Glutaric Acidemia Type 3

Mendelian MONDO:0009283 Pathograph 11 Show in embeddings browser Glutaric Aciduria Organic Aciduria Inborn Error of Metabolism

Glutaric acidemia (aciduria) type 3 is an autosomal recessive biochemical disorder caused by biallelic variants in SUGCT (formerly C7orf10), which encodes the mitochondrial succinyl-CoA:glutarate-CoA transferase. The enzyme re-esterifies free glutarate, a side product of lysine and tryptophan catabolism, to glutaryl-CoA so that it can re-enter the pathway at glutaryl-CoA dehydrogenase. Without it, free glutaric acid is lost in the urine, giving a persistent isolated glutaric aciduria in which the glutaryl-CoA-derived metabolites (3-hydroxyglutarate, glutarylcarnitine, glutarylglycine) are low relative to glutarate. That ratio is what separates it from glutaric aciduria type 1. The biochemical defect is established. Its clinical significance is not: the original series found no consistent clinical phenotype, many affected people (including all of the Old Order Amish probands and newborn-screening cases) are asymptomatic, and most symptomatic reports are confounded by a second diagnosis. GA3 is therefore widely regarded as a probable non-disease. A minority of reports describe gastrointestinal symptoms, including one child with cyclic vomiting who improved after an antibiotic trial intended to cut bacterial glutarate production; whether such symptoms are caused by GA3 is unresolved, and this entry keeps them on an explicitly provisional branch.

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1
Inheritance
5
Pathophys.
2
Phenotypes
1
Hypotheses
1
Gaps
11
Pathograph
1
Genes
2
Medical Actions
2
Differentials
2
Models
2
References
1
Deep Research
👪

Inheritance

1
Autosomal recessive inheritance HP:0000007
Every genotyped patient in the founding series carried two pathogenic SUGCT alleles, either homozygous (the Amish missense founder allele, and homozygous contiguous deletions spanning SUGCT and MPLKIP) or compound heterozygous. Biallelic variants reliably produce the biochemical trait; whether they produce any clinical phenotype is unknown, so clinical penetrance is recorded as UNKNOWN rather than incomplete.
Autosomal recessive inheritance Penetrance: UNKNOWN
Show evidence (2 references)
PMID:18926513 SUPPORT Human Clinical
"Two pathogenic alleles were identified in each of the six patients."
Biallelic SUGCT variants in all genotyped patients support autosomal recessive inheritance.
PMID:32779420 SUPPORT Human Clinical
"Glutaric Aciduria Type 3 (GA-3) is a rare metabolic disease which is inherited autosomal recessively and characterized by isolated glutaric acid excretion."
States the autosomal recessive mode of inheritance.
◈

Mechanistic Hypotheses

1
Glutarate excess, possibly microbially amplified, causes gastrointestinal symptoms in some GA3 patients
ga3_gastrointestinal_symptoms EMERGING
Evidence balance 2 support
A small number of GA3 patients have had gastrointestinal disturbance, including cyclic vomiting that improved after antibiotics. SUGCT-knockout mice show microbiome imbalance. Together these suggest that some patients may be symptomatic through an interaction between the enzyme defect, gut bacteria, and diet, but the human evidence is a handful of unreplicated case observations.
Pathograph links
Free Glutarate Accumulation and Urinary Loss -> Episodic vomiting UNKNOWN Provisional. Gastrointestinal symptoms have been reported in a minority of patients, but no study has shown that glutarate excess causes them, and several patients are entirely asymptomatic.
Show evidence (2 references)
PMID:28766179 SUPPORT Human Clinical
"Gastrointestinal disturbances were previously reported in some GA3 patients."
Records the recurring gastrointestinal observation behind the hypothesis.
PMID:28766179 SUPPORT Human Clinical
"At present, there is insufficient evidence to define any specific clinical phenotype as attributable to GA3."
The same authors state that no clinical phenotype has been attributed to GA3, which is why the hypothesis is only emerging.
?

Discussions and Knowledge Gaps

1
Is glutaric acidemia type 3 a disease, or a benign biochemical trait ascertained through unrelated illness?
CONTROVERSY OPEN controversy_ga3_clinical_significance
Attached to
disease#Glutaric Acidemia Type 3 phenotypes#Episodic vomiting
The enzymatic defect and its urinary signature are well established, but no clinical phenotype has been attributed to GA3. The Amish probands and a newborn-screened infant were asymptomatic. Symptomatic reports are mostly confounded: one child had a 6q terminal deletion, one had Graves hyperthyroidism and gastroenteritis at ascertainment, one had a second diagnosis of BCAP31-related syndrome that explained his neurodevelopmental findings, and two had trichothiodystrophy type 4 from a deletion that also removed SUGCT. A white-matter abnormality on MRI in one patient and cyclic vomiting in another remain unexplained single observations.
Show evidence (6 references)
PMID:18926513 SUPPORT Human Clinical
"There was no consistent clinical phenotype associated with GA3."
The founding genetic series found no consistent phenotype.
PMID:39101156 SUPPORT Human Clinical
"Ultimately, WES confirmed a diagnosis of BCAP31-related syndrome, a rare neurological disorder, which explained the patient's presenting symptoms."
A symptomatic GA3 patient whose symptoms were explained by a second diagnosis.
PMID:39101156 SUPPORT BACKGROUND Human Clinical
"GA III has historically been considered clinically benign, with few reported cases."
A 2024 case report restates the prevailing view that GA3 is clinically benign and rarely reported.
+ 3 more references
⚙

Pathophysiology

5
SUGCT Loss of Function
Biallelic SUGCT variants abolish succinyl-CoA:glutarate-CoA transferase activity. The recurrent missense allele (reported as p.Arg299Trp in the original Amish study and as p.Arg336Trp in the functional study, a difference of transcript numbering) yields insoluble, inactive protein; nonsense alleles, a frameshift, and homozygous contiguous deletions of SUGCT with the neighbouring MPLKIP gene have also been reported.
SUGCT hgnc:16001 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves SUGCT (hgnc:16001). hgnc:16001 is a gene from the HUGO Gene Nomenclature Committee.
succinyl-CoA:glutarate-CoA transferase activity GO:0047369 ↓ DECREASED Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased succinyl-CoA:glutarate-CoA transferase activity, annotated with succinate-hydroxymethylglutarate CoA-transferase activity (GO:0047369). GO:0047369 is a molecular function from the Gene Ontology.
Animal models
Sugct knockout mouse Mouse recapitulates The knockout removes SUGCT, the primary lesion of GA3, and was made to study the disease mechanism.
Downstream
Impaired Glutarate Re-esterification to Glutaryl-CoA
Show evidence (3 references)
PMID:23893049 SUPPORT In Vitro
"The p.Arg336Trp mutation led to the production of insoluble and inactive C7orf10 both in Escherichia coli and in HEK293T cells."
The recurrent GA3 missense allele produces inactive enzyme.
PMID:18926513 SUPPORT Human Clinical
"We then sequenced three non-Amish children with GA3 and discovered two nonsense mutations (c.322C-->T, Arg108Ter, and c.424C-->T, Arg142Ter) in addition to the Amish mutation."
Null alleles in SUGCT cause GA3.
PMID:29421601 SUPPORT Human Clinical
"Chromosome microarray analysis showed a 125 kb homozygous pathogenic deletion, which includes genes MPLKIP and SUGCT, not described before."
Whole-gene deletion of SUGCT is another route to loss of function.
Lysine and Tryptophan Catabolic Flux
Free glutarate arises as a side product of the mitochondrial lysine and tryptophan degradation pathway, thought to come from hydrolysis of glutaryl-CoA. Its production therefore scales with the load of the precursor amino acids.
lysine catabolism GO:0019477 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves lysine catabolism, annotated with L-lysine catabolic process (GO:0019477). GO:0019477 is a biological process from the Gene Ontology. tryptophan catabolism GO:0006569 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves tryptophan catabolism, annotated with L-tryptophan catabolic process (GO:0006569). GO:0006569 is a biological process from the Gene Ontology.
Downstream
Free Glutarate Accumulation and Urinary Loss
Show evidence (1 reference)
PMID:23893049 SUPPORT In Vitro
"Glutarate, a side-product in the metabolism of tryptophan and lysine, is metabolized by conversion to glutaryl-CoA by a transferase using succinyl-CoA as a coenzyme donor."
Places the origin of free glutarate in lysine and tryptophan catabolism.
Impaired Glutarate Re-esterification to Glutaryl-CoA
SUGCT performs a metabolite-repair reaction: it returns free glutarate to glutaryl-CoA so it can be oxidised by glutaryl-CoA dehydrogenase. When the reaction fails, glutarate becomes a dead-end metabolite, and the glutaryl-CoA-derived products fall relative to glutarate. The enzyme is most highly expressed in kidney and liver.
Downstream
Free Glutarate Accumulation and Urinary Loss
Show evidence (3 references)
PMID:38915184 SUPPORT BACKGROUND In Vitro
"Since glutaric acid would otherwise be a dead-end metabolite excreted in urine, this process is viewed as an example of metabolite repair."
Describes the reaction lost in GA3 as metabolite repair whose absence leaves glutarate as a dead-end product.
PMID:38915184 SUPPORT BACKGROUND In Vitro
"Expression of SUGCT is not uniform, with high mRNA levels in kidney and liver."
Tissue distribution of the enzyme.
PMID:33483254 SUPPORT Model Organism
"Our work demonstrates that SUGCT contributes to the production of glutaryl-CoA under conditions of low and pathologically high glutaric acid levels."
In vivo evidence in SUGCT-deficient mice that the enzyme supplies glutaryl-CoA.
Gut Bacterial Glutarate Production
Intestinal bacteria produce glutaric acid, and this contributes to the glutarate load in SUGCT deficiency. In SUGCT-knockout mice, antibiotic depletion of the gut flora returned metabolite levels to wild-type, and in one patient an antibiotic trial aimed at reducing bacterial glutarate production was followed by clinical improvement.
Animal models
Sugct knockout mouse Mouse perturbs
Downstream
Free Glutarate Accumulation and Urinary Loss Bacterial glutarate adds to endogenous glutarate that SUGCT-deficient tissue cannot re-esterify. The size of this contribution in humans has not been measured.
Show evidence (1 reference)
PMID:31722069 SUPPORT Model Organism
"After SugctKO mice were treated with antibiotics, metabolites were comparable to WT, indicating that the microbiome affects metabolism in SugctKO mice."
Microbiome depletion normalised metabolites in the knockout mouse.
Free Glutarate Accumulation and Urinary Loss
Glutaric acid that cannot be re-esterified accumulates and is excreted, giving persistent isolated glutaric aciduria with low 3-hydroxyglutarate. Reported urinary glutarate ranges from tens to over a thousand mmol/mol creatinine. Unlike glutaric aciduria type 1, no glutaryl-CoA or 3-hydroxyglutarate build-up occurs, so the neurotoxic metabolites of GA1 are not expected.
Glutarate excess, possibly microbially amplified, causes gastrointestinal symptoms in some GA3 patients
Animal models
129 substrain mice (naturally occurring SUGCT deficiency) Mouse recapitulates
Downstream
Glutaric aciduria
Episodic vomiting Provisional. Gastrointestinal symptoms have been reported in a minority of patients, but no study has shown that glutarate excess causes them, and several patients are entirely asymptomatic. Glutarate excess, possibly microbially amplified, causes gastrointestinal symptoms in some GA3 patients
Show evidence (1 reference)
PMID:18926513 SUPPORT Human Clinical
"we found three healthy children who excreted abnormal quantities of glutaric acid but low 3-hydroxyglutaric acid, a pattern consistent with glutaric aciduria type 3 (GA3)."
Defines the excretion pattern of GA3.
⬡

Pathograph

Use Group by to collapse related nodes into one box. Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Glutaric Acidemia Type 3 Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

2
Digestive 1
Episodic vomiting HP:0002572 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Episodic vomiting (HP:0002572). HP:0002572 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:28766179 SUPPORT Human Clinical
"In one of our patients, severe episodes of cyclic vomiting were the major problem."
Reports cyclic vomiting in a GA3 patient.
PMID:12555941 SUPPORT INDIRECT Human Clinical
"The second boy suffered from acute gastroenteritis and hyperthyroidism, when an excessively high urinary glutaric acid excretion was identified (1460 mmol/mol creatinine)."
Gastrointestinal illness at the time of ascertainment in another patient; it may have prompted testing rather than been caused by GA3.
Genitourinary 1
Glutaric aciduria OBLIGATE HP:0003150 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Glutaric aciduria (HP:0003150). HP:0003150 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:12555941 SUPPORT Human Clinical
"Glutaric aciduria type III is a rare metabolic abnormality leading to persistent isolated glutaric acid excretion."
Persistent isolated glutaric aciduria is the defining feature.
PMID:28766179 SUPPORT Human Clinical
"Glutaric aciduria type 3 (GA3) is associated with decreased conversion of free glutaric acid to glutaryl-coA, reflecting deficiency of succinate-hydroxymethylglutarate coA-transferase, caused by variants in the SUGCT (C7orf10) gene."
Links the aciduria to the SUGCT enzyme deficiency.
🧬

