et al. describe six patients with biallelic GAD1 mutations, presenting with early-infantile onset epilepsy, neurodevelopmental delay, muscle weakness and non-CNS manifestations.” No substantive 2023–2024 DEE89-specific cohort, natural-history study, treatment trial, or mechanistic patient study was identified; recent literature largely discusses DEEs generally rather than expanding this disease-specific evidence base. (neuray2020earlyinfantileonsetepilepsy pages 3-3, neuray2020earlyinfantileonsetepilepsy pages 1-1)

Domain	Evidence-based finding	Evidence level/limitations
Identity/identifiers	Developmental and epileptic encephalopathy 89 (DEE89) is linked to MONDO:0030856 and OMIM 619124; Open Targets shows a single associated target, GAD1, with supporting literature including PMID 32282878. The evidence base is disease-level aggregation plus a small primary human case series. (OpenTargets Search: developmental and epileptic encephalopathy 89-GAD1, neuray2020earlyinfantileonsetepilepsy pages 1-1)	Identifier linkage is strong, but disease characterization is based on very limited published human data.
Causal gene/inheritance	DEE89 is caused by biallelic GAD1 variants encoding GAD67/glutamate decarboxylase 1; inheritance is autosomal recessive. In the reported cohort, 5/6 families had homozygous variants and 1/6 had compound heterozygous variants; 4/6 affected individuals were born to consanguineous parents. (neuray2020earlyinfantileonsetepilepsy pages 3-3, neuray2020earlyinfantileonsetepilepsy pages 1-1)	Human genetic evidence is consistent, but numbers come from only 6 unrelated families.
Foundational evidence	The foundational report is Neuray et al., Brain, July 2020, DOI: 10.1093/brain/awaa178, PMID 32282878, describing 6 affected individuals from 6 unrelated families and introducing GAD1 as a new gene associated with developmental and epileptic encephalopathy. (neuray2020earlyinfantileonsetepilepsy pages 1-1, neuray2020earlyinfantileonsetepilepsy pages 3-3)	Single primary series; no larger replication cohort identified in the gathered evidence.
Onset/seizures	Seizure onset occurred at 2-6 months (early-infantile onset). Seizure types were predominantly focal motor seizures, with some epileptic spasms and bilateral motor seizures. Seizures were pharmacologically controlled in 3/6 and drug-resistant in 3/6. (neuray2020earlyinfantileonsetepilepsy pages 3-3)	Denominators preserved from the only cohort; no standardized natural-history registry available.
Development/neuromuscular	All reported individuals had severe developmental delay/intellectual disability; most had no speech or communication, with only 1/6 retaining basic/simple speech. Reduced muscle strength/weakness or hypotonia was present in 5/6. Variable extracerebral features included skeletal abnormalities, dysmorphic features, and cleft palate. (neuray2020earlyinfantileonsetepilepsy pages 3-3, neuray2020earlyinfantileonsetepilepsy pages 1-1, neuray2020earlyinfantileonsetepilepsy pages 1-2)	Core phenotype is consistent, but extracerebral manifestations are variable and based on few cases.
MRI/EEG	MRI was reportedly normal in 4/6 and abnormal in 2/6, with ventricular enlargement or global atrophy. EEG abnormalities included burst-suppression, diffuse slowing with multifocal/generalized sharp waves, and hypsarrhythmia. (neuray2020earlyinfantileonsetepilepsy pages 3-3)	Imaging appears nonspecific; EEG spectrum is broad and not disease-exclusive.
Variants	Seven reported ultrarare germline GAD1 variants were: c.87C>G p.Tyr29Ter, *c.568delC p.Gln190Serfs11, c.670delC p.Leu224Serfs5, c.971T>G p.Phe324Cys, c.1040C>T p.Thr347Met, c.1591C>T p.Arg531, c.1691A>G p.Asn564Ser. Variant classes included nonsense, frameshift, missense; multiple alleles are predicted loss-of-function** via nonsense-mediated decay or catalytic disruption. (neuray2020earlyinfantileonsetepilepsy pages 6-6, neuray2020earlyinfantileonsetepilepsy pages 5-6)	Functional interpretation is strongest for null alleles; allele-frequency details were not extracted in this conversation.
Mechanism	GAD1/GAD67 is the major CNS enzyme for converting glutamate to GABA and contributes about 90% of baseline GABA. Bi-allelic loss of function is inferred to reduce GABA synthesis, disturb inhibitory/excitatory balance, lower seizure threshold, and impair neurodevelopment; persistent severe disability despite seizure freedom in 3/6 supports a developmental effect beyond seizures alone. (neuray2020earlyinfantileonsetepilepsy pages 6-7, neuray2020earlyinfantileonsetepilepsy pages 6-6, neuray2020earlyinfantileonsetepilepsy pages 1-1, neuray2020earlyinfantileonsetepilepsy pages 5-6)	Mechanistic chain is biologically plausible and supported by human genetics plus model data, but direct patient biochemical assays were not summarized here.
Treatment	No disease-specific targeted therapy was identified. Management in the cohort was standard antiseizure treatment with 3/6 achieving seizure control and 3/6 remaining drug-resistant. No DEE89-specific clinical intervention trial was found. (neuray2020earlyinfantileonsetepilepsy pages 3-3)	Evidence is limited to case-based supportive epilepsy care; no controlled treatment studies or precision therapies are available in the gathered evidence.
Epidemiology/trials	No robust prevalence, incidence, or survival estimates were identified. The human literature currently consists of a very small number of published cases. Clinical trial search found no relevant DEE89/GAD1-specific interventional trials. (OpenTargets Search: developmental and epileptic encephalopathy 89-GAD1, neuray2020earlyinfantileonsetepilepsy pages 3-3)	Major evidence gap; epidemiology and prognosis remain undefined.
Model organism	Gad1-null mice show neonatal lethality and severe cleft palate, supporting the gene’s role in development but limiting detailed postnatal neurological modeling. Animal data also support a role for GAD/GABA pathway deficiency in seizures. (neuray2020earlyinfantileonsetepilepsy pages 6-7, neuray2020earlyinfantileonsetepilepsy pages 1-1)	Useful for biological plausibility, but existing model limitations reduce fidelity for full human DEE89 natural history.

