CaseEPI4Kn2: Female, 1 month onset

CasePresentingHPOs: HP:0002521, HP:0011167, HP:0032794, HP:0000618, HP:0003089, HP:0000473, HP:0003487, HP:0032988, HP:0008936, HP:0001276, HP:0010864 (Hypsarrhythmia, Focal tonic seizure, Myoclonic seizure, Blindness, Hamstring contractures, Torticollis, Babinski sign, Persistent head lag, Muscular hypotonia of the trunk, Hypertonia, Severe intellectual disability)

HPOsFreeText: N/A

CaseNotHPOs: HP:0001263 (Global developmental delay)

NotHPOsFreeText: N/A

CaseAddInfo: N/A

CasePreviousTesting: Currently on vigabatrin, topiramate, and oxcarbazepine; Previously on phenobarbitone and levetriacetam; Bifrontal central frequent discharges on EEG; Normal brain imaging; No confirmed genetic or metabolic diagnosis, and no history of congenital TORCH infection, premature birth (before 32 weeks gestation), neonatal hypoxic-ischemic encephalopathy or neonatal seizures, meningitis/encephalitis, stroke, intra-cranial hemorrhage, significant head trauma, or evidence of acquired epilepsy

CaseGenotypingMethod: Exome sequencing was performed from primary DNA in parental leukocytes. Coding regions of the genome were sequenced in a trio in order to determine which loci bearing de novo mutations were present according to specifications. All candidate de novo variants were confirmed with Sanger sequencing of the proband and parents.

Variant: NM_004171.4(SLC1A2):c.244G>C (p.Gly82Arg)

ClinVar: 254265, https://www.ncbi.nlm.nih.gov/clinvar/variation/254265/

gnomAD: Not in gnomAD

CaseST: Female, 2 days onset

CasePresentingHPOs: HP:0002521, HP:0010841, HP:0012000, HP:0032842, HP:0011468, HP:0007289, HP:0100704, HP:0000639, HP:0001601, HP:0012820, HP:0002835, HP:0001252, HP:0001257, HP:0001263, HP:0002079, HP:0011757, HP:0003429 (Hypsarrhythmia, Multifocal epileptiform discharges, EEG with generalized spikes, Generalized-onset epileptic spasm, Facial tics, Limb fasciculations, Cerebral visual impairment, Nystagmus, Laryngomalacia, Bilateral vocal cord paralysis, Aspiration, Muscular hypotonia, Spasticity, Global developmental delay, Hypoplasia of the corpus callosum, Posterior pituitary hypoplasia, CNS hypomyelination)

HPOsFreeText: Lack of normal sleep or wake features on EEG

CaseNotHPOs: HP:0002650 (Scoliosis)

NotHPOsFreeText: N/A

CaseAddInfo: Proband is confirmed de novo heterozygous

CasePreviousTesting: Currently on vigabatrin, levetiracetam, Rufinamide and ketogenic diet, previously on phenobarbatol, ACTH, Cannabidiol oil and Prednisolone; MRS with small lactate peaks in the basal ganglia and supratentorial white matter

CaseGenotypingMethod: Whole exome sequencing revealed a pathogenic heterozygous c.254T>C (p.Leu85Pro) variant in the SLC1A2 gene, which was classified as de novo using parental testing.

Variant: NM_004171.4(SLC1A2):c.254T>C (p.Leu85Pro)

ClinVar: 254266, https://www.ncbi.nlm.nih.gov/clinvar/variation/254266/

gnomAD: Not in gnomAD

CaseT23159: Female, 2 days onset

CasePresentingHPOs: HP:0200134, HP:0011167, HP:0010818, HP:0032667, HP:0031475, HP:0032816, HP:0010841, HP:0010845, HP:0006808, HP:0002079, HP:0012753, HP:0002059, HP:0007266, HP:0002273, HP:0011471, HP:0000121, HP:0000141, HP:0000696, HP:0001662, HP:0002045, HP:0000253, HP:0000341, HP:0001525, HP:0001007, HP:0002751, HP:0001371, HP:0001182 (Epileptic encephalopathy, Focal tonic seizure, Generalized tonic seizure, Myoclonic status epilepticus, Nonconvulsive status epilepticus, Neonatal multifocal myoclonic seizure, Multifocal epileptiform discharges, EEG with generalized slow activity, Cerebral hypomyelination, Hypoplasia of the corpus callosum, T2 hypointense basal ganglia, Cerebral atrophy, White matter dysmyelination/demyelination, Tetraparesis, Gastrostomy tube feeding in infancy, Nephrocalcinosis, Amenorrhea, Delayed eruption of permanent teeth, Bradycardia, Hypothermia, Progressive microcephaly, Narrow forehead, Severe failure to thrive, Hirsutism, Kyphoscoliosis, Flexion contracture, Tapered finger)

