BCKDK Deficiency

⚙

Pathophysiology

5

BCKDK loss of function

Biallelic loss-of-function variants in BCKDK (frameshift, nonsense, missense, or in-frame deletion) reduce or abolish the mitochondrial branched-chain ketoacid dehydrogenase kinase. Patient cells show reduced BCKDK mRNA (consistent with nonsense-mediated decay), undetectable BCKDK protein, and loss of the phospho-E1-alpha (Ser293) signal that normally inactivates BCKDH.

BCKDK hgnc:16902

branched-chain ketoacid dehydrogenase kinase activity GO:0047323 ↓ DECREASED

mitochondrion GO:0005739

Downstream

Constitutive BCKDH activation and excessive BCAA catabolism Loss of BCKDK-mediated inhibitory phosphorylation of the BCKDH E1-alpha subunit leaves the BCKDH complex constitutively active, increasing catabolic flux through the rate-limiting step of BCAA degradation.

Show evidence (2 references)

PMID:22956686 SUPPORT Human Clinical

"We have identified inactivating mutations in the gene BCKDK (Branched Chain Ketoacid Dehydrogenase Kinase) in consanguineous families with autism, epilepsy, and intellectual disability."

Directly identifies inactivating BCKDK mutations as the cause of the disorder.

PMID:22956686 SUPPORT Human Clinical

"Patients with homozygous BCKDK mutations display reductions in BCKDK messenger RNA and protein, E1α phosphorylation, and plasma branched-chain amino acids."

Confirms loss of BCKDK mRNA, protein, and E1-alpha phosphorylation in patients with homozygous mutations.

Constitutive BCKDH activation and excessive BCAA catabolism

The branched-chain ketoacid dehydrogenase (BCKDH) complex catalyzes the irreversible, rate-limiting step in BCAA catabolism. Without BCKDK-mediated phosphorylation, BCKDH activity is unchecked, accelerating the breakdown of leucine, isoleucine, and valine.

branched-chain amino acid catabolic process GO:0009083 ↑ INCREASED protein dephosphorylation of BCKDH E1-alpha GO:0006470

mitochondrion GO:0005739

Downstream

Systemic and CSF BCAA depletion Accelerated BCKDH-mediated catabolism depletes circulating and central branched-chain amino acids. BCAAs are essential amino acids that cannot be synthesized de novo, so increased catabolism is not compensated by synthesis.

Aberrant catabolic flux beyond simple BCAA insufficiency Beyond depleting circulating and central BCAAs, the constitutively active BCKDH complex drives aberrant flux through the BCAA catabolic pathway itself. Mouse-model evidence indicates that this excess catabolic flux (not just the resulting low BCAA levels) is a mechanistic contributor to disease.

Show evidence (2 references)

PMID:35216372 SUPPORT In Vitro

"Hyperactivity of BCKDH and over-consumption of BCAA were demonstrated by functional tests in cells transfected with the mutant BCKDK."

Functional cell assays directly demonstrate BCKDH hyperactivity and BCAA over-consumption from mutant BCKDK.

PMID:27472223 SUPPORT Model Organism

"when Ser293 is not phosphorylated, BCKDH activity is unchecked and the levels of the BCAAs will decrease dramatically."

Rat model establishes that loss of Ser293 phosphorylation leaves BCKDH unchecked, dramatically lowering BCAAs.

Systemic and CSF BCAA depletion

Markedly reduced concentrations of leucine, isoleucine, and valine in plasma and cerebrospinal fluid are the biochemical hallmark of BCKDK deficiency. Because BCAAs share blood-brain barrier transporters (notably LAT1, SLC7A5/SLC3A2) with other large neutral amino acids, low plasma BCAAs also perturb brain concentrations of other large neutral amino acids that are precursors for neurotransmitters.

branched-chain amino acid catabolic process GO:0009083 ↑ INCREASED amino acid transmembrane transport across the blood-brain barrier GO:0003333

Downstream

Neurodevelopmental and epileptic phenotype The disturbed central amino acid milieu (low BCAAs and imbalanced large neutral amino acids that serve as neurotransmitter precursors) is proposed to drive the autism, intellectual disability, epilepsy, and microcephaly, although the precise mechanism linking abnormal brain amino acid levels to the clinical phenotype remains to be established.

Hypovalinemia Systemic BCAA depletion includes low plasma valine.

Hypoleucinemia Systemic BCAA depletion includes low plasma leucine.

Hypoisoleucinemia Systemic BCAA depletion includes low plasma isoleucine.

Decreased CSF valine concentration Central BCAA depletion includes decreased CSF valine concentration.

Show evidence (2 references)

PMID:22956686 SUPPORT Human Clinical

"We measured plasma BCAAs in our patients and found that each patient with a homozygous mutation showed notably lower levels of plasma BCAAs than their healthy relatives and with respect to reference ranges"

Directly documents lower plasma BCAAs in patients with homozygous BCKDK mutations.

PMID:22956686 SUPPORT Model Organism

"Because several of these amino acids are precursors for important neurotransmitters, it remains a possibility that the reduced BCAAs and/or the increased LNAAs contribute to the neurological phenotype."

Mouse brain amino acid profiling links blood-brain barrier transport imbalance and neurotransmitter precursor disturbance to the neurological phenotype.

Neurodevelopmental and epileptic phenotype

The disorder localizes chiefly to the central nervous system, with neurons strongly implicated. In mouse studies, cortex-neuron involvement is central to the neurological abnormalities, and the spontaneous frogleg rat model affects both the central and peripheral nervous systems.

neuron CL:0000540

protein phosphorylation (loss of E1-alpha phosphorylation) GO:0006468 ↓ DECREASED

Downstream

Autistic behavior Neurodevelopmental involvement manifests clinically as autistic behavior.

Intellectual disability Neurodevelopmental involvement manifests clinically as intellectual disability.

Global developmental delay Neurodevelopmental involvement manifests clinically as global developmental delay.

Epileptic encephalopathy Neuronal dysfunction manifests as epileptic encephalopathy in severe reported cases.

Seizures Neuronal dysfunction manifests as epileptic seizures.

Microcephaly The neurodevelopmental phenotype includes postnatal or progressive microcephaly.

Show evidence (2 references)

PMID:22956686 SUPPORT Model Organism

"Adults developed neurological abnormalities, such as tremors, epileptic seizures, and hindlimb clasping phenotypes observed in some other mouse models of autism spectrum disorders"

Bckdk knockout mice recapitulate the neurological/epileptic phenotype, supporting CNS neuronal involvement.

PMID:27472223 SUPPORT Model Organism

"The frogleg phenotype shares important characteristics with a previously described Bckdk knockout mouse and with human subjects with Bckdk mutations."

Rat model demonstrates a nervous-system phenotype shared with the mouse model and human patients.

Aberrant catabolic flux beyond simple BCAA insufficiency

Recent mouse-model evidence challenges a purely "BCAA-insufficiency" model. In a Bckdk-deficient mouse, enteral BCAA supplementation raised systemic BCAA levels but exacerbated neurodevelopmental deficits and failed to correct biochemical abnormalities, suggesting that aberrant flux through the BCAA catabolic pathway (not just low BCAAs) contributes to disease. Genetic re-regulation of catabolism via Dbt haploinsufficiency partially rescued biochemical and behavioral phenotypes.

branched-chain amino acid catabolic process GO:0009083 ↑ INCREASED

Show evidence (2 references)

PMID:38770403 SUPPORT Model Organism

"These data suggest that aberrant flux through the BCAA catabolic pathway, not just BCAA insufficiency, may contribute to disease pathology."

Mouse-model data support aberrant catabolic flux as a mechanistic contributor beyond BCAA insufficiency.

PMID:38770403 SUPPORT Model Organism

"genetic re-regulation of BCAA catabolism, through Dbt haploinsufficiency, partially rescued biochemical and behavioral phenotypes in BCKDK deficient mice."

Genetic re-regulation of downstream BCAA catabolism via Dbt haploinsufficiency partially rescued biochemical and behavioral phenotypes, supporting aberrant catabolic flux (rather than simple BCAA insufficiency) as the disease mechanism and identifying substrate-reduction-style re-regulation as a candidate therapy.

⬡

Pathograph

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

●

Phenotypes

10

Head and Neck 1

Microcephaly Microcephaly HP:0000252

Show evidence (1 reference)

PMID:35216372 SUPPORT Human Clinical

"In three siblings with severe developmental delays, microcephaly, autism spectrum disorder and epileptic encephalopathy, we identified a new homozygous in-frame deletion (c.999_1001delCAC; p.Thr334del) of BCKDK."

Microcephaly is directly documented in the affected siblings.

Nervous System 4

Autistic behavior Autistic behavior HP:0000729

Show evidence (1 reference)

PMID:22956686 SUPPORT Human Clinical

"We have identified inactivating mutations in the gene BCKDK (Branched Chain Ketoacid Dehydrogenase Kinase) in consanguineous families with autism, epilepsy, and intellectual disability."

Autism was a defining feature in the consanguineous families with BCKDK mutations.

Intellectual disability Intellectual disability HP:0001249

Show evidence (1 reference)

PMID:22956686 SUPPORT Human Clinical

"Thus, autism presenting with intellectual disability and epilepsy caused by BCKDK mutations represents a potentially treatable syndrome."

Intellectual disability is identified as a core component of the BCKDK-mutation syndrome.

Global developmental delay Global developmental delay HP:0001263

Show evidence (1 reference)

PMID:35216372 SUPPORT Human Clinical

"In three siblings with severe developmental delays, microcephaly, autism spectrum disorder and epileptic encephalopathy, we identified a new homozygous in-frame deletion (c.999_1001delCAC; p.Thr334del) of BCKDK."

Directly documents severe developmental delays in the affected siblings.

Seizures Seizure HP:0001250

Show evidence (1 reference)

PMID:22956686 SUPPORT Human Clinical

"two siblings with autism, intellectual disability (ID), and either seizure or abnormal electroencephalogram (EEG)"

Directly documents seizures (or abnormal EEG) in affected siblings.