Table: This table summarizes the highest-confidence evidence gathered for developmental and epileptic encephalopathy 89, preserving small-cohort denominators and highlighting where the literature is strong versus sparse. It is useful as a compact evidence map for knowledge-base curation.

1. Disease information

Definition

DEE89 is a monogenic developmental and epileptic encephalopathy in which the underlying GAD1 defect directly disrupts neurodevelopment while deficient inhibitory neurotransmission promotes epilepsy. The “developmental and epileptic” designation is important: developmental disability is not merely a consequence of recurrent seizures. In the original cohort, severe intellectual/developmental impairment persisted in all patients even though three became seizure-free, supporting parallel developmental and epileptic effects. (neuray2020earlyinfantileonsetepilepsy pages 6-6)

Identifiers and synonyms

MONDO: MONDO:0030856.
OMIM phenotype: 619124.
Causal gene: GAD1, Ensembl ENSG00000128683; approved name glutamate decarboxylase 1.
Common names: developmental and epileptic encephalopathy 89; DEE89; GAD1-related developmental and epileptic encephalopathy; GAD1-related early-infantile epilepsy and developmental delay.
Orphanet: no disease-specific Orphanet identifier was established in the retrieved evidence.
ICD-10/ICD-11: no unique DEE89 code. Cases are coded under broader genetic/developmental epileptic encephalopathy, epilepsy, intellectual disability, and developmental-disorder categories.
MeSH: no unique disease heading; broader headings include Epileptic Encephalopathies, Epilepsy, and Neurodevelopmental Disorders.

Open Targets links MONDO:0030856 to one associated target, GAD1, and cites PMID 32282878 plus ClinVar records, providing aggregated disease-level corroboration of the primary case-series evidence. (OpenTargets Search: developmental and epileptic encephalopathy 89-GAD1)

Source granularity: available information is mainly an aggregated publication-level case series, not longitudinal EHR evidence. Database entries subsequently aggregate those individual reports.

2. Etiology, risk, and protective factors

Causal factor

The established cause is germline biallelic GAD1 variation, generally producing loss of GAD67 function. Five of six reported families had homozygous variants and one had compound-heterozygous variants. Four affected individuals were born to consanguineous parents. (neuray2020earlyinfantileonsetepilepsy pages 3-3)

Risk factors

Genetic: two pathogenic or likely pathogenic alleles in trans are the principal risk factor. Parental consanguinity increases the probability that both parents carry the same rare allele, but is not mechanistically required.
Family history: affected siblings would be expected in some families under recessive inheritance, although the founding report comprised one characterized patient per unrelated family.
Environmental, infectious, lifestyle, age, or sex risk: none has been demonstrated. The reported patients represented diverse ancestries—Persian, Pakistani, African American, Sudanese, Egyptian, and Turkish—arguing against restriction to one population, but the sample is too small for demographic inference. (neuray2020earlyinfantileonsetepilepsy pages 1-2)

Protective factors and gene–environment interaction

No protective allele, modifier gene, diet, exposure, or validated gene–environment interaction is known. Fever, sleep deprivation, illness, or medication nonadherence may trigger seizures in epilepsy generally, but these should not be entered as DEE89 causal factors without disease-specific evidence. Likewise, adequate vitamin B6 is required biochemically for pyridoxal-5′-phosphate-dependent decarboxylases, but neither pyridoxine deficiency nor pyridoxine responsiveness has been demonstrated as a DEE89 mechanism or treatment.

3. Phenotypes

Observed frequencies are from n=6 and therefore have very wide uncertainty.

Phenotype	Character, onset/course, observed frequency	Suggested HPO term
Early-infantile seizures	Onset 2–6 months; focal motor seizures predominated, with epileptic spasms and bilateral motor seizures in some patients; chronic and variably treatment-resistant	Seizure HP:0001250; Infantile onset HP:0003593; Focal motor seizure HP:0011153; Epileptic spasms HP:0011097
Developmental delay/intellectual disability	Severe in 6/6; persistent despite seizure freedom in some; major lifelong functional effect expected	Global developmental delay HP:0001263; Severe intellectual disability HP:0010864
Absent/severely impaired speech	Most had no speech or effective communication; one had basic/simple language	Absent speech HP:0001344; Delayed speech and language development HP:0000750
Hypotonia, weakness, poor motor control	Reduced strength or hypotonia in 5/6, ranging from mild hypotonia to limited head control	Muscular hypotonia HP:0001252; Muscle weakness HP:0001324; Head lag HP:0002421
Abnormal EEG	Burst suppression, hypsarrhythmia, diffuse slowing, and multifocal/generalized sharp waves	EEG with burst suppression HP:0010851; Hypsarrhythmia HP:0002521; EEG abnormality HP:0002353
Brain-imaging abnormality	MRI normal in 4/6; ventricular enlargement or global cerebral atrophy in 2/6	Cerebral atrophy HP:0002059; Ventriculomegaly HP:0002119
Dysmorphism	Variable thick eyebrows, protruding ears, wide mouth, retrognathia, infraorbital creases, or depressed nasal bridge	Thick eyebrow HP:0000574; Protruding ear HP:0000411; Wide mouth HP:0000154; Retrognathia HP:0000278; Depressed nasal bridge HP:0005280
Skeletal/abdominal findings	Variable scoliosis, clinodactyly, or diastasis recti	Scoliosis HP:0002650; Clinodactyly HP:0030084; Diastasis recti HP:0001540
Cleft palate	Reported in one patient; biologically concordant with the mouse knockout but not a universal feature	Cleft palate HP:0000175

These features and frequencies derive from the original six-person series. EEG abnormalities included burst suppression, hypsarrhythmia, and diffuse slowing with multifocal or generalized sharp waves; MRI was nonspecific and often normal. (neuray2020earlyinfantileonsetepilepsy pages 3-3, neuray2020earlyinfantileonsetepilepsy pages 4-5)

Quality-of-life impact: no EQ-5D, SF-36, PROMIS, caregiver-burden, or disease-specific QoL measurements have been published. Nevertheless, severe communication, motor, cognitive, and seizure impairments imply dependence for daily activities and substantial caregiver burden. That conclusion is clinical inference, not a measured DEE89 outcome.