HPOsFreeText: Thinning of cortical gray matter

CaseNotHPOs: HP:0001272 (Cerebellar atrophy)

NotHPOsFreeText: Hypomyelination of cerebellum and brain stem

CaseAddInfo: Proband confirmed de novo heterozygous by parental sequencing

CasePreviousTesting: Currently on carbamazepime, lamotrigine and lacosamide; previously on pyridoxine, clonazepam, acetazolamide, valproate, phenobarbitone, phenytoin, prednisolone, vigabatrin, topiramate and ketogenic diet

CaseGenotypingMethod: About 10% of the original 290 genes where a single de novo variant had been identified was chosen for targeted sequencing in a new cohort. Most of these individuals had been tested for mutations of known and novel candidate genes as well as pathogenic copy-number variants. These genes were sequenced in the parents and proband to look for de novo variants.

Variant: NM_004171.4(SLC1A2):c.254T>C (p.Leu85Pro)

ClinVar: 254266, https://www.ncbi.nlm.nih.gov/clinvar/variation/254266/

gnomAD: Not in gnomAD

CaseT23159: Female, 2 days onset

CasePresentingHPOs: HP:0200134, HP:0011167, HP:0010818, HP:0032667, HP:0031475, HP:0032816, HP:0010841, HP:0010845, HP:0006808, HP:0002079, HP:0012753, HP:0002059, HP:0007266, HP:0002273, HP:0011471, HP:0000121, HP:0000141, HP:0000696, HP:0001662, HP:0002045, HP:0000253, HP:0000341, HP:0001525, HP:0001007, HP:0002751, HP:0001371, HP:0001182 (Epileptic encephalopathy, Focal tonic seizure, Generalized tonic seizure, Myoclonic status epilepticus, Nonconvulsive status epilepticus, Neonatal multifocal myoclonic seizure, Multifocal epileptiform discharges, EEG with generalized slow activity, Cerebral hypomyelination, Hypoplasia of the corpus callosum, T2 hypointense basal ganglia, Cerebral atrophy, White matter dysmyelination/demyelination, Tetraparesis, Gastrostomy tube feeding in infancy, Nephrocalcinosis, Amenorrhea, Delayed eruption of permanent teeth, Bradycardia, Hypothermia, Progressive microcephaly, Narrow forehead, Severe failure to thrive, Hirsutism, Kyphoscoliosis, Flexion contracture, Tapered finger)

HPOsFreeText: Thinning of cortical gray matter

CaseNotHPOs: HP:0001272 (Cerebellar atrophy)

NotHPOsFreeText: Hypomyelination of cerebellum and brain stem

CaseAddInfo: Proband confirmed de novo heterozygous by parental sequencing

CasePreviousTesting: Currently on carbamazepime, lamotrigine and lacosamide; previously on pyridoxine, clonazepam, acetazolamide, valproate, phenobarbitone, phenytoin, prednisolone, vigabatrin, topiramate and ketogenic diet

CaseGenotypingMethod: About 10% of the original 290 genes where a single de novo variant had been identified was chosen for targeted sequencing in a new cohort. Most of these individuals had been tested for mutations of known and novel candidate genes as well as pathogenic copy-number variants. These genes were sequenced in the parents and proband to look for de novo variants.

