L-2-Hydroxyglutaric Aciduria

Mendelian MONDO:0009370 Pathograph 36 Organic Acidemia Inborn Error of Metabolism

L-2-Hydroxyglutaric aciduria (L2HGA) is a rare autosomal recessive neurometabolic disorder caused by biallelic pathogenic variants in the L2HGDH gene, which encodes a mitochondrial FAD-dependent L-2-hydroxyglutarate dehydrogenase. Loss of this metabolite-repair enzyme leads to systemic accumulation of L-2-hydroxyglutarate (L-2-HG), particularly in the brain and cerebrospinal fluid. The disease follows a slowly progressive course characterized by psychomotor delay, intellectual disability, epilepsy, cerebellar ataxia, and movement disorders. Brain MRI shows a distinctive pattern of subcortical white matter abnormalities with basal ganglia and dentate nuclei involvement. L2HGA patients also have an increased lifetime risk of central nervous system tumors. Treatment is primarily supportive with riboflavin and levocarnitine supplementation.

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6
Pathophys.
15
Phenotypes
36
Pathograph
1
Genes
7
Treatments
9
References
1
Deep Research
⚙

Pathophysiology

6
L2HGDH enzymatic deficiency
Biallelic pathogenic variants in L2HGDH reduce mitochondrial L-2-hydroxyglutarate dehydrogenase metabolite-repair activity, impairing conversion of L-2-hydroxyglutarate back to 2-ketoglutarate.
neuron link
L2HGDH link
organic acid metabolic process link
mitochondrion link
Downstream
L-2-hydroxyglutarate accumulation Loss of L2HGDH metabolite-repair activity causes progressive L-2-HG buildup in body fluids and brain.
Show evidence (2 references)
PMID:22391998 SUPPORT Human Clinical
"L-2-HG accumulates in L-2-HGA patients when L-2-HGDH is impaired"
Directly links impaired L-2-HGDH metabolite-repair activity to L-2-HG accumulation in L2HGA patients.
PMID:37113859 SUPPORT Human Clinical
"Targeted L2HGDH sequencing identified a homozygous pathogenic variant, c.829C>T (p.Arg227*) in L2HGDH gene in both girls."
Human case series confirms biallelic L2HGDH pathogenic variation in affected patients.
L-2-hydroxyglutarate accumulation
Loss of L-2-hydroxyglutarate dehydrogenase activity impairs the metabolite-repair pathway that clears L-2-hydroxyglutarate (L-2-HG), an aberrant off-pathway metabolite produced from alpha-ketoglutarate by L-malate dehydrogenase. L-2-HG accumulates in body fluids, with urinary L-2-HG 10-300 times above normal and plasma and CSF also elevated.
neuron link
organic acid metabolic process link
mitochondrion link
Downstream
L-2-hydroxyglutaric acid (urine) Systemic L-2-HG buildup is reflected by markedly increased urinary L-2-HG.
L-2-hydroxyglutaric acid (CSF) L-2-HG also accumulates in CSF, consistent with CNS enrichment of the metabolite.
L-2-hydroxyglutaric acid (plasma) L-2-HG accumulation is measurable in plasma as well as urine and CSF.
Urinary 2-OH-glutaric acid Standard urine organic acid testing detects elevated 2-hydroxyglutaric acid, with chiral testing assigning the L-enantiomer.
White-matter vulnerability and progressive leukoencephalopathy Chronic L-2-HG elevation drives selective white-matter injury and neuroinflammatory remodeling.
Mitochondrial dysfunction and metabolic reprogramming L-2-HG perturbs mitochondrial bioenergetics and shifts cellular metabolism toward anaerobic pathways.
Epigenetic dysregulation via inhibition of alpha-KG-dependent dioxygenases L-2-HG can interfere with alpha-KG-dependent chromatin enzymes, altering epigenetic regulation.
CNS neoplasm L2HGA is associated with increased CNS tumor risk, but human tumor methylation data indicate that the oncogenic intermediates are unresolved and not simply IDH-mutant-like hypermethylation.
Basal ganglia and cerebellar circuit involvement L2HGA neuroimaging repeatedly involves basal ganglia and dentate/cerebellar structures that map to extrapyramidal and cerebellar motor phenotypes.
Show evidence (2 references)
PMID:22391998 SUPPORT Human Clinical
"Accumulation of D-2-hydroxyglutarate (D-2-HG) and/or L-2-hydroxyglutarate (L-2-HG) in body fluids are the biochemical hallmarks of these disorders."
Directly supports L-2-HG accumulation as the biochemical hallmark of L2HGA.
PMID:22391998 SUPPORT Human Clinical
"The biochemical hallmark of L-2-HGA is the accumulation of urinary L-2-HG, which is 10 to 300 times increased in comparison to controls"
Supports the magnitude of urinary L-2-HG elevation in L2HGA.
White-matter vulnerability and progressive leukoencephalopathy
L-2-HG accumulation leads to selective vulnerability of subcortical cerebral white matter with basal ganglia and dentate nucleus involvement. In mouse models, L2HGDH deficiency causes progressive leukoencephalopathy with white matter abnormalities, extensive gliosis, microglia-mediated neuroinflammation, and expansion of oligodendrocyte progenitor cells.
oligodendrocyte link oligodendrocyte precursor cell link microglial cell link
myelination link reactive gliosis link
white matter link basal ganglion link dentate nucleus link
Downstream
Subcortical leukoencephalopathy White-matter vulnerability produces the characteristic centripetal subcortical leukoencephalopathy pattern on MRI.
Intellectual disability Chronic L2HGA white-matter and neurodegenerative involvement contributes to delayed cognitive development and intellectual disability.
Psychomotor retardation The slowly progressive neurodegenerative and white-matter phenotype presents as psychomotor delay from childhood.
Seizures Epilepsy is a frequent neurological consequence of the chronic L2HGA brain disease, though the immediate seizure mechanism is not fully resolved.
Hypotonia Early-stage motor pathway involvement may present with generalized hypotonia before later pyramidal signs become more prominent.
Spasticity Progressive white-matter and motor-pathway involvement can manifest as upper motor neuron signs and spasticity.
Macrocephaly Macrocephaly is frequently associated with the L2HGA cerebral white-matter disease pattern, but the exact growth intermediate remains uncertain.
Behavioral abnormality Behavioral problems occur with L2HGA neurodevelopmental involvement, though the specific circuit-level intermediate is unresolved.
Show evidence (2 references)
PMID:28137912 SUPPORT Model Organism
"KO mice exhibit white matter abnormalities, extensive gliosis, microglia-mediated neuroinflammation, and an expansion of oligodendrocyte progenitor cells (OPCs)."
Mouse model demonstrates leukoencephalopathy, gliosis, neuroinflammation, and OPC expansion.
PMID:37113859 SUPPORT Human Clinical
"Neuroradiological features of centripetal subcortical leukoencephalopathy with basal ganglia and dentate nuclei involvement are rather specific to L2HGA"
Human neuroimaging confirms the characteristic white matter and deep gray matter pattern.
Basal ganglia and cerebellar circuit involvement
L2HGA affects basal ganglia, globus pallidus/putamen/caudate, dentate nucleus, and cerebellar circuits on neuroimaging and neurological examination. These lesions provide a mechanistic bridge from the metabolic brain disease to extrapyramidal movement disorders and cerebellar signs.
basal ganglion link globus pallidus link putamen link caudate nucleus link dentate nucleus link cerebellum link
Downstream
Cerebellar ataxia Dentate/cerebellar involvement manifests clinically as ataxia.
Dystonia Basal ganglia involvement maps to extrapyramidal dystonia, including severe GPi-DBS-treated disease.
Dysarthria Cerebellar and basal ganglia circuit involvement produces slurred speech and dysarthria.
Intention tremor Dentate/cerebellar circuit involvement manifests as intention tremor.
Chorea Basal ganglia circuit involvement can present with choreic movements.
Gait ataxia Cerebellar and basal ganglia dysfunction manifests as a wide-based gait.
Show evidence (2 references)
PMID:37113859 SUPPORT Human Clinical
"Neuroradiological features of centripetal subcortical leukoencephalopathy with basal ganglia and dentate nuclei involvement are rather specific to L2HGA"
Human neuroimaging supports basal ganglia and dentate involvement as part of the L2HGA lesion pattern.
PMID:38714179 SUPPORT Human Clinical
"Brain MRI showed extensive supratentorial subcortical white matter signal abnormalities predominantly involving the U fibers and bilateral basal ganglia."
The DBS case confirms bilateral basal ganglia involvement in a patient with severe L2HGA movement disorder.
Mitochondrial dysfunction and metabolic reprogramming
Elevated L-2-HG perturbs mitochondrial bioenergetics, inhibits energy-buffering enzymes in experimental tissue systems, induces oxidative stress, and shifts neuronal cell metabolism toward anaerobic glycolysis.
oxidative phosphorylation link glycolytic process link response to oxidative stress link
mitochondrion link
Show evidence (2 references)
PMID:38862727 SUPPORT In Vitro
"both enantiomers of 2HG comparably stimulate anaerobic metabolism of glucose and inhibit the uptake of several essential amino acids from the culture media"
In vitro neuronal cell model demonstrates metabolic reprogramming under L-2-HG exposure.
PMID:22391998 SUPPORT In Vitro
"Exposure of rat brain tissues to increased L-2-HG significantly inhibited creatine kinase activity in rat cerebellum homogenates (da Silva et al 2003c), induced oxidative stress"
Experimental tissue evidence supports oxidative stress and energy-enzyme impairment downstream of elevated L-2-HG.
Epigenetic dysregulation via inhibition of alpha-KG-dependent dioxygenases
L-2-HG is a structural analog of alpha-ketoglutarate and can inhibit alpha-KG-dependent dioxygenases, including TET DNA hydroxylases and JmjC histone demethylases. In L2HGDH-deficient mouse brain, this manifests as increased histone methylation, linking metabolite accumulation to epigenetic perturbation.
DNA demethylation link
histone demethylase activity link
nucleus link
Show evidence (2 references)
PMID:38716347 REFUTE Human Clinical
"These findings were against all our expectations given the inhibitory potential of 2-HG on DNA-demethylation enzymes."
L-2-HGA-associated glioma did NOT show the G-CIMP hypermethylation phenotype expected from dioxygenase inhibition, unlike IDH-mutant tumors with D-2-HG accumulation. This argues against a simple epigenetic oncogenic mechanism in L-2-HGA.
PMID:28137912 SUPPORT Model Organism
"a corresponding increase in histone methylation in these tissues"
L2hgdh KO mice show increased histone methylation in brain, directly demonstrating that L-2-HG accumulation causes epigenetic dysregulation via inhibition of histone demethylases in vivo.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for L-2-Hydroxyglutaric Aciduria 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

15
Head and Neck 1
Macrocephaly FREQUENT Macrocephaly (HP:0000256)
Show evidence (1 reference)
PMID:24321868 SUPPORT Human Clinical
"Macrocephaly is present in half of the cases."
Reports macrocephaly in approximately 50% of L2HGA cases.
Musculoskeletal 2
Hypotonia Generalized hypotonia (HP:0001290)
Show evidence (1 reference)
PMID:22391998 SUPPORT Human Clinical
"Hypotonia was most prevalent in the earlier stages and spasticity in the latter stages of disease in their cohort."
Human cohort review identifies hypotonia as most prevalent in earlier disease stages.
Spasticity FREQUENT Spasticity (HP:0001257)
Show evidence (2 references)
PMID:37113859 SUPPORT Human Clinical
"Exaggerated tendon reflexes and bilateral sustained ankle clonus were observed in addition to cerebellar signs."
Upper motor neuron signs consistent with spasticity were present in both patients.
PMID:38714179 SUPPORT Human Clinical
"Brisk deep tendon reflexes, clonus, and bilateral Babinski signs were present."
Pyramidal signs documented in the DBS case report.
Nervous System 11
Intellectual disability VERY_FREQUENT Intellectual disability (HP:0001249)
Show evidence (2 references)
PMID:37113859 SUPPORT Human Clinical
"L-2-hydroxyglutaric aciduria (L2HGA) is an autosomal recessive, slowly progressive neurodegenerative disease characterized by psychomotor delay and cerebellar dysfunction."
Psychomotor delay leading to intellectual disability is a defining feature of L2HGA.
PMID:37275239 SUPPORT Human Clinical
"The most common clinical symptoms were developmental delay, intellectual disability, and movement disorders."
Confirms intellectual disability as one of the most common symptoms in a Turkish cohort.
Psychomotor retardation VERY_FREQUENT Global developmental delay (HP:0001263)
Show evidence (1 reference)
PMID:37113859 SUPPORT Human Clinical
"L-2-hydroxyglutaric aciduria (L2HGA) is an autosomal recessive, slowly progressive neurodegenerative disease characterized by psychomotor delay and cerebellar dysfunction."
Psychomotor delay is listed as a defining characteristic.
Seizures FREQUENT Seizure (HP:0001250)
Show evidence (2 references)
PMID:37113859 SUPPORT Human Clinical
"The 15- and 17-year-old girls presented with psychomotor delay, seizures, ataxia, intentional tremors, and dysarthria."
Seizures are part of the core clinical presentation described in this case series.
PMID:24321868 SUPPORT Human Clinical
"It occurs in childhood with mental retardation, cerebellar ataxia, and epilepsy."
Confirms epilepsy as a core feature of L2HGA alongside mental retardation and cerebellar ataxia.
Cerebellar ataxia VERY_FREQUENT Ataxia (HP:0001251)
Show evidence (2 references)
PMID:37113859 SUPPORT Human Clinical
"L-2-hydroxyglutaric aciduria (L2HGA) is an autosomal recessive, slowly progressive neurodegenerative disease characterized by psychomotor delay and cerebellar dysfunction."
Cerebellar dysfunction is described as a defining feature of L2HGA.
PMID:37113859 SUPPORT Human Clinical
"The 15- and 17-year-old girls presented with psychomotor delay, seizures, ataxia, intentional tremors, and dysarthria."
Ataxia was present in both patients in this case series.
Dystonia FREQUENT Dystonia (HP:0001332)
Show evidence (2 references)
PMID:38714179 SUPPORT Human Clinical
"Neurological exam revealed generalized dystonia, significant choreic movements in the upper extremities, slurred speech, bilateral dysmetria, and a wide-based gait."
Describes generalized dystonia in a patient with L2HGA requiring DBS intervention.
PMID:38714179 SUPPORT Human Clinical
"Following minimal response to pharmacotherapy, GPi-DBS was performed."
Documents that dystonia in L2HGA can be pharmacoresistant, confirming its clinical significance as a distinct movement disorder phenotype.
Dysarthria FREQUENT Dysarthria (HP:0001260)
Show evidence (2 references)
PMID:37113859 SUPPORT Human Clinical
"The 15- and 17-year-old girls presented with psychomotor delay, seizures, ataxia, intentional tremors, and dysarthria."
Dysarthria was present in both reported patients.
PMID:38714179 SUPPORT Human Clinical
"Neurological exam revealed generalized dystonia, significant choreic movements in the upper extremities, slurred speech, bilateral dysmetria, and a wide-based gait."
Slurred speech observed in the DBS case report patient.
Subcortical leukoencephalopathy VERY_FREQUENT Leukoencephalopathy (HP:0002352)
Show evidence (2 references)
PMID:37113859 SUPPORT Human Clinical
"Brain MRI of the 15-year-old showed diffuse subcortical white matter changes evident by T2/FLAIR hyperintense signals bilaterally, particularly in the frontal region in the centripetal distribution"
Describes the characteristic centripetal subcortical white matter MRI pattern.
PMID:37113859 SUPPORT Human Clinical
"Neuroradiological features of centripetal subcortical leukoencephalopathy with basal ganglia and dentate nuclei involvement are rather specific to L2HGA"
Confirms the diagnostic specificity of the MRI pattern.
Intention tremor FREQUENT Intention tremor (HP:0002080)
Show evidence (1 reference)
PMID:37113859 SUPPORT Human Clinical
"The 15- and 17-year-old girls presented with psychomotor delay, seizures, ataxia, intentional tremors, and dysarthria."
Intentional tremors documented in both patients.
Behavioral abnormality FREQUENT Atypical behavior (HP:0000708)
Show evidence (1 reference)
PMID:37275239 SUPPORT Human Clinical
"Behavioural problems were more common in L2HGA than in GA-I patients."
Documents increased behavioral problems in L2HGA compared to glutaric aciduria type I.
Chorea OCCASIONAL Chorea (HP:0002072)
Show evidence (1 reference)
PMID:38714179 SUPPORT Human Clinical
"Neurological exam revealed generalized dystonia, significant choreic movements in the upper extremities, slurred speech, bilateral dysmetria, and a wide-based gait."
Choreic movements were documented in the DBS case report patient.
Gait ataxia FREQUENT Gait ataxia (HP:0002066)
Show evidence (1 reference)
PMID:38714179 SUPPORT Human Clinical
"Neurological exam revealed generalized dystonia, significant choreic movements in the upper extremities, slurred speech, bilateral dysmetria, and a wide-based gait."
Wide-based gait documented in L2HGA patient.
Neoplasm 1
CNS neoplasm VERY_RARE Malignant neoplasm of the central nervous system (HP:0100836)
Show evidence (1 reference)
PMID:38716347 SUPPORT Human Clinical
"L-2-HGA patients have a significantly increased lifetime risk of central nervous system (CNS) tumors."
Directly states increased CNS tumor risk in L2HGA patients.
🧬

