The neuropathology of glycine encephalopathy: a report of five cases with immunohistochemical and ultrastructural observations.

We studied the spongy myelinopathy of glycine encephalopathy in five patients by using specific antisera. The walls of the vacuoles were stained with the myelin basic protein but not with the myelin associated glycoprotein or the glial fibrillary acidic protein immunostains. The pattern suggested that the vacuoles originated in compact myelin and not from the adaxonal portion of the sheath or from glial processes. Ultrastructural study revealed myelin vacuoles resulting from intraperiod splitting, and there were unusual intranuclear and cytoplasmic inclusions in skeletal muscle in two cases. In addition to the action of glycine as an inhibitory neurotransmitter, structural alterations of myelin may be important in the pathogenesis of the neurologic disorder of glycine encephalopathy.