L2HGDH and L-2-hydroxyglutaric aciduria: This gene provides L-2-hydroxyglutarate dehydrogenase, a mitochondrial enzyme involved in the conversion of L-2-hydroxyglutarate to 2-ketoglutarate.63 Studies in mice have shown that a defective form of L-2-hydroxyglutarate dehydrogenase leads to white matter abnormalities, neuroinflammation, improper neurogenesis of the hippocampal region, and neurodegeneration.64 Mutations in this gene cause L-2-hydroxyglutaric aciduria, characterized by ID, cerebellar ataxia, epilepsy, speech problems, and an increased amount of L-2-hydroxyglutaric acid in urine, blood, and cerebrospinal fluid.63