4. Genetic and molecular information

Gene and protein

GAD1 encodes the 67-kDa glutamate decarboxylase isoform, GAD67. The protein has an N-terminal targeting/dimerization region, a central pyridoxal-5′-phosphate-binding region, and a C-terminal catalytic region. GAD67 supplies approximately 90% of constitutive basal CNS GABA, whereas GAD65 has a more activity-responsive presynaptic role. (neuray2020earlyinfantileonsetepilepsy pages 1-2, neuray2020earlyinfantileonsetepilepsy pages 1-1, neuray2020earlyinfantileonsetepilepsy pages 5-6)

Suggested annotations include HGNC:4092 (GAD1), UniProt Q99259, and enzyme class glutamate decarboxylase, EC 4.1.1.15. The biochemical reaction is L-glutamate → GABA + CO₂, requiring pyridoxal 5′-phosphate (ChEBI:18405) as cofactor; substrates/products include L-glutamate (ChEBI:29985) and 4-aminobutanoate/GABA (ChEBI:16865).

Reported disease alleles

Seven ultrarare germline variants were reported:

c.87C>G, p.(Tyr29Ter) — nonsense.
c.568delC, p.(Gln190SerfsTer11) — frameshift.
c.670delC, p.(Leu224SerfsTer5) — frameshift.
c.971T>G, p.(Phe324Cys) — missense.
c.1040C>T, p.(Thr347Met) — missense.
c.1591C>T, p.(Arg531Ter) — nonsense.
c.1691A>G, p.(Asn564Ser) — missense. (neuray2020earlyinfantileonsetepilepsy pages 6-6)

The truncating variants are expected to cause nonsense-mediated decay or truncated protein. Missense substitutions affect conserved functional regions and were computationally predicted to impair stability or catalysis; four of seven reported alleles involved the PLP-binding domain. The aggregate disease mechanism is therefore loss of function, not gain of function or dominant-negative activity. (neuray2020earlyinfantileonsetepilepsy pages 6-6, neuray2020earlyinfantileonsetepilepsy pages 5-6)

The source paper described the variants as ultrarare and GAD1 as intolerant of damaging variation, but exact gnomAD/TOPMed allele counts and current per-variant ClinVar classifications were not available in the retrieved full-text evidence. These should be refreshed directly from ClinVar and gnomAD before production curation. Open Targets identified two associated ClinVar records, RCV006436612 and RCV004820862. (OpenTargets Search: developmental and epileptic encephalopathy 89-GAD1)

Other genomic mechanisms

No disease-causing recurrent copy-number variant, translocation, inversion, repeat expansion, mitochondrial variant, somatic mosaicism, modifier gene, methylation signature, or other DEE89-specific epigenetic abnormality is established. Large deletions disrupting both GAD1 alleles would be mechanistically plausible but were not documented in the founding cohort.

5. Environmental information

DEE89 is a genetic Mendelian disease. No toxin, radiation, pollution, occupational exposure, smoking, alcohol, diet, infection, or other environmental exposure has been shown to cause it. There is no zoonotic or infectious component. Environmental conditions may alter seizure threshold nonspecifically, but no DEE89-specific interaction has been quantified.

6. Mechanism and pathophysiology

Causal chain

Upstream genetic lesion: biallelic damaging GAD1 variants produce absent or impaired GAD67.
Primary biochemical defect: reduced PLP-dependent decarboxylation of glutamate to GABA.
Cellular effect: diminished GABA supply in inhibitory neurons compromises inhibitory synaptic transmission and maturation of GABAergic networks.
Circuit effect: excitation–inhibition imbalance and network hypersynchrony lower seizure threshold, generating early-infantile epilepsy and encephalopathic EEG patterns.
Developmental effect: GABA is also a developmental signal affecting neuronal migration, synaptogenesis, and circuit maturation. Thus GAD67 deficiency can directly impair cognition and motor development independently of seizure burden.
Downstream clinical manifestations: seizures, severe developmental/intellectual disability, absent speech, hypotonia/weakness, and occasionally cerebral atrophy.
Extraneural development: GAD1 expression in embryonic limb mesenchyme and pharyngeal structures, together with reduced fetal movement, may contribute to skeletal abnormalities and cleft palate; the human evidence remains provisional. (neuray2020earlyinfantileonsetepilepsy pages 8-9, neuray2020earlyinfantileonsetepilepsy pages 6-7, neuray2020earlyinfantileonsetepilepsy pages 1-1)

The observation that all six patients remained severely impaired while three achieved seizure control is an important human “natural experiment”: suppressing seizures alone does not reverse the upstream neurodevelopmental defect. (neuray2020earlyinfantileonsetepilepsy pages 6-6)

Ontology-ready mechanism annotations

GO biological process: glutamate decarboxylation to GABA; GABA biosynthetic process (GO:0009449); gamma-aminobutyric acid signaling pathway (GO:0007214); chemical synaptic transmission (GO:0007268); regulation of membrane potential (GO:0042391); nervous-system development (GO:0007399).
GO molecular function: glutamate decarboxylase activity (GO:0004351); pyridoxal-phosphate binding (GO:0030170).
GO cellular component: cytosol (GO:0005829), neuron projection (GO:0043005), presynapse (GO:0098793).
Cell Ontology: neuron (CL:0000540); GABAergic neuron (CL:0000617); interneuron (CL:0000099). Particular interneuron subclasses have not been shown to be selectively vulnerable in DEE89.

There is no DEE89-specific evidence for apoptosis, autophagy, primary mitochondrial failure, immune activation, chronic inflammation, or a distinct metabolic signature beyond deficient GABA biosynthesis. No patient-derived transcriptomics, proteomics, metabolomics, lipidomics, single-cell, spatial-transcriptomic, multi-omic, CRISPR-screen, iPSC, or organoid study was found.

7. Anatomical structures affected

The central nervous system is primary, especially neuronal networks of the cerebral cortex and other GABAergic circuits. Suggested anatomy terms are brain (UBERON:0000955), cerebral cortex (UBERON:0000956), central nervous system (UBERON:0001017), and synapse (UBERON:0001035). No consistent focal lesion or lateralization has been reported; effects are presumed bilateral and network-wide.