Genetic Associations

1
L2HGDH variants (Causative)
Autosomal recessive
Show evidence (1 reference)
PMID:22391998 SUPPORT Human Clinical
"We report on the clinical, genetic, enzymatic and metabolic characterization of D-2-HGA type I, D-2-HGA type II, L-2-HGA and D,L-2-HGA"
Comprehensive review of genetic, enzymatic, and metabolic characterization of L2HGA.
💊

Treatments

7
Riboflavin supplementation
Action: B vitamin supplementation MAXO:0000761
Agent: riboflavin ↗
Riboflavin (vitamin B2), the precursor of FAD cofactor required by L2HGDH, is the cornerstone therapy for L2HGA. FAD supplementation aims to enhance any residual enzyme activity and accelerate conversion of L-2-HG to alpha-ketoglutarate. In cohort studies, riboflavin combined with levocarnitine produced significant decreases in urinary 2-HG levels and limited neurologic improvement.
Mechanism Target:
MODULATES L2HGDH enzymatic deficiency — Riboflavin supplies the precursor for the FAD cofactor required by L2HGDH, potentially improving residual enzyme flux.
Show evidence (1 reference)
PMID:37275239 SUPPORT Human Clinical
"FAD, the cofactor of L2HGD, accelerates the conversion of L-2-hydoxy glutarate to alpha-ketoglutarate."
Human cohort background links the riboflavin-derived FAD cofactor to L2HGDH-mediated L-2-HG conversion.
INHIBITS L-2-hydroxyglutarate accumulation — Riboflavin-containing therapy is associated with lower urinary 2-HG in treated L2HGA patients.
Show evidence (1 reference)
PMID:37275239 SUPPORT Human Clinical
"In all L2HGA patients, there was a significant decrease in the mean urinary 2- hydoxy glutarate with treatment."
Cohort data support a biochemical treatment-response edge from riboflavin-based therapy to reduced L-2-HG accumulation.
Show evidence (3 references)
PMID:37275239 SUPPORT Human Clinical
"In all L2HGA patients, there was a significant decrease in the mean urinary 2- hydoxy glutarate with treatment."
Demonstrates significant biochemical response to riboflavin/levocarnitine in L2HGA cohort.
PMID:37275239 SUPPORT Human Clinical
"Relative neurologic improvement was seen in three L2HGA patients."
Documents some clinical improvement with riboflavin-based treatment.
PMID:24321868 SUPPORT Human Clinical
"Under specific treatment, the progression of the disease was subsequently stopped."
Reports halting of disease progression under riboflavin treatment.
Levocarnitine supplementation
Action: carnitine supplementation MAXO:0010006
Agent: levocarnitine ↗
Levocarnitine is used alongside riboflavin as part of standard metabolic therapy for L2HGA. It supports organic acid detoxification and excretion pathways.
Mechanism Target:
MODULATES L-2-hydroxyglutarate accumulation — Levocarnitine is used in combination with riboflavin in L2HGA treatment regimens associated with lower urinary 2-HG.
Show evidence (1 reference)
PMID:37275239 SUPPORT Human Clinical
"Riboflavin and levocarnitine have been reported to improve not only clinical symptoms but also urinary 2-HGA levels."
Cohort background supports levocarnitine-containing treatment as a modifier of urinary 2-HGA levels, though not as monotherapy.
Show evidence (2 references)
PMID:37275239 SUPPORT Human Clinical
"Current treatment strategies are based on levocarnitine, vitamin B2, and diet."
Confirms levocarnitine as a component of standard treatment for L2HGA.
PMID:37275239 SUPPORT Human Clinical
"In L2HGA patients, we used levocarnitine and vitamin B2."
Documents use of levocarnitine in all L2HGA patients in this cohort.
Deep brain stimulation
Action: deep brain stimulation MAXO:0000943
Bilateral globus pallidus internus deep brain stimulation (GPi-DBS) has been used for L2HGA-related refractory dystonia with reported significant improvements in mobility and dystonia severity. This represents an emerging intervention for severe, pharmacoresistant movement disorders in L2HGA.
Mechanism Target:
MODULATES Basal ganglia and cerebellar circuit involvement — GPi-DBS modulates basal ganglia output circuits driving refractory dystonia.
Show evidence (1 reference)
PMID:38714179 SUPPORT Human Clinical
"Significant increases in mobility and decrease in dystonia were observed at 3 weeks, 6 months, and 12 months postoperatively."
Postoperative improvement supports a circuit-modulating treatment edge for severe L2HGA dystonia.
Target Phenotypes: Dystonia ↗
Show evidence (2 references)
PMID:38714179 SUPPORT Human Clinical
"Significant increases in mobility and decrease in dystonia were observed at 3 weeks, 6 months, and 12 months postoperatively."
Documents significant improvement with GPi-DBS in L2HGA-related dystonia.
PMID:38714179 SUPPORT Human Clinical
"This is the first utilization of DBS as treatment for L2HGA-related dystonia."
Establishes GPi-DBS as a novel therapeutic option for L2HGA dystonia.
Supportive care and rehabilitation
Action: supportive care MAXO:0000950
Comprehensive supportive care including physical therapy, occupational therapy, speech therapy, and educational support is essential for managing the chronic neurological disabilities of L2HGA.
Target Phenotypes: Cerebellar ataxia ↗ Dysarthria ↗ Psychomotor retardation ↗ Intellectual disability ↗
Show evidence (1 reference)
PMID:37275239 SUPPORT Human Clinical
"Relative neurologic improvement was seen in three L2HGA patients."
Some patients show improvement with comprehensive treatment approach, supporting role of ongoing supportive care.
Genetic counseling
Action: genetic counseling MAXO:0000079
Genetic counseling for affected families addressing autosomal recessive inheritance, 25% recurrence risk, carrier testing for at-risk relatives, and prenatal/preimplantation testing options. Consanguinity is a significant factor in many reported families.
Mechanism Target:
MODULATES L2HGDH enzymatic deficiency — Genetic counseling uses the L2HGDH molecular diagnosis for recurrence-risk and carrier counseling rather than directly altering enzyme activity.
Show evidence (1 reference)
PMID:37113859 SUPPORT Human Clinical
"Targeted L2HGDH sequencing identified a homozygous pathogenic variant, c.829C>T (p.Arg227*) in L2HGDH gene in both girls."
Molecular confirmation of the familial L2HGDH variant supports variant-informed counseling.
Show evidence (1 reference)
PMID:37113859 SUPPORT Human Clinical
"Both parents were heterozygous carriers of the familial variant."
Carrier status in parents supports autosomal recessive counseling approach.
Dietary intervention
Action: dietary intervention MAXO:0000088
Dietary management may be employed as part of the treatment approach, though the evidence base is less established than for other organic acidemias. Unlike glutaric aciduria type I, there is no specific amino acid restriction protocol for L2HGA.
Mechanism Target:
MODULATES L-2-hydroxyglutarate accumulation — Diet is part of current L2HGA treatment strategies, although the specific metabolite-lowering contribution is less established than riboflavin/levocarnitine.
Show evidence (1 reference)
PMID:37275239 PARTIAL Human Clinical
"Current treatment strategies are based on levocarnitine, vitamin B2, and diet."
The cohort identifies diet as part of treatment strategy but does not isolate a diet-specific effect on L-2-HG.
Show evidence (1 reference)
PMID:37275239 SUPPORT Human Clinical
"Current treatment strategies are based on levocarnitine, vitamin B2, and diet."
Diet is listed as one component of current treatment strategies.
Neuroimaging surveillance
Action: supportive care MAXO:0000950
Regular brain MRI monitoring to track disease progression and to screen for CNS tumor development, given the elevated tumor risk in L2HGA patients. MR spectroscopy can provide additional metabolic information.
Target Phenotypes: CNS neoplasm ↗ Subcortical leukoencephalopathy ↗
Show evidence (1 reference)
PMID:38716347 SUPPORT Human Clinical
"L-2-HGA patients have a significantly increased lifetime risk of central nervous system (CNS) tumors."
Increased CNS tumor risk mandates ongoing neuroimaging surveillance.
🔬

Biochemical Markers

4
L-2-hydroxyglutaric acid (urine) (INCREASED)
Context: Urinary L-2-hydroxyglutaric acid is markedly elevated (10-300 fold above normal) and is the primary diagnostic biomarker for L2HGA. Chiral differentiation is needed to distinguish L from D enantiomer.
Pathograph Readouts
Readout Of L-2-hydroxyglutarate accumulation Positive Diagnostic
Markedly increased urinary L-2-HG is the primary diagnostic readout of impaired L2HGDH-mediated metabolite repair.
Show evidence (1 reference)
PMID:22391998 SUPPORT Human Clinical
"The biochemical hallmark of L-2-HGA is the accumulation of urinary L-2-HG, which is 10 to 300 times increased in comparison to controls"
Directly supports urinary L-2-HG as a diagnostic readout of the accumulation node.
Show evidence (2 references)
PMID:22391998 SUPPORT Human Clinical
"Accumulation of D-2-hydroxyglutarate (D-2-HG) and/or L-2-hydroxyglutarate (L-2-HG) in body fluids are the biochemical hallmarks of these disorders."
Establishes L-2-HG accumulation in body fluids as the biochemical hallmark.
PMID:37113859 SUPPORT Human Clinical
"Urine organic acids analysis showed marked excretion of 2-hydroxyglutaric acid, chiral differentiation of 2-hydroxyglutaric acid showed it to be L2HGA."
Confirms elevated urinary L-2-HG with chiral differentiation establishing the L-enantiomer.
L-2-hydroxyglutaric acid (CSF) (INCREASED)
Context: CSF L-2-HG is elevated with a CSF/plasma ratio that may exceed 1, consistent with preferential brain accumulation. CSF analysis provides additional diagnostic value and reflects the degree of CNS metabolite burden.
Pathograph Readouts
Readout Of L-2-hydroxyglutarate accumulation Positive Diagnostic
Elevated CSF L-2-HG reports CNS-enriched L-2-HG accumulation.
Show evidence (1 reference)
PMID:22391998 SUPPORT Human Clinical
"L-2-HG levels in plasma and CSF are elevated as well, with a CSF/plasma ratio >1"
Directly supports CSF L-2-HG elevation as a CNS-biased readout.
Show evidence (2 references)
PMID:22391998 SUPPORT Human Clinical
"Accumulation of D-2-hydroxyglutarate (D-2-HG) and/or L-2-hydroxyglutarate (L-2-HG) in body fluids are the biochemical hallmarks of these disorders."
CSF is one of the body fluids in which L-2-HG accumulates.
PMID:28137912 SUPPORT Model Organism
"The highest levels of L-2-HG were observed in the brain and testis"
Mouse model demonstrates preferential brain accumulation supporting elevated CSF levels.
L-2-hydroxyglutaric acid (plasma) (INCREASED)
Context: Plasma L-2-HG levels are elevated in L2HGA but typically to a lesser degree than urinary and CSF concentrations. Plasma analysis can support diagnosis alongside urine organic acid studies.
Pathograph Readouts
Readout Of L-2-hydroxyglutarate accumulation Positive Diagnostic
Plasma L-2-HG elevation supports systemic L-2-HG accumulation, with CSF/plasma comparison indicating CNS enrichment.
Show evidence (1 reference)
PMID:22391998 SUPPORT Human Clinical
"L-2-HG levels in plasma and CSF are elevated as well, with a CSF/plasma ratio >1"
Directly supports plasma L-2-HG as part of the diagnostic accumulation pattern.
Show evidence (1 reference)
PMID:22391998 SUPPORT Human Clinical
"Accumulation of D-2-hydroxyglutarate (D-2-HG) and/or L-2-hydroxyglutarate (L-2-HG) in body fluids are the biochemical hallmarks of these disorders."
Plasma is one of the body fluids in which L-2-HG is elevated.
Urinary 2-OH-glutaric acid (INCREASED)
Context: Significantly elevated urine 2-OH-glutaric acid level is a key diagnostic finding. The metabolite is detectable by standard urine organic acid chromatography and confirmable by chiral analysis.
Pathograph Readouts
Readout Of L-2-hydroxyglutarate accumulation Positive Diagnostic
Non-chiral urinary 2-OH-glutaric acid is a screening readout that requires chiral differentiation to assign the L-enantiomer.
Show evidence (1 reference)
PMID:37113859 SUPPORT Human Clinical
"Urine organic acids analysis showed marked excretion of 2-hydroxyglutaric acid, chiral differentiation of 2-hydroxyglutaric acid showed it to be L2HGA."
Directly supports urinary 2-OH-glutaric acid with chiral confirmation as a readout of L2HGA.
Show evidence (1 reference)
PMID:38714179 SUPPORT Human Clinical
"Urine 2-OH-glutaric acid level was significantly elevated."
Documents significantly elevated urinary 2-OH-glutaric acid in an L2HGA patient.
{ }