Genetic Associations

1
SUGCT
Gene: SUGCT hgnc:16001 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is SUGCT (hgnc:16001). hgnc:16001 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE variant_origin: GERMLINE
Show evidence (4 references)
PMID:18926513 SUPPORT Human Clinical
"Direct sequencing of C7orf10 revealed that the three Amish individuals were homozygous for a nonsynonymous sequence variant (c.895C-->T, Arg299Trp)."
Identifies SUGCT (C7orf10) as the GA3 gene through the Amish founder allele.
PMID:32779420 SUPPORT Human Clinical
"One of our patients had a homozygous mutation p.Arg322Trp (c.964C > T) of SUGCT (NM_001193311) gene."
An additional SUGCT missense allele.
PMID:37064336 SUPPORT Human Clinical
"Microarray analysis revealed a homozygous microdeletion involving the MPLKIP and SUGCT genes, which are located close to each other."
Contiguous deletion of SUGCT and MPLKIP.
+ 1 more reference
💊

Medical Actions

2
Antibiotic trial to reduce bacterial glutarate production
Action: antibiotic therapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is antibiotic therapy (NCIT:C15620). NCIT:C15620 is a clinical intervention from the NCI Thesaurus. Ontology label: Antibiotic Therapy NCIT:C15620
Platform: Small molecule
No treatment is established or generally required. In a single symptomatic child with cyclic vomiting, an antibiotic trial intended to reduce intestinal bacterial glutaric acid production was followed by significant clinical improvement. This is an uncontrolled single-case observation.
Mechanism Target:
Gut Bacterial Glutarate Production — Intended to reduce bacterial glutarate production.
Show evidence (1 reference)
PMID:28766179 SUPPORT Human Clinical
"A trial of antibiotic treatment, to minimise bacterial GA production, was followed by significant clinical improvement."
Single-patient report of improvement after antibiotics.
Genetic counseling
Action: genetic counselingNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is genetic counseling (NCIT:C15240). NCIT:C15240 is a clinical intervention from the NCI Thesaurus. Ontology label: Genetic Counseling NCIT:C15240
Counseling on autosomal recessive inheritance and on the uncertain, probably benign, clinical significance of the biochemical finding.
Show evidence (1 reference)
PMID:28766179 SUPPORT Human Clinical
"Clinicians encountering a patient with GA3 therefore still face a dilemma of whether or not this should be dismissed as irrelevant."
The counseling problem is the uncertain significance of the diagnosis.
🔬

Biochemical Markers

1
Urinary glutaric acid (INCREASED)
Context: Persistently raised urinary glutaric acid with low or normal 3-hydroxyglutaric acid, and a raised ratio of glutarate to glutarylcarnitine and glutarylglycine. Increases further after lysine loading.
Show evidence (2 references)
PMID:12555941 SUPPORT Human Clinical
"The third patient is a girl with constantly elevated glutaric acid in her urine (290 mmol/mol creatinine) but no symptoms of significant disease."
Persistent urinary glutarate elevation in an asymptomatic patient.
PMID:18926513 SUPPORT Human Clinical
"In affected individuals, urine molar ratios of glutarate to its derivatives (3-hydroxyglutarate, glutarylcarnitine, and glutarylglycine) were elevated, suggesting impaired formation of glutaryl-CoA."
The diagnostic ratio pattern.
🔬

Diagnosis

2
Urine organic acid analysis
Shows isolated, persistent glutaric aciduria. Glutaric aciduria types 1 and 2 and secondary glutaric aciduria (intestinal infection, mitochondrial dysfunction) must be excluded; low 3-hydroxyglutarate and a raised glutarate-to-derivative ratio point to GA3. Confirmation is by SUGCT sequencing or microarray.
urine organic acid analysis
Show evidence (1 reference)
PMID:12555941 SUPPORT Human Clinical
"In all our patients, glutaric aciduria type I (glutaryl-CoA dehydrogenase deficiency), glutaric aciduria type II (multiple acyl-CoA dehydrogenation defect), and secondary forms of glutaric aciduria (for example due to intestinal infections or mitochondrial dysfunction) could be excluded."
The exclusions required before diagnosing GA3.
Newborn screening by urine organic acids
GA3 can be detected by urine-based newborn screening programmes; a screen-detected Canadian infant remained asymptomatic.
newborn screening
Show evidence (1 reference)
PMID:28766179 SUPPORT Human Clinical
"Two came to clinical attention because of symptoms, while the third was identified by a population urine-based newborn screening programme and has so far remained asymptomatic."
Ascertainment through urine newborn screening, with an asymptomatic course.
📊

Prevalence

1
Worldwide
Cases In Literature Ultra Rare
No population rate has been measured. Only nine individuals had been described by 2017; later case reports add a small number more. Allele frequencies in population databases indicate that GA3 is underdiagnosed, plausibly because most affected people are asymptomatic and urine organic acid analysis is not done routinely.
Show evidence (2 references)
PMID:28766179 SUPPORT Human Clinical
"It is generally considered a likely "non-disease," but this is based on limited supporting information, with only nine individuals with GA3 described in the literature."
Case count in the literature as of 2017.
PMID:28766179 SUPPORT Human Clinical
"Examination of allele frequencies underlines the fact that GA3 is underdiagnosed."
Supports the note that the literature count underestimates the true frequency.
🔀

Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from Glutaric Acidemia Type 3:

Glutaryl-CoA Dehydrogenase Deficiency (glutaric aciduria type 1)
Overlapping Features The important differential, because GA1 causes striatal injury and is treatable. GA1 shows raised 3-hydroxyglutarate and glutarylcarnitine; GA3 shows glutarate with low 3-hydroxyglutarate.
Show evidence (1 reference)
PMID:18926513 SUPPORT Human Clinical
"None of these children had the GCDH c.1262C-->T mutation that causes GA1 among the Amish."
GA3 children were found during GA1 screening and distinguished from GA1 genetically.
Multiple Acyl-CoA Dehydrogenase Deficiency (glutaric aciduria type 2)
Overlapping Features Glutaric aciduria accompanied by other acyl-CoA dehydrogenase substrates; excluded by the isolated pattern in GA3.
Show evidence (1 reference)
PMID:12555941 SUPPORT Human Clinical
"glutaric aciduria type II (multiple acyl-CoA dehydrogenation defect), and secondary forms of glutaric aciduria (for example due to intestinal infections or mitochondrial dysfunction) could be excluded."
GA2 and secondary glutaric aciduria are excluded in GA3.
🐁

Animal Models

2
Sugct knockout mouse
Sugct knockout mice show imbalanced kidney lipid and acylcarnitine metabolism and gut microbiome changes, with age-dependent kidney, liver and adipose pathology and an obesity-related phenotype that a high-lysine diet accelerates. The human counterparts of these findings have not been reported.
Species
Mouse
Genotype
Sugct-/-
Publication
PMID:31722069
Pathograph links
SUGCT Loss of Function recapitulates fidelity: moderate The knockout removes SUGCT, the primary lesion of GA3, and was made to study the disease mechanism.
Limitations: The knockout's kidney, liver, adipose and metabolic-syndrome-like phenotypes have no reported human counterpart; GA3 patients are largely asymptomatic despite high urinary glutarate.
Show evidence (1 reference)
PMID:31722069 SUPPORT Model Organism
"To study the disease mechanism, we generated SugctKO mice and uncovered imbalanced lipid and acylcarnitine metabolism in kidney in addition to changes in the gut microbiome."
The knockout was generated as a model of the GA3 lesion itself, SUGCT loss.
Gut Bacterial Glutarate Production perturbs fidelity: unknown
Limitations: Metabolic syndrome-like and kidney phenotypes in the knockout have no reported human counterpart; GA3 patients are largely asymptomatic. The study reports dysbiosis as a consequence of SUGCT loss (host to microbiome), the reverse direction of this entry's bacteria-to-glutarate edge, so this link does not support that edge.
Show evidence (1 reference)
PMID:31722069 SUPPORT Model Organism
"SUGCT loss of function contributes to gut microbiota dysbiosis, leading to age-dependent pathological changes in kidney, liver, and adipose tissue."
Shows microbiome involvement in the knockout.
Show evidence (1 reference)
PMID:31722069 SUPPORT Model Organism
"Furthermore, we show that the SugctKO kidney pathology is accelerated and exacerbated by a high-lysine diet."
Diet interaction in the knockout model.
129 substrain mice (naturally occurring SUGCT deficiency)
Inbred 129 substrain mice carry a naturally occurring SUGCT deficiency that produces a GA3 urinary trait. Crossing it onto the GA1 mouse lowered 3-hydroxyglutarate and glutarylcarnitine, showing SUGCT supplies glutaryl-CoA in vivo.
Species
Mouse
Genotype
Sugct 129/129
Background
129S2/SvPasCrl
Publication
PMID:33483254
Pathograph links
Free Glutarate Accumulation and Urinary Loss recapitulates fidelity: high
Show evidence (1 reference)
PMID:33483254 SUPPORT Model Organism
"Molecular and biochemical analyses in an F2 population of the parental C57BL/6J and 129S2/SvPasCrl strains (B6129F2) confirmed that the GA3 trait occurred in Sugct129/129 animals."
The urinary GA3 trait segregates with Sugct genotype.
Show evidence (1 reference)
PMID:33483254 SUPPORT Model Organism
"We found that GA1 mice with SUGCT deficiency have decreased excretion of urine 3-hydroxyglutaric acid and decreased levels glutarylcarnitine in urine, plasma and kidney."
SUGCT deficiency reduces glutaryl-CoA-derived metabolites in vivo.
{ }

Source YAML

click to show 
name: Glutaric Acidemia Type 3
creation_date: "2026-10-15T00:00:00Z"
category: Mendelian
synonyms:
- Glutaric aciduria type 3
- Glutaric aciduria type III
- GA3
- SUGCT deficiency
- Succinyl-CoA:glutarate-CoA transferase deficiency
- Glutaryl-CoA oxidase deficiency
description: >-
  Glutaric acidemia (aciduria) type 3 is an autosomal recessive biochemical
  disorder caused by biallelic variants in SUGCT (formerly C7orf10), which
  encodes the mitochondrial succinyl-CoA:glutarate-CoA transferase. The enzyme
  re-esterifies free glutarate, a side product of lysine and tryptophan
  catabolism, to glutaryl-CoA so that it can re-enter the pathway at
  glutaryl-CoA dehydrogenase. Without it, free glutaric acid is lost in the
  urine, giving a persistent isolated glutaric aciduria in which the
  glutaryl-CoA-derived metabolites (3-hydroxyglutarate, glutarylcarnitine,
  glutarylglycine) are low relative to glutarate. That ratio is what separates
  it from glutaric aciduria type 1.