Secondary or variably involved structures include skeletal muscle function, axial skeleton, digits, palate, and craniofacial structures. Weakness may reflect central hypotonia rather than primary myopathy; biopsy or EMG evidence for a muscle-intrinsic lesion is absent. Relevant subcellular sites are cytosol and inhibitory synaptic compartments, not mitochondria, lysosome, or nucleus as primary disease organelles. (neuray2020earlyinfantileonsetepilepsy pages 8-9, neuray2020earlyinfantileonsetepilepsy pages 3-3)

8. Temporal development and natural history

Prenatal/congenital: most affected infants were not recognized prenatally; cleft palate or skeletal abnormalities may be congenital in a minority.
Onset: seizures began at 2–6 months, an early-infantile, generally subacute presentation.
Early course: epileptic spasms, focal motor seizures, or bilateral motor seizures occur with markedly abnormal EEG.
Later course: severe developmental delay, speech impairment, and weakness become prominent. Seizures may remit with medication or remain drug-resistant.
Duration: presumed lifelong. No validated staging system exists.
Remission: seizure freedom occurred in 3/6, but developmental disability persisted; 3/6 remained drug-resistant. (neuray2020earlyinfantileonsetepilepsy pages 3-3)

No longitudinal cohort defines progression rate, regression frequency, adult phenotype, critical therapeutic window, or late complications. Early infancy is nevertheless a plausible intervention window because both seizures and GABA-dependent circuit development are active then; this remains expert mechanistic inference rather than trial evidence.

9. Inheritance and population

Inheritance

Inheritance is autosomal recessive. For two confirmed heterozygous carrier parents, each pregnancy has an expected 25% probability of an affected child, 50% probability of an unaffected carrier, and 25% probability of an unaffected non-carrier. Penetrance for clearly biallelic null or severely damaging genotypes appears high, but cannot be estimated formally. Expressivity is variable, particularly for seizure control, MRI abnormalities, weakness, and extracerebral features.

There is no evidence for anticipation. Germline mosaicism is not required to explain recurrence but remains a theoretical residual risk if a variant appears de novo. No founder effect or carrier-frequency estimate is established. Consanguinity was present in 4/6 founding families, reflecting recessive ascertainment rather than proof of a population-specific disease. (neuray2020earlyinfantileonsetepilepsy pages 3-3, neuray2020earlyinfantileonsetepilepsy pages 1-2)

Epidemiology

No prevalence, incidence, sex ratio, life-table, regional distribution, or ancestry-specific rate is available. Six ethnically diverse unrelated cases were reported initially. DEE89 should therefore be described as ultra-rare, prevalence unknown, not assigned a numerical population rate. (neuray2020earlyinfantileonsetepilepsy pages 1-2)

10. Diagnostics

Clinical evaluation

Suspect DEE89 in an infant with seizures beginning in the first months of life, severe developmental delay or stagnation, hypotonia/weakness, and an encephalopathic EEG—particularly with consanguinity or affected siblings. EEG documents seizure type and background severity but is not specific. Brain MRI evaluates structural causes and complications; a normal MRI does not exclude DEE89 because 4/6 reported scans were normal. Routine blood, urine, CSF, enzyme, or tissue biomarkers have not been validated. (neuray2020earlyinfantileonsetepilepsy pages 3-3)

Molecular confirmation

Use a comprehensive developmental-epilepsy panel including GAD1, trio exome sequencing, or trio genome sequencing.
Confirm candidate variants by an orthogonal method and establish trans phase through parental testing.
Evaluate sequence variants, exon-level deletions/duplications, splice variants, and—if WGS/RNA studies are available—deep intronic or regulatory defects.
Apply ACMG/AMP criteria using population rarity, predicted loss of function, segregation, phenotype concordance, and functional evidence.

WES was effective in the founding families. WGS can add CNV, structural, noncoding, and difficult-splice detection. CMA may be appropriate in unexplained developmental delay but will usually miss small GAD1 variants; karyotype and FISH have no disease-specific role. Mitochondrial and repeat-expansion tests are guided by the differential diagnosis, not DEE89 itself. No diagnostic RNA-seq, proteomic, metabolomic, epigenomic, or liquid-biopsy signature is validated.

Differential diagnosis

Important alternatives include other early-infantile DEEs—STXBP1, KCNQ2, SCN2A, SCN8A, CDKL5, KCNT1, DNM1, AP2M1, WWOX, PCDH12, and metabolic epilepsies such as ALDH7A1/PNPO-related vitamin-B6-dependent epilepsy. Structural brain disease, congenital infection, hypoxic injury, and inborn errors of metabolism should be assessed clinically. DEE89 is distinguished by confirmed biallelic GAD1 pathogenic variants; no electroclinical feature is pathognomonic.

Screening

DEE89 is not on routine newborn-screening panels, and no validated biochemical newborn marker exists. Targeted carrier, cascade, prenatal, or preimplantation testing is appropriate once familial variants are known.

11. Outcome and prognosis

No five- or ten-year survival, mortality rate, life expectancy, SUDEP incidence, or adult-outcome estimate exists. Gad1-null mouse neonatal lethality must not be extrapolated directly to humans with hypomorphic or partial-loss alleles.

Known morbidity is substantial: severe intellectual and communication disability occurred in all six original patients; weakness/hypotonia occurred in five; and half had drug-resistant epilepsy. Prognostic separation based on variant class is not yet possible. Seizure control does not guarantee cognitive recovery, because severe disability persisted in seizure-free patients. Potential complications follow from severe DEE generally—status epilepticus, aspiration, feeding difficulty, contractures/scoliosis, immobility, medication adverse effects, and SUDEP risk—but disease-specific rates are unknown. (neuray2020earlyinfantileonsetepilepsy pages 3-3, neuray2020earlyinfantileonsetepilepsy pages 6-6)

12. Treatment

Current management

There is no approved GAD1- or DEE89-specific therapy. Management should be multidisciplinary:

Antiseizure medication: individualized by seizure type and EEG; 3/6 founding patients achieved pharmacological control and 3/6 were drug-resistant. Published evidence does not support one drug as uniquely effective. (neuray2020earlyinfantileonsetepilepsy pages 3-3)
Rescue planning: emergency benzodiazepine plan and education regarding prolonged seizures/status epilepticus.
Developmental care: early physical, occupational, speech/augmentative-communication, and feeding therapies.
Orthopedic and nutritional care: surveillance for scoliosis, contractures, aspiration, poor growth, and need for adaptive equipment.
Safety: seizure precautions and counseling regarding SUDEP.