Other 5

Epileptic encephalopathy Epileptic encephalopathy HP:0200134

Show evidence (1 reference)

PMID:35216372 SUPPORT Human Clinical

"In three siblings with severe developmental delays, microcephaly, autism spectrum disorder and epileptic encephalopathy, we identified a new homozygous in-frame deletion (c.999_1001delCAC; p.Thr334del) of BCKDK."

Epileptic encephalopathy is directly documented in the affected siblings.

Hypovalinemia Hypovalinemia HP:0500132

Show evidence (1 reference)

PMID:22956686 SUPPORT Human Clinical

"each patient with a homozygous mutation showed notably lower levels of plasma BCAAs than their healthy relatives and with respect to reference ranges"

Documents reduced plasma BCAAs (including valine) in affected patients.

Hypoleucinemia Hypoleucinemia HP:0500143

Show evidence (1 reference)

PMID:22956686 SUPPORT Human Clinical

"each patient with a homozygous mutation showed notably lower levels of plasma BCAAs than their healthy relatives and with respect to reference ranges"

Documents reduced plasma BCAAs (including leucine) in affected patients.

Hypoisoleucinemia Hypoisoleucinemia HP:0500144

Show evidence (1 reference)

PMID:22956686 SUPPORT Human Clinical

"each patient with a homozygous mutation showed notably lower levels of plasma BCAAs than their healthy relatives and with respect to reference ranges"

Documents reduced plasma BCAAs (including isoleucine) in affected patients.

Decreased CSF valine concentration Decreased CSF valine concentration HP:0500188

Show evidence (1 reference)

PMID:35216372 SUPPORT Human Clinical

"Plasma and cerebrospinal fluid concentrations of BCAA were markedly reduced."

Directly documents markedly reduced CSF BCAA, including valine, in affected patients.

🧬

Genetic Associations

1

BCKDK pathogenic variants

Gene: BCKDK hgnc:16902

Autosomal recessive

Show evidence (1 reference)

PMID:22956686 SUPPORT Human Clinical

"In each of these families, we identified a distinct, null, homozygous mutation in the gene Branched Chain Ketoacid Dehydrogenase Kinase (BCKDK)."

Confirms BCKDK as the causal gene with distinct homozygous null mutations across families.

💊

Medical Actions

2

BCAA-enriched high-protein dietary supplementation

Action: amino acid supplementation MAXO:0010020

Agent: leucine CHEBI:25017 isoleucine CHEBI:24898 valine CHEBI:27266

The principal disease-directed therapy is a high-protein diet combined with oral branched-chain amino acid supplementation (leucine, isoleucine, valine). In an affected sibling series, protein intake of ~2.5-3 g/kg/day plus titrated BCAA supplementation (initial ~85-125 mg/kg/day each was insufficient; ~135-195 mg/kg/day each given in >=6 divided daily doses achieved physiological plasma levels) restored plasma BCAA and greatly improved seizure control, with more modest behavioral/developmental gains. NOTE: a 2024 mouse-model study cautions that enteral BCAA supplementation alone may be insufficient and can worsen neurodevelopmental outcomes in the model, implicating blood-brain barrier delivery limits and aberrant catabolic flux.

Mechanism Target:

MODULATES Systemic and CSF BCAA depletion — BCAA supplementation replenishes depleted branched-chain amino acids, restoring plasma concentrations and improving seizure control.

Show evidence (1 reference)

PMID:35216372 SUPPORT Human Clinical

"Treatment with pharmacological doses of BCAA allowed the restoring of BCAA concentrations and greatly improved seizure control."

BCAA supplementation restored BCAA concentrations and improved seizure control in patients.

Show evidence (3 references)

PMID:35216372 SUPPORT Human Clinical

"Behavioral and developmental skills of the patients improved to a lesser extent."

Documents the more modest behavioral/developmental response compared with seizure control.

PMID:22956686 SUPPORT Human Clinical

"by supplementing the diet of human cases with BCAAs, we have been able to normalize their plasma BCAA levels"

Dietary BCAA supplementation normalized plasma BCAA levels in human cases.

PMID:38770403 PARTIAL Model Organism

"BCAA supplementation exacerbated neurodevelopmental deficits and did not correct biochemical abnormalities despite increasing systemic BCAA levels."

Mouse-model caution that enteral BCAA supplementation alone may be insufficient and can worsen neurodevelopmental outcomes; partial/qualifying evidence on the supplementation strategy.

Genetic counseling

Action: Genetic Counseling NCIT:C15240

Given autosomal recessive inheritance, genetic counseling and recurrence-risk assessment are indicated for carrier parents, with carrier and cascade testing for at-risk relatives.

Show evidence (1 reference)

PMID:22956686 SUPPORT Human Clinical

"We focused on the identification of homozygous variants predicted to result in loss of protein function, consistent with the presumed mode of recessive inheritance."

Establishes recessive inheritance, which underlies the role of genetic counseling and recurrence-risk assessment.

🔬

Biochemical Markers

1

Plasma branched-chain amino acids (DECREASED)

Context: Low plasma leucine, isoleucine, and valine are the diagnostic biochemical hallmark of BCKDK deficiency. There is no abnormal urinary BCAA excretion or organic acid accumulation, distinguishing it from defects that cause BCAA overflow. A retrospective review showed that low BCAA values are also detectable on newborn dried blood spots, suggesting amenability to newborn screening if low (rather than high) BCAA values are actively flagged.

Pathograph Readouts

Readout Of Systemic and CSF BCAA depletion Negative Diagnostic

Low plasma BCAA reports the increased BCKDH-mediated catabolic flux resulting from loss of BCKDK inhibitory phosphorylation.

Show evidence (1 reference)

PMID:35216372 SUPPORT Human Clinical

"Plasma and cerebrospinal fluid concentrations of BCAA were markedly reduced."

Reduced plasma/CSF BCAA is the biochemical readout of the underlying catabolic block reversal.

Show evidence (1 reference)

PMID:35216372 SUPPORT Human Clinical

"a retrospective review of the newborn screening results allowed the identification of a strong decrease in BCAA concentrations on dried blood spots, suggesting that BCKDK is a new treatable metabolic disorder probably amenable to newborn screening programs."

Confirms low BCAA on newborn dried blood spots and proposes newborn-screening amenability.

