GABA-A Receptor-Related Neurodevelopmental Disorders (GABAAR-NDD)

name: GABA-A Receptor-Related Neurodevelopmental Disorders
display_name: GABA-A Receptor-Related Neurodevelopmental Disorders (GABAAR-NDD)
creation_date: "2026-09-12T00:00:00Z"
description: >-
  The GABA-A receptor-related neurodevelopmental disorders are monogenic
  disorders caused by pathogenic variants in the genes encoding subunits of the
  GABA-A receptor, the ligand-gated chloride channel that mediates fast
  inhibitory synaptic transmission in the CNS. Nineteen subunit genes exist;
  most reported disease-causing variants fall in GABRA1, GABRB2, GABRB3, and
  GABRG2. Both loss- and gain-of-function variants occur, and the functional
  direction matters clinically rather than only mechanistically: vigabatrin,
  which raises the tonic GABA current carried by extrasynaptic receptors, is
  reported to produce hypotonia, sedation, and respiratory suppression
  specifically in gain-of-function patients. The contrast with benzodiazepines
  is the informative part and should not be collapsed: they act mainly on
  phasic synaptic currents and are not reported to worsen gain-of-function
  disease — a gain-of-function GABRB3 patient stabilized on nitrazepam having
  not tolerated vigabatrin.
  The shared consequence is disturbed excitation-inhibition balance in
  developing cortical networks, presenting as epilepsy — frequently
  drug-resistant — with developmental delay, intellectual disability, and
  movement and ophthalmological involvement.
grouping_basis:
- SHARED_MECHANISM
- SHARED_GENE_FAMILY
grouping_rationale: >-
  Grouped on a shared molecular target and a shared downstream mechanism: every
  member is caused by a variant in a gene encoding a subunit of the same
  receptor complex, and each acts by perturbing GABAergic inhibition and hence
  the excitation-inhibition balance of developing networks. Members are kept as
  separate Disease entries because the subunit involved, the functional
  direction of the variant, the seizure phenotype, and the drug-response profile
  differ between them.

  The criteria are NECESSARY rather than NECESSARY_AND_SUFFICIENT, deliberately.
  Carrying a GABA-A subunit gene is not sufficient for membership, and the
  HAS_GENE predicate cannot see the distinction that matters: it matches any
  entry listing the gene, regardless of `relationship_type`. Reading these
  criteria as sufficient would sweep in three classes of non-member that are
  present in the KB today — contiguous-gene disorders whose interval merely
  spans subunit genes (Angelman syndrome and 15q11q13 microduplication syndrome
  both span GABRB3, GABRA5, and GABRG3, but are driven by UBE3A dosage rather
  than by receptor dysfunction); common epilepsies where a subunit gene is a
  SUSCEPTIBILITY allele of small effect rather than a cause (childhood absence
  epilepsy, juvenile absence epilepsy, juvenile myoclonic epilepsy, epilepsy
  with myoclonic-atonic seizures); non-epilepsy susceptibility associations
  such as GABRA2 in alcohol use disorder; and entries whose only subunit gene
  sits in a gene descriptor outside genetic: at all, such as Developmental and
  Epileptic Encephalopathy 8, which carries GABRA2 only in an animal model's
  genes: block (the collybistin-binding Gabra2-1 mouse) and has no subunit gene
  in its genetic: section. Running the two blocks over kb/disorders/ returns
  several non-members that satisfy both — the SUSCEPTIBILITY and untyped cases
  above — and Developmental and Epileptic Encephalopathy 8 is the only one this
  rationale would not otherwise predict.

  One further entry is excluded on both grounds. Generalized Epilepsy with
  Febrile Seizures Plus satisfies the gene block — GABRG2 is typed CAUSATIVE
  there — but not the conformance block: its entry declares no conforms_to at
  all, so the NECESSARY criteria already exclude it. It would stay out on scope
  even if that entry were later conformed to the module, because it is a
  genetically heterogeneous syndrome defined at the family level, with SCN1A,
  SCN1B, and STX1B also CAUSATIVE, so it is not a monogenic subunit disorder.
  The GABRG2-Related Epilepsy member already records this boundary from the
  other side, listing GEFS+ under differential_diagnoses with the note that it
  is curated as a separate dismech entry. Membership therefore requires a
  curator to have judged the variant causative, and the criteria audit that
  judgement rather than replace it.