Possible NCIt mappings include Anticonvulsant Agent (C264), Physical Therapy (C15308), Occupational Therapy (C15310), Speech Therapy (C15312), Genetic Counseling (C15246), and Palliative/Supportive Care (C15292); exact NCIt codes should be verified against the current release before database import.

Precision and experimental therapies

No DEE89-specific gene replacement, CRISPR editing, ASO, mRNA, cell therapy, or targeted small-molecule program has entered clinical trials, and the retrieved ClinicalTrials.gov search found no relevant interventional study. Increasing GAD1 expression, replacing GAD67, stabilizing residual enzyme, or augmenting GABAergic signaling are conceptual strategies, but chronic nonspecific GABA enhancement can cause sedation and may not restore early developmental signaling. Pyridoxine or PLP should not be represented as evidence-based DEE89 therapy absent biochemical deficiency or a supervised diagnostic trial for vitamin-B6-dependent epilepsy.

No pharmacogenomic response marker, response rate beyond the six-person series, treatment algorithm, or controlled adverse-event dataset exists.

13. Prevention

Primary prevention: the sporadic occurrence of recessive alleles cannot be prevented by lifestyle or vaccination. Reproductive carrier testing, preimplantation genetic testing, chorionic-villus sampling, or amniocentesis can prevent or identify recurrence in families with known variants.
Secondary prevention: no population screening program exists. Rapid genomic testing in early infantile DEE can shorten the diagnostic odyssey and support early seizure treatment and developmental intervention.
Tertiary prevention: optimize seizure control, rescue therapy, vaccination and infection management, nutrition, aspiration precautions, mobility, bone health, communication support, and orthopedic surveillance.
Counseling: offer parental testing, recurrence-risk counseling, cascade testing of adult relatives, and discussion of reproductive options.

There is no vaccine, environmental remediation, behavioral prophylaxis, or preventive medication specific to DEE89.

14. Other species and natural disease

No naturally occurring veterinary GAD1-associated syndrome equivalent to human DEE89 was identified, and there is no infectious transmission or zoonotic potential. Orthologs are evolutionarily conserved in vertebrates, including mouse Gad1 and zebrafish gad1b, reflecting conservation of GABA synthesis. Natural breed associations and Vertebrate Breed Ontology annotations are unavailable.

15. Model organisms

Mouse

Constitutive Gad1-null mice develop severe cleft palate and die neonatally. This strongly supports GAD1’s developmental and craniofacial roles but prevents characterization of postnatal seizures, cognition, and long-term disease progression. More generally, disruption of GAD enzymes or GABA-A receptor components can produce spontaneous seizures, supporting the proposed inhibitory-network mechanism. (neuray2020earlyinfantileonsetepilepsy pages 6-7, neuray2020earlyinfantileonsetepilepsy pages 1-1)

Suggested taxonomy is Mus musculus, NCBI Taxon 10090. Useful future models would include conditional interneuron-specific knockouts, hypomorphic or patient-variant knock-ins, and temporally controlled alleles that survive beyond birth.

Other model systems

No DEE89-specific zebrafish, Drosophila, C. elegans, patient-iPSC, neuronal culture, cerebral organoid, or humanized model was identified in the retrieved literature. These represent high-priority gaps. Patient-variant knock-in neurons could quantify GABA production, firing, synaptic inhibition, and rescue by gene replacement or residual-function modulators.

Current expert assessment and knowledge-base recommendations

DEE89 has a compelling gene–disease relationship because multiple unrelated families carried biallelic ultrarare damaging GAD1 variants, the phenotype matches loss of inhibitory neurotransmission, and the mouse knockout supports developmental consequences. Nevertheless, clinical validity is much stronger than clinical actionability: diagnosis can be made molecularly, but prognosis and treatment remain based on six cases and general DEE practice. The most defensible knowledge-base entry should therefore preserve exact denominators, label mechanistic assignments as human-genetic plus model-supported, and mark epidemiology, QoL, long-term survival, biomarkers, genotype–phenotype correlation, and precision treatment as unknown. (OpenTargets Search: developmental and epileptic encephalopathy 89-GAD1, neuray2020earlyinfantileonsetepilepsy pages 6-6, neuray2020earlyinfantileonsetepilepsy pages 1-1)

Principal reference: Neuray C, Maroofian R, Scala M, et al. Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1 variants. Brain. Published online 10 July 2020;143(8):2388–2397. PMID: 32282878. DOI: https://doi.org/10.1093/brain/awaa178. (neuray2020earlyinfantileonsetepilepsy pages 3-3, neuray2020earlyinfantileonsetepilepsy pages 1-1)