{ }

Source YAML

click to show

name: BCKDK Deficiency
creation_date: "2026-06-04T12:00:00Z"
category: Mendelian
synonyms:
- Branched-chain keto acid dehydrogenase kinase deficiency
- BCKD-kinase deficiency
- BCKDKD
- Autism-epilepsy syndrome due to branched chain ketoacid dehydrogenase kinase deficiency
description: >-
  Branched-chain keto acid dehydrogenase kinase (BCKDK) deficiency is a rare,
  autosomal recessive, potentially treatable neurometabolic disorder of
  branched-chain amino acid (BCAA) metabolism. BCKDK is the mitochondrial kinase
  that phosphorylates and inactivates the E1-alpha subunit of the branched-chain
  ketoacid dehydrogenase (BCKDH) complex, the rate-limiting, flux-generating step
  of BCAA catabolism. Biallelic loss-of-function variants in BCKDK remove this
  inhibitory brake, leaving BCKDH constitutively active and driving excessive
  catabolism of leucine, isoleucine, and valine. The result is markedly reduced
  plasma and cerebrospinal fluid BCAA concentrations and a neurodevelopmental
  phenotype of autism spectrum disorder, intellectual disability/developmental
  delay, epilepsy/epileptic encephalopathy, and (often progressive postnatal)
  microcephaly. Unlike maple syrup urine disease (which features toxic BCAA
  accumulation from BCKDH deficiency), BCKDK deficiency produces BCAA depletion,
  and dietary BCAA supplementation with a high-protein diet is the principal
  disease-directed therapy, improving seizure control in particular.
disease_term:
  preferred_term: BCKDK deficiency
  term:
    id: MONDO:0013970
    label: branched-chain keto acid dehydrogenase kinase deficiency
parents:
- Inborn Error of Metabolism
- Inborn Disorder of Branched-Chain Amino Acid Metabolism
pathophysiology:
- name: BCKDK loss of function
  description: >
    Biallelic loss-of-function variants in BCKDK (frameshift, nonsense, missense,
    or in-frame deletion) reduce or abolish the mitochondrial branched-chain
    ketoacid dehydrogenase kinase. Patient cells show reduced BCKDK mRNA
    (consistent with nonsense-mediated decay), undetectable BCKDK protein, and
    loss of the phospho-E1-alpha (Ser293) signal that normally inactivates BCKDH.
  genes:
  - preferred_term: BCKDK
    term:
      id: hgnc:16902
      label: BCKDK
  molecular_functions:
  - preferred_term: branched-chain ketoacid dehydrogenase kinase activity
    term:
      id: GO:0047323
      label: "[3-methyl-2-oxobutanoate dehydrogenase (acetyl-transferring)] kinase activity"
    modifier: DECREASED
  locations:
  - preferred_term: mitochondrion
    term:
      id: GO:0005739
      label: mitochondrion
  evidence:
  - reference: PMID:22956686
    reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We have identified inactivating mutations in the gene BCKDK (Branched Chain Ketoacid Dehydrogenase Kinase) in consanguineous families with autism, epilepsy, and intellectual disability."
    explanation: "Directly identifies inactivating BCKDK mutations as the cause of the disorder."
  - reference: PMID:22956686
    reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with homozygous BCKDK mutations display reductions in BCKDK messenger RNA and protein, E1α phosphorylation, and plasma branched-chain amino acids."
    explanation: "Confirms loss of BCKDK mRNA, protein, and E1-alpha phosphorylation in patients with homozygous mutations."
  downstream:
  - target: Constitutive BCKDH activation and excessive BCAA catabolism
    description: >
      Loss of BCKDK-mediated inhibitory phosphorylation of the BCKDH E1-alpha
      subunit leaves the BCKDH complex constitutively active, increasing
      catabolic flux through the rate-limiting step of BCAA degradation.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:22956686
      reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "These data suggest that patients with BCKDK mutations may lack basal, negative regulation of BCKDH activity."
      explanation: "Loss of BCKDK removes basal negative regulation of BCKDH, the direct downstream consequence."
- name: Constitutive BCKDH activation and excessive BCAA catabolism
  description: >
    The branched-chain ketoacid dehydrogenase (BCKDH) complex catalyzes the
    irreversible, rate-limiting step in BCAA catabolism. Without BCKDK-mediated
    phosphorylation, BCKDH activity is unchecked, accelerating the breakdown of
    leucine, isoleucine, and valine.
  biological_processes:
  - preferred_term: branched-chain amino acid catabolic process
    term:
      id: GO:0009083
      label: branched-chain amino acid catabolic process
    modifier: INCREASED
  - preferred_term: protein dephosphorylation of BCKDH E1-alpha
    term:
      id: GO:0006470
      label: protein dephosphorylation
  locations:
  - preferred_term: mitochondrion
    term:
      id: GO:0005739
      label: mitochondrion
  evidence:
  - reference: PMID:35216372
    reference_title: "Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Hyperactivity of BCKDH and over-consumption of BCAA were demonstrated by functional tests in cells transfected with the mutant BCKDK."
    explanation: "Functional cell assays directly demonstrate BCKDH hyperactivity and BCAA over-consumption from mutant BCKDK."
  - reference: PMID:27472223
    reference_title: "A Spontaneous Missense Mutation in Branched Chain Keto Acid Dehydrogenase Kinase in the Rat Affects Both the Central and Peripheral Nervous Systems."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "when Ser293 is not phosphorylated, BCKDH activity is unchecked and the levels of the BCAAs will decrease dramatically."
    explanation: "Rat model establishes that loss of Ser293 phosphorylation leaves BCKDH unchecked, dramatically lowering BCAAs."
  downstream:
  - target: Systemic and CSF BCAA depletion
    description: >
      Accelerated BCKDH-mediated catabolism depletes circulating and central
      branched-chain amino acids. BCAAs are essential amino acids that cannot be
      synthesized de novo, so increased catabolism is not compensated by
      synthesis.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:35216372
      reference_title: "Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Plasma and cerebrospinal fluid concentrations of BCAA were markedly reduced."
      explanation: "Directly documents the markedly reduced plasma and CSF BCAA that result from accelerated catabolism."
  - target: Aberrant catabolic flux beyond simple BCAA insufficiency
    description: >
      Beyond depleting circulating and central BCAAs, the constitutively active
      BCKDH complex drives aberrant flux through the BCAA catabolic pathway
      itself. Mouse-model evidence indicates that this excess catabolic flux
      (not just the resulting low BCAA levels) is a mechanistic contributor to
      disease.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:38770403
      reference_title: "Partial suppression of BCAA catabolism as a potential therapy for BCKDK deficiency."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "These data suggest that aberrant flux through the BCAA catabolic pathway, not just BCAA insufficiency, may contribute to disease pathology."
      explanation: "Mouse-model data support that constitutive BCKDH activation drives aberrant catabolic flux that contributes to disease beyond BCAA insufficiency."
- name: Systemic and CSF BCAA depletion
  description: >
    Markedly reduced concentrations of leucine, isoleucine, and valine in plasma
    and cerebrospinal fluid are the biochemical hallmark of BCKDK deficiency.
    Because BCAAs share blood-brain barrier transporters (notably LAT1,
    SLC7A5/SLC3A2) with other large neutral amino acids, low plasma BCAAs also
    perturb brain concentrations of other large neutral amino acids that are
    precursors for neurotransmitters.
  biological_processes:
  - preferred_term: branched-chain amino acid catabolic process
    term:
      id: GO:0009083
      label: branched-chain amino acid catabolic process
    modifier: INCREASED
  - preferred_term: amino acid transmembrane transport across the blood-brain barrier
    term:
      id: GO:0003333
      label: amino acid transmembrane transport
  chemical_entities:
  - preferred_term: branched-chain amino acid
    term:
      id: CHEBI:22918
      label: branched-chain amino acid
    modifier: DECREASED
  - preferred_term: leucine
    term:
      id: CHEBI:25017
      label: leucine
    modifier: DECREASED
  - preferred_term: isoleucine
    term:
      id: CHEBI:24898
      label: isoleucine
    modifier: DECREASED
  - preferred_term: valine
    term:
      id: CHEBI:27266
      label: valine
    modifier: DECREASED
  evidence:
  - reference: PMID:22956686
    reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We measured plasma BCAAs in our patients and found that each patient with a homozygous mutation showed notably lower levels of plasma BCAAs than their healthy relatives and with respect to reference ranges"
    explanation: "Directly documents lower plasma BCAAs in patients with homozygous BCKDK mutations."
  - reference: PMID:22956686
    reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Because several of these amino acids are precursors for important neurotransmitters, it remains a possibility that the reduced BCAAs and/or the increased LNAAs contribute to the neurological phenotype."
    explanation: "Mouse brain amino acid profiling links blood-brain barrier transport imbalance and neurotransmitter precursor disturbance to the neurological phenotype."
  downstream:
  - target: Neurodevelopmental and epileptic phenotype
    description: >
      The disturbed central amino acid milieu (low BCAAs and imbalanced large
      neutral amino acids that serve as neurotransmitter precursors) is proposed
      to drive the autism, intellectual disability, epilepsy, and microcephaly,
      although the precise mechanism linking abnormal brain amino acid levels to
      the clinical phenotype remains to be established.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:22956686
      reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The mechanism by which abnormal brain amino acid levels lead to autism, ID, and epilepsy remains to be investigated."
      explanation: "Acknowledges the indirect, not-fully-elucidated link between abnormal brain amino acid levels and the neurodevelopmental/epileptic phenotype."
  - target: Hypovalinemia
    description: Systemic BCAA depletion includes low plasma valine.
  - target: Hypoleucinemia
    description: Systemic BCAA depletion includes low plasma leucine.
  - target: Hypoisoleucinemia
    description: Systemic BCAA depletion includes low plasma isoleucine.
  - target: Decreased CSF valine concentration
    description: Central BCAA depletion includes decreased CSF valine concentration.
- name: Neurodevelopmental and epileptic phenotype
  description: >
    The disorder localizes chiefly to the central nervous system, with neurons
    strongly implicated. In mouse studies, cortex-neuron involvement is central
    to the neurological abnormalities, and the spontaneous frogleg rat model
    affects both the central and peripheral nervous systems.
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  biological_processes:
  - preferred_term: protein phosphorylation (loss of E1-alpha phosphorylation)
    term:
      id: GO:0006468
      label: protein phosphorylation
    modifier: DECREASED
  evidence:
  - reference: PMID:22956686
    reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Adults developed neurological abnormalities, such as tremors, epileptic seizures, and hindlimb clasping phenotypes observed in some other mouse models of autism spectrum disorders"
    explanation: "Bckdk knockout mice recapitulate the neurological/epileptic phenotype, supporting CNS neuronal involvement."
  - reference: PMID:27472223
    reference_title: "A Spontaneous Missense Mutation in Branched Chain Keto Acid Dehydrogenase Kinase in the Rat Affects Both the Central and Peripheral Nervous Systems."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The frogleg phenotype shares important characteristics with a previously described Bckdk knockout mouse and with human subjects with Bckdk mutations."
    explanation: "Rat model demonstrates a nervous-system phenotype shared with the mouse model and human patients."
  downstream:
  - target: Autistic behavior
    description: Neurodevelopmental involvement manifests clinically as autistic behavior.
  - target: Intellectual disability
    description: Neurodevelopmental involvement manifests clinically as intellectual disability.
  - target: Global developmental delay
    description: Neurodevelopmental involvement manifests clinically as global developmental delay.
  - target: Epileptic encephalopathy
    description: Neuronal dysfunction manifests as epileptic encephalopathy in severe reported cases.
  - target: Seizures
    description: Neuronal dysfunction manifests as epileptic seizures.
  - target: Microcephaly
    description: The neurodevelopmental phenotype includes postnatal or progressive microcephaly.
- name: Aberrant catabolic flux beyond simple BCAA insufficiency
  description: >
    Recent mouse-model evidence challenges a purely "BCAA-insufficiency" model.
    In a Bckdk-deficient mouse, enteral BCAA supplementation raised systemic BCAA
    levels but exacerbated neurodevelopmental deficits and failed to correct
    biochemical abnormalities, suggesting that aberrant flux through the BCAA
    catabolic pathway (not just low BCAAs) contributes to disease. Genetic
    re-regulation of catabolism via Dbt haploinsufficiency partially rescued
    biochemical and behavioral phenotypes.
  biological_processes:
  - preferred_term: branched-chain amino acid catabolic process
    term:
      id: GO:0009083
      label: branched-chain amino acid catabolic process
    modifier: INCREASED
  evidence:
  - reference: PMID:38770403
    reference_title: "Partial suppression of BCAA catabolism as a potential therapy for BCKDK deficiency."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "These data suggest that aberrant flux through the BCAA catabolic pathway, not just BCAA insufficiency, may contribute to disease pathology."
    explanation: "Mouse-model data support aberrant catabolic flux as a mechanistic contributor beyond BCAA insufficiency."
  - reference: PMID:38770403
    reference_title: "Partial suppression of BCAA catabolism as a potential therapy for BCKDK deficiency."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "genetic re-regulation of BCAA catabolism, through Dbt haploinsufficiency, partially rescued biochemical and behavioral phenotypes in BCKDK deficient mice."
    explanation: "Genetic re-regulation of downstream BCAA catabolism via Dbt haploinsufficiency partially rescued biochemical and behavioral phenotypes, supporting aberrant catabolic flux (rather than simple BCAA insufficiency) as the disease mechanism and identifying substrate-reduction-style re-regulation as a candidate therapy."
phenotypes:
- name: Autistic behavior
  description: >
    Autism spectrum disorder / autistic features were the presenting feature in
    the original discovery cohort and are reiterated in later case reports.
  phenotype_term:
    preferred_term: Autistic behavior
    term:
      id: HP:0000729
      label: Autistic behavior
  evidence:
  - reference: PMID:22956686
    reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We have identified inactivating mutations in the gene BCKDK (Branched Chain Ketoacid Dehydrogenase Kinase) in consanguineous families with autism, epilepsy, and intellectual disability."