Source YAML

click to show 
name: L-2-Hydroxyglutaric Aciduria
category: Mendelian
creation_date: '2025-06-12T20:16:27Z'
updated_date: '2026-05-18T17:01:31Z'
synonyms:
- L2HGA
- L-2-HGA
- L-2-hydroxyglutaric acidemia
- L2HGDH deficiency
description: 'L-2-Hydroxyglutaric aciduria (L2HGA) is a rare autosomal recessive neurometabolic disorder caused by biallelic pathogenic variants in the L2HGDH gene, which encodes a mitochondrial FAD-dependent L-2-hydroxyglutarate dehydrogenase. Loss of this metabolite-repair enzyme leads to systemic accumulation of L-2-hydroxyglutarate (L-2-HG), particularly in the brain and cerebrospinal fluid. The disease follows a slowly progressive course characterized by psychomotor delay, intellectual disability, epilepsy, cerebellar ataxia, and movement disorders. Brain MRI shows a distinctive pattern of subcortical white matter abnormalities with basal ganglia and dentate nuclei involvement. L2HGA patients also have an increased lifetime risk of central nervous system tumors. Treatment is primarily supportive with riboflavin and levocarnitine supplementation.

  '
disease_term:
  preferred_term: L-2-hydroxyglutaric aciduria
  term:
    id: MONDO:0009370
    label: L-2-hydroxyglutaric aciduria
parents:
- Organic Acidemia
- Inborn Error of Metabolism
prevalence:
- population: Global
  notes: 'L2HGA is a rare disorder. Fewer than 300 cases have been reported worldwide. Higher prevalence is observed in populations with high consanguinity rates.

    '
progression:
- phase: Onset
  age_range: Infancy-Early childhood
  notes: 'L2HGA typically presents in early childhood with developmental delay. Unlike many organic acidemias, L2HGA does not feature acute metabolic decompensation crises. Disease progression is insidious, with gradual neurological deterioration over years to decades including progressive cerebellar dysfunction, epilepsy, and movement disorders.

    '
pathophysiology:
- name: L2HGDH enzymatic deficiency
  description: 'Biallelic pathogenic variants in L2HGDH reduce mitochondrial L-2-hydroxyglutarate dehydrogenase metabolite-repair activity, impairing conversion of L-2-hydroxyglutarate back to 2-ketoglutarate.

    '
  genes:
  - preferred_term: L2HGDH
    term:
      id: hgnc:20499
      label: L2HGDH
  biological_processes:
  - preferred_term: organic acid metabolic process
    term:
      id: GO:0006082
      label: organic acid metabolic process
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  locations:
  - preferred_term: mitochondrion
    term:
      id: GO:0005739
      label: mitochondrion
  evidence:
  - reference: PMID:22391998
    reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: L-2-HG accumulates in L-2-HGA patients when L-2-HGDH is impaired
    explanation: Directly links impaired L-2-HGDH metabolite-repair activity to L-2-HG accumulation in L2HGA patients.
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Targeted L2HGDH sequencing identified a homozygous pathogenic variant, c.829C>T (p.Arg227*) in L2HGDH gene in both girls.
    explanation: Human case series confirms biallelic L2HGDH pathogenic variation in affected patients.
  downstream:
  - target: L-2-hydroxyglutarate accumulation
    description: Loss of L2HGDH metabolite-repair activity causes progressive L-2-HG buildup in body fluids and brain.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:22391998
      reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: L-2-HG accumulates in L-2-HGA patients when L-2-HGDH is impaired
      explanation: The review states the proximal biochemical consequence of impaired L-2-HGDH.
- name: L-2-hydroxyglutarate accumulation
  description: 'Loss of L-2-hydroxyglutarate dehydrogenase activity impairs the metabolite-repair pathway that clears L-2-hydroxyglutarate (L-2-HG), an aberrant off-pathway metabolite produced from alpha-ketoglutarate by L-malate dehydrogenase. L-2-HG accumulates in body fluids, with urinary L-2-HG 10-300 times above normal and plasma and CSF also elevated.

    '
  biological_processes:
  - preferred_term: organic acid metabolic process
    term:
      id: GO:0006082
      label: organic acid metabolic process
  cell_types:
  - preferred_term: neuron
    term:
      id: CL:0000540
      label: neuron
  locations:
  - preferred_term: mitochondrion
    term:
      id: GO:0005739
      label: mitochondrion
  evidence:
  - reference: PMID:22391998
    reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Accumulation of D-2-hydroxyglutarate (D-2-HG) and/or L-2-hydroxyglutarate (L-2-HG) in body fluids are the biochemical hallmarks of these disorders.
    explanation: Directly supports L-2-HG accumulation as the biochemical hallmark of L2HGA.
  - reference: PMID:22391998
    reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The biochemical hallmark of L-2-HGA is the accumulation of urinary L-2-HG, which is 10 to 300 times increased in comparison to controls
    explanation: Supports the magnitude of urinary L-2-HG elevation in L2HGA.
  downstream:
  - target: L-2-hydroxyglutaric acid (urine)
    description: Systemic L-2-HG buildup is reflected by markedly increased urinary L-2-HG.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:22391998
      reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The biochemical hallmark of L-2-HGA is the accumulation of urinary L-2-HG, which is 10 to 300 times increased in comparison to controls
      explanation: Directly supports urinary L-2-HG as the diagnostic downstream biomarker.
  - target: L-2-hydroxyglutaric acid (CSF)
    description: L-2-HG also accumulates in CSF, consistent with CNS enrichment of the metabolite.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:22391998
      reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: L-2-HG levels in plasma and CSF are elevated as well, with a CSF/plasma ratio >1
      explanation: Directly supports elevated CSF L-2-HG downstream of the accumulation mechanism.
  - target: L-2-hydroxyglutaric acid (plasma)
    description: L-2-HG accumulation is measurable in plasma as well as urine and CSF.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:22391998
      reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: L-2-HG levels in plasma and CSF are elevated as well, with a CSF/plasma ratio >1
      explanation: Directly supports elevated plasma L-2-HG downstream of the accumulation mechanism.
  - target: Urinary 2-OH-glutaric acid
    description: Standard urine organic acid testing detects elevated 2-hydroxyglutaric acid, with chiral testing assigning the L-enantiomer.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37113859
      reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Urine organic acids analysis showed marked excretion of 2-hydroxyglutaric acid, chiral differentiation of 2-hydroxyglutaric acid showed it to be L2HGA.
      explanation: Directly supports the urinary 2-OH-glutaric acid finding and chiral confirmation.
  - target: White-matter vulnerability and progressive leukoencephalopathy
    description: Chronic L-2-HG elevation drives selective white-matter injury and neuroinflammatory remodeling.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Gliosis, microglia-mediated neuroinflammation, and oligodendrocyte progenitor expansion in L2hgdh-deficient brain.
    - Progressive white-matter and deep gray signal abnormalities visible on MRI.
    evidence:
    - reference: PMID:28137912
      reference_title: "L2hgdh Deficiency Accumulates l-2-Hydroxyglutarate with Progressive Leukoencephalopathy and Neurodegeneration."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: Our data provide in vivo evidence that L2hgdh mutation leads to L-2-HG accumulation, leukoencephalopathy, and neurodegeneration in mice
      explanation: Mouse knockout data links L2hgdh-driven L-2-HG accumulation to leukoencephalopathy and neurodegeneration.
  - target: Mitochondrial dysfunction and metabolic reprogramming
    description: L-2-HG perturbs mitochondrial bioenergetics and shifts cellular metabolism toward anaerobic pathways.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Creatine kinase inhibition, oxidative stress, and altered glucose metabolism under high L-2-HG exposure.
    - Reduced mitochondrial respiratory reserve with increased anaerobic glycolytic flux in neuronal cells.
    evidence:
    - reference: PMID:38862727
      reference_title: "Both Enantiomers of 2-Hydroxyglutarate Modulate the Metabolism of Cultured Human Neuroblastoma Cells."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: both enantiomers of 2HG comparably stimulate anaerobic metabolism of glucose and inhibit the uptake of several essential amino acids from the culture media
      explanation: In vitro neuronal-cell evidence supports metabolic reprogramming downstream of 2-HG exposure.
    - reference: PMID:22391998
      reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Exposure of rat brain tissues to increased L-2-HG significantly inhibited creatine kinase activity in rat cerebellum homogenates (da Silva et al 2003c), induced oxidative stress
      explanation: Tissue experiments summarized in the review support oxidative and energy-enzyme effects of L-2-HG.
  - target: Epigenetic dysregulation via inhibition of alpha-KG-dependent dioxygenases
    description: L-2-HG can interfere with alpha-KG-dependent chromatin enzymes, altering epigenetic regulation.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - L-2-HG acts as a 2-ketoglutarate analog that can impair histone and DNA demethylase activity.
    - L2hgdh-deficient tissues show increased histone methylation in vivo.
    evidence:
    - reference: PMID:28137912
      reference_title: "L2hgdh Deficiency Accumulates l-2-Hydroxyglutarate with Progressive Leukoencephalopathy and Neurodegeneration."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: The highest levels of L-2-HG were observed in the brain and testis, with a corresponding increase in histone methylation in these tissues.
      explanation: Model evidence links tissue L-2-HG accumulation to increased histone methylation.
  - target: CNS neoplasm
    description: L2HGA is associated with increased CNS tumor risk, but human tumor methylation data indicate that the oncogenic intermediates are unresolved and not simply IDH-mutant-like hypermethylation.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:38716347
      reference_title: "Malignant glioma in L-2-Hydroxyglutaric Aciduria: thorough molecular characterization of a case and literature review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: L-2-HGA patients have a significantly increased lifetime risk of central nervous system (CNS) tumors.
      explanation: Human clinical literature supports increased CNS tumor risk while the precise intermediate mechanism remains unresolved.
  - target: Basal ganglia and cerebellar circuit involvement
    description: L2HGA neuroimaging repeatedly involves basal ganglia and dentate/cerebellar structures that map to extrapyramidal and cerebellar motor phenotypes.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Deep gray nuclei and dentate nucleus MRI abnormalities.
    - Cerebellar signs and extrapyramidal movement disorder.
    evidence:
    - reference: PMID:37113859
      reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Neuroradiological features of centripetal subcortical leukoencephalopathy with basal ganglia and dentate nuclei involvement are rather specific to L2HGA
      explanation: Human neuroimaging supports basal ganglia and dentate involvement downstream of L2HGA biochemistry.
- name: White-matter vulnerability and progressive leukoencephalopathy
  description: 'L-2-HG accumulation leads to selective vulnerability of subcortical cerebral white matter with basal ganglia and dentate nucleus involvement. In mouse models, L2HGDH deficiency causes progressive leukoencephalopathy with white matter abnormalities, extensive gliosis, microglia-mediated neuroinflammation, and expansion of oligodendrocyte progenitor cells.