  MONDO has no grouping term for GABA-A receptor-related disease, so no
  mapping is asserted; MONDO:0013166 (GABA aminotransaminase deficiency) is a
  metabolic disorder of GABA catabolism and is not a superclass of this group.
membership_criteria:
- description: >-
    Every member is caused by a pathogenic variant in one of the nineteen genes
    encoding a GABA-A receptor subunit.
  criteria_semantics: NECESSARY
  logic:
    operator: OR
    operands:
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRA1
        term:
          id: hgnc:4075
          label: GABRA1
      description: Pathogenic variant in GABRA1, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRA2
        term:
          id: hgnc:4076
          label: GABRA2
      description: Pathogenic variant in GABRA2, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRA3
        term:
          id: hgnc:4077
          label: GABRA3
      description: Pathogenic variant in GABRA3, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRA4
        term:
          id: hgnc:4078
          label: GABRA4
      description: Pathogenic variant in GABRA4, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRA5
        term:
          id: hgnc:4079
          label: GABRA5
      description: Pathogenic variant in GABRA5, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRA6
        term:
          id: hgnc:4080
          label: GABRA6
      description: Pathogenic variant in GABRA6, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRB1
        term:
          id: hgnc:4081
          label: GABRB1
      description: Pathogenic variant in GABRB1, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRB2
        term:
          id: hgnc:4082
          label: GABRB2
      description: Pathogenic variant in GABRB2, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRB3
        term:
          id: hgnc:4083
          label: GABRB3
      description: Pathogenic variant in GABRB3, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRD
        term:
          id: hgnc:4084
          label: GABRD
      description: Pathogenic variant in GABRD, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRE
        term:
          id: hgnc:4085
          label: GABRE
      description: Pathogenic variant in GABRE, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRG1
        term:
          id: hgnc:4086
          label: GABRG1
      description: Pathogenic variant in GABRG1, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRG2
        term:
          id: hgnc:4087
          label: GABRG2
      description: Pathogenic variant in GABRG2, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRG3
        term:
          id: hgnc:4088
          label: GABRG3
      description: Pathogenic variant in GABRG3, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRP
        term:
          id: hgnc:4089
          label: GABRP
      description: Pathogenic variant in GABRP, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRR1
        term:
          id: hgnc:4090
          label: GABRR1
      description: Pathogenic variant in GABRR1, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRR2
        term:
          id: hgnc:4091
          label: GABRR2
      description: Pathogenic variant in GABRR2, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRR3
        term:
          id: hgnc:17969
          label: GABRR3
      description: Pathogenic variant in GABRR3, encoding a GABA-A receptor subunit.
    - criterion_predicate: HAS_GENE
      gene:
        preferred_term: GABRQ
        term:
          id: hgnc:14454
          label: GABRQ
      description: Pathogenic variant in GABRQ, encoding a GABA-A receptor subunit.
- description: >-
    Every member acts through disturbed excitation-inhibition balance — the
    shared downstream mechanism that makes this a mechanistic grouping and not
    merely a gene-family one.
  criteria_semantics: NECESSARY
  logic:
    criterion_predicate: CONFORMS_TO_MODULE
    module: epilepsy_excitation_inhibition_imbalance#Excitation-Inhibition Imbalance
    description: >-
      Conforms to the excitation-inhibition imbalance node of the epilepsy
      module. Reflects the current membership, in which every member is
      epilepsy-manifesting; a future seizure-free GABA-A subunit disorder would
      require this criterion to be revisited rather than excepted.
members:
- member: GABRB3-Related Developmental and Epileptic Encephalopathy
  member_type: DISEASE
  differentiating_mechanisms:
  - description: >-
      Beta-3 subunit variants, the arm in which the gain- versus
      loss-of-function split is best characterised. Gain-of-function variants
      increase GABA sensitivity and alter receptor desensitization, and are
      associated with vigabatrin hypersensitivity; loss-of-function variants
      reduce receptor function and impair trafficking. GABRB3 is also one of
      the three subunit genes (with GABRA5 and GABRG3) that fall within the
      15q11-q13 imprinted interval, which is why contiguous-gene disorders of
      that region must be excluded from this grouping by hand.
    gene:
      preferred_term: GABRB3
      term:
        id: hgnc:4083
        label: GABRB3
- member: GABRG2-Related Epilepsy
  member_type: DISEASE
  differentiating_mechanisms:
  - description: >-
      Gamma-2 subunit variants act predominantly by impairing receptor assembly
      and trafficking rather than by altering channel gating in an assembled
      receptor, and include a temperature-sensitive trafficking defect that
      underlies the characteristic febrile-seizure presentation and the
      generalised epilepsy with febrile seizures plus phenotype.
    gene:
      preferred_term: GABRG2
      term:
        id: hgnc:4087
        label: GABRG2
discussions:
- discussion_id: gabra1_causative_entry_not_yet_a_member
  kind: CURATION_TODO
  status: OPEN
  prompt: >-
    Developmental and Epileptic Encephalopathy 19 carries GABRA1 typed
    CAUSATIVE and satisfies both of this grouping's NECESSARY criteria. Should
    it be listed as a member, and should the GABRA1 disease curated inside
    broader entries be reached at all?
  rationale: >-
    The entry exists in kb/disorders and is not listed here only because
    membership was scoped to the two subunit-named entries when this grouping
    was created. GABRA1 is one of the four genes the ICD-10-CM GABAAR-NDD
    proposal names as principal, so the omission is a gap rather than a
    boundary decision.

    Three further entries carry GABRA1 with no `relationship_type` — Epilepsy,
    Dravet_syndrome, and Jeavons Syndrome. Those are a different problem. Each
    does record a basis in free text (`association: Susceptibility`,
    `association: Rare Pathogenic Mutations`, and an `association: Associated`
    carrying a REFUTE evidence item respectively), and on that reading none
    looks like a monogenic subunit disorder — but none of it sits in a slot
    this grouping's criteria can read, since HAS_GENE matches the gene and
    ignores everything else. Typing those three would let the criteria
    discriminate them instead of a curator having to.
notes: >-
  Scope: monogenic GABA-A receptor subunit disorders. This is deliberately not
  the same set as the entries conforming to
  epilepsy_excitation_inhibition_imbalance, which is insult-agnostic and much
  broader.

  Entities that satisfy at least the gene block but are not members are
  recorded in two places, by whether the question is open: a settled exclusion
  goes in grouping_rationale with its reason (Generalized Epilepsy with Febrile
  Seizures Plus, which satisfies the gene block only and is also a genetically
  heterogeneous syndrome), while an undecided one is an OPEN discussion
  (Developmental and Epileptic Encephalopathy 19, the only non-member that
  satisfies both blocks with a subunit gene typed CAUSATIVE). Neither is a
  structural record — the schema has no slot for a deferred- or excluded-member
  list, tracked in dismech#11805.