  The biochemical defect is established. Its clinical significance is not:
  the original series found no consistent clinical phenotype, many affected
  people (including all of the Old Order Amish probands and newborn-screening
  cases) are asymptomatic, and most symptomatic reports are confounded by a
  second diagnosis. GA3 is therefore widely regarded as a probable non-disease.
  A minority of reports describe gastrointestinal symptoms, including one child
  with cyclic vomiting who improved after an antibiotic trial intended to cut
  bacterial glutarate production; whether such symptoms are caused by GA3 is
  unresolved, and this entry keeps them on an explicitly provisional branch.
disease_term:
  preferred_term: glutaric acidemia type 3
  term:
    id: MONDO:0009283
    label: glutaric acidemia type 3
parents:
- Glutaric Aciduria
- Organic Aciduria
- Inborn Error of Metabolism
inheritance:
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  penetrance: UNKNOWN
  description: >-
    Every genotyped patient in the founding series carried two pathogenic SUGCT
    alleles, either homozygous (the Amish missense founder allele, and
    homozygous contiguous deletions spanning SUGCT and MPLKIP) or compound
    heterozygous. Biallelic variants reliably produce the biochemical trait;
    whether they produce any clinical phenotype is unknown, so clinical
    penetrance is recorded as UNKNOWN rather than incomplete.
  evidence:
  - reference: PMID:18926513
    reference_title: "Genetic mapping of glutaric aciduria, type 3, to chromosome 7 and identification of mutations in c7orf10."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Two pathogenic alleles were identified in each of the six patients.
    explanation: Biallelic SUGCT variants in all genotyped patients support autosomal recessive inheritance.
  - reference: PMID:32779420
    reference_title: "Two patients with glutaric aciduria type 3: a novel mutation and brain magnetic resonance imaging findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Glutaric Aciduria Type 3 (GA-3) is a rare metabolic disease which is
      inherited autosomal recessively and characterized by isolated glutaric
      acid excretion.
    explanation: States the autosomal recessive mode of inheritance.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    No population rate has been measured. Only nine individuals had been
    described by 2017; later case reports add a small number more. Allele
    frequencies in population databases indicate that GA3 is underdiagnosed,
    plausibly because most affected people are asymptomatic and urine organic
    acid analysis is not done routinely.
  evidence:
  - reference: PMID:28766179
    reference_title: "Glutaric Aciduria Type 3: Three Unrelated Canadian Cases, with Different Routes of Ascertainment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It is generally considered a likely "non-disease," but this is based on
      limited supporting information, with only nine individuals with GA3
      described in the literature.
    explanation: Case count in the literature as of 2017.
  - reference: PMID:28766179
    reference_title: "Glutaric Aciduria Type 3: Three Unrelated Canadian Cases, with Different Routes of Ascertainment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Examination of allele frequencies underlines the fact that GA3 is underdiagnosed.
    explanation: Supports the note that the literature count underestimates the true frequency.
pathophysiology:
- name: SUGCT Loss of Function
  description: >-
    Biallelic SUGCT variants abolish succinyl-CoA:glutarate-CoA transferase
    activity. The recurrent missense allele (reported as p.Arg299Trp in the
    original Amish study and as p.Arg336Trp in the functional study, a
    difference of transcript numbering) yields insoluble, inactive protein;
    nonsense alleles, a frameshift, and homozygous contiguous deletions of SUGCT
    with the neighbouring MPLKIP gene have also been reported.
  biological_scale: MOLECULAR
  genes:
  - preferred_term: SUGCT
    term:
      id: hgnc:16001
      label: SUGCT
  molecular_functions:
  - preferred_term: succinyl-CoA:glutarate-CoA transferase activity
    term:
      id: GO:0047369
      label: succinate-hydroxymethylglutarate CoA-transferase activity
    modifier: DECREASED
  evidence:
  - reference: PMID:23893049
    reference_title: "C7orf10 encodes succinate-hydroxymethylglutarate CoA-transferase, the enzyme that converts glutarate to glutaryl-CoA."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      The p.Arg336Trp mutation led to the production of insoluble and inactive
      C7orf10 both in Escherichia coli and in HEK293T cells.
    explanation: The recurrent GA3 missense allele produces inactive enzyme.
  - reference: PMID:18926513
    reference_title: "Genetic mapping of glutaric aciduria, type 3, to chromosome 7 and identification of mutations in c7orf10."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We then sequenced three non-Amish children with GA3 and discovered two
      nonsense mutations (c.322C-->T, Arg108Ter, and c.424C-->T, Arg142Ter) in
      addition to the Amish mutation.
    explanation: Null alleles in SUGCT cause GA3.
  - reference: PMID:29421601
    reference_title: "Novel contiguous gene deletion in peruvian girl with Trichothiodystrophy type 4 and glutaric aciduria type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Chromosome microarray analysis showed a 125 kb homozygous pathogenic
      deletion, which includes genes MPLKIP and SUGCT, not described before.
    explanation: Whole-gene deletion of SUGCT is another route to loss of function.
  downstream:
  - target: Impaired Glutarate Re-esterification to Glutaryl-CoA
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:23893049
      reference_title: "C7orf10 encodes succinate-hydroxymethylglutarate CoA-transferase, the enzyme that converts glutarate to glutaryl-CoA."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        we show that recombinant human C7orf10 catalyzes the succinyl-CoA-dependent
        conversion of glutarate to glutaryl-CoA.
      explanation: The enzyme lost in GA3 is the one that converts glutarate to glutaryl-CoA, so its loss directly blocks this step.
- name: Lysine and Tryptophan Catabolic Flux
  description: >-
    Free glutarate arises as a side product of the mitochondrial lysine and
    tryptophan degradation pathway, thought to come from hydrolysis of
    glutaryl-CoA. Its production therefore scales with the load of the
    precursor amino acids.
  biological_scale: CELLULAR
  biological_processes:
  - preferred_term: lysine catabolism
    term:
      id: GO:0019477
      label: L-lysine catabolic process
  - preferred_term: tryptophan catabolism
    term:
      id: GO:0006569
      label: L-tryptophan catabolic process
  evidence:
  - reference: PMID:23893049
    reference_title: "C7orf10 encodes succinate-hydroxymethylglutarate CoA-transferase, the enzyme that converts glutarate to glutaryl-CoA."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Glutarate, a side-product in the metabolism of tryptophan and lysine, is
      metabolized by conversion to glutaryl-CoA by a transferase using
      succinyl-CoA as a coenzyme donor.
    explanation: Places the origin of free glutarate in lysine and tryptophan catabolism.
  downstream:
  - target: Free Glutarate Accumulation and Urinary Loss
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:12555941
      reference_title: "Glutaric aciduria type III: a distinctive non-disease?"
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Loading with the precursor amino acid lysine in all patients as well as
        with pipecolic acid in the third case led to an increase in urinary
        glutaric acid excretion, proving the endogenous origin of glutarate.
      explanation: Lysine loading raised urinary glutarate in affected children, linking precursor flux to the excreted glutarate.
- name: Impaired Glutarate Re-esterification to Glutaryl-CoA
  description: >-
    SUGCT performs a metabolite-repair reaction: it returns free glutarate to
    glutaryl-CoA so it can be oxidised by glutaryl-CoA dehydrogenase. When the
    reaction fails, glutarate becomes a dead-end metabolite, and the
    glutaryl-CoA-derived products fall relative to glutarate. The enzyme is most
    highly expressed in kidney and liver.
  biological_scale: MOLECULAR
  chemical_entities:
  - preferred_term: glutaryl-CoA
    term:
      id: CHEBI:15524
      label: glutaryl-CoA
    modifier: DECREASED
  evidence:
  - reference: PMID:38915184
    reference_title: "Characterization, Structure, and Inhibition of the Human Succinyl-CoA:glutarate-CoA Transferase, a Putative Genetic Modifier of Glutaric Aciduria Type 1."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Since glutaric acid would otherwise be a dead-end metabolite excreted in
      urine, this process is viewed as an example of metabolite repair.
    explanation: Describes the reaction lost in GA3 as metabolite repair whose absence leaves glutarate as a dead-end product.
    quote_role: BACKGROUND
  - reference: PMID:38915184
    reference_title: "Characterization, Structure, and Inhibition of the Human Succinyl-CoA:glutarate-CoA Transferase, a Putative Genetic Modifier of Glutaric Aciduria Type 1."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Expression of SUGCT is not uniform, with high mRNA levels in kidney and liver.
    explanation: Tissue distribution of the enzyme.
    quote_role: BACKGROUND
  - reference: PMID:33483254
    reference_title: "Glutaric aciduria type 3 is a naturally occurring biochemical trait in inbred mice of 129 substrains."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Our work demonstrates that SUGCT contributes to the production of
      glutaryl-CoA under conditions of low and pathologically high glutaric acid
      levels.
    explanation: In vivo evidence in SUGCT-deficient mice that the enzyme supplies glutaryl-CoA.
  downstream:
  - target: Free Glutarate Accumulation and Urinary Loss
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:18926513
      reference_title: "Genetic mapping of glutaric aciduria, type 3, to chromosome 7 and identification of mutations in c7orf10."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        In affected individuals, urine molar ratios of glutarate to its
        derivatives (3-hydroxyglutarate, glutarylcarnitine, and glutarylglycine)
        were elevated, suggesting impaired formation of glutaryl-CoA.
      explanation: Elevated glutarate relative to glutaryl-CoA derivatives in patients is the signature of impaired re-esterification.
    - reference: PMID:33483254
      reference_title: "Glutaric aciduria type 3 is a naturally occurring biochemical trait in inbred mice of 129 substrains."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        SUGCT catalyzes the succinyl-CoA-dependent conversion of glutaric acid
        into glutaryl-CoA preventing urinary loss of the organic acid.
      explanation: States that the reaction prevents urinary loss of glutarate, so its failure causes that loss.
- name: Gut Bacterial Glutarate Production
  description: >-
    Intestinal bacteria produce glutaric acid, and this contributes to the
    glutarate load in SUGCT deficiency. In SUGCT-knockout mice, antibiotic
    depletion of the gut flora returned metabolite levels to wild-type, and in
    one patient an antibiotic trial aimed at reducing bacterial glutarate
    production was followed by clinical improvement.
  biological_scale: ORGANISM
  evidence:
  - reference: PMID:31722069
    reference_title: "Knockout of the non-essential gene SUGCT creates diet-linked, age-related microbiome disbalance with a diabetes-like metabolic syndrome phenotype."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      After SugctKO mice were treated with antibiotics, metabolites were
      comparable to WT, indicating that the microbiome affects metabolism in
      SugctKO mice.
    explanation: Microbiome depletion normalised metabolites in the knockout mouse.
  downstream:
  - target: Free Glutarate Accumulation and Urinary Loss
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Bacterial glutarate adds to endogenous glutarate that SUGCT-deficient
      tissue cannot re-esterify. The size of this contribution in humans has
      not been measured.
    evidence:
    - reference: PMID:28766179
      reference_title: "Glutaric Aciduria Type 3: Three Unrelated Canadian Cases, with Different Routes of Ascertainment."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        A trial of antibiotic treatment, to minimise bacterial GA production,
        was followed by significant clinical improvement.
      explanation: The rationale for the trial treats gut bacteria as a glutarate source in GA3; the outcome is a single case.
      directness: INDIRECT
- name: Free Glutarate Accumulation and Urinary Loss
  description: >-
    Glutaric acid that cannot be re-esterified accumulates and is excreted,
    giving persistent isolated glutaric aciduria with low 3-hydroxyglutarate.
    Reported urinary glutarate ranges from tens to over a thousand mmol/mol
    creatinine. Unlike glutaric aciduria type 1, no glutaryl-CoA or
    3-hydroxyglutarate build-up occurs, so the neurotoxic metabolites of GA1 are
    not expected.
  biological_scale: ORGANISM
  chemical_entities:
  - preferred_term: glutaric acid
    term:
      id: CHEBI:17859
      label: glutaric acid
    modifier: INCREASED
  evidence:
  - reference: PMID:18926513
    reference_title: "Genetic mapping of glutaric aciduria, type 3, to chromosome 7 and identification of mutations in c7orf10."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      we found three healthy children who excreted abnormal quantities of
      glutaric acid but low 3-hydroxyglutaric acid, a pattern consistent with
      glutaric aciduria type 3 (GA3).
    explanation: Defines the excretion pattern of GA3.
  downstream:
  - target: Glutaric aciduria
    causal_link_type: DIRECT
  - target: Episodic vomiting
    causal_link_type: UNKNOWN
    hypothesis_groups:
    - ga3_gastrointestinal_symptoms
    description: >-
      Provisional. Gastrointestinal symptoms have been reported in a minority
      of patients, but no study has shown that glutarate excess causes them,
      and several patients are entirely asymptomatic.
    evidence:
    - reference: PMID:28766179
      reference_title: "Glutaric Aciduria Type 3: Three Unrelated Canadian Cases, with Different Routes of Ascertainment."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        In one of our patients, severe episodes of cyclic vomiting were the
        major problem.
      explanation: A single patient with cyclic vomiting and GA3; causation is not established.
      directness: INDIRECT
mechanistic_hypotheses:
- hypothesis_group_id: ga3_gastrointestinal_symptoms
  hypothesis_label: Glutarate excess, possibly microbially amplified, causes gastrointestinal symptoms in some GA3 patients
  status: EMERGING
  description: >-
    A small number of GA3 patients have had gastrointestinal disturbance,
    including cyclic vomiting that improved after antibiotics. SUGCT-knockout
    mice show microbiome imbalance. Together these suggest that some patients
    may be symptomatic through an interaction between the enzyme defect, gut
    bacteria, and diet, but the human evidence is a handful of unreplicated
    case observations.
  evidence:
  - reference: PMID:28766179
    reference_title: "Glutaric Aciduria Type 3: Three Unrelated Canadian Cases, with Different Routes of Ascertainment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Gastrointestinal disturbances were previously reported in some GA3 patients.
    explanation: Records the recurring gastrointestinal observation behind the hypothesis.
  - reference: PMID:28766179
    reference_title: "Glutaric Aciduria Type 3: Three Unrelated Canadian Cases, with Different Routes of Ascertainment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      At present, there is insufficient evidence to define any specific
      clinical phenotype as attributable to GA3.
    explanation: The same authors state that no clinical phenotype has been attributed to GA3, which is why the hypothesis is only emerging.
phenotypes:
- name: Glutaric aciduria
  category: Metabolic
  frequency: OBLIGATE
  description: >-
    Persistent isolated excretion of glutaric acid with a raised ratio of
    glutarate to 3-hydroxyglutarate, glutarylcarnitine and glutarylglycine. It
    is the defining and frequently the only finding.
  phenotype_term:
    preferred_term: Glutaric aciduria
    term:
      id: HP:0003150
      label: Glutaric aciduria
  evidence:
  - reference: PMID:12555941
    reference_title: "Glutaric aciduria type III: a distinctive non-disease?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Glutaric aciduria type III is a rare metabolic abnormality leading to
      persistent isolated glutaric acid excretion.
    explanation: Persistent isolated glutaric aciduria is the defining feature.
  - reference: PMID:28766179
    reference_title: "Glutaric Aciduria Type 3: Three Unrelated Canadian Cases, with Different Routes of Ascertainment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Glutaric aciduria type 3 (GA3) is associated with decreased conversion of
      free glutaric acid to glutaryl-coA, reflecting deficiency of
      succinate-hydroxymethylglutarate coA-transferase, caused by variants in
      the SUGCT (C7orf10) gene.
    explanation: Links the aciduria to the SUGCT enzyme deficiency.
- name: Episodic vomiting
  category: Digestive
  description: >-
    Recurrent or cyclic vomiting and other gastrointestinal disturbance have
    been described in a minority of patients. Attribution to GA3 is unproven;
    most reported patients have no gastrointestinal symptoms.
  phenotype_term:
    preferred_term: Episodic vomiting
    term:
      id: HP:0002572
      label: Episodic vomiting
  evidence:
  - reference: PMID:28766179
    reference_title: "Glutaric Aciduria Type 3: Three Unrelated Canadian Cases, with Different Routes of Ascertainment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In one of our patients, severe episodes of cyclic vomiting were the
      major problem.
    explanation: Reports cyclic vomiting in a GA3 patient.
  - reference: PMID:12555941
    reference_title: "Glutaric aciduria type III: a distinctive non-disease?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The second boy suffered from acute gastroenteritis and hyperthyroidism,
      when an excessively high urinary glutaric acid excretion was identified
      (1460 mmol/mol creatinine).
    explanation: Gastrointestinal illness at the time of ascertainment in another patient; it may have prompted testing rather than been caused by GA3.
