L-2-Hydroxyglutaric Aciduria is a condition with relevance to the neurodegenerative disease landscape. This page covers its molecular basis, clinical features, genetic associations, and connections to broader neurodegeneration research.
Path: /diseases/l-2-hydroxyglutaric-aciduria
L-2-Hydroxyglutaric aciduria (L2GA) is a rare autosomal recessive neurometabolic disorder characterized by the accumulation of L-2-hydroxyglutaric acid in body fluids and tissues, particularly in the brain. The disease is caused by deficiency of L-2-hydroxyglutarate dehydrogenase (L2HGDH), an enzyme involved in the metabolism of L-2-hydroxyglutarate, a metabolite produced during normal cellular processes. This accumulation leads to progressive neurodegeneration, with clinical manifestations including cerebellar ataxia, intellectual disability, and characteristic MRI findings of leukoencephalopathy[@lhydroxyglutaric2020].
Genetics
L2HGDH Gene
L-2-hydroxyglutaric aciduria is caused by homozygous or compound heterozygous mutations in the L2HGDH gene (chromosome 14q22.1), which encodes the enzyme L-2-hydroxyglutarate dehydrogenase. This enzyme catalyzes the oxidation of L-2-hydroxyglutarate to 2-ketoglutarate (alpha-ketoglutarate) in the mitochondrial matrix, using FAD as a cofactor[@lhgdh2004].
Inheritance
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L-2-Hydroxyglutaric Aciduria
Overview
L-2-Hydroxyglutaric Aciduria is a condition with relevance to the neurodegenerative disease landscape. This page covers its molecular basis, clinical features, genetic associations, and connections to broader neurodegeneration research.
Path: /diseases/l-2-hydroxyglutaric-aciduria
L-2-Hydroxyglutaric aciduria (L2GA) is a rare autosomal recessive neurometabolic disorder characterized by the accumulation of L-2-hydroxyglutaric acid in body fluids and tissues, particularly in the brain. The disease is caused by deficiency of L-2-hydroxyglutarate dehydrogenase (L2HGDH), an enzyme involved in the metabolism of L-2-hydroxyglutarate, a metabolite produced during normal cellular processes. This accumulation leads to progressive neurodegeneration, with clinical manifestations including cerebellar ataxia, intellectual disability, and characteristic MRI findings of leukoencephalopathy[@lhydroxyglutaric2020].
Genetics
L2HGDH Gene
L-2-hydroxyglutaric aciduria is caused by homozygous or compound heterozygous mutations in the L2HGDH gene (chromosome 14q22.1), which encodes the enzyme L-2-hydroxyglutarate dehydrogenase. This enzyme catalyzes the oxidation of L-2-hydroxyglutarate to 2-ketoglutarate (alpha-ketoglutarate) in the mitochondrial matrix, using FAD as a cofactor[@lhgdh2004].
Inheritance
L2GA follows an autosomal recessive inheritance pattern. Parents of an affected individual are typically asymptomatic carriers, with a 25% recurrence risk for subsequent pregnancies. The disease has been reported in various ethnic groups, with higher prevalence in populations with consanguinity.
Prevalence
L-2-hydroxyglutaric aciduria is an extremely rare disorder, with approximately 100 cases reported in the literature worldwide. The exact prevalence is unknown but estimated to be less than 1 per million population.
