White matter disease in cerebral organic acid disorders: clinical implications and suggested pathomechanisms.

White matter abnormalities (including dys-, hypo-, demyelination and delayed myelation) are frequently found in cerebral organic acid disorders, a recently delineated subgroup of inherited organic acid disorders presenting predominantly with a neurological symptomatology. Biochemically, this disease subgroup lacks metabolic derangements, such as hypoglycemia, hyperammonemia and acidosis, and is characterized by an accumulation of organic acids that share structural similarities with the excitatory amino acid glutamate (D-2-, L-2-, 3-hydroxyglutarate, glutarate) or have been suggested as neurotransmitters/neuromodulators ( N-acetylaspartylglutamate). Evidence from in vitro and in vivo studies is growing that relevant organic acids significantly contribute to the neuropathology of these diseases via interference with glutamatergic or GABAergic neurotransmission or impairment of energy metabolism. This article provides an overview on the clinical and neuroradiological presentation of white matter disease in cerebral organic acid disorders, focusing on the suggested pathomechanistic relevance of excitotoxicity, oxidative stress, and impaired energy metabolism.