Neonatal Glycine Encephalopathy

Neonatal glycine encephalopathy is a frequent, usually severe form of glycine encephalopathy (GE; see this term) characterized by coma, apnea, hypotonia, seizure and myoclonic jerks in the neonatal period, and subsequent developmental delay.

Epidemiology

The prevalence of neonatal glycine encephalopathy is not known.

Clinical description

Patients develop disease manifestations within the first hours or days of life. Symptoms include progressive lethargy, hypotonia, myoclonic jerks leading to apnea. In the absence of intubation and ventilation, apnea may be fatal. With supportive measures, most patients regain spontaneous respiration and some show improvement in alertness over time. Subsequently, they have profound intellectual deficit and increasingly intractable seizures over the first year of life, which often require multiple anticonvulsants. In the vast majority of cases (85%), the course is severe, but some patients have a milder course and less severe clinical outcome. In severe cases, patients make little developmental progress and have limited interaction with their environment. Early spasticity, scoliosis and club feet have also been reported. In milder cases, developmental progress is considerably greater with patients learning to walk and interact, and seizures are generally easier to treat.

Etiology

Mutations in two genes are known to cause glycine encephalopathy: GLDC (9p22), AMT (3p21.2-p21.1).

Genetic counseling

Neonatal GE is inherited in an autosomal recessive manner.