Pathophysiology
Metabolic Block
The primary metabolic defect in L2GA involves impairment of L-2-hydroxyglutarate dehydrogenase activity:
L-2-hydroxyglutarate is produced endogenously through various metabolic processes, including:
Lysine degradation via the pipecolic acid pathway
Hydroxylation of 2-ketoglutarate in a side reaction of various enzymes
L2HGDH normally converts L-2-hydroxyglutarate to 2-ketoglutarate:
This reaction is part of the mitochondrial metabolic network
2-ketoglutarate enters the TCA cycle for further metabolism
In L2GA, the enzymatic deficiency leads to:
Accumulation of L-2-hydroxyglutarate in the brain and other tissues
Elevated levels in cerebrospinal fluid, plasma, and urine
Secondary effects on brain development and function[@biochemical2015]
Neurotoxicity
The mechanisms by which L-2-hydroxyglutarate accumulation causes neurodegeneration include:
Oxidative stress: L-2-hydroxyglutarate can generate [reactive oxygen species](/entities/reactive-oxygen-species)
Energy metabolism impairment: Secondary mitochondrial dysfunction
Epigenetic effects: 2-ketoglutarate is a cofactor for DNA demethylases; accumulation of L-2-hydroxyglutarate may interfere with epigenetic regulation
Excitotoxicity: Potential effects on glutamate signaling
Neuropathology
Postmortem studies show:
Diffuse cerebral leukoencephalopathy
Vacuolation of white matter
Cerebellar atrophy, particularly of the dentate nucleus
Variable neuronal loss
Myelin abnormalities
Clinical Presentation
Age of Onset
Symptoms typically begin in early childhood, usually between ages 1-5 years, though milder forms may present later.
Core Clinical Features
Neurological Symptoms:
Cerebellar ataxia: The most consistent feature, characterized by:
Gait instability and truncal ataxia
Limb incoordination
Dysarthria (slurred speech)
Nystagmus
Cognitive impairment:
Variable intellectual disability (mild to severe)
Developmental delays
Learning difficulties
Movement disorders:
Dystonia
Chorea
Tremor
Myoclonus (in some cases)
Seizures: Occur in approximately 30-50% of patients
Systemic Features:
Macrocephaly (enlarged head circumference) in some patients
Short stature may be present
No significant organ involvement outside the nervous system
Disease Progression
L2GA is typically slowly progressive:
Motor symptoms often worsen over years
Cognitive decline may be gradual or stepwise
Life expectancy varies; many patients survive into adulthood
Some patients experience periods of acute regression, sometimes triggered by illness or metabolic stress[@clinical2019]
Diagnosis
Biochemical Testing
Urine Organic Acid Analysis:
Elevated urinary excretion of L-2-hydroxyglutarate is the biochemical hallmark
Levels are typically markedly elevated (10-100x normal)
Analysis by GC-MS or LC-MS/MS is the standard method
Plasma and CSF Analysis:
Elevated L-2-hydroxyglutarate in plasma
Even higher levels in cerebrospinal fluid
Normal levels of other organic acids help distinguish from related disorders
Neuroimaging
MRI Findings:
Diffuse, symmetric cerebral leukoencephalopathy
T2/FLAIR hyperintensities in the deep white matter
Relative preservation of subcortical U-fibers early in disease
Cerebellar involvement, particularly of the dentate nuclei
Brainstem may be affected in advanced disease
Progressive atrophy over time[@neuroimaging2018]
Genetic Testing
Sequencing of the L2HGDH gene confirms the diagnosis
[Guo Q, Löhr T, Giavalisco P et al., A Pathogenic L2HGDH Variant Impairs Mitochondrial Targeting and Enzyme Activity (2025)](https://pubmed.ncbi.nlm.nih.gov/40870031/) - Genes (Basel)
[Engin Erdal A, Özbey SZ, Civelek Ürey GB et al., Genetic, neuroimaging, and clinical characteristics of a cohort of patients (2025)](https://pubmed.ncbi.nlm.nih.gov/40660807/) - J Pediatr Endocrinol Metab
[Radhakrishnan DM, Kaur R, Prajapati B et al., L-2-Hydroxyglutaric Aciduria Complicated by Cerebral Neoplasm (2025)](https://pubmed.ncbi.nlm.nih.gov/40462650/) - Mov Disord Clin Pract
[Lipiński P, Ciara E, Bogdańska A et al., Riboflavin treatment in L-2-hydroxyglutaric aciduria: report on a pediatric case (2025)](https://pubmed.ncbi.nlm.nih.gov/40380983/) - J Appl Genet
[Shimozato M, Sakurai T, Yaguchi T et al., A case of L-2-hydroxyglutaric aciduria diagnosed with involuntary movements (2025)](https://pubmed.ncbi.nlm.nih.gov/39880652/) - Rinsho Shinkeigaku