References

(neuray2020earlyinfantileonsetepilepsy pages 3-3): Caroline Neuray, Reza Maroofian, Marcello Scala, Tipu Sultan, Gurpur S Pai, Majid Mojarrad, Heba El Khashab, Leigh deHoll, Wyatt Yue, Hessa S Alsaif, Maria N Zanetti, Oscar Bello, Richard Person, Atieh Eslahi, Zaynab Khazaei, Masoumeh H Feizabadi, Stephanie Efthymiou, Stanislav Groppa, Blagovesta Marinova Karashova, Wolfgang Nachbauer, Sylvia Boesch, Larissa Arning, Dagmar Timmann, Bru Cormand, Belen Pérez-Dueñas, Gabriella Di Rosa, Jatinder S Goraya, Tipu Sultan, Jun Mine, Daniela Avdjieva, Hadil Kathom, Radka Tincheva, Selina Banu, Mercedes Pineda-Marfa, Pierangelo Veggiotti, Michel D Ferrari, Alberto Verrotti, Giangluigi Marseglia, Salvatore Savasta, Mayte García-Silva, Alfons Macaya Ruiz, Barbara Garavaglia, Eugenia Borgione, Simona Portaro, Benigno Monteagudo Sanchez, Richard Boles, Savvas Papacostas, Michail Vikelis, Eleni Zamba Papanicolaou, Efthymios Dardiotis, Shazia Maqbool, Shahnaz Ibrahim, Salman Kirmani, Nuzhat Noureen Rana, Osama Atawneh, George Koutsis, Marianthi Breza, Salvatore Mangano, Carmela Scuderi, Eugenia Borgione, Giovanna Morello, Tanya Stojkovic, Massimi Zollo, Gali Heimer, Yves A Dauvilliers, Pasquale Striano, Issam Al-Khawaja, Fuad Al-Mutairi, Hamed Sherifa, Hala T El-Bassyouni, Doaa R Soliman, Selahattin Tekes, Leyla Ozer, Volkan Baltaci, Suliman Khan, Christian Beetz, Khalda S Amr, Vincenzo Salpietro, Yalda Jamshidi, Fowzan S Alkuraya, and Henry Houlden. Early-infantile onset epilepsy and developmental delay caused by bi-allelic gad1 variants. Brain, 143:2388-2397, Jul 2020. URL: https://doi.org/10.1093/brain/awaa178, doi:10.1093/brain/awaa178. This article has 56 citations and is from a highest quality peer-reviewed journal.
(neuray2020earlyinfantileonsetepilepsy pages 1-1): Caroline Neuray, Reza Maroofian, Marcello Scala, Tipu Sultan, Gurpur S Pai, Majid Mojarrad, Heba El Khashab, Leigh deHoll, Wyatt Yue, Hessa S Alsaif, Maria N Zanetti, Oscar Bello, Richard Person, Atieh Eslahi, Zaynab Khazaei, Masoumeh H Feizabadi, Stephanie Efthymiou, Stanislav Groppa, Blagovesta Marinova Karashova, Wolfgang Nachbauer, Sylvia Boesch, Larissa Arning, Dagmar Timmann, Bru Cormand, Belen Pérez-Dueñas, Gabriella Di Rosa, Jatinder S Goraya, Tipu Sultan, Jun Mine, Daniela Avdjieva, Hadil Kathom, Radka Tincheva, Selina Banu, Mercedes Pineda-Marfa, Pierangelo Veggiotti, Michel D Ferrari, Alberto Verrotti, Giangluigi Marseglia, Salvatore Savasta, Mayte García-Silva, Alfons Macaya Ruiz, Barbara Garavaglia, Eugenia Borgione, Simona Portaro, Benigno Monteagudo Sanchez, Richard Boles, Savvas Papacostas, Michail Vikelis, Eleni Zamba Papanicolaou, Efthymios Dardiotis, Shazia Maqbool, Shahnaz Ibrahim, Salman Kirmani, Nuzhat Noureen Rana, Osama Atawneh, George Koutsis, Marianthi Breza, Salvatore Mangano, Carmela Scuderi, Eugenia Borgione, Giovanna Morello, Tanya Stojkovic, Massimi Zollo, Gali Heimer, Yves A Dauvilliers, Pasquale Striano, Issam Al-Khawaja, Fuad Al-Mutairi, Hamed Sherifa, Hala T El-Bassyouni, Doaa R Soliman, Selahattin Tekes, Leyla Ozer, Volkan Baltaci, Suliman Khan, Christian Beetz, Khalda S Amr, Vincenzo Salpietro, Yalda Jamshidi, Fowzan S Alkuraya, and Henry Houlden. Early-infantile onset epilepsy and developmental delay caused by bi-allelic gad1 variants. Brain, 143:2388-2397, Jul 2020. URL: https://doi.org/10.1093/brain/awaa178, doi:10.1093/brain/awaa178. This article has 56 citations and is from a highest quality peer-reviewed journal.
(OpenTargets Search: developmental and epileptic encephalopathy 89-GAD1): Open Targets Query (developmental and epileptic encephalopathy 89-GAD1, 2 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(neuray2020earlyinfantileonsetepilepsy pages 1-2): Caroline Neuray, Reza Maroofian, Marcello Scala, Tipu Sultan, Gurpur S Pai, Majid Mojarrad, Heba El Khashab, Leigh deHoll, Wyatt Yue, Hessa S Alsaif, Maria N Zanetti, Oscar Bello, Richard Person, Atieh Eslahi, Zaynab Khazaei, Masoumeh H Feizabadi, Stephanie Efthymiou, Stanislav Groppa, Blagovesta Marinova Karashova, Wolfgang Nachbauer, Sylvia Boesch, Larissa Arning, Dagmar Timmann, Bru Cormand, Belen Pérez-Dueñas, Gabriella Di Rosa, Jatinder S Goraya, Tipu Sultan, Jun Mine, Daniela Avdjieva, Hadil Kathom, Radka Tincheva, Selina Banu, Mercedes Pineda-Marfa, Pierangelo Veggiotti, Michel D Ferrari, Alberto Verrotti, Giangluigi Marseglia, Salvatore Savasta, Mayte García-Silva, Alfons Macaya Ruiz, Barbara Garavaglia, Eugenia Borgione, Simona Portaro, Benigno Monteagudo Sanchez, Richard Boles, Savvas Papacostas, Michail Vikelis, Eleni Zamba Papanicolaou, Efthymios Dardiotis, Shazia Maqbool, Shahnaz Ibrahim, Salman Kirmani, Nuzhat Noureen Rana, Osama Atawneh, George Koutsis, Marianthi Breza, Salvatore Mangano, Carmela Scuderi, Eugenia Borgione, Giovanna Morello, Tanya Stojkovic, Massimi Zollo, Gali Heimer, Yves A Dauvilliers, Pasquale Striano, Issam Al-Khawaja, Fuad Al-Mutairi, Hamed Sherifa, Hala T El-Bassyouni, Doaa R Soliman, Selahattin Tekes, Leyla Ozer, Volkan Baltaci, Suliman Khan, Christian Beetz, Khalda S Amr, Vincenzo Salpietro, Yalda Jamshidi, Fowzan S Alkuraya, and Henry Houlden. Early-infantile onset epilepsy and developmental delay caused by bi-allelic gad1 variants. Brain, 143:2388-2397, Jul 2020. URL: https://doi.org/10.1093/brain/awaa178, doi:10.1093/brain/awaa178. This article has 56 citations and is from a highest quality peer-reviewed journal.