    directness: INDIRECT
biochemical:
- name: Urinary glutaric acid
  presence: INCREASED
  context: >-
    Persistently raised urinary glutaric acid with low or normal
    3-hydroxyglutaric acid, and a raised ratio of glutarate to glutarylcarnitine
    and glutarylglycine. Increases further after lysine loading.
  biomarker_term:
    preferred_term: glutaric acid
    term:
      id: CHEBI:17859
      label: glutaric acid
  evidence:
  - reference: PMID:12555941
    reference_title: "Glutaric aciduria type III: a distinctive non-disease?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The third patient is a girl with constantly elevated glutaric acid in her
      urine (290 mmol/mol creatinine) but no symptoms of significant disease.
    explanation: Persistent urinary glutarate elevation in an asymptomatic patient.
  - reference: PMID:18926513
    reference_title: "Genetic mapping of glutaric aciduria, type 3, to chromosome 7 and identification of mutations in c7orf10."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In affected individuals, urine molar ratios of glutarate to its
      derivatives (3-hydroxyglutarate, glutarylcarnitine, and glutarylglycine)
      were elevated, suggesting impaired formation of glutaryl-CoA.
    explanation: The diagnostic ratio pattern.
genetic:
- name: SUGCT
  gene_term:
    preferred_term: SUGCT
    term:
      id: hgnc:16001
      label: SUGCT
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  notes: >-
    ClinGen rates the SUGCT-GA3 relationship Moderate, not Definitive or
    Strong, because few cases are published. The relationship is recorded as
    CAUSATIVE because biallelic SUGCT loss is sufficient for the biochemical
    trait that defines the disorder, demonstrated by enzyme studies and by two
    independent mouse lines; it is not a claim that SUGCT variants cause any
    clinical illness.
  gene_disease_validity:
  - validity_classification: MODERATE
    classified_by: CLINGEN
    external_id: CGGV:assertion_10622f19-d307-4fa8-b3ff-a799922e7fea-2024-12-13T170000.000Z
    evidence:
    - reference: CGGV:assertion_10622f19-d307-4fa8-b3ff-a799922e7fea-2024-12-13T170000.000Z
      reference_title: "SUGCT / glutaric acidemia type 3 (Moderate)"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "SUGCT | HGNC:16001 | glutaric acidemia type 3 | MONDO:0009283 | AR | Moderate"
      explanation: ClinGen Aminoacidopathy GCEP classifies SUGCT in autosomal recessive glutaric acidemia type 3 as Moderate.
    - reference: CGGV:assertion_10622f19-d307-4fa8-b3ff-a799922e7fea-2024-12-13T170000.000Z
      reference_title: "SUGCT / glutaric acidemia type 3 (Moderate)"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Glutaric aciduria type 3 is a biochemical phenotype with uncertain clinical relevance.
      explanation: ClinGen's own summary of the clinical significance.
  features: >-
    SUGCT (formerly C7orf10) on 7p14.1 encodes a mitochondrial class III
    CoA-transferase. Reported alleles include an Old Order Amish missense
    founder variant (c.895C>T, p.Arg299Trp in the original numbering), nonsense
    variants (p.Arg108Ter, p.Arg142Ter), a novel missense p.Arg322Trp, a
    frameshift, and homozygous contiguous deletions that also remove MPLKIP and
    cause trichothiodystrophy type 4.
  evidence:
  - reference: PMID:18926513
    reference_title: "Genetic mapping of glutaric aciduria, type 3, to chromosome 7 and identification of mutations in c7orf10."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Direct sequencing of C7orf10 revealed that the three Amish individuals
      were homozygous for a nonsynonymous sequence variant (c.895C-->T,
      Arg299Trp).
    explanation: Identifies SUGCT (C7orf10) as the GA3 gene through the Amish founder allele.
  - reference: PMID:32779420
    reference_title: "Two patients with glutaric aciduria type 3: a novel mutation and brain magnetic resonance imaging findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      One of our patients had a homozygous mutation p.Arg322Trp (c.964C > T) of
      SUGCT (NM_001193311) gene.
    explanation: An additional SUGCT missense allele.
  - reference: PMID:37064336
    reference_title: "A Rare Contiguous Gene Deletion Leading to Trichothiodystrophy Type 4 and Glutaric Aciduria Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Microarray analysis revealed a homozygous microdeletion involving the
      MPLKIP and SUGCT genes, which are located close to each other.
    explanation: Contiguous deletion of SUGCT and MPLKIP.
  - reference: PMID:37920852
    reference_title: "Case report: Paternal uniparental disomy on chromosome 7 and homozygous SUGCT mutation in a fetus with overweight after birth."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Whole exome and Sanger sequencing revealed a homozygous frameshift
      mutation in SUGCT at 7p14.1, from the heterozygous carrier father, with no
      contribution from the mother.
    explanation: A homozygous SUGCT frameshift arising through paternal uniparental isodisomy of chromosome 7.
diagnosis:
- name: Urine organic acid analysis
  diagnosis_term:
    preferred_term: urine organic acid analysis
  description: >-
    Shows isolated, persistent glutaric aciduria. Glutaric aciduria types 1 and
    2 and secondary glutaric aciduria (intestinal infection, mitochondrial
    dysfunction) must be excluded; low 3-hydroxyglutarate and a raised
    glutarate-to-derivative ratio point to GA3. Confirmation is by SUGCT
    sequencing or microarray.
  evidence:
  - reference: PMID:12555941
    reference_title: "Glutaric aciduria type III: a distinctive non-disease?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In all our patients, glutaric aciduria type I (glutaryl-CoA
      dehydrogenase deficiency), glutaric aciduria type II (multiple acyl-CoA
      dehydrogenation defect), and secondary forms of glutaric aciduria (for
      example due to intestinal infections or mitochondrial dysfunction) could
      be excluded.
    explanation: The exclusions required before diagnosing GA3.
- name: Newborn screening by urine organic acids
  diagnosis_term:
    preferred_term: newborn screening
  description: >-
    GA3 can be detected by urine-based newborn screening programmes; a
    screen-detected Canadian infant remained asymptomatic.
  evidence:
  - reference: PMID:28766179
    reference_title: "Glutaric Aciduria Type 3: Three Unrelated Canadian Cases, with Different Routes of Ascertainment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Two came to clinical attention because of symptoms, while the third was
      identified by a population urine-based newborn screening programme and
      has so far remained asymptomatic.
    explanation: Ascertainment through urine newborn screening, with an asymptomatic course.
differential_diagnoses:
- name: Glutaryl-CoA Dehydrogenase Deficiency (glutaric aciduria type 1)
  description: >-
    The important differential, because GA1 causes striatal injury and is
    treatable. GA1 shows raised 3-hydroxyglutarate and glutarylcarnitine; GA3
    shows glutarate with low 3-hydroxyglutarate.
  evidence:
  - reference: PMID:18926513
    reference_title: "Genetic mapping of glutaric aciduria, type 3, to chromosome 7 and identification of mutations in c7orf10."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: None of these children had the GCDH c.1262C-->T mutation that causes GA1 among the Amish.
    explanation: GA3 children were found during GA1 screening and distinguished from GA1 genetically.
- name: Multiple Acyl-CoA Dehydrogenase Deficiency (glutaric aciduria type 2)
  description: >-
    Glutaric aciduria accompanied by other acyl-CoA dehydrogenase substrates;
    excluded by the isolated pattern in GA3.
  evidence:
  - reference: PMID:12555941
    reference_title: "Glutaric aciduria type III: a distinctive non-disease?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      glutaric aciduria type II (multiple acyl-CoA dehydrogenation defect), and
      secondary forms of glutaric aciduria (for example due to intestinal
      infections or mitochondrial dysfunction) could be excluded.
    explanation: GA2 and secondary glutaric aciduria are excluded in GA3.
treatments:
- name: Antibiotic trial to reduce bacterial glutarate production
  description: >-
    No treatment is established or generally required. In a single
    symptomatic child with cyclic vomiting, an antibiotic trial intended to
    reduce intestinal bacterial glutaric acid production was followed by
    significant clinical improvement. This is an uncontrolled single-case
    observation.
  treatment_term:
    preferred_term: antibiotic therapy
    term:
      id: NCIT:C15620
      label: Antibiotic Therapy
  therapeutic_modality: SMALL_MOLECULE
  target_mechanisms:
  - target: Gut Bacterial Glutarate Production
    description: Intended to reduce bacterial glutarate production.
  evidence:
  - reference: PMID:28766179
    reference_title: "Glutaric Aciduria Type 3: Three Unrelated Canadian Cases, with Different Routes of Ascertainment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A trial of antibiotic treatment, to minimise bacterial GA production,
      was followed by significant clinical improvement.
    explanation: Single-patient report of improvement after antibiotics.
- name: Genetic counseling
  description: >-
    Counseling on autosomal recessive inheritance and on the uncertain,
    probably benign, clinical significance of the biochemical finding.
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:28766179
    reference_title: "Glutaric Aciduria Type 3: Three Unrelated Canadian Cases, with Different Routes of Ascertainment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Clinicians encountering a patient with GA3 therefore still face a dilemma
      of whether or not this should be dismissed as irrelevant.
    explanation: The counseling problem is the uncertain significance of the diagnosis.
animal_models:
- name: Sugct knockout mouse
  species: Mouse
  genotype: Sugct-/-
  publication: PMID:31722069
  description: >-
    Sugct knockout mice show imbalanced kidney lipid and acylcarnitine
    metabolism and gut microbiome changes, with age-dependent kidney, liver and
    adipose pathology and an obesity-related phenotype that a high-lysine diet
    accelerates. The human counterparts of these findings have not been
    reported.
  modeled_mechanisms:
  - target: SUGCT Loss of Function
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      The knockout removes SUGCT, the primary lesion of GA3, and was made to
      study the disease mechanism.
    limitations: >-
      The knockout's kidney, liver, adipose and metabolic-syndrome-like
      phenotypes have no reported human counterpart; GA3 patients are largely
      asymptomatic despite high urinary glutarate.
    evidence:
    - reference: PMID:31722069
      reference_title: "Knockout of the non-essential gene SUGCT creates diet-linked, age-related microbiome disbalance with a diabetes-like metabolic syndrome phenotype."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        To study the disease mechanism, we generated SugctKO mice and uncovered
        imbalanced lipid and acylcarnitine metabolism in kidney in addition to
        changes in the gut microbiome.
      explanation: The knockout was generated as a model of the GA3 lesion itself, SUGCT loss.
  - target: Gut Bacterial Glutarate Production
    relationship: PERTURBS
    fidelity: UNKNOWN
    limitations: >-
      Metabolic syndrome-like and kidney phenotypes in the knockout have no
      reported human counterpart; GA3 patients are largely asymptomatic. The
      study reports dysbiosis as a consequence of SUGCT loss (host to
      microbiome), the reverse direction of this entry's bacteria-to-glutarate
      edge, so this link does not support that edge.
    evidence:
    - reference: PMID:31722069
      reference_title: "Knockout of the non-essential gene SUGCT creates diet-linked, age-related microbiome disbalance with a diabetes-like metabolic syndrome phenotype."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        SUGCT loss of function contributes to gut microbiota dysbiosis, leading
        to age-dependent pathological changes in kidney, liver, and adipose
        tissue.
      explanation: Shows microbiome involvement in the knockout.
  evidence:
  - reference: PMID:31722069
    reference_title: "Knockout of the non-essential gene SUGCT creates diet-linked, age-related microbiome disbalance with a diabetes-like metabolic syndrome phenotype."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Furthermore, we show that the SugctKO kidney pathology is accelerated and
      exacerbated by a high-lysine diet.
    explanation: Diet interaction in the knockout model.
- name: 129 substrain mice (naturally occurring SUGCT deficiency)
  species: Mouse
  genotype: Sugct 129/129
  background: 129S2/SvPasCrl
  publication: PMID:33483254
  description: >-
    Inbred 129 substrain mice carry a naturally occurring SUGCT deficiency that
    produces a GA3 urinary trait. Crossing it onto the GA1 mouse lowered
    3-hydroxyglutarate and glutarylcarnitine, showing SUGCT supplies
    glutaryl-CoA in vivo.
  modeled_mechanisms:
  - target: Free Glutarate Accumulation and Urinary Loss
    relationship: RECAPITULATES
    fidelity: HIGH
    evidence:
    - reference: PMID:33483254
      reference_title: "Glutaric aciduria type 3 is a naturally occurring biochemical trait in inbred mice of 129 substrains."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Molecular and biochemical analyses in an F2 population of the parental
        C57BL/6J and 129S2/SvPasCrl strains (B6129F2) confirmed that the GA3
        trait occurred in Sugct129/129 animals.
      explanation: The urinary GA3 trait segregates with Sugct genotype.
  evidence:
  - reference: PMID:33483254
    reference_title: "Glutaric aciduria type 3 is a naturally occurring biochemical trait in inbred mice of 129 substrains."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      We found that GA1 mice with SUGCT deficiency have decreased excretion of
      urine 3-hydroxyglutaric acid and decreased levels glutarylcarnitine in
      urine, plasma and kidney.
    explanation: SUGCT deficiency reduces glutaryl-CoA-derived metabolites in vivo.
discussions:
- discussion_id: controversy_ga3_clinical_significance
  prompt: Is glutaric acidemia type 3 a disease, or a benign biochemical trait ascertained through unrelated illness?
  kind: CONTROVERSY
  status: OPEN
  attaches_to:
  - disease#Glutaric Acidemia Type 3
  - phenotypes#Episodic vomiting
  rationale: >-
    The enzymatic defect and its urinary signature are well established, but
    no clinical phenotype has been attributed to GA3. The Amish probands and a
    newborn-screened infant were asymptomatic. Symptomatic reports are mostly
    confounded: one child had a 6q terminal deletion, one had Graves
    hyperthyroidism and gastroenteritis at ascertainment, one had a second
    diagnosis of BCAP31-related syndrome that explained his neurodevelopmental
    findings, and two had trichothiodystrophy type 4 from a deletion that also
    removed SUGCT. A white-matter abnormality on MRI in one patient and cyclic
    vomiting in another remain unexplained single observations.
  evidence:
  - reference: PMID:18926513
    reference_title: "Genetic mapping of glutaric aciduria, type 3, to chromosome 7 and identification of mutations in c7orf10."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: There was no consistent clinical phenotype associated with GA3.
    explanation: The founding genetic series found no consistent phenotype.
  - reference: PMID:39101156
    reference_title: "Whole exome sequencing reveals a dual diagnosis of BCAP31-related syndrome and glutaric aciduria III."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ultimately, WES confirmed a diagnosis of BCAP31-related syndrome, a rare
      neurological disorder, which explained the patient's presenting symptoms.
    explanation: A symptomatic GA3 patient whose symptoms were explained by a second diagnosis.
  - reference: PMID:39101156
    reference_title: "Whole exome sequencing reveals a dual diagnosis of BCAP31-related syndrome and glutaric aciduria III."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: GA III has historically been considered clinically benign, with few reported cases.
    explanation: A 2024 case report restates the prevailing view that GA3 is clinically benign and rarely reported.
  - reference: PMID:31722069
    reference_title: "Knockout of the non-essential gene SUGCT creates diet-linked, age-related microbiome disbalance with a diabetes-like metabolic syndrome phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      Although mutations in Sugct lead to Glutaric Aciduria Type 3 disease in
      humans, patients remain largely asymptomatic despite high levels of
      glutarate in the urine.
    explanation: >-
      The knockout-mouse study's framing of the human clinical picture: most
      patients are asymptomatic despite marked glutaric aciduria. Graded from
      the quoted sentence, which describes human patients, not the mouse work.
  - reference: PMID:32779420
    reference_title: "Two patients with glutaric aciduria type 3: a novel mutation and brain magnetic resonance imaging findings."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Symmetrical periventricular and deep cerebral white matter abnormalities
      were detected on his brain magnetic resonance imaging (MRI).
    explanation: An unexplained imaging finding in one patient, which keeps the question open.
  - reference: PMID:28766179
    reference_title: "Glutaric Aciduria Type 3: Three Unrelated Canadian Cases, with Different Routes of Ascertainment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      However, we consider that it would be premature to assume that this
      condition is completely benign in all individuals at all times.
    explanation: Argues against declaring GA3 fully benign.
references:
- reference: PMID:18926513
  title: Genetic mapping of glutaric aciduria, type 3, to chromosome 7 and identification of mutations in c7orf10.
- reference: PMID:28766179
  title: "Glutaric Aciduria Type 3: Three Unrelated Canadian Cases, with Different Routes of Ascertainment."
notes: >-
  The recurrent missense allele is numbered p.Arg299Trp (c.895C>T) in the
  original mapping paper, p.Arg336Trp in the enzyme characterisation, and
  p.Arg329Trp in a later case-series table; these refer to different reference
  transcripts. The older synonym "glutaryl-CoA oxidase deficiency" reflects a
  pre-2008 hypothesis of a peroxisomal defect that the identification of SUGCT
  superseded. No GeneReviews chapter covers this disorder (Bookshelf index
  snapshot 2026-09-10 and live PubMed title search both returned none).
📚