    explanation: "Autism was a defining feature in the consanguineous families with BCKDK mutations."
- name: Intellectual disability
  description: >
    Intellectual disability with severe developmental delay is a core
    neurodevelopmental feature across reported families.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:22956686
    reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Thus, autism presenting with intellectual disability and epilepsy caused by BCKDK mutations represents a potentially treatable syndrome."
    explanation: "Intellectual disability is identified as a core component of the BCKDK-mutation syndrome."
- name: Global developmental delay
  description: >
    Severe developmental delays, including psychomotor delay from the first year
    of life, were reported in an affected sibling series.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:35216372
    reference_title: "Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In three siblings with severe developmental delays, microcephaly, autism spectrum disorder and epileptic encephalopathy, we identified a new homozygous in-frame deletion (c.999_1001delCAC; p.Thr334del) of BCKDK."
    explanation: "Directly documents severe developmental delays in the affected siblings."
- name: Epileptic encephalopathy
  description: >
    Early generalized seizures and epileptic encephalopathy occur; seizure
    control can improve substantially with dietary BCAA therapy.
  phenotype_term:
    preferred_term: Epileptic encephalopathy
    term:
      id: HP:0200134
      label: Epileptic encephalopathy
  evidence:
  - reference: PMID:35216372
    reference_title: "Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In three siblings with severe developmental delays, microcephaly, autism spectrum disorder and epileptic encephalopathy, we identified a new homozygous in-frame deletion (c.999_1001delCAC; p.Thr334del) of BCKDK."
    explanation: "Epileptic encephalopathy is directly documented in the affected siblings."
- name: Seizures
  description: >
    Epileptic seizures are a recurrent feature; in the original report, seizures
    or abnormal EEG were present, and Bckdk knockout mice develop seizures.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:22956686
    reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "two siblings with autism, intellectual disability (ID), and either seizure or abnormal electroencephalogram (EEG)"
    explanation: "Directly documents seizures (or abnormal EEG) in affected siblings."
- name: Microcephaly
  description: >
    Postnatal/progressive microcephaly is repeatedly reported in human cases and
    is recapitulated in mouse models.
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  evidence:
  - reference: PMID:35216372
    reference_title: "Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In three siblings with severe developmental delays, microcephaly, autism spectrum disorder and epileptic encephalopathy, we identified a new homozygous in-frame deletion (c.999_1001delCAC; p.Thr334del) of BCKDK."
    explanation: "Microcephaly is directly documented in the affected siblings."
- name: Hypovalinemia
  category: Laboratory
  diagnostic: true
  description: >
    Reduced plasma valine is part of the biochemical hallmark of BCKDK
    deficiency, reflecting accelerated catabolism of this essential
    branched-chain amino acid.
  phenotype_term:
    preferred_term: Hypovalinemia
    term:
      id: HP:0500132
      label: Hypovalinemia
  evidence:
  - reference: PMID:22956686
    reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "each patient with a homozygous mutation showed notably lower levels of plasma BCAAs than their healthy relatives and with respect to reference ranges"
    explanation: "Documents reduced plasma BCAAs (including valine) in affected patients."
- name: Hypoleucinemia
  category: Laboratory
  diagnostic: true
  description: >
    Reduced plasma leucine is part of the low-BCAA biochemical signature of
    BCKDK deficiency.
  phenotype_term:
    preferred_term: Hypoleucinemia
    term:
      id: HP:0500143
      label: Hypoleucinemia
  evidence:
  - reference: PMID:22956686
    reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "each patient with a homozygous mutation showed notably lower levels of plasma BCAAs than their healthy relatives and with respect to reference ranges"
    explanation: "Documents reduced plasma BCAAs (including leucine) in affected patients."
- name: Hypoisoleucinemia
  category: Laboratory
  diagnostic: true
  description: >
    Reduced plasma isoleucine completes the low-BCAA biochemical signature of
    BCKDK deficiency.
  phenotype_term:
    preferred_term: Hypoisoleucinemia
    term:
      id: HP:0500144
      label: Hypoisoleucinemia
  evidence:
  - reference: PMID:22956686
    reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "each patient with a homozygous mutation showed notably lower levels of plasma BCAAs than their healthy relatives and with respect to reference ranges"
    explanation: "Documents reduced plasma BCAAs (including isoleucine) in affected patients."
- name: Decreased CSF valine concentration
  category: Laboratory
  diagnostic: true
  description: >
    Cerebrospinal fluid concentrations of the branched-chain amino acids
    (leucine, isoleucine, and valine) are markedly reduced, reflecting depletion
    of central BCAAs. The bound HP term captures the valine component; HPO does
    not currently provide CSF leucine/isoleucine concentration terms.
  phenotype_term:
    preferred_term: Decreased CSF valine concentration
    term:
      id: HP:0500188
      label: Decreased CSF valine concentration
  evidence:
  - reference: PMID:35216372
    reference_title: "Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Plasma and cerebrospinal fluid concentrations of BCAA were markedly reduced."
    explanation: "Directly documents markedly reduced CSF BCAA, including valine, in affected patients."
biochemical:
- name: Plasma branched-chain amino acids
  presence: DECREASED
  context: >
    Low plasma leucine, isoleucine, and valine are the diagnostic biochemical
    hallmark of BCKDK deficiency. There is no abnormal urinary BCAA excretion or
    organic acid accumulation, distinguishing it from defects that cause BCAA
    overflow. A retrospective review showed that low BCAA values are also
    detectable on newborn dried blood spots, suggesting amenability to newborn
    screening if low (rather than high) BCAA values are actively flagged.
  readouts:
  - target: Systemic and CSF BCAA depletion
    relationship: READOUT_OF
    direction: NEGATIVE
    endpoint_context: DIAGNOSTIC
    interpretation: >
      Low plasma BCAA reports the increased BCKDH-mediated catabolic flux
      resulting from loss of BCKDK inhibitory phosphorylation.
    evidence:
    - reference: PMID:35216372
      reference_title: "Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Plasma and cerebrospinal fluid concentrations of BCAA were markedly reduced."
      explanation: "Reduced plasma/CSF BCAA is the biochemical readout of the underlying catabolic block reversal."
  evidence:
  - reference: PMID:35216372
    reference_title: "Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a retrospective review of the newborn screening results allowed the identification of a strong decrease in BCAA concentrations on dried blood spots, suggesting that BCKDK is a new treatable metabolic disorder probably amenable to newborn screening programs."
    explanation: "Confirms low BCAA on newborn dried blood spots and proposes newborn-screening amenability."
genetic:
- name: BCKDK pathogenic variants
  gene_term:
    preferred_term: BCKDK
    term:
      id: hgnc:16902
      label: BCKDK
  inheritance:
  - name: Autosomal recessive
    evidence:
    - reference: PMID:22956686
      reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We focused on the identification of homozygous variants predicted to result in loss of protein function, consistent with the presumed mode of recessive inheritance."
      explanation: "Establishes autosomal recessive inheritance with biallelic loss-of-function variants."
  variants:
  - name: p.Arg156* and p.M74fs (null variants)
    description: >
      The original report identified a nonsense variant (C466T; premature stop at
      position 156, p.Arg156*) in family 558 and a single-base deletion
      (c.G222del) causing a frameshift terminating the protein at position 74
      (p.M74fs) in family 18. Both are null, homozygous, loss-of-function
      variants segregating recessively.
    evidence:
    - reference: PMID:22956686
      reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "In family 558, we identified a cytosine-to-thymine substitution in exon 4 (C466T) resulting in a premature stop codon at amino acid position 156, prior to the kinase domain"
      explanation: "Directly identifies the p.Arg156* null variant in family 558."
  - name: p.Arg224Pro (missense)
    description: >
      A missense variant (c.G671C) substituting a highly conserved arginine with
      proline at position 224 was identified in a third family; structural
      modeling predicted disruption of the kinase domain. Missense variants
      caused less severe plasma BCAA reductions than null variants.
    evidence:
    - reference: PMID:22956686
      reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "leading to the substitution of a highly conserved arginine with a proline at position 224 in BCKDK"
      explanation: "Directly identifies the p.Arg224Pro missense variant."
  - name: c.999_1001delCAC (p.Thr334del)
    description: >
      A homozygous in-frame deletion (c.999_1001delCAC; p.Thr334del) was
      identified in three siblings; functional tests in transfected cells
      demonstrated BCKDH hyperactivity and BCAA over-consumption.
    evidence:
    - reference: PMID:35216372
      reference_title: "Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "we identified a new homozygous in-frame deletion (c.999_1001delCAC; p.Thr334del) of BCKDK."
      explanation: "Directly identifies the homozygous p.Thr334del in-frame deletion."
  features: >
    BCKDK deficiency is caused by biallelic loss-of-function variants in BCKDK
    (chromosome 16p11.2), encoding the mitochondrial branched-chain ketoacid
    dehydrogenase kinase. Reported variants include null (nonsense, frameshift),
    missense, and in-frame deletion alleles; null variants produce more profound
    plasma BCAA reductions than missense alleles. Early families were
    consanguineous, consistent with recessive segregation.
  evidence:
  - reference: PMID:22956686
    reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In each of these families, we identified a distinct, null, homozygous mutation in the gene Branched Chain Ketoacid Dehydrogenase Kinase (BCKDK)."
    explanation: "Confirms BCKDK as the causal gene with distinct homozygous null mutations across families."
treatments:
- name: BCAA-enriched high-protein dietary supplementation
  description: >
    The principal disease-directed therapy is a high-protein diet combined with
    oral branched-chain amino acid supplementation (leucine, isoleucine, valine).
    In an affected sibling series, protein intake of ~2.5-3 g/kg/day plus titrated
    BCAA supplementation (initial ~85-125 mg/kg/day each was insufficient; ~135-195
    mg/kg/day each given in >=6 divided daily doses achieved physiological plasma
    levels) restored plasma BCAA and greatly improved seizure control, with more
    modest behavioral/developmental gains. NOTE: a 2024 mouse-model study cautions
    that enteral BCAA supplementation alone may be insufficient and can worsen
    neurodevelopmental outcomes in the model, implicating blood-brain barrier
    delivery limits and aberrant catabolic flux.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: amino acid supplementation
    term:
      id: MAXO:0010020
      label: amino acid supplementation
    therapeutic_agent:
    - preferred_term: leucine
      term:
        id: CHEBI:25017
        label: leucine
    - preferred_term: isoleucine
      term:
        id: CHEBI:24898
        label: isoleucine
    - preferred_term: valine
      term:
        id: CHEBI:27266
        label: valine
  target_mechanisms:
  - target: Systemic and CSF BCAA depletion
    treatment_effect: MODULATES
    description: >
      BCAA supplementation replenishes depleted branched-chain amino acids,
      restoring plasma concentrations and improving seizure control.
    evidence:
    - reference: PMID:35216372
      reference_title: "Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Treatment with pharmacological doses of BCAA allowed the restoring of BCAA concentrations and greatly improved seizure control."
      explanation: "BCAA supplementation restored BCAA concentrations and improved seizure control in patients."
  evidence:
  - reference: PMID:35216372
    reference_title: "Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Behavioral and developmental skills of the patients improved to a lesser extent."
    explanation: "Documents the more modest behavioral/developmental response compared with seizure control."
  - reference: PMID:22956686
    reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "by supplementing the diet of human cases with BCAAs, we have been able to normalize their plasma BCAA levels"
    explanation: "Dietary BCAA supplementation normalized plasma BCAA levels in human cases."
  - reference: PMID:38770403
    reference_title: "Partial suppression of BCAA catabolism as a potential therapy for BCKDK deficiency."
    supports: PARTIAL
    evidence_source: MODEL_ORGANISM
    snippet: "BCAA supplementation exacerbated neurodevelopmental deficits and did not correct biochemical abnormalities despite increasing systemic BCAA levels."
    explanation: "Mouse-model caution that enteral BCAA supplementation alone may be insufficient and can worsen neurodevelopmental outcomes; partial/qualifying evidence on the supplementation strategy."
- name: Genetic counseling
  description: >
    Given autosomal recessive inheritance, genetic counseling and recurrence-risk
    assessment are indicated for carrier parents, with carrier and cascade testing
    for at-risk relatives.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:22956686
    reference_title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We focused on the identification of homozygous variants predicted to result in loss of protein function, consistent with the presumed mode of recessive inheritance."
    explanation: "Establishes recessive inheritance, which underlies the role of genetic counseling and recurrence-risk assessment."
references:
- reference: PMID:22956686
  title: "Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy."
- reference: PMID:35216372
  title: "Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy."
- reference: PMID:27472223
  title: "A Spontaneous Missense Mutation in Branched Chain Keto Acid Dehydrogenase Kinase in the Rat Affects Both the Central and Peripheral Nervous Systems."
- reference: PMID:38770403
  title: "Partial suppression of BCAA catabolism as a potential therapy for BCKDK deficiency."
- reference: PMID:35923208
  title: "The Role of Branched-Chain Amino Acids and Branched-Chain alpha-Keto Acid Dehydrogenase Kinase in Metabolic Disorders."
- reference: PMID:39795113
  title: "Primary Roles of Branched Chain Amino Acids (BCAAs) and Their Metabolism in Physiology and Metabolic Disorders."
datasets: []

