Abstract

Nonketotic hyperglycinemia, is an autosomal recessively inherited disorder of the aminoacid metabolism caused by a deficiency in the mitochondrial glycine cleavage system. Neonatal type is the most common form. Infants are usually normal at birth and clinical manifestations such as severe hypotonia, poor feding, seizures, and lethargy progressing rapidly to a deep coma develop during the first few days of life. Most affected infants die during the first weeks of life. Those who survive develop severe neurological complications. The aim of this case series is to evaluate the clinical features, treatment approaches and short term prognosis of the infants diagnosed with neonatal nonketotic hyperglycinemia during the last 5 years in our department. Data were collected retrospectively from patients’ files whose postnatal age at diagnosis varied between 2 to 14 days. All patients were admitted with failure to suck and lethargy, and all had severe hypotonia and decreased newborn reflexes on physical examination. Four patients developed resistant myoclonic seizures and deep apnea requiring mechanical ventilation. In all patients diagnosis was made by high plasma and cerebrospinal fluid glycine levels. Genetic study could be performed in only one patient. However enzymatic analysis could not be performed in any patient. All patients had pathological neuroimaging studies and electroencephalography including multifocal epileptiform abnormalities and “burst supression” pattern. All patients received low protein diet and drugs reducing plasma glycine levels. Resistant seizures could only be controlled by levetiracetam in four patients. While two patients died in follow up, remaining three survived with severe neurological sequels. Physicians should consider nonketotic hyperglycinemia in differential diagnosis in our country where consanguineous marriages are frequent, especially when a newborn is initially stable but develops severe hypotonia, resistant seizures and encephalopathy with normal routine laboratory tests on follow-up.