References & Deep Research

References

2
PMID:18926513
Genetic mapping of glutaric aciduria, type 3, to chromosome 7 and identification of mutations in c7orf10.
No top-level findings curated for this source.
PMID:28766179
Glutaric Aciduria Type 3: Three Unrelated Canadian Cases, with Different Routes of Ascertainment.
No top-level findings curated for this source.

Deep Research

1

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

Evaluations and curation notes (2)

Review rounds 1-2 and OpenScientist deep-research reconciliation · 2026-10-15T04:28:59Z · View source

Review round 1: added reference_title to every evidence item, each copied from the title frontmatter of its references_cache file (commit e30f152e1). Review round 2: linked the Sugct knockout mouse to the SUGCT Loss of Function node with relationship RECAPITULATES (fidelity MODERATE), and added a limitations note to its Gut Bacterial Glutarate Production link stating that the study reports dysbiosis as a consequence of SUGCT loss, the reverse direction of the entry's bacteria-to-glutarate edge, so that link does not support the edge (commit 2ee7cbca4). The genetic record keeps relationship_type CAUSATIVE although ClinGen rates SUGCT-GA3 Moderate; the record's notes explain that CAUSATIVE refers to the biochemical trait that defines the disorder, not to any clinical illness, and the ClinGen Moderate assertion is recorded under gene_disease_validity. Deep research: Falcon was unavailable. The Asta report was off-topic and was not committed. A claude_code report was produced without PubMed access and was not committed. The first OpenScientist run hit the provider's one-hour timeout. A second OpenScientist run completed (16/16 references resolved; one unresolved term, CHEBI:45009, which was not bound) and is committed with its citations file and artifacts. Reconciliation against that report. Added two evidence items to the controversy_ga3_clinical_significance discussion, both from references the entry already cites: PMID:39101156 ('GA III has historically been considered clinically benign, with few reported cases.') and PMID:31722069 ('patients remain largely asymptomatic despite high levels of glutarate in the urine'). Both are graded HUMAN_CLINICAL with quote_role BACKGROUND, since each sentence states the human clinical picture in the paper's framing rather than reporting the paper's own result; 31722069 is a mouse study. Left out, and why. The eight PMIDs the report cites that the entry did not: 17879145, 20923787, 21431622 and 27853989 are about glutaric aciduria type 1 (pathogenesis and management guidelines), which the report itself uses only as contrast. 26098869 (pancreatic cancer GWAS) and 41733842 (frailty GWAS) report common-variant associations at the SUGCT locus, which are not the Mendelian disorder. 38228059 is a chicken selection scan. 35500672 is a GC-MS method for separating 2- and 3-hydroxyglutarate whose abstract does not mention GA3. The report's gnomAD constraint figures, carrier-frequency estimate (about 1 in 440) and biallelic birth-prevalence estimate are the provider's own calculations with no citable source, so no number was taken from them. Its statements that tandem-MS acylcarnitine newborn screening misses GA3 and that lysine restriction is rational were not added because the report gives no source that states them. The ClinVar counts and the PDB structure identifiers were also not added. Everything else in the report was already in the entry. Validation: just validate, count-verified-snippets (50/50), validate-terms, check-entity-refs, check-causal-targets, check-duplicate-keys, check-enum-values, check-snippet-grading, check-retired-support-prose, normalize-cache, validate-disorders all passed; check-gene-activity-grounding reports nothing for this entry.

Create: Glutaric_Acidemia_Type_3 · 2026-10-15T02:22:44Z · View source

New entry for glutaric acidemia type 3 (MONDO:0009283, SUGCT), claim issue #14246. Lump/split decision: DISEASE. MONDO carries a dedicated term with a causal gene, ClinGen has a gene-disease validity curation for exactly this MONDO term, and the disorder is a distinct biochemical entity separate from GA1 and GA2; the clinical-significance question is recorded as a CONTROVERSY discussion rather than resolved by declaring the term out of scope. Deep research: falcon was requested but failed authentication (503) twice, including with --fallback, which did not fall back; a claude_code report was then generated, but its own text states that PubMed access was denied, that it made one web search, and that it gives no verified quotes; its 4 cited PMIDs were all found independently and are used here. The report was not committed because it contributes no content beyond those identifiers. Literature research was therefore done directly through PubMed search (SUGCT, glutaric aciduria type 3/III, C7orf10). just preflight-dr was not run because the local MONDO build is absent and the shared disk was too full to download it; the report is plainly about SUGCT/GA3. Pathograph: SUGCT loss of function -> impaired glutarate re-esterification -> free glutarate accumulation and urinary loss -> glutaric aciduria; lysine/tryptophan catabolic flux and gut bacterial glutarate production feed the accumulation node. Gastrointestinal symptoms (episodic vomiting) hang off an EMERGING mechanistic hypothesis with causal_link_type UNKNOWN because attribution to GA3 is unproven. ClinGen Moderate tier copied from its CGGV record; relationship_type kept CAUSATIVE with a note explaining it refers to the biochemical trait. No GeneReviews chapter exists (just check-genereviews --online: NO_CHAPTER). Validation: just validate, validate-terms, count-verified-snippets, check-entity-refs, check-causal-targets, check-duplicate-keys, validate-disorders.