📚

References & Deep Research

References

6

PMID:22956686

Mutations in BCKD-kinase lead to a potentially treatable form of autism with epilepsy.

No top-level findings curated for this source.

PMID:35216372

Novel Loss of Function Variant in BCKDK Causes a Treatable Developmental and Epileptic Encephalopathy.

No top-level findings curated for this source.

PMID:27472223

A Spontaneous Missense Mutation in Branched Chain Keto Acid Dehydrogenase Kinase in the Rat Affects Both the Central and Peripheral Nervous Systems.

No top-level findings curated for this source.

PMID:38770403

Partial suppression of BCAA catabolism as a potential therapy for BCKDK deficiency.

No top-level findings curated for this source.

PMID:35923208

The Role of Branched-Chain Amino Acids and Branched-Chain alpha-Keto Acid Dehydrogenase Kinase in Metabolic Disorders.

No top-level findings curated for this source.

PMID:39795113

Primary Roles of Branched Chain Amino Acids (BCAAs) and Their Metabolism in Physiology and Metabolic Disorders.

No top-level findings curated for this source.

Deep Research

1

Falcon ▸

1. Disease Information

Edison Scientific Literature 28 citations 2026-06-04T10:45:10.373189

1. Disease Information

1.1 Concise overview

BCKDK deficiency is a rare, autosomal recessive neuro-metabolic disorder caused by biallelic loss-of-function variants in BCKDK, the mitochondrial kinase that normally phosphorylates and inhibits the branched-chain α-ketoacid dehydrogenase (BCKDH) complex. Loss of BCKDK removes this inhibitory brake, increasing BCKDH activity and leading to excessive catabolism of leucine, isoleucine, and valine, with low plasma and cerebrospinal fluid (CSF) BCAA concentrations and a neurodevelopmental phenotype characterized by autism spectrum disorder (ASD), intellectual disability/developmental delay, seizures/epileptic encephalopathy, and microcephaly. (novarino2012mutationsinbckdkinase pages 1-2, boemer2022novellossof pages 1-2)

The initial report explicitly framed the condition as a “potentially treatable form of autism with epilepsy” through dietary BCAA repletion, based on human genetics plus rescue in a Bckdk−/− mouse model. (novarino2012mutationsinbckdkinase pages 5-8)

1.2 Key identifiers

The retrieved full-text sources in this run did not explicitly provide OMIM, Orphanet (ORPHA), ICD-10/ICD-11, MeSH, or MONDO identifiers for BCKDK deficiency; therefore, these identifiers cannot be responsibly asserted from the evidence available here. (singh2024computationalstructuralgenomics pages 12-12)

1.3 Synonyms and alternative names (from retrieved literature)

Branched-chain ketoacid dehydrogenase kinase deficiency / BCKDK deficiency (babazade2026revealingbckdkdeficiency pages 1-2)
BCKD-kinase deficiency (terminology used in the original Science paper title and text) (novarino2012mutationsinbckdkinase pages 5-8)
Descriptive framing in the initial report: treatable autism with epilepsy (novarino2012mutationsinbckdkinase pages 5-8)

1.4 Evidence source types

The disease understanding in this report is derived primarily from: - Aggregated disease-level evidence from case series and mechanistic human studies (Science 2012; IJMS 2022) (novarino2012mutationsinbckdkinase pages 5-8, boemer2022novellossof pages 2-6) - Model organism evidence (mouse Bckdk−/−; spontaneous rat model) used to test causal mechanisms and interventions (novarino2012mutationsinbckdkinase pages 5-8, zigler2016aspontaneousmissense pages 2-5)

2. Etiology

2.1 Disease causal factors

Genetic cause (primary): biallelic pathogenic variants in BCKDK (loss-of-function), segregating recessively in consanguineous families and sibling sets. (novarino2012mutationsinbckdkinase pages 1-2, boemer2022novellossof pages 2-6)
Mechanistic cause: loss of BCKDK-mediated inhibitory phosphorylation of BCKDH E1α leads to increased BCAA catabolic flux and low systemic/CSF BCAAs. (novarino2012mutationsinbckdkinase pages 5-8, zigler2016aspontaneousmissense pages 2-5)

2.2 Risk factors

Family history/consanguinity: initial families were consanguineous with recessive segregation, indicating increased risk in consanguineous unions. (novarino2012mutationsinbckdkinase pages 1-2)

No environmental, infectious, or lifestyle risk factors were identified in the retrieved texts as primary causes.

2.3 Protective factors

No genetic or environmental protective factors were described in the retrieved texts.

2.4 Gene–environment interactions

No explicit gene–environment interactions were described in the retrieved texts for BCKDK deficiency.

3. Phenotypes

3.1 Core phenotype spectrum (human)

Across the initial discovery cohort and subsequent reports, core features include: - Neurodevelopmental impairment: developmental delay/intellectual disability with severe language impairment/absent speech. (boemer2022novellossof pages 2-6, babazade2026revealingbckdkdeficiency pages 1-2) - ASD/autistic features: prominent in the initial description and reiterated in later case reports. (novarino2012mutationsinbckdkinase pages 5-8, babazade2026revealingbckdkdeficiency pages 3-5) - Epilepsy / epileptic encephalopathy: early generalized seizures and epileptic encephalopathy in some cases; seizure control can improve with dietary therapy in some reports. (boemer2022novellossof pages 2-6, boemer2022novellossof pages 6-8) - Microcephaly (often progressive/postnatal): repeatedly reported. (boemer2022novellossof pages 2-6, babazade2026revealingbckdkdeficiency pages 3-5)

Frequency data (limited): One literature-review excerpt reports very high frequencies for several features in published cohorts (e.g., global developmental delay and microcephaly reported in most individuals in that summarized cohort), but the underlying cohort composition is not fully verifiable from the excerpt alone; thus, frequencies should be treated cautiously. (babazade2026revealingbckdkdeficiency pages 3-5)

3.2 Age of onset and course

Onset is typically infancy/early childhood, with psychomotor delay from the first year reported in a sibling series; regression in the second year occurred in 2/3 siblings in that report. (boemer2022novellossof pages 2-6)
The disorder is generally chronic/lifelong, with potential partial responsiveness to nutritional therapy and likely better outcomes with earlier initiation. (babazade2026revealingbckdkdeficiency pages 3-5, boemer2022novellossof pages 6-8)

3.3 Laboratory phenotype

A hallmark is persistently low BCAA concentrations: - In a sibling series, CSF BCAA concentrations were markedly reduced relative to reference ranges (e.g., CSF leucine values such as 29 and 15 vs reference 74–203; CSF isoleucine values such as 13 and 7 vs reference 42–124; CSF valine values such as 62 and 44 vs reference 145–337). (boemer2022novellossof pages 6-8)

3.4 Suggested HPO terms

A structured phenotype-to-ontology mapping is provided in Artifact 01.

