Nystagmus and subnormal electroretinographic response in nonketotic hyperglycinemia

We examined ophthalmologically two siblings with nonketotic hyperglycinemia who had negligible activities of glycine cleavage system in the liver. Both had jerky nystagmus. The elder brother had a normal electroretinographic response, while the younger brother's response was subnormal. There may be a close association of subnormal electroretinographic response and hyperglycinemia, because glycine can act as an inhibitory neurotransmitter in the retina.