    '
  biological_processes:
  - preferred_term: myelination
    term:
      id: GO:0042552
      label: myelination
  - preferred_term: reactive gliosis
    term:
      id: GO:0150103
      label: reactive gliosis
  cell_types:
  - preferred_term: oligodendrocyte
    term:
      id: CL:0000128
      label: oligodendrocyte
  - preferred_term: oligodendrocyte precursor cell
    term:
      id: CL:0002453
      label: oligodendrocyte precursor cell
  - preferred_term: microglial cell
    term:
      id: CL:0000129
      label: microglial cell
  locations:
  - preferred_term: white matter
    term:
      id: UBERON:0002316
      label: white matter
  - preferred_term: basal ganglion
    term:
      id: UBERON:0002420
      label: basal ganglion
  - preferred_term: dentate nucleus
    term:
      id: UBERON:0002132
      label: dentate nucleus
  evidence:
  - reference: PMID:28137912
    reference_title: "L2hgdh Deficiency Accumulates l-2-Hydroxyglutarate with Progressive Leukoencephalopathy and Neurodegeneration."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: KO mice exhibit white matter abnormalities, extensive gliosis, microglia-mediated neuroinflammation, and an expansion of oligodendrocyte progenitor cells (OPCs).
    explanation: Mouse model demonstrates leukoencephalopathy, gliosis, neuroinflammation, and OPC expansion.
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Neuroradiological features of centripetal subcortical leukoencephalopathy with basal ganglia and dentate nuclei involvement are rather specific to L2HGA
    explanation: Human neuroimaging confirms the characteristic white matter and deep gray matter pattern.
  downstream:
  - target: Subcortical leukoencephalopathy
    description: White-matter vulnerability produces the characteristic centripetal subcortical leukoencephalopathy pattern on MRI.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:37113859
      reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Brain MRI of the 15-year-old showed diffuse subcortical white matter changes evident by T2/FLAIR hyperintense signals bilaterally, particularly in the frontal region in the centripetal distribution
      explanation: Directly supports subcortical leukoencephalopathy as the imaging expression of the white-matter mechanism.
  - target: Intellectual disability
    description: Chronic L2HGA white-matter and neurodegenerative involvement contributes to delayed cognitive development and intellectual disability.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:22391998
      reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Virtually all patients display delayed mental and motor development, and about two-third of them epilepsy and cerebellar dysfunction.
      explanation: Human cohort review supports neurodevelopmental impairment as a common clinical consequence of L2HGA.
  - target: Psychomotor retardation
    description: The slowly progressive neurodegenerative and white-matter phenotype presents as psychomotor delay from childhood.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:37113859
      reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: L-2-hydroxyglutaric aciduria (L2HGA) is an autosomal recessive, slowly progressive neurodegenerative disease characterized by psychomotor delay and cerebellar dysfunction.
      explanation: Directly supports psychomotor delay as part of the clinical neurodegenerative phenotype.
  - target: Seizures
    description: Epilepsy is a frequent neurological consequence of the chronic L2HGA brain disease, though the immediate seizure mechanism is not fully resolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:22391998
      reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: An insidious onset of disease starting in childhood, developmental delay, epilepsy and cerebellar ataxia were the cardinal clinical signs
      explanation: Human review supports epilepsy as a core clinical feature of L2HGA brain disease.
  - target: Hypotonia
    description: Early-stage motor pathway involvement may present with generalized hypotonia before later pyramidal signs become more prominent.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:22391998
      reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Hypotonia was most prevalent in the earlier stages and spasticity in the latter stages of disease in their cohort.
      explanation: Human cohort review supports hypotonia as an early-stage motor phenotype in L2HGA.
  - target: Spasticity
    description: Progressive white-matter and motor-pathway involvement can manifest as upper motor neuron signs and spasticity.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:22391998
      reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Hypotonia was most prevalent in the earlier stages and spasticity in the latter stages of disease in their cohort.
      explanation: Human cohort review supports spasticity as a later-stage clinical feature of L2HGA.
  - target: Macrocephaly
    description: Macrocephaly is frequently associated with the L2HGA cerebral white-matter disease pattern, but the exact growth intermediate remains uncertain.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:22391998
      reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: In about half of patients, macrocephaly and extrapyramidal symptoms including tremor and dystonia are observed.
      explanation: Human review supports macrocephaly as a common feature in the L2HGA clinical spectrum.
  - target: Behavioral abnormality
    description: Behavioral problems occur with L2HGA neurodevelopmental involvement, though the specific circuit-level intermediate is unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:37275239
      reference_title: "Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Behavioural problems were more common in L2HGA than in GA-I patients.
      explanation: Human cohort evidence supports behavioral involvement in L2HGA.
- name: Basal ganglia and cerebellar circuit involvement
  description: 'L2HGA affects basal ganglia, globus pallidus/putamen/caudate, dentate nucleus, and cerebellar circuits on neuroimaging and neurological examination. These lesions provide a mechanistic bridge from the metabolic brain disease to extrapyramidal movement disorders and cerebellar signs.

    '
  locations:
  - preferred_term: basal ganglion
    term:
      id: UBERON:0002420
      label: basal ganglion
  - preferred_term: globus pallidus
    term:
      id: UBERON:0001875
      label: globus pallidus
  - preferred_term: putamen
    term:
      id: UBERON:0001874
      label: putamen
  - preferred_term: caudate nucleus
    term:
      id: UBERON:0001873
      label: caudate nucleus
  - preferred_term: dentate nucleus
    term:
      id: UBERON:0002132
      label: dentate nucleus
  - preferred_term: cerebellum
    term:
      id: UBERON:0002037
      label: cerebellum
  evidence:
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Neuroradiological features of centripetal subcortical leukoencephalopathy with basal ganglia and dentate nuclei involvement are rather specific to L2HGA
    explanation: Human neuroimaging supports basal ganglia and dentate involvement as part of the L2HGA lesion pattern.
  - reference: PMID:38714179
    reference_title: "Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Brain MRI showed extensive supratentorial subcortical white matter signal abnormalities predominantly involving the U fibers and bilateral basal ganglia.
    explanation: The DBS case confirms bilateral basal ganglia involvement in a patient with severe L2HGA movement disorder.
  downstream:
  - target: Cerebellar ataxia
    description: Dentate/cerebellar involvement manifests clinically as ataxia.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Dentate nucleus and cerebellar white-matter involvement.
    evidence:
    - reference: PMID:37113859
      reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The 15- and 17-year-old girls presented with psychomotor delay, seizures, ataxia, intentional tremors, and dysarthria.
      explanation: Case-series evidence connects the characteristic CNS involvement to ataxia.
  - target: Dystonia
    description: Basal ganglia involvement maps to extrapyramidal dystonia, including severe GPi-DBS-treated disease.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Bilateral basal ganglia and globus pallidus circuit involvement.
    evidence:
    - reference: PMID:38714179
      reference_title: "Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Neurological exam revealed generalized dystonia, significant choreic movements in the upper extremities, slurred speech, bilateral dysmetria, and a wide-based gait.
      explanation: Human case report documents generalized dystonia with basal ganglia imaging involvement.
  - target: Dysarthria
    description: Cerebellar and basal ganglia circuit involvement produces slurred speech and dysarthria.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Cerebellar signs and extrapyramidal motor impairment affecting speech.
    evidence:
    - reference: PMID:37113859
      reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The 15- and 17-year-old girls presented with psychomotor delay, seizures, ataxia, intentional tremors, and dysarthria.
      explanation: Case-series evidence supports dysarthria with the cerebellar motor phenotype.
  - target: Intention tremor
    description: Dentate/cerebellar circuit involvement manifests as intention tremor.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Dentate nucleus and cerebellar motor-circuit dysfunction.
    evidence:
    - reference: PMID:37113859
      reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The 15- and 17-year-old girls presented with psychomotor delay, seizures, ataxia, intentional tremors, and dysarthria.
      explanation: Case-series evidence directly supports intentional tremor as part of the L2HGA motor phenotype.
  - target: Chorea
    description: Basal ganglia circuit involvement can present with choreic movements.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Extrapyramidal basal ganglia dysfunction.
    evidence:
    - reference: PMID:38714179
      reference_title: "Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Neurological exam revealed generalized dystonia, significant choreic movements in the upper extremities, slurred speech, bilateral dysmetria, and a wide-based gait.
      explanation: Human case report documents choreic movements within the L2HGA movement-disorder spectrum.
  - target: Gait ataxia
    description: Cerebellar and basal ganglia dysfunction manifests as a wide-based gait.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Cerebellar dysmetria and basal ganglia motor involvement.
    evidence:
    - reference: PMID:38714179
      reference_title: "Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Neurological exam revealed generalized dystonia, significant choreic movements in the upper extremities, slurred speech, bilateral dysmetria, and a wide-based gait.
      explanation: Human case report documents a wide-based gait with the severe movement-disorder phenotype.
- name: Mitochondrial dysfunction and metabolic reprogramming
  description: 'Elevated L-2-HG perturbs mitochondrial bioenergetics, inhibits energy-buffering enzymes in experimental tissue systems, induces oxidative stress, and shifts neuronal cell metabolism toward anaerobic glycolysis.

    '
  biological_processes:
  - preferred_term: oxidative phosphorylation
    term:
      id: GO:0006119
      label: oxidative phosphorylation
  - preferred_term: glycolytic process
    term:
      id: GO:0006096
      label: glycolytic process
  - preferred_term: response to oxidative stress
    term:
      id: GO:0006979
      label: response to oxidative stress
  locations:
  - preferred_term: mitochondrion
    term:
      id: GO:0005739
      label: mitochondrion
  evidence:
  - reference: PMID:38862727
    reference_title: "Both Enantiomers of 2-Hydroxyglutarate Modulate the Metabolism of Cultured Human Neuroblastoma Cells."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: both enantiomers of 2HG comparably stimulate anaerobic metabolism of glucose and inhibit the uptake of several essential amino acids from the culture media
    explanation: In vitro neuronal cell model demonstrates metabolic reprogramming under L-2-HG exposure.
  - reference: PMID:22391998
    reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Exposure of rat brain tissues to increased L-2-HG significantly inhibited creatine kinase activity in rat cerebellum homogenates (da Silva et al 2003c), induced oxidative stress
    explanation: Experimental tissue evidence supports oxidative stress and energy-enzyme impairment downstream of elevated L-2-HG.
- name: Epigenetic dysregulation via inhibition of alpha-KG-dependent dioxygenases
  description: 'L-2-HG is a structural analog of alpha-ketoglutarate and can inhibit alpha-KG-dependent dioxygenases, including TET DNA hydroxylases and JmjC histone demethylases. In L2HGDH-deficient mouse brain, this manifests as increased histone methylation, linking metabolite accumulation to epigenetic perturbation.

    '
  biological_processes:
  - preferred_term: DNA demethylation
    term:
      id: GO:0141166
      label: chromosomal 5-methylcytosine DNA demethylation pathway
  molecular_functions:
  - preferred_term: histone demethylase activity
    term:
      id: GO:0032452
      label: histone demethylase activity
  locations:
  - preferred_term: nucleus
    term:
      id: GO:0005634
      label: nucleus
  evidence:
  - reference: PMID:38716347
    reference_title: "Malignant glioma in L-2-Hydroxyglutaric Aciduria: thorough molecular characterization of a case and literature review."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: These findings were against all our expectations given the inhibitory potential of 2-HG on DNA-demethylation enzymes.
    explanation: L-2-HGA-associated glioma did NOT show the G-CIMP hypermethylation phenotype expected from dioxygenase inhibition, unlike IDH-mutant tumors with D-2-HG accumulation. This argues against a simple epigenetic oncogenic mechanism in L-2-HGA.
  - reference: PMID:28137912
    reference_title: "L2hgdh Deficiency Accumulates l-2-Hydroxyglutarate with Progressive Leukoencephalopathy and Neurodegeneration."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: a corresponding increase in histone methylation in these tissues
    explanation: L2hgdh KO mice show increased histone methylation in brain, directly demonstrating that L-2-HG accumulation causes epigenetic dysregulation via inhibition of histone demethylases in vivo.
phenotypes:
- name: Intellectual disability
  frequency: VERY_FREQUENT
  description: 'Intellectual disability is present in the majority of L2HGA patients. Severity ranges from mild to severe and is progressive.

    '
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: L-2-hydroxyglutaric aciduria (L2HGA) is an autosomal recessive, slowly progressive neurodegenerative disease characterized by psychomotor delay and cerebellar dysfunction.
    explanation: Psychomotor delay leading to intellectual disability is a defining feature of L2HGA.
  - reference: PMID:37275239
    reference_title: "Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The most common clinical symptoms were developmental delay, intellectual disability, and movement disorders.
    explanation: Confirms intellectual disability as one of the most common symptoms in a Turkish cohort.
- name: Psychomotor retardation
  frequency: VERY_FREQUENT
  description: 'Delayed motor and cognitive milestones are typically the earliest presenting features of L2HGA in childhood.

    '
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: L-2-hydroxyglutaric aciduria (L2HGA) is an autosomal recessive, slowly progressive neurodegenerative disease characterized by psychomotor delay and cerebellar dysfunction.
    explanation: Psychomotor delay is listed as a defining characteristic.
- name: Seizures
  frequency: FREQUENT
  description: 'Epilepsy occurs in a significant proportion of L2HGA patients, with seizures reported in 30-75% of cases across different cohorts. Seizure types are variable.

    '
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The 15- and 17-year-old girls presented with psychomotor delay, seizures, ataxia, intentional tremors, and dysarthria.
    explanation: Seizures are part of the core clinical presentation described in this case series.
  - reference: PMID:24321868
    reference_title: "[L-2-hydroxyglutaric aciduria: report on two cases]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: It occurs in childhood with mental retardation, cerebellar ataxia, and epilepsy.
    explanation: Confirms epilepsy as a core feature of L2HGA alongside mental retardation and cerebellar ataxia.
- name: Hypotonia
  description: 'Generalized hypotonia is reported as a prominent early-stage motor phenotype in L2HGA, preceding later spasticity in some patients.

    '
  phenotype_term:
    preferred_term: Generalized hypotonia
    term:
      id: HP:0001290
      label: Generalized hypotonia
  evidence:
  - reference: PMID:22391998
    reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Hypotonia was most prevalent in the earlier stages and spasticity in the latter stages of disease in their cohort.
    explanation: Human cohort review identifies hypotonia as most prevalent in earlier disease stages.
- name: Cerebellar ataxia
  frequency: VERY_FREQUENT
  description: 'Cerebellar ataxia is a hallmark feature of L2HGA, correlating with dentate nucleus and cerebellar white matter involvement on MRI. It manifests as gait instability, dysmetria, and intention tremor.

    '
  phenotype_term:
    preferred_term: Ataxia
    term:
      id: HP:0001251
      label: Ataxia
  evidence:
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: L-2-hydroxyglutaric aciduria (L2HGA) is an autosomal recessive, slowly progressive neurodegenerative disease characterized by psychomotor delay and cerebellar dysfunction.
    explanation: Cerebellar dysfunction is described as a defining feature of L2HGA.
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The 15- and 17-year-old girls presented with psychomotor delay, seizures, ataxia, intentional tremors, and dysarthria.
    explanation: Ataxia was present in both patients in this case series.
- name: Dystonia
  frequency: FREQUENT
  description: 'Generalized dystonia occurs in L2HGA, relating to basal ganglia involvement. In severe cases, dystonia may be refractory to pharmacotherapy and require deep brain stimulation.

    '
  phenotype_term:
    preferred_term: Dystonia
    term:
      id: HP:0001332
      label: Dystonia
  evidence:
  - reference: PMID:38714179
    reference_title: "Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Neurological exam revealed generalized dystonia, significant choreic movements in the upper extremities, slurred speech, bilateral dysmetria, and a wide-based gait.
    explanation: Describes generalized dystonia in a patient with L2HGA requiring DBS intervention.
  - reference: PMID:38714179
    reference_title: "Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Following minimal response to pharmacotherapy, GPi-DBS was performed.
    explanation: Documents that dystonia in L2HGA can be pharmacoresistant, confirming its clinical significance as a distinct movement disorder phenotype.
- name: Dysarthria
  frequency: FREQUENT
  description: 'Speech difficulties including slurred speech are common in L2HGA, related to cerebellar and basal ganglia dysfunction.