OpenScientist ▸
Glutaric Acidemia Type 3 (GA3): A Comprehensive Disease Characteristics Report
openscientist-autonomous 16 citations 2026-10-15T04:21:58.773113

Glutaric Acidemia Type 3 (GA3): A Comprehensive Disease Characteristics Report

Disease: Glutaric Acidemia Type 3 (Glutaric Aciduria Type 3, GA3) MONDO ID: MONDO:0009283 | OMIM: 231690 | Gene: SUGCT (C7orf10), gene OMIM 609187 Category: Mendelian, autosomal recessive inborn error of metabolism

Summary

Glutaric acidemia type 3 (GA3) is a rare autosomal-recessive inborn error of organic-acid metabolism caused by biallelic loss-of-function variants in SUGCT (also called C7orf10), which encodes the mitochondrial enzyme succinyl-CoA:glutarate CoA-transferase. The enzyme's normal function is to recapture free glutarate — generated during lysine and tryptophan catabolism, and substantially by the gut microbiome — by transferring a CoA moiety from succinyl-CoA to produce glutaryl-CoA. When SUGCT activity is lost, free glutarate accumulates and spills into the urine, producing an isolated glutaric aciduria with characteristically normal-to-low 3-hydroxyglutaric acid and low glutarylcarnitine/glutarylglycine — a biochemical signature that cleanly distinguishes GA3 from the clinically severe glutaric acidemia type 1 (GA1/GCDH deficiency) and from GA2/MADD.

The central conclusion of this investigation is that GA3 is, in the overwhelming majority of cases, a benign biochemical trait — a likely "non-disease." Only roughly nine individuals had been described in the literature as of 2018, most affected people remain asymptomatic despite markedly elevated urinary glutarate, and the original cohort of six patients showed no consistent clinical phenotype. Population-genetics data reinforce this: SUGCT is loss-of-function tolerant and non-essential in gnomAD (pLI ≈ 0; observed/expected LoF ≈ 0.75), meaning that heterozygous and even biallelic loss of the gene is well tolerated at the population level. When severe multisystem disease is reported in a "GA3 patient," it most often reflects ascertainment bias, coincidental comorbidity, or a contiguous-gene deletion that removes the neighbouring MPLKIP gene (causing trichothiodystrophy type 4) in addition to SUGCT.

Mechanistically, the glutarate burden is strongly modulated by gene–environment interactions: the gut microbiome is a major source of glutarate, and in both a Sugct-knockout mouse and a symptomatic human patient, antibiotic treatment reduced glutarate and improved outcomes. Dietary lysine load similarly worsens metabolic phenotypes in the mouse model. Diagnosis rests on urine organic acid analysis (GC-MS) followed by SUGCT molecular confirmation; because glutarylcarnitine is not elevated, standard tandem-MS acylcarnitine newborn screening does not detect GA3. There is no disease-specific therapy; management is supportive, and genetic counseling is the principal preventive measure. The main clinical risk GA3 poses is not organ damage but a diagnostic odyssey — an isolated urinary glutarate elevation can trigger extensive workup and risks mis-attribution of unrelated symptoms to SUGCT deficiency.

Key Findings

Finding 1 — GA3 is caused by biallelic SUGCT (C7orf10) variants, inherited autosomal recessively

GA3 is a Mendelian autosomal-recessive disorder. In the landmark mapping study, six unrelated GA3 patients each carried two pathogenic SUGCT/C7orf10 alleles, and homozygosity mapping localized the locus to a 4.7 Mb region on chromosome 7p14 (PMID: 18926513). The reported alleles included the Amish founder missense c.895C>T (p.Arg299Trp) together with two nonsense alleles, c.322C>T (p.Arg108Ter) and c.424C>T (p.Arg142Ter). The study concluded: "Two pathogenic alleles were identified in each of the six patients. There was no consistent clinical phenotype associated with GA3." A further pathogenic missense allele, p.Arg322Trp (c.964C>T), was later reported in a homozygous patient (PMID: 32779420). The enzymatic basis is unambiguous: "GA3 is associated with decreased conversion of free glutaric acid to glutaryl-coA, reflecting deficiency of succinate-hydroxymethylglutarate coA-transferase, caused by variants in the SUGCT (C7orf10) gene" (PMID: 28766179).

Note on nomenclature: transcript-dependent residue numbering means p.Arg299Trp, p.Arg322Trp, and p.Arg329Trp can refer to the same underlying residue across isoforms (e.g., NM_001193311). Care is needed when reconciling variants across reports.

Finding 2 — SUGCT enzyme mechanism: succinyl-CoA-dependent conversion of glutarate to glutaryl-CoA

SUGCT is a mitochondrial CoA-transferase operating in the lysine/tryptophan catabolic pathway. It converts free glutarate to glutaryl-CoA using succinyl-CoA as the CoA donor, thereby preventing urinary loss of the organic acid: "SUGCT catalyzes the succinyl-CoA-dependent conversion of glutaric acid into glutaryl-CoA preventing urinary loss of the organic acid" (PMID: 33483254). When the enzyme is deficient, the hallmark is an isolated elevation of urinary free glutarate with elevated molar ratios of glutarate to its downstream derivatives — "urine molar ratios of glutarate to its derivatives (3-hydroxyglutarate, glutarylcarnitine, and glutarylglycine) were elevated, suggesting impaired formation of glutaryl-CoA" (PMID: 18926513). Critically, 3-hydroxyglutaric acid is low/normal, which is the key biochemical discriminator from GA1.

Finding 3 — GA3 is largely a benign biochemical trait ("non-disease")

The accumulated clinical literature indicates GA3 is generally a benign trait. As of 2018 only nine individuals had been described, and the condition is "generally considered a likely 'non-disease,' but this is based on limited supporting information, with only nine individuals with GA3 described in the literature" (PMID: 28766179). The original six-patient cohort showed no consistent clinical phenotype (PMID: 18926513). Mouse data concur: "Although mutations in Sugct lead to Glutaric Aciduria Type 3 disease in humans, patients remain largely asymptomatic despite high levels of glutarate in the urine" (PMID: 31722069). Non-specific symptoms occasionally reported (developmental delay, hypotonia, GI disturbance/cyclic vomiting, white-matter MRI changes) are confounded by ascertainment bias and co-occurring conditions.

Finding 4 — The gut microbiome is a major source of glutarate; antibiotics reduce it (gene–environment interaction)

A defining feature of GA3 biology is that much of the circulating/urinary glutarate is of microbial origin. In Sugct-knockout mice, "After SugctKO mice were treated with antibiotics, metabolites were comparable to WT, indicating that the microbiome affects metabolism in SugctKO mice" (PMID: 31722069). This was mirrored clinically: in a GA3 patient with severe cyclic vomiting, "A trial of antibiotic treatment, to minimise bacterial GA production, was followed by significant clinical improvement" (PMID: 28766179). The knockout mouse also develops diet- and age-dependent metabolic syndrome, with gut dysbiosis, imbalanced lipid/acylcarnitine metabolism in kidney, obesity, and kidney/liver pathology accelerated by a high-lysine diet. This establishes a clear gene–environment axis in which diet (lysine) and microbiome composition set the glutarate burden.

Finding 5 — Contiguous-gene deletions of SUGCT + adjacent MPLKIP cause combined trichothiodystrophy type 4 and GA3

Several of the more severe "GA3" presentations are explained by contiguous-gene deletions at chromosome 7p14 that remove both MPLKIP (the gene for trichothiodystrophy type 4, TTD4) and SUGCT. A 125 kb homozygous deletion including both genes was reported in a Peruvian girl with microcephaly, short stature, intellectual disability and brittle hair: "Chromosome microarray analysis showed a 125 kb homozygous pathogenic deletion, which includes genes MPLKIP and SUGCT, not described before" (PMID: 29421601). A second independent case confirmed the mechanism: "To the best of our knowledge, our patient is the second case with co-occurrence of trichothiodystrophy type 4 and glutaric aciduria type 3, resulting from a contiguous gene deletion" (PMID: 37064336), presenting with hypotonia, failure to thrive, microcephaly, brittle hair and hypertransaminasemia. The severe neurocutaneous features in these patients derive from MPLKIP loss (TTD4), not SUGCT deficiency.

Finding 6 — SUGCT gene structure and ClinVar variant landscape support uncertain pathogenicity

SUGCT = ENSG00000175600, located chr7:40,135,005–40,860,763 (GRCh38, ~725 kb), HGNC:16001, gene OMIM 609187; disease OMIM 231690. The ClinVar landscape reflects genuine uncertainty about pathogenicity: of 169 SUGCT ClinVar variants, only 1 Pathogenic and 4 Likely pathogenic (e.g., c.514C>T p.Arg172Ter; splice c.152+1G>A, c.313-1G>C; nonsense c.782G>A p.Trp261Ter, c.1014G>A p.Trp338Ter), versus 87 VUS, 24 benign, 41 likely benign, and 8 conflicting. Pathogenic variant types are predominantly nonsense/splice/frameshift (loss-of-function) plus missense hypomorphs.

Finding 7 — Common SUGCT variants show GWAS associations distinct from Mendelian GA3

Common non-coding/regulatory variation at the SUGCT locus (7p13/7p14) associates with complex traits independent of biallelic GA3. A genome-wide significant, protective association with pancreatic cancer susceptibility was reported: "7p13 (SUGCT, rs17688601, OR = 0.88, 95% CI = 0.84-0.92, P = 1.41 × 10(-8))" (PMID: 26098869). SUGCT also appears among frailty GWAS loci — "rs12672085 (SUGCT)" (PMID: 41733842) — and in selection/adaptation scans in chickens (PMID: 38228059). These complex-trait signals are mechanistically distinct from the rare Mendelian GA3 phenotype.

Finding 8 — SUGCT is LoF-tolerant (non-constrained) in gnomAD, consistent with a non-essential gene

gnomAD constraint metrics for SUGCT (MANE transcript ENST00000335693 / NM_001193313) demonstrate no depletion of loss-of-function variants: pLI ≈ 6.1×10⁻¹¹ (~0), observed/expected LoF (oe_lof) = 0.745 (90% CI 0.58–0.97), observed LoF = 41 vs expected 55, and missense Z = −0.37 (no missense constraint). This independently predicts that losing SUGCT is well tolerated — concordant with the mouse literature, which emphasizes "the importance of non-essential genes with no readily detectable early phenotype" (PMID: 31722069).

Finding 9 — Estimated carrier frequency ~1 in 440 (pLoF lower bound); GA3 is underdiagnosed

Summing gnomAD v4 predicted loss-of-function (pLoF) SUGCT allele frequencies gives q(pLoF) ≈ 1.15×10⁻³, implying a heterozygous carrier frequency ≈ 0.23% (~1 in 437) and a biallelic-pLoF birth prevalence ≈ q² ≈ 1.3×10⁻⁶ (~0.13 per 100,000). The most common pLoF alleles are p.Arg101Ter (AF 2.3×10⁻⁴), splice c.152+1G>A (1.5×10⁻⁴) and c.484+1G>A (1.3×10⁻⁴). The true biochemical GA3 prevalence is higher, because common missense hypomorphs (e.g., the founder p.Arg299Trp) also cause the trait. The primary literature concluded directly: "Examination of allele frequencies underlines the fact that GA3 is underdiagnosed" (PMID: 28766179).

Finding 10 — Mouse models: naturally occurring GA3 in 129 substrains and engineered SugctKO

GA3 exists as a naturally occurring biochemical trait in inbred 129-substrain mice (e.g., 129S2/SvPasCrl) due to Sugct deficiency, confirmed in a C57BL/6J × 129S2 F2 population: "we describe the presence of a GA3 trait in mice of 129 substrains due to SUGCT deficiency" (PMID: 33483254). An engineered SugctKO mouse reproduces urinary glutarate elevation and reveals the diet/age-dependent pathology: "we generated SugctKO mice and uncovered imbalanced lipid and acylcarnitine metabolism in kidney in addition to changes in the gut microbiome" (PMID: 31722069), with an obesity-related phenotype, lipid accumulation in kidney/liver, adipocyte "crown-like" structures, and kidney pathology worsened by high-lysine diet and normalized by antibiotics.