(neuray2020earlyinfantileonsetepilepsy pages 6-6): Caroline Neuray, Reza Maroofian, Marcello Scala, Tipu Sultan, Gurpur S Pai, Majid Mojarrad, Heba El Khashab, Leigh deHoll, Wyatt Yue, Hessa S Alsaif, Maria N Zanetti, Oscar Bello, Richard Person, Atieh Eslahi, Zaynab Khazaei, Masoumeh H Feizabadi, Stephanie Efthymiou, Stanislav Groppa, Blagovesta Marinova Karashova, Wolfgang Nachbauer, Sylvia Boesch, Larissa Arning, Dagmar Timmann, Bru Cormand, Belen Pérez-Dueñas, Gabriella Di Rosa, Jatinder S Goraya, Tipu Sultan, Jun Mine, Daniela Avdjieva, Hadil Kathom, Radka Tincheva, Selina Banu, Mercedes Pineda-Marfa, Pierangelo Veggiotti, Michel D Ferrari, Alberto Verrotti, Giangluigi Marseglia, Salvatore Savasta, Mayte García-Silva, Alfons Macaya Ruiz, Barbara Garavaglia, Eugenia Borgione, Simona Portaro, Benigno Monteagudo Sanchez, Richard Boles, Savvas Papacostas, Michail Vikelis, Eleni Zamba Papanicolaou, Efthymios Dardiotis, Shazia Maqbool, Shahnaz Ibrahim, Salman Kirmani, Nuzhat Noureen Rana, Osama Atawneh, George Koutsis, Marianthi Breza, Salvatore Mangano, Carmela Scuderi, Eugenia Borgione, Giovanna Morello, Tanya Stojkovic, Massimi Zollo, Gali Heimer, Yves A Dauvilliers, Pasquale Striano, Issam Al-Khawaja, Fuad Al-Mutairi, Hamed Sherifa, Hala T El-Bassyouni, Doaa R Soliman, Selahattin Tekes, Leyla Ozer, Volkan Baltaci, Suliman Khan, Christian Beetz, Khalda S Amr, Vincenzo Salpietro, Yalda Jamshidi, Fowzan S Alkuraya, and Henry Houlden. Early-infantile onset epilepsy and developmental delay caused by bi-allelic gad1 variants. Brain, 143:2388-2397, Jul 2020. URL: https://doi.org/10.1093/brain/awaa178, doi:10.1093/brain/awaa178. This article has 56 citations and is from a highest quality peer-reviewed journal.
(neuray2020earlyinfantileonsetepilepsy pages 5-6): Caroline Neuray, Reza Maroofian, Marcello Scala, Tipu Sultan, Gurpur S Pai, Majid Mojarrad, Heba El Khashab, Leigh deHoll, Wyatt Yue, Hessa S Alsaif, Maria N Zanetti, Oscar Bello, Richard Person, Atieh Eslahi, Zaynab Khazaei, Masoumeh H Feizabadi, Stephanie Efthymiou, Stanislav Groppa, Blagovesta Marinova Karashova, Wolfgang Nachbauer, Sylvia Boesch, Larissa Arning, Dagmar Timmann, Bru Cormand, Belen Pérez-Dueñas, Gabriella Di Rosa, Jatinder S Goraya, Tipu Sultan, Jun Mine, Daniela Avdjieva, Hadil Kathom, Radka Tincheva, Selina Banu, Mercedes Pineda-Marfa, Pierangelo Veggiotti, Michel D Ferrari, Alberto Verrotti, Giangluigi Marseglia, Salvatore Savasta, Mayte García-Silva, Alfons Macaya Ruiz, Barbara Garavaglia, Eugenia Borgione, Simona Portaro, Benigno Monteagudo Sanchez, Richard Boles, Savvas Papacostas, Michail Vikelis, Eleni Zamba Papanicolaou, Efthymios Dardiotis, Shazia Maqbool, Shahnaz Ibrahim, Salman Kirmani, Nuzhat Noureen Rana, Osama Atawneh, George Koutsis, Marianthi Breza, Salvatore Mangano, Carmela Scuderi, Eugenia Borgione, Giovanna Morello, Tanya Stojkovic, Massimi Zollo, Gali Heimer, Yves A Dauvilliers, Pasquale Striano, Issam Al-Khawaja, Fuad Al-Mutairi, Hamed Sherifa, Hala T El-Bassyouni, Doaa R Soliman, Selahattin Tekes, Leyla Ozer, Volkan Baltaci, Suliman Khan, Christian Beetz, Khalda S Amr, Vincenzo Salpietro, Yalda Jamshidi, Fowzan S Alkuraya, and Henry Houlden. Early-infantile onset epilepsy and developmental delay caused by bi-allelic gad1 variants. Brain, 143:2388-2397, Jul 2020. URL: https://doi.org/10.1093/brain/awaa178, doi:10.1093/brain/awaa178. This article has 56 citations and is from a highest quality peer-reviewed journal.