    '
  phenotype_term:
    preferred_term: Dysarthria
    term:
      id: HP:0001260
      label: Dysarthria
  evidence:
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The 15- and 17-year-old girls presented with psychomotor delay, seizures, ataxia, intentional tremors, and dysarthria.
    explanation: Dysarthria was present in both reported patients.
  - reference: PMID:38714179
    reference_title: "Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Neurological exam revealed generalized dystonia, significant choreic movements in the upper extremities, slurred speech, bilateral dysmetria, and a wide-based gait.
    explanation: Slurred speech observed in the DBS case report patient.
- name: Macrocephaly
  frequency: FREQUENT
  description: 'Macrocephaly has been reported in approximately 50-75% of L2HGA patients in various cohorts and is a useful diagnostic clue.

    '
  phenotype_term:
    preferred_term: Macrocephaly
    term:
      id: HP:0000256
      label: Macrocephaly
  evidence:
  - reference: PMID:24321868
    reference_title: "[L-2-hydroxyglutaric aciduria: report on two cases]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Macrocephaly is present in half of the cases.
    explanation: Reports macrocephaly in approximately 50% of L2HGA cases.
- name: Subcortical leukoencephalopathy
  frequency: VERY_FREQUENT
  description: 'Brain MRI shows a characteristic pattern of subcortical white matter T2/FLAIR hyperintensity in a centripetal distribution, particularly involving the U-fibers, along with basal ganglia and dentate nuclei signal abnormalities. This pattern is highly specific for L2HGA.

    '
  phenotype_term:
    preferred_term: Leukoencephalopathy
    term:
      id: HP:0002352
      label: Leukoencephalopathy
  diagnostic: true
  evidence:
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Brain MRI of the 15-year-old showed diffuse subcortical white matter changes evident by T2/FLAIR hyperintense signals bilaterally, particularly in the frontal region in the centripetal distribution
    explanation: Describes the characteristic centripetal subcortical white matter MRI pattern.
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Neuroradiological features of centripetal subcortical leukoencephalopathy with basal ganglia and dentate nuclei involvement are rather specific to L2HGA
    explanation: Confirms the diagnostic specificity of the MRI pattern.
- name: Spasticity
  frequency: FREQUENT
  description: 'Upper motor neuron signs including exaggerated tendon reflexes, clonus, and Babinski signs are common in L2HGA, reflecting corticospinal tract involvement.

    '
  phenotype_term:
    preferred_term: Spasticity
    term:
      id: HP:0001257
      label: Spasticity
  evidence:
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Exaggerated tendon reflexes and bilateral sustained ankle clonus were observed in addition to cerebellar signs.
    explanation: Upper motor neuron signs consistent with spasticity were present in both patients.
  - reference: PMID:38714179
    reference_title: "Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Brisk deep tendon reflexes, clonus, and bilateral Babinski signs were present.
    explanation: Pyramidal signs documented in the DBS case report.
- name: Intention tremor
  frequency: FREQUENT
  description: 'Intention tremor is a cerebellar sign commonly observed in L2HGA, reflecting cerebellar and dentate nucleus dysfunction.

    '
  phenotype_term:
    preferred_term: Intention tremor
    term:
      id: HP:0002080
      label: Intention tremor
  evidence:
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The 15- and 17-year-old girls presented with psychomotor delay, seizures, ataxia, intentional tremors, and dysarthria.
    explanation: Intentional tremors documented in both patients.
- name: Behavioral abnormality
  frequency: FREQUENT
  description: 'Behavioral problems are commonly reported in L2HGA patients and may be more prevalent than in other cerebral organic acidurias.

    '
  phenotype_term:
    preferred_term: Atypical behavior
    term:
      id: HP:0000708
      label: Atypical behavior
  evidence:
  - reference: PMID:37275239
    reference_title: "Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Behavioural problems were more common in L2HGA than in GA-I patients.
    explanation: Documents increased behavioral problems in L2HGA compared to glutaric aciduria type I.
- name: Chorea
  frequency: OCCASIONAL
  description: 'Choreic movements may occur in L2HGA, particularly affecting the upper extremities, as part of the extrapyramidal movement disorder spectrum.

    '
  phenotype_term:
    preferred_term: Chorea
    term:
      id: HP:0002072
      label: Chorea
  evidence:
  - reference: PMID:38714179
    reference_title: "Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Neurological exam revealed generalized dystonia, significant choreic movements in the upper extremities, slurred speech, bilateral dysmetria, and a wide-based gait.
    explanation: Choreic movements were documented in the DBS case report patient.
- name: Gait ataxia
  frequency: FREQUENT
  description: 'Wide-based and unsteady gait is a common manifestation of cerebellar dysfunction in L2HGA.

    '
  phenotype_term:
    preferred_term: Gait ataxia
    term:
      id: HP:0002066
      label: Gait ataxia
  evidence:
  - reference: PMID:38714179
    reference_title: "Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Neurological exam revealed generalized dystonia, significant choreic movements in the upper extremities, slurred speech, bilateral dysmetria, and a wide-based gait.
    explanation: Wide-based gait documented in L2HGA patient.
- name: CNS neoplasm
  frequency: VERY_RARE
  description: 'L2HGA patients have a significantly increased lifetime risk of central nervous system tumors, including malignant glioma. Despite the theoretical epigenetic effects of L-2-HG on TET enzymes, L2HGA-associated tumors do not typically show IDH-mutant-like methylation profiles, suggesting a distinct oncogenetic mechanism.

    '
  phenotype_term:
    preferred_term: Malignant neoplasm of the central nervous system
    term:
      id: HP:0100836
      label: Malignant neoplasm of the central nervous system
  evidence:
  - reference: PMID:38716347
    reference_title: "Malignant glioma in L-2-Hydroxyglutaric Aciduria: thorough molecular characterization of a case and literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: L-2-HGA patients have a significantly increased lifetime risk of central nervous system (CNS) tumors.
    explanation: Directly states increased CNS tumor risk in L2HGA patients.
biochemical:
- name: L-2-hydroxyglutaric acid (urine)
  presence: INCREASED
  context: 'Urinary L-2-hydroxyglutaric acid is markedly elevated (10-300 fold above normal) and is the primary diagnostic biomarker for L2HGA. Chiral differentiation is needed to distinguish L from D enantiomer.

    '
  readouts:
  - target: L-2-hydroxyglutarate accumulation
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Markedly increased urinary L-2-HG is the primary diagnostic readout of impaired L2HGDH-mediated metabolite repair.
    evidence:
    - reference: PMID:22391998
      reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The biochemical hallmark of L-2-HGA is the accumulation of urinary L-2-HG, which is 10 to 300 times increased in comparison to controls
      explanation: Directly supports urinary L-2-HG as a diagnostic readout of the accumulation node.
  evidence:
  - reference: PMID:22391998
    reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Accumulation of D-2-hydroxyglutarate (D-2-HG) and/or L-2-hydroxyglutarate (L-2-HG) in body fluids are the biochemical hallmarks of these disorders.
    explanation: Establishes L-2-HG accumulation in body fluids as the biochemical hallmark.
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Urine organic acids analysis showed marked excretion of 2-hydroxyglutaric acid, chiral differentiation of 2-hydroxyglutaric acid showed it to be L2HGA.
    explanation: Confirms elevated urinary L-2-HG with chiral differentiation establishing the L-enantiomer.
- name: L-2-hydroxyglutaric acid (CSF)
  presence: INCREASED
  context: 'CSF L-2-HG is elevated with a CSF/plasma ratio that may exceed 1, consistent with preferential brain accumulation. CSF analysis provides additional diagnostic value and reflects the degree of CNS metabolite burden.

    '
  readouts:
  - target: L-2-hydroxyglutarate accumulation
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Elevated CSF L-2-HG reports CNS-enriched L-2-HG accumulation.
    evidence:
    - reference: PMID:22391998
      reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: L-2-HG levels in plasma and CSF are elevated as well, with a CSF/plasma ratio >1
      explanation: Directly supports CSF L-2-HG elevation as a CNS-biased readout.
  evidence:
  - reference: PMID:22391998
    reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Accumulation of D-2-hydroxyglutarate (D-2-HG) and/or L-2-hydroxyglutarate (L-2-HG) in body fluids are the biochemical hallmarks of these disorders.
    explanation: CSF is one of the body fluids in which L-2-HG accumulates.
  - reference: PMID:28137912
    reference_title: "L2hgdh Deficiency Accumulates l-2-Hydroxyglutarate with Progressive Leukoencephalopathy and Neurodegeneration."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: The highest levels of L-2-HG were observed in the brain and testis
    explanation: Mouse model demonstrates preferential brain accumulation supporting elevated CSF levels.
- name: L-2-hydroxyglutaric acid (plasma)
  presence: INCREASED
  context: 'Plasma L-2-HG levels are elevated in L2HGA but typically to a lesser degree than urinary and CSF concentrations. Plasma analysis can support diagnosis alongside urine organic acid studies.

    '
  readouts:
  - target: L-2-hydroxyglutarate accumulation
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Plasma L-2-HG elevation supports systemic L-2-HG accumulation, with CSF/plasma comparison indicating CNS enrichment.
    evidence:
    - reference: PMID:22391998
      reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: L-2-HG levels in plasma and CSF are elevated as well, with a CSF/plasma ratio >1
      explanation: Directly supports plasma L-2-HG as part of the diagnostic accumulation pattern.
  evidence:
  - reference: PMID:22391998
    reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Accumulation of D-2-hydroxyglutarate (D-2-HG) and/or L-2-hydroxyglutarate (L-2-HG) in body fluids are the biochemical hallmarks of these disorders.
    explanation: Plasma is one of the body fluids in which L-2-HG is elevated.
- name: Urinary 2-OH-glutaric acid
  presence: INCREASED
  context: 'Significantly elevated urine 2-OH-glutaric acid level is a key diagnostic finding. The metabolite is detectable by standard urine organic acid chromatography and confirmable by chiral analysis.

    '
  readouts:
  - target: L-2-hydroxyglutarate accumulation
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Non-chiral urinary 2-OH-glutaric acid is a screening readout that requires chiral differentiation to assign the L-enantiomer.
    evidence:
    - reference: PMID:37113859
      reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Urine organic acids analysis showed marked excretion of 2-hydroxyglutaric acid, chiral differentiation of 2-hydroxyglutaric acid showed it to be L2HGA.
      explanation: Directly supports urinary 2-OH-glutaric acid with chiral confirmation as a readout of L2HGA.
  evidence:
  - reference: PMID:38714179
    reference_title: "Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Urine 2-OH-glutaric acid level was significantly elevated.
    explanation: Documents significantly elevated urinary 2-OH-glutaric acid in an L2HGA patient.
genetic:
- name: L2HGDH variants
  association: Causative
  relationship_type: CAUSATIVE
  gene_term:
    preferred_term: L2HGDH
    term:
      id: hgnc:20499
      label: L2HGDH
  variant_origin: GERMLINE
  inheritance:
  - name: Autosomal recessive
    evidence:
    - reference: PMID:37113859
      reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: L-2-hydroxyglutaric aciduria (L2HGA) is an autosomal recessive, slowly progressive neurodegenerative disease
      explanation: Directly states autosomal recessive inheritance.
  variants:
  - name: c.829C>T (p.Arg227*)
    description: 'Nonsense variant creating a premature stop codon, identified in a consanguineous Pakistani family. Both affected sisters were homozygous.

      '
    gene:
      preferred_term: L2HGDH
      term:
        id: hgnc:20499
        label: L2HGDH
  - name: c.164G>A (p.Gly55Asp)
    description: 'Missense variant affecting a conserved glycine residue, identified in a patient with severe dystonia requiring DBS intervention.

      '
    gene:
      preferred_term: L2HGDH
      term:
        id: hgnc:20499
        label: L2HGDH
  - name: c.407delA and c.699_700insA compound heterozygous
    description: 'Compound heterozygous frameshift mutations leading to premature termination codons and truncated FAD/NAD(P)-binding domain. Identified in a Chinese patient with psychomotor retardation and progressive ataxia.

      '
    gene:
      preferred_term: L2HGDH
      term:
        id: hgnc:20499
        label: L2HGDH
    evidence:
    - reference: PMID:29980873
      reference_title: "A novel compound heterozygous mutation of the L2HGDH gene in a Chinese boy with L-2-hydroxyglutaric aciduria: case report and literature review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Next-generation sequencing (NGS) revealed two novel compound heterozygous frameshift mutations, c.407 del A (p.K136SfsTer3) and c.699_c700 ins A (p.D234RfsTer42), in the L-2-hydroxyglutarate dehydrogenase (L2HGDH) gene
      explanation: Documents compound heterozygous variants disrupting the FAD-binding domain.
  features: 'L2HGDH encodes a mitochondrial FAD-dependent enzyme that catalyzes oxidation of L-2-hydroxyglutarate to alpha-ketoglutarate. Biallelic pathogenic variants including missense, nonsense, frameshift, and splice site mutations have been reported. The enzyme functions as a metabolite-repair enzyme clearing an aberrant byproduct of L-malate dehydrogenase activity. Consanguinity is a significant risk factor given the autosomal recessive inheritance.

    '
  evidence:
  - reference: PMID:22391998
    reference_title: "Progress in understanding 2-hydroxyglutaric acidurias."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We report on the clinical, genetic, enzymatic and metabolic characterization of D-2-HGA type I, D-2-HGA type II, L-2-HGA and D,L-2-HGA
    explanation: Comprehensive review of genetic, enzymatic, and metabolic characterization of L2HGA.
treatments:
- name: Riboflavin supplementation
  description: 'Riboflavin (vitamin B2), the precursor of FAD cofactor required by L2HGDH, is the cornerstone therapy for L2HGA. FAD supplementation aims to enhance any residual enzyme activity and accelerate conversion of L-2-HG to alpha-ketoglutarate. In cohort studies, riboflavin combined with levocarnitine produced significant decreases in urinary 2-HG levels and limited neurologic improvement.