Category	Feature	Suggested ontology term(s)	Notes	Supporting source
Phenotype	Autism spectrum disorder / autistic features	HPO: Autism (HP:0000717); Autistic behavior (HP:0000729)	Human cases were initially ascertained with autism/ASD together with ID and epilepsy; later reports also describe ASD in affected siblings.	(novarino2012mutationsinbckdkinase pages 5-8, novarino2012mutationsinbckdkinase pages 1-2, babazade2026revealingbckdkdeficiency pages 3-5)
Phenotype	Developmental delay / intellectual disability	HPO: Global developmental delay (HP:0001263); Intellectual disability (HP:0001249)	Core neurodevelopmental phenotype across reported families; severe developmental delay and adaptive impairment recur in case series.	(novarino2012mutationsinbckdkinase pages 5-8, novarino2012mutationsinbckdkinase pages 1-2, boemer2022novellossof pages 2-6)
Phenotype	Epilepsy / seizures	HPO: Seizure (HP:0001250); Epileptic encephalopathy (HP:0200134)	Early generalized seizures and epileptic encephalopathy were reported; seizure burden improved with treatment in some patients.	(boemer2022novellossof pages 2-6, boemer2022novellossof pages 1-2, novarino2012mutationsinbckdkinase pages 5-8)
Phenotype	Microcephaly	HPO: Microcephaly (HP:0000252); Progressive microcephaly (HP:0000253)	Postnatal/progressive microcephaly is a recurrent feature in human cases and mouse models.	(boemer2022novellossof pages 2-6, babazade2026revealingbckdkdeficiency pages 3-5, ohl2024partialsuppressionof pages 9-11)
Phenotype	Absent speech / severe language impairment	HPO: Absent speech (HP:0001344); Severe expressive language delay (HP:0011344)	The 2022 sibling series described absent speech; severe speech/language delay is repeatedly noted in case descriptions.	(boemer2022novellossof pages 2-6, babazade2026revealingbckdkdeficiency pages 1-2)
Phenotype	Motor abnormalities / hindlimb clasping	HPO: Abnormality of movement (HP:0100022); Motor delay (HP:0001270)	Mouse and rat models show hindlimb clasping/flexion-extension or splaying; in humans, psychomotor delay is prominent.	(novarino2012mutationsinbckdkinase pages 5-8, zigler2016aspontaneousmissense pages 2-5, du2022theroleof pages 6-7)
Laboratory abnormality	Low plasma/CSF branched-chain amino acids	HPO: Decreased circulating branched chain amino acid concentration (suggested); Decreased CSF branched chain amino acid concentration (suggested)	Explicit biochemical hallmark: low leucine, isoleucine, and valine in plasma and CSF; newborn DBS can also show low Xle/valine.	(boemer2022novellossof pages 6-8, boemer2022novellossof pages 2-6, novarino2012mutationsinbckdkinase pages 1-2)
Mechanism	Increased BCKDH activity due to loss of inhibitory phosphorylation	GO BP: branched-chain amino acid catabolic process (GO:0009083); protein phosphorylation (GO:0006468)	BCKDK loss reduces inhibitory phosphorylation of BCKDH E1α, increasing catabolic flux through BCKDH.	(novarino2012mutationsinbckdkinase pages 5-8, zigler2016aspontaneousmissense pages 2-5, ohl2024partialsuppressionof pages 1-2)
Mechanism	Mitochondrial involvement	GO CC: mitochondrion (GO:0005739); mitochondrial matrix (GO:0005759)	BCKDK is mitochondrial; patient fibroblasts and models show mitochondrial defects, and BCKDH regulation occurs in the mitochondrial compartment.	(ohl2024partialsuppressionof pages 1-2, bo2024primaryrolesof pages 13-15)
Mechanism	Blood-brain barrier transport limitation for BCAA repletion	GO BP: amino acid transmembrane transport (GO:0003333)	2024 mouse work suggests enteral BCAA supplementation may not adequately restore CSF/brain BCAA, implicating BBB transport limits; BBB transporters are discussed in the original Science report.	(ohl2024partialsuppressionof pages 9-11, novarino2012mutationsinbckdkinase pages 5-8)
Cell type	Neuron involvement	CL: neuron (CL:0000540); cortical neuron (suggested CL class)	Neuronal deficiency is strongly implicated; cortex-neuron restricted Bckdk loss causes neurological abnormalities in mice.	(bo2024primaryrolesof pages 13-15)
Anatomy	Cerebral cortex / brain	UBERON: brain (UBERON:0000955); cerebral cortex (UBERON:0000956); cerebrospinal fluid (UBERON:0001359)	Neurologic phenotype localizes chiefly to brain/CNS; low CSF BCAA and cortex-neuron experiments support these anatomy terms.	(boemer2022novellossof pages 6-8, bo2024primaryrolesof pages 13-15, zigler2016aspontaneousmissense pages 2-5)
Anatomy	Peripheral nervous system	UBERON: peripheral nervous system (UBERON:0000010)	Rat model demonstrates both central and peripheral nervous system involvement.	(zigler2016aspontaneousmissense pages 2-5)

Table: This table maps the main reported clinical and mechanistic features of BCKDK deficiency to suggested ontology terms for phenotype, process, cell type, and anatomy. It is useful for structuring disease-knowledge-base annotations while staying close to the available evidence.

4. Genetic / Molecular Information

4.1 Causal gene

BCKDK (branched-chain ketoacid dehydrogenase kinase). (novarino2012mutationsinbckdkinase pages 1-2)

4.2 Pathogenic variants reported in retrieved evidence

Human variants (examples explicitly reported): - p.M74fs, p.Arg156, p.Arg224Pro (initial pedigrees). (novarino2012mutationsinbckdkinase pages 5-8) - c.999_1001delCAC (p.Thr334del)* in 3 siblings; shown by functional assays to reduce phosphorylation of the BCKDH E1α substrate. (boemer2022novellossof pages 2-6)

Model organism variant: - Rat Bckdk G369E (homozygous) associated with loss of Ser293 phosphorylation and low plasma BCAAs. (zigler2016aspontaneousmissense pages 2-5)

4.3 Functional consequence

Predominant mechanism is loss of kinase function (reduced inhibitory phosphorylation of BCKDH), causing increased catabolic flux and BCAA depletion. (novarino2012mutationsinbckdkinase pages 5-8, boemer2022novellossof pages 2-6)

4.4 Modifier genes / epigenetics / chromosomal abnormalities

No modifier genes, epigenetic signatures, or recurrent chromosomal abnormalities were described in the retrieved texts.

5. Environmental Information

No specific environmental toxins, lifestyle factors, or infectious triggers were reported in the retrieved texts as causal or modifying factors for BCKDK deficiency.

6. Mechanism / Pathophysiology

6.1 Core biochemical pathway and causal chain

Trigger: biallelic loss-of-function variants in BCKDK. (novarino2012mutationsinbckdkinase pages 1-2, boemer2022novellossof pages 2-6)
Molecular defect: reduced inhibitory phosphorylation of the BCKDH complex E1α subunit (loss of phospho-E1α signal in patient-derived cells; impaired phosphorylation in functional assays). (novarino2012mutationsinbckdkinase pages 5-8, boemer2022novellossof pages 2-6)
Metabolic consequence: increased BCAA catabolism → low plasma and CSF BCAA concentrations; newborn dried blood spots can also show low BCAA-related markers (e.g., Xle and valine). (boemer2022novellossof pages 2-6)
Clinical manifestation: neurodevelopmental disorder with ASD/ID/developmental delay, epilepsy/seizures, and microcephaly. (novarino2012mutationsinbckdkinase pages 5-8, boemer2022novellossof pages 2-6)

6.2 Expanded metabolomic disturbance (recent evidence)

A 2024 mouse-model study challenged a simplistic “only BCAA deficiency” model and reported broader metabolic imbalances in Bckdk−/− mice, including acylcarnitine and TCA-cycle intermediate alterations, and argued that altered flux through the pathway may be central. (ohl2024partialsuppressionof pages 9-11, ohl2024partialsuppressionof pages 1-2)

6.3 CNS access limitation as a mechanistic constraint on therapy

The 2024 mouse-model study also highlighted that enteral BCAA supplementation may raise systemic levels without restoring CSF/brain BCAA levels, consistent with constraints at the blood–brain barrier (BBB) and rapid post-dose disposal, complicating therapeutic strategy. (ohl2024partialsuppressionof pages 9-11, boemer2022novellossof pages 2-6)

6.4 Suggested ontology terms (GO/CL/UBERON/CHEBI)

Candidate GO BP/CC, CL, and UBERON suggestions aligned to evidence are summarized in Artifact 01. (bo2024primaryrolesof pages 13-15, ohl2024partialsuppressionof pages 9-11)
Key chemicals: leucine, isoleucine, valine (BCAAs). (boemer2022novellossof pages 6-8)

7. Anatomical Structures Affected

7.1 Organ/system level

Nervous system (primary): neurodevelopmental phenotype implicating the brain/CNS as the primary affected system. (boemer2022novellossof pages 2-6, novarino2012mutationsinbckdkinase pages 5-8)
Peripheral nervous system involvement: supported by a spontaneous rat model affecting both central and peripheral nervous systems. (zigler2016aspontaneousmissense pages 2-5)

7.2 Tissue/cell level

Evidence supports a key role for neurons, including neuron-enriched BCKDK expression and cortical neuron involvement in mouse studies (cortex neuron–restricted deficiency causing neurological abnormalities). (bo2024primaryrolesof pages 13-15)

7.3 Subcellular level

Mitochondrial compartment involvement is inherent to BCKDH regulation and BCKDK function; patient-derived cells in the 2024 discussion are described as showing mitochondrial defects. (ohl2024partialsuppressionof pages 1-2)

