2-Hydroxyglutaric Aciduria

2-Hydroxyglutaric aciduria is a group of neurometabolic disorders with a wide clinical spectrum ranging from severe neonatal presentations to progressive forms, and asymptomatic cases, characterized biochemically by increased levels of 2-hydroxyglutaric acid in the plasma, cerebrospinal fluid and urine.

Epidemiology

The exact prevalence and incidence of the disorders are not known, but fewer than 300 patients have been reported to date.

Clinical description

There are two enantiomeric forms of 2-hydroxyglutaric acid, i.e. D-2-hydroxyglutaric acid and L-2-hydroxyglutaric acid. L-2-hydroxyglutaric aciduria (see this term) is characterized by psychomotor retardation, cerebellar ataxia and epilepsy, and D-2-hydroxyglutaric aciduria (see this term) is characterized by variable metabolic, neurological and dysmorphic manifestations.

Etiology

Mutations in the L2HGDH gene (14q22.1) gene have been implicated in L-2-hydroxyglutaric aciduria, and mutations in the D2HGDH (2q37.3) and IDH2 (15q26.1) genes in D-2-hydroxyglutaric aciduria.

Genetic counseling

L-2-hydroxyglutaric aciduria and D-2-hydroxyglutaric aciduria caused by mutations in the L2HGDH and D2HGDH genes, respectively, follow an autosomal recessive pattern of inheritance. In contrast, D-2-hydroxyglutaric aciduria caused by a specific heterozygous gain-of-function mutation in the IDH2 gene, is an autosomal dominant trait and is usually caused by de novo mutations.