Finding 11 — Diagnosis rests on urine organic acids (isolated glutarate, low 3-OHGA) plus SUGCT sequencing

GA3 is identified by urine organic acid analysis (GC-MS) showing isolated elevation of free glutaric acid with normal/low 3-hydroxyglutaric acid and low glutarylcarnitine/glutarylglycine (PMID: 18926513). This distinguishes GA3 from GA1 (high 3-OHGA, elevated C5DC glutarylcarnitine, striatal injury, macrocephaly) and GA2/MADD (broad organic acid/acylcarnitine abnormalities). Because glutarylcarnitine (C5DC) is NOT elevated, standard tandem-MS acylcarnitine newborn screening typically does not flag GA3; instead, a population urine-based newborn screening program detected one asymptomatic case: "the third was identified by a population urine-based newborn screening programme and has so far remained asymptomatic" (PMID: 28766179). Confirmation is by SUGCT molecular testing (single-gene, panel, WES, or WGS); chromosomal microarray detects contiguous-gene deletions (with MPLKIP).

Finding 12 — SUGCT protein (UniProt Q9HAC7): mitochondrial 438-aa CoA-transferase with broad dicarboxylate specificity

UniProt Q9HAC7: Succinyl-CoA:glutarate CoA-transferase, 438 amino acids, localized to mitochondrion. The primary reaction is glutarate + succinyl-CoA ⇌ glutaryl-CoA + succinate (reversible). It prefers succinyl-CoA/glutarate-CoA donors but also acts on 3-hydroxy-3-methylglutarate, hexanedioate (adipate), and itaconate, participating in a dicarboxylate-CoA recycling process. Experimental structures have been deposited: PDB 9BR6, 9BR7.

Finding 13 — Clinical bottom-line: historically benign, but isolated glutarate can trigger a diagnostic odyssey

In a patient with developmental delay, microcephaly, hypotonia and feeding difficulties, biochemical testing revealed an isolated marked elevation of glutaric acid without related-metabolite elevations, and WES was needed to resolve the picture, which included GA3: "GA III has historically been considered clinically benign, with few reported cases" (PMID: 39101156). The lesson is that an isolated glutarate finding is biochemically non-specific for severe disease and warrants genetic confirmation plus evaluation for alternative/co-occurring diagnoses (e.g., contiguous-gene TTD4, or unrelated conditions) before attributing symptoms to SUGCT deficiency.

Report by Template Section

1. Disease Information

  • Overview: GA3 is a rare autosomal-recessive inborn error of lysine/tryptophan metabolism characterized by isolated glutaric aciduria due to deficiency of succinyl-CoA:glutarate CoA-transferase (SUGCT). It is generally benign.
  • Identifiers: MONDO:0009283; OMIM 231690 (disease); gene OMIM 609187; HGNC:16001 (SUGCT); Ensembl ENSG00000175600; UniProt Q9HAC7. ICD-10: E72.3 (disorders of lysine and hydroxylysine metabolism, the closest code). MeSH indexing falls under amino-acid metabolism inborn errors (no GA3-specific MeSH term).
  • Synonyms: Glutaric aciduria type 3; glutaric aciduria type III; GA3; GA-III; C7orf10 deficiency; SUGCT deficiency; succinyl-CoA:glutarate CoA-transferase deficiency.
  • Information source: A blend of individual case reports (clinical case level) and aggregated disease-level resources (OMIM, Orphanet) plus population databases (gnomAD, ClinVar). Evidence is dominated by small case series given rarity.

2. Etiology

  • Causal factor: Genetic — biallelic pathogenic SUGCT variants (Finding 1). Loss-of-function (nonsense/splice/frameshift) and hypomorphic missense alleles.
  • Genetic risk: Inheriting two SUGCT pathogenic alleles; founder allele p.Arg299Trp (Amish). Carrier frequency ~1/440 (Finding 9).
  • Environmental risk/modifiers: Dietary lysine load and gut-microbiome glutarate production raise the glutarate burden (Findings 4, 10). These are modifiers of the biochemical phenotype, not independent causes.
  • Protective factors: Antibiotic suppression of glutarate-producing gut bacteria lowers glutarate (Finding 4). No established germline protective alleles for GA3.
  • Gene–environment interaction: Strong — SUGCT genotype sets baseline; microbiome + diet set the realized glutarate level and any symptoms (Findings 4, 10).

3. Phenotypes

GA3 has no obligate clinical phenotype; the defining feature is a laboratory abnormality (Findings 2, 3).

Phenotype Type HPO term Onset Severity Frequency
Glutaric aciduria (isolated) Laboratory abnormality HP:0003150 (Glutaric aciduria) Congenital/lifelong Biochemical ~100% (defining)
Asymptomatic — — — — Majority
Developmental delay Clinical sign HP:0001263 Childhood Variable Rare, likely confounded
Muscular hypotonia Clinical sign HP:0001252 Infancy Variable Rare
Cyclic vomiting / GI disturbance Symptom HP:0002572 / HP:0011968 Variable Variable Rare, microbiome-linked
White-matter MRI abnormality Imaging/lab HP:0002500 (Leukoencephalopathy) Variable Variable Rare, non-specific

Quality of life: For the asymptomatic majority, negligible impact. Severe QoL impact in reported cases is generally attributable to comorbidities or contiguous-gene TTD4 (Finding 5).

4. Genetic/Molecular Information

  • Causal gene: SUGCT / C7orf10 (HGNC:16001; gene OMIM 609187) — Findings 1, 6.
  • Variant classes: nonsense (p.Arg108Ter, p.Arg142Ter, p.Arg101Ter, p.Trp261Ter, p.Trp338Ter, p.Arg172Ter), splice (c.152+1G>A, c.313-1G>C, c.484+1G>A), missense hypomorphs (p.Arg299Trp founder; p.Arg322Trp) — Findings 1, 6, 9.
  • ClinVar: 169 variants; 1 P / 4 LP / 87 VUS / 24 B / 41 LB / 8 conflicting (Finding 6) — high VUS burden reflecting uncertain pathogenicity.
  • Allele frequency: pLoF q ≈ 1.15×10⁻³; p.Arg101Ter AF 2.3×10⁻⁴ (Finding 9).
  • Origin: Germline (constitutional); no somatic relevance.
  • Functional consequence: Loss of function (enzyme deficiency) — Findings 2, 12.
  • Modifier genes: None established within GA3; MPLKIP is a contiguous neighbour whose co-deletion adds the TTD4 phenotype (Finding 5), not a severity modifier of SUGCT per se.
  • Epigenetic/chromosomal: No GA3-specific epigenetic mechanism. Chromosomal relevance = 7p14 microdeletions spanning SUGCT+MPLKIP (Finding 5).

5. Environmental Information

  • Environmental/metabolic factors: Dietary lysine; gut microbiome glutarate production (Findings 4, 10). Multiple gut bacterial pathways produce glutarate, consistent with the microbiome as a glutarate source.
  • Lifestyle: Diet composition (protein/lysine) is the main modifiable factor.
  • Infectious agents: None cause GA3; however, commensal/pathogenic gut bacteria are the relevant glutarate-producing agents, and antibiotics reduce glutarate (Finding 4).

6. Mechanism / Pathophysiology

Ordered causal chain (initiating lesion → clinical manifestation):

  1. Biallelic loss-of-function/hypomorphic variants in SUGCT → leads to reduced/absent mitochondrial succinyl-CoA:glutarate CoA-transferase activity. (demonstrated — Findings 1, 12)
  2. Loss of enzyme activity → results in failure to convert free glutarate to glutaryl-CoA using succinyl-CoA as donor. (demonstrated — Finding 2)
  3. Failure of glutarate recapture → leads to accumulation of free glutarate from (a) endogenous lysine/tryptophan catabolism and (b) gut-microbiome production. (demonstrated; microbiome contribution shown in mouse + human — Findings 4, 10)
  4. Glutarate accumulation → results in isolated glutaric aciduria with elevated glutarate:derivative molar ratios and low 3-hydroxyglutarate / low glutarylcarnitine. (demonstrated — Findings 2, 11)
  5. BRANCH A (majority): Because glutarate at these levels is not substantially neurotoxic and SUGCT is non-essential → leads to an asymptomatic/benign biochemical trait. (demonstrated — Findings 3, 8)
  6. BRANCH B (modifier-dependent, mouse-demonstrated / human-inferred): High-lysine diet + dysbiotic microbiome → leads to elevated glutarate/acylcarnitine and lipid imbalance → kidney/liver lipid accumulation, obesity-like metabolic syndrome, and in a human, severe cyclic vomiting improved by antibiotics. (mouse demonstrated; human inferred — Findings 4, 10)

  7. BRANCH C (contiguous-gene deletion): 7p14 microdeletion removing MPLKIP + SUGCT → results in combined trichothiodystrophy type 4 (brittle hair, microcephaly, ID, failure to thrive) plus GA3; the severe features derive from MPLKIP loss. (demonstrated — Finding 5)

  8. Molecular pathway: Lysine/tryptophan catabolism; dicarboxylate-CoA recycling (KEGG lysine degradation).

  9. Protein dysfunction: Loss of function of a 438-aa mitochondrial CoA-transferase (Q9HAC7); broad dicarboxylate specificity (adipate, itaconate, HMG) — Finding 12.
  10. Metabolic change: Amino-acid (lysine) catabolism defect; secondary lipid/acylcarnitine imbalance in mouse kidney (Finding 10).
  11. Subcellular compartment: Mitochondrion (GO:0005739). Biological process: GO:0019477 (L-lysine catabolic process); molecular function: GO:0008410 (CoA-transferase activity).
  12. Cell/tissue types (mouse, modifier branch): renal tubular cells, hepatocytes, adipocytes.
  13. CHEBI entities: glutaric acid (CHEBI:17859), glutaryl-CoA (CHEBI:57378), succinyl-CoA (CHEBI:57292), 3-hydroxyglutaric acid (CHEBI:45009).

7. Anatomical Structures Affected

  • Human (majority): None definitively; GA3 is a systemic biochemical trait detectable in urine (UBERON:0001088) and blood.
  • Reported/modifier involvement: CNS white matter (UBERON:0002316) — non-specific MRI changes; GI tract (UBERON:0001555) — cyclic vomiting.
  • Mouse modifier branch: kidney (UBERON:0002113), liver (UBERON:0002107), adipose tissue (UBERON:0001013).
  • Subcellular: mitochondrion (GO:0005739).
  • Lateralization: Not applicable (systemic/metabolic).

8. Temporal Development

  • Onset: Biochemical abnormality is congenital/lifelong (present from birth, detectable by urine screening). Clinical symptoms (when present) are variable and non-specific (Findings 11, 13).
  • Progression: The biochemical trait is stable/persistent. No progressive neurodegeneration characteristic of GA1. Modifier-driven metabolic syndrome in mice is age- and diet-dependent (Finding 10).
  • Course: Chronic lifelong biochemical trait; most individuals remain well.
  • Critical periods: None established as neurotoxic windows (unlike GA1's striatal vulnerability in infancy).

9. Inheritance and Population

  • Inheritance: Autosomal recessive (Finding 1).
  • Prevalence/incidence: Very rare in the literature (~9 reported by 2018); pLoF-based biallelic birth prevalence ≈ 0.13/100,000 as a lower bound, with true biochemical prevalence higher due to missense hypomorphs — underdiagnosed (Finding 9).
  • Carrier frequency: ~1 in 440 (pLoF-only lower bound) — Finding 9.
  • Penetrance: Biochemical penetrance appears high/complete (biallelic loss → glutaric aciduria); clinical penetrance is low (most asymptomatic) — Findings 3, 8.
  • Expressivity: Highly variable clinically; no consistent phenotype (Findings 1, 3).
  • Founder effect: p.Arg299Trp in the Amish population (Finding 1).
  • Consanguinity: Relevant (homozygous cases including contiguous-gene deletions in consanguineous families — Finding 5).
  • Sex ratio / anticipation / mosaicism: No sex bias reported; no anticipation (not a repeat disorder); no mosaicism specific to GA3.

10. Diagnostics

  • First-line: Urine organic acid analysis (GC-MS) — isolated ↑glutarate, low 3-OHGA, low glutarylglycine (Finding 11). Accurate 3-OHGA quantitation can require second-tier GC-MS methods to resolve the 2-/3-OHGA isomers (PMID: 35500672).
  • Acylcarnitine (plasma/DBS): C5DC (glutarylcarnitine) not elevated — standard MS/MS newborn screening misses GA3 (Finding 11).
  • Confirmation: SUGCT molecular testing — single-gene, metabolic gene panel, WES, or WGS; chromosomal microarray for contiguous-gene deletions with MPLKIP (Findings 5, 11).
  • Differential diagnosis: GA1 (GCDH; ↑3-OHGA, ↑C5DC, macrocephaly, striatal injury), GA2/MADD (broad acylcarnitine/organic acid abnormality), other organic acidurias.
  • Screening: Urine-based NBS can detect asymptomatic GA3 (Finding 11); not captured by MS/MS acylcarnitine NBS.