    '
  treatment_term:
    preferred_term: B vitamin supplementation
    term:
      id: MAXO:0000761
      label: B vitamin supplementation
    therapeutic_agent:
    - preferred_term: riboflavin
      term:
        id: CHEBI:17015
        label: riboflavin
  evidence:
  - reference: PMID:37275239
    reference_title: "Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In all L2HGA patients, there was a significant decrease in the mean urinary 2- hydoxy glutarate with treatment.
    explanation: Demonstrates significant biochemical response to riboflavin/levocarnitine in L2HGA cohort.
  - reference: PMID:37275239
    reference_title: "Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Relative neurologic improvement was seen in three L2HGA patients.
    explanation: Documents some clinical improvement with riboflavin-based treatment.
  - reference: PMID:24321868
    reference_title: "[L-2-hydroxyglutaric aciduria: report on two cases]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Under specific treatment, the progression of the disease was subsequently stopped.
    explanation: Reports halting of disease progression under riboflavin treatment.
  target_mechanisms:
  - target: L2HGDH enzymatic deficiency
    treatment_effect: MODULATES
    description: Riboflavin supplies the precursor for the FAD cofactor required by L2HGDH, potentially improving residual enzyme flux.
    evidence:
    - reference: PMID:37275239
      reference_title: "Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: FAD, the cofactor of L2HGD, accelerates the conversion of L-2-hydoxy glutarate to alpha-ketoglutarate.
      explanation: Human cohort background links the riboflavin-derived FAD cofactor to L2HGDH-mediated L-2-HG conversion.
  - target: L-2-hydroxyglutarate accumulation
    treatment_effect: INHIBITS
    description: Riboflavin-containing therapy is associated with lower urinary 2-HG in treated L2HGA patients.
    evidence:
    - reference: PMID:37275239
      reference_title: "Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: In all L2HGA patients, there was a significant decrease in the mean urinary 2- hydoxy glutarate with treatment.
      explanation: Cohort data support a biochemical treatment-response edge from riboflavin-based therapy to reduced L-2-HG accumulation.
- name: Levocarnitine supplementation
  description: 'Levocarnitine is used alongside riboflavin as part of standard metabolic therapy for L2HGA. It supports organic acid detoxification and excretion pathways.

    '
  treatment_term:
    preferred_term: carnitine supplementation
    term:
      id: MAXO:0010006
      label: carnitine supplementation
    therapeutic_agent:
    - preferred_term: levocarnitine
      term:
        id: CHEBI:16347
        label: (R)-carnitine
  evidence:
  - reference: PMID:37275239
    reference_title: "Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Current treatment strategies are based on levocarnitine, vitamin B2, and diet.
    explanation: Confirms levocarnitine as a component of standard treatment for L2HGA.
  - reference: PMID:37275239
    reference_title: "Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In L2HGA patients, we used levocarnitine and vitamin B2.
    explanation: Documents use of levocarnitine in all L2HGA patients in this cohort.
  target_mechanisms:
  - target: L-2-hydroxyglutarate accumulation
    treatment_effect: MODULATES
    description: Levocarnitine is used in combination with riboflavin in L2HGA treatment regimens associated with lower urinary 2-HG.
    evidence:
    - reference: PMID:37275239
      reference_title: "Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Riboflavin and levocarnitine have been reported to improve not only clinical symptoms but also urinary 2-HGA levels.
      explanation: Cohort background supports levocarnitine-containing treatment as a modifier of urinary 2-HGA levels, though not as monotherapy.
- name: Deep brain stimulation
  description: 'Bilateral globus pallidus internus deep brain stimulation (GPi-DBS) has been used for L2HGA-related refractory dystonia with reported significant improvements in mobility and dystonia severity. This represents an emerging intervention for severe, pharmacoresistant movement disorders in L2HGA.

    '
  treatment_term:
    preferred_term: deep brain stimulation
    term:
      id: MAXO:0000943
      label: deep brain stimulation
  evidence:
  - reference: PMID:38714179
    reference_title: "Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Significant increases in mobility and decrease in dystonia were observed at 3 weeks, 6 months, and 12 months postoperatively.
    explanation: Documents significant improvement with GPi-DBS in L2HGA-related dystonia.
  - reference: PMID:38714179
    reference_title: "Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: This is the first utilization of DBS as treatment for L2HGA-related dystonia.
    explanation: Establishes GPi-DBS as a novel therapeutic option for L2HGA dystonia.
  target_phenotypes:
  - preferred_term: Dystonia
    term:
      id: HP:0001332
      label: Dystonia
  target_mechanisms:
  - target: Basal ganglia and cerebellar circuit involvement
    treatment_effect: MODULATES
    description: GPi-DBS modulates basal ganglia output circuits driving refractory dystonia.
    evidence:
    - reference: PMID:38714179
      reference_title: "Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Significant increases in mobility and decrease in dystonia were observed at 3 weeks, 6 months, and 12 months postoperatively.
      explanation: Postoperative improvement supports a circuit-modulating treatment edge for severe L2HGA dystonia.
- name: Supportive care and rehabilitation
  description: 'Comprehensive supportive care including physical therapy, occupational therapy, speech therapy, and educational support is essential for managing the chronic neurological disabilities of L2HGA.

    '
  treatment_term:
    preferred_term: supportive care
    term:
      id: MAXO:0000950
      label: supportive care
  evidence:
  - reference: PMID:37275239
    reference_title: "Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Relative neurologic improvement was seen in three L2HGA patients.
    explanation: Some patients show improvement with comprehensive treatment approach, supporting role of ongoing supportive care.
  target_phenotypes:
  - preferred_term: Cerebellar ataxia
    term:
      id: HP:0001251
      label: Ataxia
  - preferred_term: Dysarthria
    term:
      id: HP:0001260
      label: Dysarthria
  - preferred_term: Psychomotor retardation
    term:
      id: HP:0001263
      label: Global developmental delay
  - preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
- name: Genetic counseling
  description: 'Genetic counseling for affected families addressing autosomal recessive inheritance, 25% recurrence risk, carrier testing for at-risk relatives, and prenatal/preimplantation testing options. Consanguinity is a significant factor in many reported families.

    '
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: MAXO:0000079
      label: genetic counseling
  evidence:
  - reference: PMID:37113859
    reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Both parents were heterozygous carriers of the familial variant.
    explanation: Carrier status in parents supports autosomal recessive counseling approach.
  target_mechanisms:
  - target: L2HGDH enzymatic deficiency
    treatment_effect: MODULATES
    description: Genetic counseling uses the L2HGDH molecular diagnosis for recurrence-risk and carrier counseling rather than directly altering enzyme activity.
    evidence:
    - reference: PMID:37113859
      reference_title: "L-2-hydroxyglutaric aciduria - review of literature and case series."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Targeted L2HGDH sequencing identified a homozygous pathogenic variant, c.829C>T (p.Arg227*) in L2HGDH gene in both girls.
      explanation: Molecular confirmation of the familial L2HGDH variant supports variant-informed counseling.
- name: Dietary intervention
  description: 'Dietary management may be employed as part of the treatment approach, though the evidence base is less established than for other organic acidemias. Unlike glutaric aciduria type I, there is no specific amino acid restriction protocol for L2HGA.

    '
  treatment_term:
    preferred_term: dietary intervention
    term:
      id: MAXO:0000088
      label: dietary intervention
  evidence:
  - reference: PMID:37275239
    reference_title: "Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Current treatment strategies are based on levocarnitine, vitamin B2, and diet.
    explanation: Diet is listed as one component of current treatment strategies.
  target_mechanisms:
  - target: L-2-hydroxyglutarate accumulation
    treatment_effect: MODULATES
    description: Diet is part of current L2HGA treatment strategies, although the specific metabolite-lowering contribution is less established than riboflavin/levocarnitine.
    evidence:
    - reference: PMID:37275239
      reference_title: "Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey."
      supports: PARTIAL
      evidence_source: HUMAN_CLINICAL
      snippet: Current treatment strategies are based on levocarnitine, vitamin B2, and diet.
      explanation: The cohort identifies diet as part of treatment strategy but does not isolate a diet-specific effect on L-2-HG.
- name: Neuroimaging surveillance
  description: 'Regular brain MRI monitoring to track disease progression and to screen for CNS tumor development, given the elevated tumor risk in L2HGA patients. MR spectroscopy can provide additional metabolic information.

    '
  treatment_term:
    preferred_term: supportive care
    term:
      id: MAXO:0000950
      label: supportive care
  evidence:
  - reference: PMID:38716347
    reference_title: "Malignant glioma in L-2-Hydroxyglutaric Aciduria: thorough molecular characterization of a case and literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: L-2-HGA patients have a significantly increased lifetime risk of central nervous system (CNS) tumors.
    explanation: Increased CNS tumor risk mandates ongoing neuroimaging surveillance.
  target_phenotypes:
  - preferred_term: CNS neoplasm
    term:
      id: HP:0100836
      label: Malignant neoplasm of the central nervous system
  - preferred_term: Subcortical leukoencephalopathy
    term:
      id: HP:0002352
      label: Leukoencephalopathy
notes: 'L2HGA is classified as a disorder of metabolite repair rather than a classic enzyme-deficiency organic acidemia. Unlike most organic acidemias, L2HGA does not feature acute metabolic decompensation episodes. The disease was first described in 1980 and the causative gene L2HGDH was identified in 2004. The relationship between chronic L-2-HG accumulation and brain tumorigenesis is an active area of investigation, with emerging evidence suggesting a two-hit oncogenesis model where L-2-HG elevation may prime tissue for tumor development but a secondary somatic mutation is required.

  '
references:
- reference: PMID:22391998
  title: Progress in understanding 2-hydroxyglutaric acidurias.
  found_in:
  - L-2-Hydroxyglutaric_Aciduria-deep-research-falcon.md
  findings: []
- reference: PMID:37113859
  title: L-2-hydroxyglutaric aciduria - review of literature and case series.
  found_in:
  - L-2-Hydroxyglutaric_Aciduria-deep-research-falcon.md
  findings: []
- reference: PMID:37275239
  title: 'Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey.'
  found_in:
  - L-2-Hydroxyglutaric_Aciduria-deep-research-falcon.md
  findings: []
- reference: PMID:38714179
  title: Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria.
  found_in:
  - L-2-Hydroxyglutaric_Aciduria-deep-research-falcon.md
  findings: []
- reference: PMID:38716347
  title: 'Malignant glioma in L-2-Hydroxyglutaric Aciduria: thorough molecular characterization of a case and literature review.'
  found_in:
  - L-2-Hydroxyglutaric_Aciduria-deep-research-falcon.md
  findings: []
- reference: PMID:28137912
  title: L2hgdh Deficiency Accumulates l-2-Hydroxyglutarate with Progressive Leukoencephalopathy and Neurodegeneration.
  found_in:
  - L-2-Hydroxyglutaric_Aciduria-deep-research-falcon.md
  findings: []
- reference: PMID:38862727
  title: Both Enantiomers of 2-Hydroxyglutarate Modulate the Metabolism of Cultured Human Neuroblastoma Cells.
  found_in:
  - L-2-Hydroxyglutaric_Aciduria-deep-research-falcon.md
  findings: []
- reference: PMID:24321868
  title: '[L-2-hydroxyglutaric aciduria: report on two cases].'
  found_in:
  - L-2-Hydroxyglutaric_Aciduria-deep-research-falcon.md
  findings: []
- reference: PMID:29980873
  title: 'A novel compound heterozygous mutation of the L2HGDH gene in a Chinese boy with L-2-hydroxyglutaric aciduria: case report and literature review.'
  found_in:
  - L-2-Hydroxyglutaric_Aciduria-deep-research-falcon.md
  findings: []
📚

References & Deep Research

References

9
PMID:22391998
Progress in understanding 2-hydroxyglutaric acidurias.
No top-level findings curated for this source.
PMID:37113859
L-2-hydroxyglutaric aciduria - review of literature and case series.
No top-level findings curated for this source.
PMID:37275239
Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey.
No top-level findings curated for this source.
PMID:38714179
Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria.
No top-level findings curated for this source.
PMID:38716347
Malignant glioma in L-2-Hydroxyglutaric Aciduria: thorough molecular characterization of a case and literature review.
No top-level findings curated for this source.
PMID:28137912
L2hgdh Deficiency Accumulates l-2-Hydroxyglutarate with Progressive Leukoencephalopathy and Neurodegeneration.
No top-level findings curated for this source.
PMID:38862727
Both Enantiomers of 2-Hydroxyglutarate Modulate the Metabolism of Cultured Human Neuroblastoma Cells.
No top-level findings curated for this source.
PMID:24321868
[L-2-hydroxyglutaric aciduria: report on two cases].
No top-level findings curated for this source.
PMID:29980873
A novel compound heterozygous mutation of the L2HGDH gene in a Chinese boy with L-2-hydroxyglutaric aciduria: case report and literature review.
No top-level findings curated for this source.

Deep Research

1
Falcon ▸
Disease Pathophysiology Research Template
Edison Scientific Literature 38 citations 2026-02-23T23:50:01.816674

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Disease Pathophysiology Research Template

Target Disease

  • Disease Name: L-2-Hydroxyglutaric Aciduria
  • MONDO ID: (if available)
  • Category: Genetic

Research Objectives

Please provide a comprehensive research report on the pathophysiology of L-2-Hydroxyglutaric Aciduria. Focus on the molecular and cellular mechanisms underlying disease progression.

Required Information

1. Core Pathophysiology

  • What are the primary pathophysiological mechanisms?
  • What molecular pathways are dysregulated?
  • What cellular processes are affected?

2. Key Molecular Players

  • Genes/Proteins: Which genes are causally involved or implicated?
  • Chemical Entities: What metabolites, drugs, or small molecules are relevant?
  • Cell Types: Which cell types are primarily affected?
  • Anatomical Locations: Which tissues/organs are involved?

3. Biological Processes (for GO annotation)

  • What biological processes (GO terms) are disrupted?
  • Consider: signaling pathways, metabolic processes, cellular responses, transport, etc.

4. Cellular Components

  • Where in the cell do key processes occur?
  • Consider: organelles, membrane compartments, extracellular space, etc.

5. Disease Progression

  • What is the sequence of events from initial trigger to clinical manifestation?
  • Are there distinct stages or phases?

6. Phenotypic Manifestations

  • What are the key clinical phenotypes?
  • How do they relate to the underlying mechanisms?

