P85 – 2818: Nonketotic hyperglycinemia: A cause of severe epileptic encephalopathy and hypotonia in children

Objective Nonketotic hyperglycinemia is an autosomal recessive metabolic disorder characterized by the accumulation of glycine in all body tissues especially the central nervous system. It is considered a rare disorder, but the exact worldwide incidence is not known. Methods In this report, we present 5 cases of classical nonketotic hyperglycinemia referred to our pediatric hospital. These patients were diagnosed in the last three months in our center in the capital city of Turkey. The patients' common findings were severe hypotonia, head lag, poor sucking and intractable seizures. Only one patient had hiccups in the neonatal period. The other 4 patients had flexor and mixed spasms. The patient with hiccups developed asymmetric tonic spasms after 1 month. All patients were taking multiple antiepileptic drugs for their seizures before the diagnosis. All the patients' cerebrospinal fluid to plasma glycine ratio was over 0.08 at the diagnosis. The initial ratio of the patient with hiccups was 0.031 (over 0.02), but the second evaluation ratio was over 0.08. 2 of 5 patients are mutation positive. The first patient's mutations in the AMT gene are p.E211K homozygous and p.R320H heterozygous. The other patient's mutation in the GLDC gene is p.D880E heterozygous. The other 3 patients' mutation analyses are on research. 4/5 patients have also been evaluated with MRS consolidating the diagnosis. Results All of the 5 patients were seizure free after Na benzoate treatment for a while. Conclusion We speculate that glycine encephalopathy is not a rare neurometabolic disorder in our ethnical geography. We should be aware of this disorder if the baby is severe hypotonic and should early evaluate EEG records even without clinical seizures. We offer that cerebrospinal fluid to plasma glycine ratio should be evaluated more than once if there is a strong clinical suspicion.