11. Outcome / Prognosis

  • Survival/mortality: No evidence of reduced survival attributable to isolated SUGCT deficiency; generally benign prognosis (Findings 3, 13).
  • Morbidity: Low in isolated GA3. Significant morbidity in reported cases is typically due to contiguous-gene TTD4 or unrelated comorbidity (Findings 5, 13).
  • Prognostic factors: Presence/absence of a contiguous-gene deletion (MPLKIP) is the strongest determinant of severe outcome; dietary/microbiome state modifies the biochemical and GI burden.
  • Recovery: Microbiome-driven symptoms (e.g., cyclic vomiting) may respond to antibiotics (Finding 4).

12. Treatment

  • No disease-specific therapy is established. Management is supportive (NCIT:C19678 supportive care).
  • Dietary: Lysine-restriction is biologically rational (mouse data, Finding 10) but not formally validated as beneficial in human GA3; it is a cornerstone in GA1.
  • Antibiotics: Rational for symptomatic, microbiome-driven cases (e.g., severe cyclic vomiting) — produced clinical improvement in one patient (Finding 4) — NCIT antibiotic therapy (NCIT:C15844).
  • Supportive care: Symptom management, nutrition support.
  • Pharmacogenomics / gene / cell / RNA therapies: None developed or applicable given the benign nature.
  • Combined TTD4+GA3 patients: managed for the TTD4 features (photosensitivity, hair/skin, developmental support).

13. Prevention

  • Primary: Not applicable in a classical sense; genetic counseling of carrier couples is the principal measure (Finding 9).
  • Secondary: Urine-based newborn/high-risk screening can detect GA3; because most cases are benign, the value of detection is mainly to avoid a diagnostic odyssey and prevent mis-attribution rather than to intervene (Findings 11, 13).
  • Genetic screening: Carrier screening, cascade testing in affected families; prenatal/PGT possible once familial variants known.
  • Tertiary: For symptomatic/modifier-driven cases, dietary lysine moderation and antibiotic trials may reduce the glutarate burden.

14. Other Species / Natural Disease

  • Taxonomy / natural model: Mus musculus (NCBI:txid10090) — GA3 occurs naturally in inbred 129 substrains due to Sugct deficiency (Finding 10).
  • Orthologous gene: mouse Sugct (Findings 8, 10).
  • Comparative biology: The mouse biochemical trait closely mirrors human (urinary glutarate elevation); SUGCT also appears in avian adaptation scans (chicken, Finding 7), indicating conservation.
  • Zoonosis: Not applicable.

15. Model Organisms

  • Natural mouse model: 129-substrain mice (e.g., 129S2/SvPasCrl) — GA3 trait (Finding 10).
  • Engineered model: SugctKO mouse — recapitulates urinary glutarate elevation; reveals diet/age-dependent microbiome dysbiosis, kidney lipid/acylcarnitine imbalance, obesity-like metabolic syndrome; high-lysine diet exacerbates, antibiotics normalize (Findings 4, 10).
  • Phenotype recapitulation: Excellent for the biochemical trait and modifier biology; the mouse actually reveals more overt metabolic pathology than typical human cases, consistent with humans being largely asymptomatic.
  • Limitations: Human clinical penetrance is lower than the metabolic-syndrome phenotype seen in mice on provocative diets.
  • Other systems: No dedicated zebrafish/Drosophila/cell/organoid GA3 models identified; cellular/CRISPR models exist for the unrelated GA1 (GCDH), not GA3.

Mechanistic Model / Interpretation

  SUGCT biallelic LoF / hypomorphic variants (chr7p14; AR)
              │
              ▼
↓ mitochondrial succinyl-CoA:glutarate CoA-transferase activity
              │
              ▼
Free glutarate NOT recaptured into glutaryl-CoA
    ┌─────────┴───────────┐
endogenous lysine/Trp        GUT MICROBIOME
catabolism                   glutarate production
    └─────────┬───────────┘
              ▼
     ISOLATED GLUTARIC ACIDURIA  (↑glutarate; LOW 3-OHGA; LOW C5DC)
              │
┌─────────────────────┼─────────────────────────┐
▼                     ▼                         ▼
  BRANCH A (majority)   BRANCH B (modifiers)      BRANCH C (contiguous
  Benign / asymptomatic  high-lysine diet +        gene deletion)
  (SUGCT non-essential,  dysbiosis → metabolic     MPLKIP+SUGCT loss
   LoF-tolerant)         syndrome (mouse); cyclic  → TTD4 + GA3
         vomiting (human) →         (severe features
         improves w/ ANTIBIOTICS    from MPLKIP, not SUGCT)

The unifying interpretation is that GA3 is a biochemical marker, not a disease, in the large majority of cases. Three independent lines of evidence converge on this: (1) clinical — no consistent phenotype across reported patients and most remain asymptomatic; (2) population-genetic — SUGCT is LoF-tolerant (pLI≈0) and non-essential; and (3) mechanistic — the accumulating metabolite (glutarate) is not substantially neurotoxic at these levels, unlike GA1's glutaric/3-hydroxyglutaric acids. Severe presentations resolve into confounding comorbidity, dietary/microbiome modifiers, or contiguous-gene MPLKIP deletion. This has direct clinical consequence: an isolated urinary glutarate elevation should prompt (a) exclusion of GA1/GA2, (b) SUGCT confirmation, (c) chromosomal microarray if dysmorphic/neurocutaneous features are present, and (d) caution before attributing any symptom to SUGCT deficiency.

A key contrast with GA1 clarifies why GA3 is benign: in GA1, loss of glutaryl-CoA dehydrogenase causes accumulation of glutaryl-CoA, glutaric acid, and the neurotoxic 3-hydroxyglutaric acid, with glutaryl-CoA uncompetitively inhibiting α-ketoglutarate dehydrogenase and driving striatal excitotoxic injury. In GA3, the block is upstream of glutaryl-CoA formation — glutaryl-CoA is never made, 3-OHGA stays low, and the only consequence is urinary loss of free glutarate. The toxic intermediates of GA1 are simply not generated in GA3.

Evidence Base

PMID Title (abbrev.) Evidence type Supports
18926513 Genetic mapping of GA3 to chr7; C7orf10 mutations Human clinical/genetic F1, F2, F3, F11 (causal gene, biochemistry, no consistent phenotype)
28766179 Three Canadian GA3 cases Human clinical F1, F3, F4, F9, F11 ("non-disease", antibiotics, underdiagnosed, urine NBS)
31722069 SugctKO knockout mouse Model organism F3, F4, F8, F10 (asymptomatic, microbiome, non-essential, KO phenotype)
33483254 GA3 natural trait in 129 mice Model organism F2, F10 (enzyme reaction, natural model)
29421601 MPLKIP+SUGCT deletion, Peru Human clinical F5 (contiguous-gene TTD4+GA3)
37064336 2nd contiguous deletion TTD4+GA3 Human clinical F5
32779420 Novel p.Arg322Trp; brain MRI Human clinical F1 (new allele, white-matter MRI)
39101156 WES dual diagnosis incl. GA3 Human clinical F13 (benign reputation, diagnostic odyssey)
26098869 Pancreatic cancer GWAS (7p13 SUGCT) GWAS/computational F7 (common-variant complex-trait signal)
41733842 Frailty GWAS GWAS F7
38228059 Chicken adaptation scan Comparative genomics F7 (conservation/selection)
35500672 GC-MS 2-/3-OHGA separation Methods F11 (diagnostic accuracy)

Supporting context on GA1 (the severe sibling disorder used throughout as a contrast) is provided by PMID: 27853989, PMID: 21431622, PMID: 17879145 and PMID: 20923787; these underscore that GA1's neurotoxicity derives from 3-hydroxyglutaric/glutaric acid accumulation and glutaryl-CoA inhibition of α-ketoglutarate dehydrogenase — a mechanism GA3 does not share because 3-OHGA remains low and glutaryl-CoA is not formed.

Limitations and Knowledge Gaps

  1. Tiny evidence base. Fewer than ~15 human GA3 patients are reported, almost all as single cases/small series. No natural-history cohort or registry exists, so prevalence, penetrance, and symptom frequencies are estimates, not measured rates.
  2. Ascertainment bias. Patients are usually detected because they are symptomatic (undergoing metabolic workup), inflating the apparent association with developmental/neurological problems. The true population of biochemically-affected but asymptomatic individuals is unknown.
  3. Causality of reported symptoms is unproven. White-matter changes, developmental delay, and hypotonia reported in GA3 patients have not been causally linked to SUGCT deficiency and are plausibly coincidental.
  4. Prevalence uncertainty. The ~1/440 carrier frequency is a pLoF-only lower bound; missense hypomorphs (p.Arg299Trp) are not counted, so true carrier/affected rates are higher but unquantified.
  5. Human modifier data are thin. The diet–microbiome–glutarate axis is robustly demonstrated in mice but rests on a single human antibiotic-response anecdote.
  6. No formal QoL, mortality, or treatment-outcome studies exist for isolated GA3.
  7. Variant interpretation is difficult — 87/169 ClinVar variants are VUS, complicating molecular confirmation.

Proposed Follow-up Experiments / Actions

  1. Establish a GA3 natural-history registry combining urine-screening-ascertained (unbiased) and clinically-ascertained cases to directly measure clinical penetrance and symptom frequency.
  2. Systematic ascertainment via urine-based newborn/population screening to capture asymptomatic individuals and estimate true prevalence independent of symptom-driven bias.
  3. Human microbiome–metabolome study: quantify the fraction of urinary glutarate attributable to gut bacteria in confirmed GA3 patients (stable-isotope / antibiotic-challenge design) to formalize the mouse finding.
  4. Reclassify SUGCT VUS using functional CoA-transferase assays (leveraging the new PDB structures 9BR6/9BR7) and in-vitro expression of missense variants to resolve the large VUS burden.
  5. Controlled dietary-lysine intervention in the SugctKO mouse to define whether lysine restriction prevents the metabolic-syndrome branch, informing whether human dietary management is warranted.
  6. Always perform chromosomal microarray in any GA3 patient with dysmorphism, brittle hair, or neurodevelopmental features to detect contiguous-gene MPLKIP deletions (TTD4) that explain severe phenotypes.
  7. Diagnostic stewardship guidance: publish a decision pathway so that isolated glutaric aciduria with low 3-OHGA/low C5DC triggers SUGCT confirmation and explicit consideration of alternative causes before symptoms are attributed to GA3.

Report compiled from 13 confirmed findings across 5 investigation iterations and 27 reviewed papers. Evidence types span human clinical case series, model-organism (mouse) studies, population-genetic constraint analysis (gnomAD), and GWAS/comparative genomics.

Artifacts

Reference Validation

Checked with linkml-reference-validator 0.3.0.

Outcome Count
References checked 16
Resolved 16
Unresolved (possible confabulation) 0
Unverifiable 0
References weighed for topical relevance 16
On topic 6
Off topic 0

All extracted references resolved successfully.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome Count
Terms checked 23
Resolved 21
Unresolved (possible confabulation) 1
Obsolete 0
Unverifiable 1
Terms whose name was checked 11
Terms named correctly 4
Terms named as a different term 4
Terms whose name is worth a second look 3

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

  • HP:0001263 (1 mention) - the report calls it "Clinical sign"; HP calls it Global developmental delay
  • HP:0001252 (1 mention) - the report calls it "Clinical sign"; HP calls it Hypotonia
  • HP:0002500 (1 mention) - the report calls it "Leukoencephalopathy"; HP calls it Abnormal cerebral white matter morphology
  • UBERON:0002113 (1 mention) - the report calls it "Mouse modifier branch: kidney"; UBERON calls it kidney**

Unresolved terms

These identifiers do not exist in an ontology that resolved other terms from the same prefix, so they were most likely invented:

  • CHEBI:45009 (1 mention) - CHEBI does not contain this term

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

  • GO:0005739 (2 mentions) - the report calls it "Subcellular compartment: Mitochondrion", "Subcellular: mitochondrion"; GO calls it mitochondrion
  • CHEBI:17859 (1 mention) - the report calls it "CHEBI entities: glutaric acid"; CHEBI calls it glutaric acid**
  • UBERON:0002316 (1 mention) - the report calls it "Reported/modifier involvement: CNS white matter"; UBERON calls it white matter**, and lists "CNS white matter" among its other names

Terms named inconsistently

The report gives these identifiers more than one name of its own:

  • GO:0005739 - called "Subcellular compartment: Mitochondrion", "Subcellular: mitochondrion"