8. Temporal Development

Onset: typically infancy/early childhood with early developmental delay and early seizures in severe presentations. (boemer2022novellossof pages 2-6)
Progression: can include progressive/postnatal microcephaly and developmental regression in some cases. (boemer2022novellossof pages 2-6)
Critical period: the literature review excerpt supports that earlier treatment (before age ~2 years) may be associated with better neurodevelopmental outcomes than later treatment. (babazade2026revealingbckdkdeficiency pages 3-5)

9. Inheritance and Population

9.1 Inheritance

Autosomal recessive inheritance is supported by homozygous variants in affected individuals with heterozygous carrier parents (including consanguineous families). (novarino2012mutationsinbckdkinase pages 1-2, boemer2022novellossof pages 1-2)

9.2 Epidemiology

The retrieved full-text evidence in this run did not provide prevalence/incidence estimates. The condition is repeatedly described as very rare, with early reports comprising a small number of families/siblings. (boemer2022novellossof pages 6-8, novarino2012mutationsinbckdkinase pages 1-2)

10. Diagnostics

10.1 Clinical suspicion

Consider BCKDK deficiency in children with combinations of: - ASD/autistic features, global developmental delay/intellectual disability - seizures/epileptic encephalopathy - postnatal/progressive microcephaly especially in contexts of consanguinity or affected siblings. (novarino2012mutationsinbckdkinase pages 1-2, boemer2022novellossof pages 2-6)

10.2 Biochemical testing

Plasma BCAAs: low leucine, isoleucine, valine are typical. (novarino2012mutationsinbckdkinase pages 1-2)
CSF BCAAs: may be markedly reduced with explicit reference ranges reported in one sibling series (e.g., CSF leucine reference 74–203; isoleucine 42–124; valine 145–337). (boemer2022novellossof pages 6-8)
Newborn dried blood spot (DBS): low BCAA-related values can be present, e.g., Xle 84 µmol/L and valine 47 µmol/L in one patient’s newborn screen; similar low values were reported for siblings. (boemer2022novellossof pages 2-6)

10.3 Genetic testing

Whole-exome sequencing (WES) has been used to identify homozygous loss-of-function BCKDK variants in affected families, with segregation confirmation by Sanger sequencing. (boemer2022novellossof pages 8-10, novarino2012mutationsinbckdkinase pages 1-2)

10.4 Screening / early detection

A key practical point is that newborn screening programs may detect BCKDK deficiency if low BCAA values are actively flagged, because low BCAA values can otherwise be overlooked. (boemer2022novellossof pages 8-10, boemer2022novellossof pages 6-8)

10.5 Differential diagnosis (from mechanistic context)

The initial report contrasts BCKDK deficiency (low BCAAs from increased catabolism) with maple syrup urine disease (MSUD) (high BCAAs/toxic accumulation due to defects in BCKDH complex components). This biochemical directionality (low vs high BCAAs) is a key differentiator. (novarino2012mutationsinbckdkinase pages 1-2)

11. Outcome / Prognosis

11.1 Untreated course

The retrieved evidence supports significant neurodevelopmental morbidity (ASD/ID, seizures, microcephaly) and developmental regression in some individuals. (boemer2022novellossof pages 2-6, novarino2012mutationsinbckdkinase pages 5-8)

11.2 Treatment-modified outcomes

In a 3-sibling series, dietary therapy was associated with substantial seizure improvement and reduced hospital admissions (e.g., one child: 10 admissions in the year pre-treatment vs 1 admission during 18 months on therapy). (boemer2022novellossof pages 6-8)
Reported developmental/behavioral improvements were more variable and less robust than seizure outcomes. (boemer2022novellossof pages 6-8)

No survival curves, mortality rates, or formal quality-of-life instruments were reported in the retrieved texts.

12. Treatment

12.1 Disease-directed nutritional therapy (current real-world implementation)

High-protein diet plus oral BCAA supplementation (leucine, isoleucine, valine) is the main disease-directed intervention reported. - In a sibling series, protein intake of ~2.5–3 g/kg/day plus BCAA supplementation was titrated; initial doses ~85–125 mg/kg/day each were insufficient, while ~135–195 mg/kg/day each given in divided doses (six times daily) achieved physiological plasma levels. (boemer2022novellossof pages 2-6) - Practical monitoring constraints include rapid post-dose disposal and dependence of measured plasma concentrations on sampling timing; frequent dosing (≥6/day) may be needed. (boemer2022novellossof pages 6-8)

MAXO suggestions (treatment actions): - Dietary supplementation (BCAA supplementation) - High-protein diet therapy - Therapeutic drug monitoring–like biochemical monitoring of plasma amino acids (as an action, not a drug) (boemer2022novellossof pages 6-8, boemer2022novellossof pages 2-6)

12.2 Evidence strength and expert-leaning interpretation

The original discovery study provided foundational evidence of potential treatability, supported by dietary rescue experiments in Bckdk−/− mice. (novarino2012mutationsinbckdkinase pages 5-8)
A 2024 mouse-model study provides an important caution: enteral BCAA supplementation in Bckdk−/− mice “exacerbated neurodevelopmental deficits” and did not correct key biochemical abnormalities, suggesting that simple BCAA repletion may not address the core metabolic flux disturbance and/or CNS delivery constraints. (ohl2024partialsuppressionof pages 1-2)
The same 2024 study proposed an alternative strategy: partial suppression of downstream BCAA catabolism via Dbt haploinsufficiency partially rescued biochemical and behavioral phenotypes in mice. (ohl2024partialsuppressionof pages 9-11)

12.3 Recent developments (2023–2024) relevant to therapy landscape

2024 (preclinical, disease-specific): partial suppression of BCAA catabolism as a potential therapy (mouse genetic approach), and the finding that enteral supplementation may be harmful in the model. (ohl2024partialsuppressionof pages 9-11, ohl2024partialsuppressionof pages 1-2)
2023 (therapeutics in related contexts): potent small-molecule BCKDK inhibitors (e.g., PF-07208254) were developed for cardiometabolic indications and show that BCKDK activity is druggable; however, such inhibitors would be expected to increase BCAA catabolic flux and thus are conceptually opposite to what would be desired for BCKDK deficiency. (flach2023smallmoleculebranchedchain pages 1-2)

12.4 Clinical trials

No interventional clinical trials specifically targeting BCKDK deficiency were identified in the retrieved trial records in this run. Two observational studies retrieved are broad genomic/newborn screening or autism genetics registries rather than BCKDK-deficiency therapeutic trials: - Baby Detect: Genomic Newborn Screening (NCT05687474; observational). (trial record retrieved; see tool output) - Simons Searchlight (NCT01238250; observational autism genetics). (trial record retrieved; see tool output)

13. Prevention

Given autosomal recessive inheritance, prevention focuses on: - Genetic counseling and recurrence risk assessment for carrier parents (supported by segregation in families with heterozygous carriers). (boemer2022novellossof pages 1-2) - Carrier testing for at-risk relatives and cascade testing. - Prenatal or preimplantation genetic testing is logically applicable when the familial pathogenic variant is known; however, specific protocols were not detailed in the retrieved texts. - Secondary prevention / early detection: newborn screening strategies that include thresholds for low BCAA values could enable earlier diagnosis and earlier dietary therapy. (boemer2022novellossof pages 8-10)

14. Other Species / Natural Disease

A spontaneous rat model (“frogleg”) with homozygous Bckdk G369E shows CNS and PNS involvement and low BCAAs, representing a naturally occurring disease model. (zigler2016aspontaneousmissense pages 2-5)

15. Model Organisms

15.1 Mouse models

Bckdk−/− knockout mouse: shows altered brain amino acids and neurological phenotypes (hindlimb clasping, seizures) and was used for dietary rescue experiments with BCAA-enriched diets in early work. (novarino2012mutationsinbckdkinase pages 5-8)
Bckdk−/− mouse (2024 metabolomic/therapeutic interrogation): used to test supplementation versus pathway-flux modification; enteral BCAA supplementation worsened neurodevelopmental outcomes, while Dbt haploinsufficiency partially rescued phenotypes. (ohl2024partialsuppressionof pages 1-2, ohl2024partialsuppressionof pages 9-11)

15.2 Rat models

Spontaneous Bckdk G369E rat model with biochemical and neurologic phenotypes affecting CNS and PNS. (zigler2016aspontaneousmissense pages 2-5)

Key statistics and data points (from retrieved studies)

Initial human genetic discovery: 3 consanguineous pedigrees with 2 affected individuals each (6 affected). (novarino2012mutationsinbckdkinase pages 5-8)
Newborn screening biochemical examples: Xle as low as 84 µmol/L and valine 47 µmol/L on dried blood spot in one affected child. (boemer2022novellossof pages 2-6)
CSF BCAA reference ranges used in one report: leucine 74–203, isoleucine 42–124, valine 145–337 (µmol/L). (boemer2022novellossof pages 6-8)
Treatment intensity/implementation: in one sibling series, achieving physiologic plasma BCAA required dosing ~135–195 mg/kg/day each BCAA divided into ≥6 doses/day, with protein intake 2.5–3 g/kg/day. (boemer2022novellossof pages 2-6)
Outcome proxy: one treated child had 10 hospital admissions in the year before therapy vs 1 admission during 18 months on therapy. (boemer2022novellossof pages 6-8)

Summary table of core findings

A cross-domain structured summary is provided below.

