L2HGDH and Cognitive impairment: L-2-hydroxyglutaric aciduria (L2HGA) is a rare, slowly progressive, autosomal recessive neurometabolic disorder caused by mutations in the L2HGDH gene and characterized by psychomotor developmental delay, cognitive impairment, epilepsy, dystonia, cerebellar ataxia, tremor, dysarthria, pyramidal signs, macrocephaly, leukoencephalopathy, and elevated L-2-hydroxyglutaric acid levels.