Citation Requirements

  • Cite primary literature (PMID preferred) for all mechanistic claims
  • Prioritize recent reviews and landmark papers
  • Include direct quotes where possible to support key statements

Output Format

Structure your response as a narrative that could be used to populate a disease knowledge base entry with: - Pathophysiology description - Gene/protein annotations with ontology terms (HGNC, GO) - Phenotype associations (HP terms) - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Evidence items with PMIDs

Title: Pathophysiology of L-2-Hydroxyglutaric Aciduria (L2HGA) — 2026 evidence-based report

Target disease: L-2-hydroxyglutaric aciduria (L2HGA) Category: Genetic neurometabolic disorder (autosomal recessive cerebral organic aciduria; “disorder of metabolite repair”) (kranendijk2012progressinunderstanding pages 7-8)

MONDO ID: Not retrieved from tools in this run (OpenTargets disease mapping failed) (ma2017l2hgdhdeficiencyaccumulates pages 1-2)

  1. Key concepts and current definitions

Disease definition and biochemical hallmark L2HGA is defined by abnormal accumulation of the metabolite L-2-hydroxyglutarate (L-2-HG) in body fluids (urine, plasma, CSF) (kranendijk2012progressinunderstanding pages 1-3). In a large review of 2-hydroxyglutaric acidurias, urinary L-2-HG was reported to be ~10–300× higher than controls, with elevated plasma and CSF; CSF/plasma ratio can exceed 1, consistent with brain enrichment (kranendijk2012progressinunderstanding pages 8-9, kranendijk2012progressinunderstanding pages 9-11).

Causative gene, enzyme function, and subcellular localization The core causal gene for L2HGA is L2HGDH, encoding the FAD-dependent enzyme L-2-hydroxyglutarate dehydrogenase (L-2-HGDH) (kranendijk2012progressinunderstanding pages 8-9, kranendijk2012progressinunderstanding pages 1-3). L-2-HGDH catalyzes oxidation of L-2-HG back to α-ketoglutarate/2-ketoglutarate (2-KG) using FAD (kranendijk2012progressinunderstanding pages 8-9, kranendijk2012progressinunderstanding pages 9-11). Mechanistically, L-2-HG is produced endogenously as an off-pathway (“non-specific side reaction”) product from 2-KG by L-malate dehydrogenase (L-malDH) using NADH; L-2-HGDH therefore functions as a metabolite-repair enzyme that clears this aberrant metabolite (kranendijk2012progressinunderstanding pages 8-9, kranendijk2012progressinunderstanding pages 1-3).

Mitochondrial localization is a key concept: L2HGDH is described as a mitochondrial enzyme in a 2024 epilepsy-focused review (direct statement: L2HGDH is “an important mitochondrial enzyme … which oxidizes the L-2-hydroxyglutarate into α-ketoglutarate”) (shi2024disordersoforganic pages 6-7). A clinical genetics/imaging review excerpt further reports L-2-HGDH is present in mitochondria and membrane-associated by subcellular fractionation (erdal2025geneticneuroimagingand pages 4-5). In mouse disease modeling, L2hgdh deficiency caused robust L-2-HG accumulation particularly in brain and testis (ma2017l2hgdhdeficiencyaccumulates pages 1-2).

  1. Core pathophysiology (molecular and cellular mechanisms)

2.1 Primary trigger: L2HGDH loss-of-function → L-2-HG accumulation The initiating event in L2HGA is biallelic loss-of-function in L2HGDH, leading to reduced conversion of L-2-HG to 2-KG and systemic/brain accumulation of L-2-HG (kranendijk2012progressinunderstanding pages 8-9, kranendijk2012progressinunderstanding pages 1-3).

2.2 White-matter vulnerability and demyelination/leukoencephalopathy Human neuroimaging is characterized by a stereotyped pattern dominated by subcortical white matter involvement with deep gray nuclei (basal ganglia/dentate nucleus) involvement (kranendijk2012progressinunderstanding pages 7-8, kranendijk2012progressinunderstanding pages 8-9). In an L2hgdh knockout mouse model, loss of L2hgdh produced “progressive leukoencephalopathy and neurodegeneration,” with findings consistent with demyelination and white matter pathology, including gliosis and microglial neuroinflammation (ma2017l2hgdhdeficiencyaccumulates pages 1-2). The corresponding figure-based evidence in that model includes T2 MRI changes, myelin staining (Luxol fast blue; FluoroMyelin), and reduced MBP readouts in affected white matter (ma2017l2hgdhdeficiencyaccumulates media 23a1cbfb).

2.3 Mitochondrial dysfunction and impaired respiratory capacity Several lines of evidence link elevated L-2-HG to impaired mitochondrial bioenergetics:

• Review-level mechanistic claims collated in the mouse model paper note that 2-HG can impair oxidative phosphorylation components (“cytochrome c oxidase and ATP synthase”) and is considered a mitochondrial stressor relevant to white-matter pathology (ma2017l2hgdhdeficiencyaccumulates pages 1-2). • In a 2024 human neuronal-cell model (SH-SY5Y neuroblastoma), exposure to 0.1 mM L-2-HG for 24 h produced a metabolic shift toward anaerobic glycolysis (e.g., increased lactate:glucose ratio) and reduced maximal respiration capacity (maximal specific respiration decreased to ~66–78% of control, while basal respiration was unchanged) (gondas2024bothenantiomersof pages 6-9, gondas2024bothenantiomersof pages 5-6). Quantitative media-metabolite changes included reduced glucose uptake (control −518 ± 141 to L-2HG −302 ± 22 nmol·h−1·mg−1), increased lactate release (135 ± 23 to 158 ± 9), and increased alanine (7 ± 2 to 13 ± 1), interpreted as less pyruvate entering the TCA cycle (gondas2024bothenantiomersof pages 5-6).

2.4 Oxidative stress and enzyme inhibition (energy metabolism/neuronal injury) In vitro tissue exposure experiments summarized in the 2012 review report that L-2-HG inhibited creatine kinase and induced oxidative stress in rat cerebellum homogenates, offering a plausible mechanism for neuronal/white-matter injury (kranendijk2012progressinunderstanding pages 8-9, kranendijk2012progressinunderstanding pages 9-11). A clinical cohort review (2025) similarly frames L2HGA pathophysiology around CNS disruption and oxidative stress, consistent with the broader literature, though the excerpted details are limited (erdal2025geneticneuroimagingand pages 1-2).

2.5 Epigenetic dysregulation via inhibition of α-KG–dependent dioxygenases (emerging/expanded mechanism) L-2-HG is an α-KG analog and can inhibit α-KG–dependent dioxygenases. In the L2hgdh-deficient mouse model, L-2-HG accumulation was associated with increased histone methylation, consistent with inhibition of JmjC histone demethylases and TET DNA hydroxylases (ma2017l2hgdhdeficiencyaccumulates pages 1-2). More recently, a 2024 glioma case/literature analysis explicitly states that L-2-HG “inhibits TET1 and TET2” and may be more potent than D-2-HG in some measures, supporting a mechanistic bridge between L-2-HG and methylome alteration (cordier2024malignantgliomain pages 7-9). Importantly, Cordier et al. also highlight that high intratumoral 2-HG production in IDH-mutant glioma differs from systemic “passive” accumulation in L2HGA, which could yield different epigenetic outcomes (cordier2024malignantgliomain pages 9-10).

  1. Key molecular players

3.1 Genes/proteins (HGNC-level)

Causal gene • L2HGDH (encodes mitochondrial FAD-dependent L-2-hydroxyglutarate dehydrogenase) (kranendijk2012progressinunderstanding pages 8-9, shi2024disordersoforganic pages 6-7).

Other implicated molecular axes (not necessarily causal) • L-malate dehydrogenase (L-malDH): the only known human enzyme generating L-2-HG from 2-KG as an off-target reaction (kranendijk2012progressinunderstanding pages 1-3). • α-KG–dependent dioxygenases (e.g., TET family; JmjC/KDM histone demethylases): mechanistic targets inhibited by 2-HG enantiomers, including L-2-HG (ma2017l2hgdhdeficiencyaccumulates pages 1-2, cordier2024malignantgliomain pages 7-9). • Mitochondrial respiratory chain/ATP synthase components: implicated as functional targets of 2-HG in mechanistic discussion (ma2017l2hgdhdeficiencyaccumulates pages 1-2).

3.2 Chemical entities (CHEBI-level) • L-2-hydroxyglutarate (L-2-HG): the main accumulated pathogenic metabolite (kranendijk2012progressinunderstanding pages 1-3). • α-ketoglutarate / 2-ketoglutarate (2-KG): substrate/product node; precursor for off-pathway L-2-HG formation and target of L-2-HG oxidation back-reaction (kranendijk2012progressinunderstanding pages 8-9, kranendijk2012progressinunderstanding pages 1-3). • FAD / riboflavin (vitamin B2 precursor): cofactor/precursor relevant to L-2-HGDH activity and a common supportive therapy; FAD is described as accelerating conversion of L-2-HG to α-ketoglutarate (bozaci2023glutaricaciduriaand pages 2-3, kranendijk2012progressinunderstanding pages 9-11). • Levocarnitine: commonly used supportive therapy in reported cohorts (bozaci2023glutaricaciduriaand pages 1-2).

3.3 Cell types (CL-level) Evidence from the L2hgdh mouse model indicates a glial/white-matter process with: • Oligodendrocyte lineage involvement (expansion of oligodendrocyte progenitor cells, OPCs) (ma2017l2hgdhdeficiencyaccumulates pages 1-2). • Microglia-mediated neuroinflammation and gliosis (ma2017l2hgdhdeficiencyaccumulates pages 1-2). • Astrocytic proliferation around dentate nucleus has been reported in human histopathology summarized in an MRS review (sherry2015invivonmr pages 10-12).

3.4 Anatomical locations (UBERON-level) Predominant CNS involvement, especially: • Subcortical cerebral white matter (U-fibers/peripheral white matter) (kranendijk2012progressinunderstanding pages 7-8, alamri2024deepbrainstimulation pages 3-4). • Basal ganglia structures (globus pallidus, putamen, caudate) and dentate nucleus (kranendijk2012progressinunderstanding pages 7-8, kranendijk2012progressinunderstanding pages 8-9). • Cerebellum/dentate nucleus involvement is frequently linked to cerebellar ataxia (kranendijk2012progressinunderstanding pages 8-9).

  1. Biological processes disrupted (GO-style candidates) The evidence supports disruption of the following process categories:

Metabolite repair / organic acid metabolism • “Disorder of metabolite repair” framing: L-2-HGDH clears off-pathway L-2-HG generated by L-malDH (kranendijk2012progressinunderstanding pages 7-8, kranendijk2012progressinunderstanding pages 1-3).

Mitochondrial energy metabolism / respiration • Decreased maximal respiration capacity and bioenergetic reprogramming toward anaerobic glycolysis under L-2-HG exposure (gondas2024bothenantiomersof pages 6-9, gondas2024bothenantiomersof pages 5-6).

Oxidative stress response • Induction of oxidative stress by L-2-HG exposure in experimental systems (kranendijk2012progressinunderstanding pages 9-11).

Myelination / white matter maintenance • Progressive leukoencephalopathy/demyelination in mouse model and characteristic white-matter imaging phenotype in humans (ma2017l2hgdhdeficiencyaccumulates pages 1-2, kranendijk2012progressinunderstanding pages 8-9).

Epigenetic regulation of gene expression (DNA/histone modification) • Increased histone methylation in L2hgdh deficiency and reported TET inhibition by L-2-HG in mechanistic discussion (ma2017l2hgdhdeficiencyaccumulates pages 1-2, cordier2024malignantgliomain pages 7-9).

Neuroinflammation / gliosis • Gliosis and microglia-mediated neuroinflammation in the L2hgdh knockout model (ma2017l2hgdhdeficiencyaccumulates pages 1-2).

  1. Cellular components (subcellular localization) • Mitochondrion / mitochondrial membrane: L2HGDH is mitochondrial and membrane-associated (shi2024disordersoforganic pages 6-7, erdal2025geneticneuroimagingand pages 4-5). • Nucleus/chromatin: downstream epigenetic effects are mediated by inhibition of nuclear α-KG–dependent dioxygenases (histone/DNA demethylation machinery), consistent with histone methylation changes observed in L2hgdh deficiency (ma2017l2hgdhdeficiencyaccumulates pages 1-2).

  2. Disease progression: sequence of events (mechanistic narrative)

Stage 1 — Metabolite repair failure and metabolite accumulation Biallelic L2HGDH loss reduces mitochondrial oxidation of L-2-HG to 2-KG, allowing L-2-HG (produced from 2-KG via non-specific L-malDH activity) to accumulate systemically and in brain/CSF (kranendijk2012progressinunderstanding pages 8-9, kranendijk2012progressinunderstanding pages 1-3).

Stage 2 — Cellular metabolic stress (mitochondrial + redox) Elevated L-2-HG perturbs cellular metabolism, shifting glucose utilization toward anaerobic pathways and reducing maximal mitochondrial respiratory capacity in neuronal cell models; additional literature points to oxidative stress and inhibition of energy enzymes like creatine kinase (gondas2024bothenantiomersof pages 5-6, kranendijk2012progressinunderstanding pages 9-11).

Stage 3 — White-matter injury, gliosis, and neuroinflammation Selective CNS vulnerability manifests as subcortical white-matter abnormalities with basal ganglia/dentate involvement on imaging; in mouse models, demyelination/leukoencephalopathy is accompanied by gliosis, microglial neuroinflammation, and altered oligodendrocyte lineage dynamics (OPC expansion) (kranendijk2012progressinunderstanding pages 8-9, ma2017l2hgdhdeficiencyaccumulates pages 1-2).

Stage 4 — Progressive neurological disability and potential tumor predisposition Clinically, L2HGA typically follows a slowly progressive course with developmental delay, epilepsy, cerebellar dysfunction/ataxia, and movement disorders (kranendijk2012progressinunderstanding pages 7-8, bozaci2023glutaricaciduriaand pages 6-7). A subset of patients appear to have increased CNS tumor risk; mechanistic hypotheses implicate L-2-HG’s ability to inhibit epigenetic regulators (e.g., TET enzymes), but molecular tumor signatures may differ from IDH-mutant (D-2-HG) gliomas (cordier2024malignantgliomain pages 1-3, cordier2024malignantgliomain pages 9-10).