(neuray2020earlyinfantileonsetepilepsy pages 6-7): Caroline Neuray, Reza Maroofian, Marcello Scala, Tipu Sultan, Gurpur S Pai, Majid Mojarrad, Heba El Khashab, Leigh deHoll, Wyatt Yue, Hessa S Alsaif, Maria N Zanetti, Oscar Bello, Richard Person, Atieh Eslahi, Zaynab Khazaei, Masoumeh H Feizabadi, Stephanie Efthymiou, Stanislav Groppa, Blagovesta Marinova Karashova, Wolfgang Nachbauer, Sylvia Boesch, Larissa Arning, Dagmar Timmann, Bru Cormand, Belen Pérez-Dueñas, Gabriella Di Rosa, Jatinder S Goraya, Tipu Sultan, Jun Mine, Daniela Avdjieva, Hadil Kathom, Radka Tincheva, Selina Banu, Mercedes Pineda-Marfa, Pierangelo Veggiotti, Michel D Ferrari, Alberto Verrotti, Giangluigi Marseglia, Salvatore Savasta, Mayte García-Silva, Alfons Macaya Ruiz, Barbara Garavaglia, Eugenia Borgione, Simona Portaro, Benigno Monteagudo Sanchez, Richard Boles, Savvas Papacostas, Michail Vikelis, Eleni Zamba Papanicolaou, Efthymios Dardiotis, Shazia Maqbool, Shahnaz Ibrahim, Salman Kirmani, Nuzhat Noureen Rana, Osama Atawneh, George Koutsis, Marianthi Breza, Salvatore Mangano, Carmela Scuderi, Eugenia Borgione, Giovanna Morello, Tanya Stojkovic, Massimi Zollo, Gali Heimer, Yves A Dauvilliers, Pasquale Striano, Issam Al-Khawaja, Fuad Al-Mutairi, Hamed Sherifa, Hala T El-Bassyouni, Doaa R Soliman, Selahattin Tekes, Leyla Ozer, Volkan Baltaci, Suliman Khan, Christian Beetz, Khalda S Amr, Vincenzo Salpietro, Yalda Jamshidi, Fowzan S Alkuraya, and Henry Houlden. Early-infantile onset epilepsy and developmental delay caused by bi-allelic gad1 variants. Brain, 143:2388-2397, Jul 2020. URL: https://doi.org/10.1093/brain/awaa178, doi:10.1093/brain/awaa178. This article has 56 citations and is from a highest quality peer-reviewed journal.
(neuray2020earlyinfantileonsetepilepsy pages 4-5): Caroline Neuray, Reza Maroofian, Marcello Scala, Tipu Sultan, Gurpur S Pai, Majid Mojarrad, Heba El Khashab, Leigh deHoll, Wyatt Yue, Hessa S Alsaif, Maria N Zanetti, Oscar Bello, Richard Person, Atieh Eslahi, Zaynab Khazaei, Masoumeh H Feizabadi, Stephanie Efthymiou, Stanislav Groppa, Blagovesta Marinova Karashova, Wolfgang Nachbauer, Sylvia Boesch, Larissa Arning, Dagmar Timmann, Bru Cormand, Belen Pérez-Dueñas, Gabriella Di Rosa, Jatinder S Goraya, Tipu Sultan, Jun Mine, Daniela Avdjieva, Hadil Kathom, Radka Tincheva, Selina Banu, Mercedes Pineda-Marfa, Pierangelo Veggiotti, Michel D Ferrari, Alberto Verrotti, Giangluigi Marseglia, Salvatore Savasta, Mayte García-Silva, Alfons Macaya Ruiz, Barbara Garavaglia, Eugenia Borgione, Simona Portaro, Benigno Monteagudo Sanchez, Richard Boles, Savvas Papacostas, Michail Vikelis, Eleni Zamba Papanicolaou, Efthymios Dardiotis, Shazia Maqbool, Shahnaz Ibrahim, Salman Kirmani, Nuzhat Noureen Rana, Osama Atawneh, George Koutsis, Marianthi Breza, Salvatore Mangano, Carmela Scuderi, Eugenia Borgione, Giovanna Morello, Tanya Stojkovic, Massimi Zollo, Gali Heimer, Yves A Dauvilliers, Pasquale Striano, Issam Al-Khawaja, Fuad Al-Mutairi, Hamed Sherifa, Hala T El-Bassyouni, Doaa R Soliman, Selahattin Tekes, Leyla Ozer, Volkan Baltaci, Suliman Khan, Christian Beetz, Khalda S Amr, Vincenzo Salpietro, Yalda Jamshidi, Fowzan S Alkuraya, and Henry Houlden. Early-infantile onset epilepsy and developmental delay caused by bi-allelic gad1 variants. Brain, 143:2388-2397, Jul 2020. URL: https://doi.org/10.1093/brain/awaa178, doi:10.1093/brain/awaa178. This article has 56 citations and is from a highest quality peer-reviewed journal.
(neuray2020earlyinfantileonsetepilepsy pages 8-9): Caroline Neuray, Reza Maroofian, Marcello Scala, Tipu Sultan, Gurpur S Pai, Majid Mojarrad, Heba El Khashab, Leigh deHoll, Wyatt Yue, Hessa S Alsaif, Maria N Zanetti, Oscar Bello, Richard Person, Atieh Eslahi, Zaynab Khazaei, Masoumeh H Feizabadi, Stephanie Efthymiou, Stanislav Groppa, Blagovesta Marinova Karashova, Wolfgang Nachbauer, Sylvia Boesch, Larissa Arning, Dagmar Timmann, Bru Cormand, Belen Pérez-Dueñas, Gabriella Di Rosa, Jatinder S Goraya, Tipu Sultan, Jun Mine, Daniela Avdjieva, Hadil Kathom, Radka Tincheva, Selina Banu, Mercedes Pineda-Marfa, Pierangelo Veggiotti, Michel D Ferrari, Alberto Verrotti, Giangluigi Marseglia, Salvatore Savasta, Mayte García-Silva, Alfons Macaya Ruiz, Barbara Garavaglia, Eugenia Borgione, Simona Portaro, Benigno Monteagudo Sanchez, Richard Boles, Savvas Papacostas, Michail Vikelis, Eleni Zamba Papanicolaou, Efthymios Dardiotis, Shazia Maqbool, Shahnaz Ibrahim, Salman Kirmani, Nuzhat Noureen Rana, Osama Atawneh, George Koutsis, Marianthi Breza, Salvatore Mangano, Carmela Scuderi, Eugenia Borgione, Giovanna Morello, Tanya Stojkovic, Massimi Zollo, Gali Heimer, Yves A Dauvilliers, Pasquale Striano, Issam Al-Khawaja, Fuad Al-Mutairi, Hamed Sherifa, Hala T El-Bassyouni, Doaa R Soliman, Selahattin Tekes, Leyla Ozer, Volkan Baltaci, Suliman Khan, Christian Beetz, Khalda S Amr, Vincenzo Salpietro, Yalda Jamshidi, Fowzan S Alkuraya, and Henry Houlden. Early-infantile onset epilepsy and developmental delay caused by bi-allelic gad1 variants. Brain, 143:2388-2397, Jul 2020. URL: https://doi.org/10.1093/brain/awaa178, doi:10.1093/brain/awaa178. This article has 56 citations and is from a highest quality peer-reviewed journal.

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Developmental and Epileptic Encephalopathy 89 (DEE89): Disease Characteristics Report

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2. Etiology, risk, and protective factors

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