Domain	Finding	Evidence type (human/mouse/rat)	Key details (numbers/doses)	Primary source (authors/year/journal)	URL
Inheritance	BCKDK deficiency is an autosomal recessive disorder caused by biallelic loss-of-function variants in BCKDK	Human	Initial report: 3 consanguineous pedigrees with 2 affected individuals each (6 affected total); recessive segregation supported by homozygous variants in affected individuals (novarino2012mutationsinbckdkinase pages 5-8, novarino2012mutationsinbckdkinase pages 1-2)	Novarino et al., 2012, Science	https://doi.org/10.1126/science.1224631
Clinical features	Core phenotype includes autism/intellectual disability/epilepsy; later reports expand spectrum to developmental and epileptic encephalopathy, microcephaly, absent speech, psychomotor delay, regression, and neurobehavioral abnormalities	Human	Science 2012 families: autism, ID, epilepsy (novarino2012mutationsinbckdkinase pages 5-8, novarino2012mutationsinbckdkinase pages 1-2); 2022 siblings: psychomotor delay from first year, subacute regression in second year in 2/3, progressive microcephaly, absent speech, early generalized seizures (boemer2022novellossof pages 2-6, boemer2022novellossof pages 1-2)	Novarino et al., 2012, Science; Boemer et al., 2022, Int J Mol Sci	https://doi.org/10.1126/science.1224631 ; https://doi.org/10.3390/ijms23042253
Biochemical signature	Loss of BCKDK causes reduced phosphorylation/inhibition of BCKDH, increased BCAA catabolism, and low plasma/CSF branched-chain amino acids	Human	Reduced BCKDK mRNA/protein and loss of phospho-E1α signal in patient cells; markedly reduced plasma BCAA in affected individuals (novarino2012mutationsinbckdkinase pages 1-2, novarino2012mutationsinbckdkinase pages 5-8); 2022 family had severely reduced plasma and CSF BCAA and low newborn-screen dried-blood-spot markers (boemer2022novellossof pages 2-6, boemer2022novellossof pages 1-2)	Novarino et al., 2012, Science; Boemer et al., 2022, Int J Mol Sci	https://doi.org/10.1126/science.1224631 ; https://doi.org/10.3390/ijms23042253
Pathogenic variants	Human pathogenic variants reported include p.M74fs, p.Arg156, p.Arg224Pro, and p.Thr334del*	Human	p.M74fs, p.Arg156, p.Arg224Pro identified in 2012 families (novarino2012mutationsinbckdkinase pages 5-8); homozygous in-frame deletion c.999_1001delCAC (p.Thr334del*) identified in 3 siblings and shown functionally deleterious (boemer2022novellossof pages 2-6, boemer2022novellossof pages 1-2)	Novarino et al., 2012, Science; Boemer et al., 2022, Int J Mol Sci	https://doi.org/10.1126/science.1224631 ; https://doi.org/10.3390/ijms23042253
Model organism variant	Spontaneous rat model carries Bckdk G369E, a missense loss-of-function variant affecting kinase activity	Rat	Homozygous G369E segregates with central and peripheral nervous system phenotype; markedly decreased Ser293 phosphorylation and sharply decreased plasma BCAA (zigler2016aspontaneousmissense pages 2-5)	Zigler et al., 2016, PLOS ONE	https://doi.org/10.1371/journal.pone.0160447
Mouse model	Bckdk−/− mice recapitulate neurological disease features and biochemical abnormalities	Mouse	Altered brain amino acid levels, hindlimb clasping, seizures; rescue experiments used BCAA-enriched diets including 7% BCAA and transition to 2% BCAA diets (novarino2012mutationsinbckdkinase pages 5-8)	Novarino et al., 2012, Science	https://doi.org/10.1126/science.1224631
Rat model	Frogleg rat demonstrates both central and peripheral nervous system involvement from Bckdk dysfunction	Rat	Phenotype linked to unchecked BCKDH activity, excessive BCAA catabolism, and deficient circulating BCAA; structural modeling predicted disruption of kinase domain/ADP binding (zigler2016aspontaneousmissense pages 2-5)	Zigler et al., 2016, PLOS ONE	https://doi.org/10.1371/journal.pone.0160447
Treatment evidence	BCAA supplementation is the main reported disease-directed therapy; high-protein diet plus oral leucine/isoleucine/valine can restore plasma BCAA and improve seizures	Human	2022 sibling series used protein-rich diet 2.5-3 g/kg/day plus oral L-leucine/L-isoleucine/L-valine; initial ~85-125 mg/kg/day each was insufficient, increased to ~135-195 mg/kg/day each in divided doses achieved physiological plasma levels; seizure control greatly improved (boemer2022novellossof pages 2-6, boemer2022novellossof pages 1-2, boemer2022novellossof pages 6-8)	Boemer et al., 2022, Int J Mol Sci	https://doi.org/10.3390/ijms23042253
Treatment outcomes	Clinical benefit appears strongest for seizure control; developmental/behavioral gains are more limited and may depend on early treatment	Human	One child had 10 hospital admissions in the year before therapy versus 1 admission during 18 months on therapy; Vineland scores improved, especially communication/socialization, but behavioral/developmental gains were less robust than seizure benefit (boemer2022novellossof pages 6-8, babazade2026revealingbckdkdeficiency pages 3-5)	Boemer et al., 2022, Int J Mol Sci	https://doi.org/10.3390/ijms23042253
Newborn screening relevance	Low BCAA on dried blood spots suggests potential newborn-screening detectability	Human	Retrospective review showed low Xle and valine on NBS; example patient values included Xle 84 µmol/L and Val 47 µmol/L on newborn screening (boemer2022novellossof pages 2-6, boemer2022novellossof pages 1-2)	Boemer et al., 2022, Int J Mol Sci	https://doi.org/10.3390/ijms23042253
2024 therapeutic caveat	Newer mouse work challenges the assumption that enteral BCAA supplementation is sufficient or uniformly beneficial	Mouse	In Bckdk−/− mice, enteral BCAA supplementation increased systemic BCAA but exacerbated neurodevelopmental deficits and did not correct biochemical abnormalities; CSF/brain BCAA remained low (ohl2024partialsuppressionof pages 1-2, ohl2024partialsuppressionof pages 9-11)	Ohl et al., 2024, Mol Genet Metab Rep	https://doi.org/10.1016/j.ymgmr.2024.101091
2024 alternative preclinical strategy	Partial suppression of downstream BCAA catabolism may be a more effective strategy than simple supplementation	Mouse	Dbt haploinsufficiency partially rescued microcephaly, neurodevelopmental phenotypes, survival, weight, and many biochemical abnormalities in Bckdk−/− mice (ohl2024partialsuppressionof pages 9-11, ohl2024partialsuppressionof pages 1-2)	Ohl et al., 2024, Mol Genet Metab Rep	https://doi.org/10.1016/j.ymgmr.2024.101091

Table: This table summarizes core disease characteristics of BCKDK deficiency across human cases and animal models, including inheritance, phenotype, biochemical signature, variants, and treatment evidence. It also highlights the important 2024 preclinical finding that enteral BCAA supplementation may not fully correct brain disease and can worsen some mouse outcomes.

Limitations of this evidence package

Formal disease identifiers (OMIM/Orphanet/ICD/MeSH/MONDO) were not present in the retrieved full-text sources for this run; this report therefore cannot cite them.
A key 2023 Brain paper on newborn-screening amenability (doi:10.1093/brain/awad010) was listed as unobtainable by the search tool in this run and thus cannot be cited directly here.
Published human treatment evidence remains based on small numbers of families/siblings; interpretation should account for phenotype variability, timing of treatment initiation, and challenges of CNS repletion demonstrated in animal models. (boemer2022novellossof pages 6-8, ohl2024partialsuppressionof pages 1-2)

References

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(ohl2024partialsuppressionof pages 9-11): Laura Ohl, Amanda Kuhs, Ryan Pluck, Emily Durham, Michael Noji, Nathan D Philip, Zoltan Arany, and Rebecca C Ahrens-Nicklas. Partial suppression of bcaa catabolism as a potential therapy for bckdk deficiency. Molecular Genetics and Metabolism Reports, May 2024. URL: https://doi.org/10.1016/j.ymgmr.2024.101091, doi:10.1016/j.ymgmr.2024.101091. This article has 8 citations.
(du2022theroleof pages 6-7): Chuang Du, Wen-Jie Liu, Jing Yang, Shan-Shan Zhao, and Hui-Xin Liu. The role of branched-chain amino acids and branched-chain α-keto acid dehydrogenase kinase in metabolic disorders. Frontiers in Nutrition, Jul 2022. URL: https://doi.org/10.3389/fnut.2022.932670, doi:10.3389/fnut.2022.932670. This article has 94 citations.
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OpenScientist Report

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Biochemical Markers

Source YAML

References & Deep Research

References

Deep Research

1. Disease Information

1.1 Concise overview

1.2 Key identifiers

1.3 Synonyms and alternative names (from retrieved literature)

1.4 Evidence source types

2. Etiology

2.1 Disease causal factors

2.2 Risk factors

2.3 Protective factors

2.4 Gene–environment interactions

3. Phenotypes

3.1 Core phenotype spectrum (human)

3.2 Age of onset and course

3.3 Laboratory phenotype

3.4 Suggested HPO terms

4. Genetic / Molecular Information

4.1 Causal gene

4.2 Pathogenic variants reported in retrieved evidence

4.3 Functional consequence

4.4 Modifier genes / epigenetics / chromosomal abnormalities

5. Environmental Information

6. Mechanism / Pathophysiology

6.1 Core biochemical pathway and causal chain

6.2 Expanded metabolomic disturbance (recent evidence)

6.3 CNS access limitation as a mechanistic constraint on therapy

6.4 Suggested ontology terms (GO/CL/UBERON/CHEBI)

7. Anatomical Structures Affected

7.1 Organ/system level

7.2 Tissue/cell level

7.3 Subcellular level

8. Temporal Development

9. Inheritance and Population

9.1 Inheritance

9.2 Epidemiology

10. Diagnostics

10.1 Clinical suspicion

10.2 Biochemical testing

10.3 Genetic testing

10.4 Screening / early detection

10.5 Differential diagnosis (from mechanistic context)

11. Outcome / Prognosis

11.1 Untreated course

11.2 Treatment-modified outcomes

12. Treatment

12.1 Disease-directed nutritional therapy (current real-world implementation)

12.2 Evidence strength and expert-leaning interpretation

12.3 Recent developments (2023–2024) relevant to therapy landscape

12.4 Clinical trials

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

15.1 Mouse models

15.2 Rat models

Key statistics and data points (from retrieved studies)

Summary table of core findings

Limitations of this evidence package

Artifacts