  1. Phenotypic manifestations (HP-style associations) and mechanistic links

Core phenotypes and linkage to mechanisms • Seizures/epilepsy: common in cohorts; interpreted in part as downstream of cortical/subcortical white-matter pathology and/or neurotransmitter system disruption; the 2024 epilepsy review links L-2-HG accumulation to GABAergic dysfunction and reports characteristic MRI/MRS changes in this disorder group (shi2024disordersoforganic pages 6-7, bozaci2023glutaricaciduriaand pages 6-7). • Developmental delay / intellectual disability: prevalent in cohort data (e.g., 2012 review and 2023 cohort) and consistent with early white-matter maturation abnormalities and chronic metabolic/epigenetic perturbation (kranendijk2012progressinunderstanding pages 7-8, bozaci2023glutaricaciduriaand pages 3-4). • Cerebellar ataxia and extrapyramidal features (dystonia/chorea): align with dentate nucleus and basal ganglia involvement on MRI (kranendijk2012progressinunderstanding pages 8-9, alamri2024deepbrainstimulation pages 3-4).

Recent cohort statistics (2023–2025) for phenotype frequency In a 2023 multicenter Turkish cohort (n=10 L2HGA), clinical counts at diagnosis included seizures 3/10, developmental delay 2/10, movement disorders 2/10, behavioral problems 2/10; at last follow-up movement disorders 5/10, epilepsy 2/10, developmental delay 4/10, behavioral problems 4/10 (bozaci2023glutaricaciduriaand pages 6-7). The same report notes literature context that macrocephaly (75%) and epilepsy are common but nonspecific (bozaci2023glutaricaciduriaand pages 6-7).

  1. Recent developments and latest research (prioritizing 2023–2024)

8.1 2024: Human neuronal-cell metabolic effects of L-2-HG A 2024 Neurochemical Research study provides quantitative evidence that L-2-HG can directly reprogram neuronal-like cell metabolism and reduce maximal respiration capacity, supporting mitochondrial/energy-pathway involvement beyond purely descriptive clinical imaging (gondas2024bothenantiomersof pages 5-6).

8.2 2024: L2HGA and malignant glioma — molecular characterization and epigenetic analysis Cordier et al. (2024) provide a detailed case plus literature review exploring whether systemic L-2-HG accumulation drives IDH-like epigenetic glioma signatures. They report that, despite mechanistic rationale (L-2-HG can inhibit TET1/2), the tumor lacked G-CIMP and clustered with IDH-wildtype glioma methylation patterns, alongside somatic alterations (TP53, NF1, BCOR) consistent with a second-hit model (cordier2024malignantgliomain pages 7-9, cordier2024malignantgliomain pages 3-6). This supports an expert interpretation that L-2-HG may contribute to tumor susceptibility but is not necessarily sufficient to impose the classic IDH-mutant methylation phenotype in all cases (cordier2024malignantgliomain pages 9-10).

8.3 2023: Natural history/real-world treatment monitoring in a multicenter cohort Bozaci et al. (2023) report structured follow-up and real-world therapy use (riboflavin + levocarnitine in all 10 L2HGA cases) and state there was a “significant decrease in urinary 2-HGA with the treatment” (bozaci2023glutaricaciduriaand pages 1-2, bozaci2023glutaricaciduriaand pages 6-7). However, subgroup comparisons by genotype did not show significant differences in biochemical response in the excerpt, and symptom improvements were limited (“relative neurologic improvement” in 3 L2HGA patients) (bozaci2023glutaricaciduriaand pages 1-2, bozaci2023glutaricaciduriaand pages 2-3).

  1. Current applications and real-world implementations

9.1 Supportive metabolic therapy (riboflavin/FAD-related; levocarnitine) Multiple clinical sources describe riboflavin (vitamin B2; FAD precursor) and levocarnitine as commonly used therapies. The 2012 review reports anecdotal responses where FAD (or riboflavin) and levocarnitine lowered urinary L-2-HG and improved some clinical features, consistent with the enzyme’s FAD dependence (kranendijk2012progressinunderstanding pages 9-11). In the 2023 cohort, all L2HGA patients were treated with riboflavin plus levocarnitine, with significant urinary 2-HGA reduction reported and limited neurologic improvement (bozaci2023glutaricaciduriaand pages 1-2).

9.2 Neuromodulation for severe movement disorder (2024 GPi-DBS case report) A 2024 peer-reviewed case report describes the first reported use of bilateral globus pallidus internus deep brain stimulation (GPi-DBS) for medically refractory dystonia in L2HGA. The family reported “approximately 50% improvement,” and the authors report “significant increases in mobility and decrease in dystonia” at serial follow-up; BFMDRS-M improved (e.g., 46/120 preop to 21.5/120 at 6 months) with subsequent fluctuations related to infection and programming (alamri2024deepbrainstimulation pages 2-3). This represents an emerging real-world intervention for advanced motor disability when pharmacotherapy is insufficient (alamri2024deepbrainstimulation pages 1-2).

9.3 Imaging and metabolite detection in practice Proton MR spectroscopy (MRS) can show a metabolite-specific peak at ~2.50 ppm attributed to L-2-hydroxyglutaric acid, and decreased NAA with increased Cho/Cr ratio, linking biochemical accumulation to in vivo neurochemical signatures (sherry2015invivonmr pages 10-12). Such imaging is used as part of diagnostic workup alongside urine organic acids and genetic testing (alamri2024deepbrainstimulation pages 2-2).

  1. Expert opinions and analysis (authoritative sources)

Metabolite-repair framing The authoritative 2012 JIMD review classifies L2HGA as a “disorder of metabolite repair,” emphasizing that the pathophysiology arises from failure to clear an abnormal byproduct metabolite rather than blockade of a canonical pathway step (kranendijk2012progressinunderstanding pages 7-8).

Two-hit oncogenesis concept Cordier et al. (2024) propose a “two-tiered oncogenesis” model: chronic L-2-HG elevation may prime tissue (first hit), but a secondary somatic mutation is required for tumor development (cordier2024malignantgliomain pages 9-10). This interpretation is grounded in their methylation/WES findings and comparison to IDH-mutant glioma biology (cordier2024malignantgliomain pages 3-6).

  1. Evidence-linked statistics and data (recent)

Cohort size and phenotype counts (2023) Bozaci et al. (2023) report 10 L2HGA patients (within a 35-patient cerebral organic aciduria cohort). At diagnosis: seizures 3/10, developmental delay 2/10, movement disorders 2/10, behavioral problems 2/10; at last visit: movement disorders 5/10, epilepsy 2/10, developmental delay 4/10, behavioral problems 4/10 (bozaci2023glutaricaciduriaand pages 6-7, bozaci2023glutaricaciduriaand pages 3-4). Treatment initiation age mean 53.36 ± 47.43 months (range 6–180) in their L2HGA subgroup (bozaci2023glutaricaciduriaand pages 6-7).

Quantitative cellular bioenergetics/metabolic data (2024) In SH-SY5Y cells exposed to 0.1 mM L-2-HG, maximal respiration capacity decreased (control maximal respiration 73 ± 3 pmol·s−1 per 10^6 cells; maximal capacity decreased to ~66–78% of control under 2-HG enantiomers), and glucose uptake decreased while lactate and alanine release increased (gondas2024bothenantiomersof pages 5-6).

DBS outcomes (2024) In the GPi-DBS L2HGA case, BFMDRS-M scores improved with stimulation (e.g., to 21.5/120 at 6 months; with longer-term values reported through 13 months) and the family reported ~50% improvement in function and dystonia severity (alamri2024deepbrainstimulation pages 2-3).

  1. Clinical trials and research infrastructure No interventional trials specific to isolated L2HGA were retrieved in this run. Two relevant ClinicalTrials.gov records were retrieved:

• NCT07125066 (start date 2025-07-30): single-patient, open-label Phase 1 study using ACER-001 (sodium phenylbutyrate; Olpruva) for combined D,L-2-hydroxyglutaric aciduria (C-2HGA), with endpoints including urine D,L-2-HG and seizure frequency (NCT07125066 chunk 1). • NCT04880356 (start date 2021-03-01): observational longitudinal natural-history data collection study of ultra-rare inherited metabolic/degenerative neurological diseases, explicitly including L-2-hydroxyglutaric aciduria; endpoints include cognitive fluency, gait/stance metrics (SARA stance, TUG), upper limb function, and QoL (EQ-5D-5L) over a planned 10-year follow-up (NCT04880356 chunk 1).

  1. Knowledge-base annotation suggestions (ontology-oriented)

Gene/protein • L2HGDH (HGNC symbol; mitochondrial FAD-dependent L-2-hydroxyglutarate dehydrogenase) (kranendijk2012progressinunderstanding pages 8-9).

Proposed GO Biological Process terms (candidate mapping) • “Organic acid metabolic process” / “2-hydroxyglutarate metabolic process” (supported by L-2-HG accumulation and enzymatic defect) (kranendijk2012progressinunderstanding pages 1-3). • “Mitochondrial respiratory chain complex activity / oxidative phosphorylation” (supported by reduced maximal respiration capacity and OXPHOS impairment discussion) (gondas2024bothenantiomersof pages 5-6, ma2017l2hgdhdeficiencyaccumulates pages 1-2). • “Response to oxidative stress” (supported by oxidative stress induction in experimental data summarized in review) (kranendijk2012progressinunderstanding pages 9-11). • “Myelination” / “axon ensheathment” / “glial cell activation” (supported by leukoencephalopathy/demyelination, gliosis, microglial neuroinflammation) (ma2017l2hgdhdeficiencyaccumulates pages 1-2, ma2017l2hgdhdeficiencyaccumulates media 23a1cbfb). • “Chromatin modification” / “DNA demethylation” / “histone demethylation” (supported by increased histone methylation and TET inhibition discussion) (ma2017l2hgdhdeficiencyaccumulates pages 1-2, cordier2024malignantgliomain pages 7-9).

Proposed GO Cellular Component terms (candidate mapping) • Mitochondrion; mitochondrial inner membrane (enzyme localization; respiratory coupling concept) (erdal2025geneticneuroimagingand pages 4-5). • Nucleus/chromatin (downstream epigenetic targets of 2-HG) (ma2017l2hgdhdeficiencyaccumulates pages 1-2).

Cell types (CL) • Oligodendrocyte progenitor cell (OPC) (mouse model shows OPC expansion) (ma2017l2hgdhdeficiencyaccumulates pages 1-2). • Microglia (microglia-mediated neuroinflammation) (ma2017l2hgdhdeficiencyaccumulates pages 1-2). • Astrocyte (gliosis; astrocytic proliferation around dentate nucleus in human pathology summary) (sherry2015invivonmr pages 10-12).

Anatomy (UBERON) • Subcortical cerebral white matter/U-fibers; basal ganglia; dentate nucleus; cerebellum (imaging/pathology distribution) (alamri2024deepbrainstimulation pages 3-4, kranendijk2012progressinunderstanding pages 8-9).

Chemicals (CHEBI) • L-2-hydroxyglutarate; α-ketoglutarate/2-oxoglutarate; FAD; riboflavin; levocarnitine (kranendijk2012progressinunderstanding pages 1-3, bozaci2023glutaricaciduriaand pages 2-3).

  1. Evidence items (PMID-focused) — limitations The retrieved excerpts in this run did not include PubMed IDs (PMIDs) in the tool outputs; therefore, this report provides DOI URLs and journal metadata but cannot reliably attach PMIDs without external lookup. Mechanistic claims and statistics are cited to retrieved sources (pqac IDs) with URLs and publication dates where available.

  2. Key references (with URLs and dates from retrieved sources)

• Ma S et al. “L2hgdh Deficiency Accumulates L-2-Hydroxyglutarate with Progressive Leukoencephalopathy and Neurodegeneration.” Molecular and Cellular Biology. Apr 2017. https://doi.org/10.1128/mcb.00492-16 (ma2017l2hgdhdeficiencyaccumulates pages 1-2) • Kranendijk M et al. “Progress in understanding 2-hydroxyglutaric acidurias.” Journal of Inherited Metabolic Disease. Mar 2012. https://doi.org/10.1007/s10545-012-9462-5 (kranendijk2012progressinunderstanding pages 8-9) • Bozaci AE et al. “Glutaric aciduria and L-2-hydroxyglutaric aciduria: Clinical and molecular findings of 35 patients from Turkey.” Molecular Genetics and Metabolism Reports. Sep 2023. https://doi.org/10.1016/j.ymgmr.2023.100979 (bozaci2023glutaricaciduriaand pages 3-4) • Gondáš E et al. “Both Enantiomers of 2-Hydroxyglutarate Modulate the Metabolism of Cultured Human Neuroblastoma Cells.” Neurochemical Research. Jun 2024. https://doi.org/10.1007/s11064-024-04188-8 (gondas2024bothenantiomersof pages 5-6) • Cordier F et al. “Malignant glioma in L-2-Hydroxy Glutaric Aciduria: thorough molecular characterization of a case and literature review.” Free Neuropathology. May 2024. https://doi.org/10.17879/freeneuropathology-2024-5377 (cordier2024malignantgliomain pages 1-3) • Alamri A et al. “Deep Brain Stimulation of the Globus Pallidus Internus in a Child with Refractory Dystonia due to L2-Hydroxyglutaric Aciduria.” Stereotactic and Functional Neurosurgery. May 2024. https://doi.org/10.1159/000538418 (alamri2024deepbrainstimulation pages 2-3) • ClinicalTrials.gov NCT04880356. “Longitudinal Study of Ultra-rare Inherited Metabolic and Degenerative Neurological Diseases.” Start: 2021-03-01. https://clinicaltrials.gov/study/NCT04880356 (retrieved text) (NCT04880356 chunk 1)

Figure evidence used • White-matter pathology/demyelination summary figure from Ma et al. 2017 (Figure 3) (ma2017l2hgdhdeficiencyaccumulates media 23a1cbfb).

End of report.

References

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  26. (NCT04880356 chunk 1): Longitudinal Study of Ultra-rare Inherited Metabolic and Degenerative Neurological Diseases.. Fondazione I.R.C.C.S. Istituto Neurologico Carlo Besta. 2021. ClinicalTrials.gov Identifier: NCT04880356