Variant: NM_004171.4(SLC1A2):c.254T>C (p.Leu85Pro)

ClinVar: 254266, https://www.ncbi.nlm.nih.gov/clinvar/variation/254266/

gnomAD: Not in gnomAD

CaseGuA: Male, 6 weeks onset

CasePresentingHPOs: HP:0200134, HP:0020217, HP:0002069, HP:0010852, HP:0012012, HP:0012017, HP:0012018, HP:0010841, HP:0025152, HP:0030211, HP:0008936, HP:0002061, HP:0006986, HP:0002187, HP:0011344, HP:0001344, HP:0012448, HP:0002283, HP:0002079, HP:0012696, HP:0002500, HP:0012751 (Epileptic encephalopathy, Focal aware motor seizure, Bilateral tonic-clonic seizure, EEG with parietal focal spike waves, EEG with parietal focal spikes, EEG with temporal focal spikes, Multifocal epileptiform discharges, Poor visual behavior for age, Slow pupillary light response, Muscular hypotonia of the trunk, Lower limb spasticity, Upper limb spasticity, Profound intellectual disability, Severe global developmental delay, Absent speech, Delayed myelination, Global brain atrophy, Thin corpus callosum, Abnormal thalamic MRI signal intensity, White matter abnormalities, Abnormal basal ganglia MRI signal intensity)

HPOsFreeText: Dyskinetic movements of arms, In ability to sit unsupported, Abnormal MRI signal in putamen and caudate

CaseNotHPOs: N/A

NotHPOsFreeText: N/A

CaseAddInfo: Variant is confirmed heterozygous de novo

CasePreviousTesting: Investigations include electroencephalography (EEG), head MRI, neurometabolic testing, and chromosome microarray; Individuals with self-limiting benign electroclinical syndromes, such as childhood absence epilepsy (onset > 4 years), were excluded; Capture of right arm jerks and chin twitching showed no EEG correlate; Head circumference was 45.1 cm at 8 months (50%), 52 cm at 5 years (50th percentile); Partial response to phenobarbital, levetiracetam, and clobazam; Longest seizure-free period was 16 months

CaseGenotypingMethod: Variants within co-expressed candidate genes in Table S1 were extracted from exome sequencing data. Variants were annotated and were verified with Sanger sequencing of the proband and parents.

Variant: NM_004171.4(SLC1A2):c.244G>A (p.Gly82Arg)

ClinVar: 438736, https://www.ncbi.nlm.nih.gov/clinvar/variation/438736/

gnomAD: Not in gnomAD

CaseGuA: Male, 6 weeks onset

CasePresentingHPOs: HP:0200134, HP:0020217, HP:0002069, HP:0010852, HP:0012012, HP:0012017, HP:0012018, HP:0010841, HP:0025152, HP:0030211, HP:0008936, HP:0002061, HP:0006986, HP:0002187, HP:0011344, HP:0001344, HP:0012448, HP:0002283, HP:0002079, HP:0012696, HP:0002500, HP:0012751 (Epileptic encephalopathy, Focal aware motor seizure, Bilateral tonic-clonic seizure, EEG with parietal focal spike waves, EEG with parietal focal spikes, EEG with temporal focal spikes, Multifocal epileptiform discharges, Poor visual behavior for age, Slow pupillary light response, Muscular hypotonia of the trunk, Lower limb spasticity, Upper limb spasticity, Profound intellectual disability, Severe global developmental delay, Absent speech, Delayed myelination, Global brain atrophy, Thin corpus callosum, Abnormal thalamic MRI signal intensity, White matter abnormalities, Abnormal basal ganglia MRI signal intensity)

HPOsFreeText: Dyskinetic movements of arms, In ability to sit unsupported, Abnormal MRI signal in putamen and caudate

CaseNotHPOs: N/A

NotHPOsFreeText: N/A

CaseAddInfo: Variant is confirmed heterozygous de novo

CasePreviousTesting: Investigations include electroencephalography (EEG), head MRI, neurometabolic testing, and chromosome microarray; Individuals with self-limiting benign electroclinical syndromes, such as childhood absence epilepsy (onset > 4 years), were excluded; Capture of right arm jerks and chin twitching showed no EEG correlate; Head circumference was 45.1 cm at 8 months (50%), 52 cm at 5 years (50th percentile); Partial response to phenobarbital, levetiracetam, and clobazam; Longest seizure-free period was 16 months

CaseGenotypingMethod: Variants within co-expressed candidate genes in Table S1 were extracted from exome sequencing data. Variants were annotated and were verified with Sanger sequencing of the proband and parents.

Variant: NM_004171.4(SLC1A2):c.244G>A (p.Gly82Arg)

ClinVar: 438736, https://www.ncbi.nlm.nih.gov/clinvar/variation/438736/

gnomAD: Not in gnomAD