Infantile Glycine Encephalopathy

Infantile glycine encephalopathy is a mild to severe form of glycine encephalopathy (GE; see this term), characterized by early hypotonia, developmental delay and seizures.

Epidemiology

The prevalence of infantile glycine encephalopathy is not known. Infantile cases are less frequent than the classical neonatal form of GE (neonatal GE; see this term).

Clinical description

Patients present with infantile-onset seizures and variable psychomotor delay after initially normal development, and often have a relatively long history of hypotonia. Seizures of any type are found in less than half of patients and some develop choreoathetosis. Developmental delay mostly affects language and behavioral problems are sometimes found including temper tantrums, irritability, aggressiveness and rage. Attention deficit-hyperactivity disorder (AD-HD) is also sometimes found. Patients do not have lethargy or coma in the neonatal period, unlike those with neonatal GE. The course may be mild or severe (50% of patients in each case).

Etiology

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

Genetic counseling

Infantile GE is inherited in an autosomal recessive manner.