<unk>  (Nonketotic Hyperglycinemia) has an autosomal recessive pattern of inheritance.<unk>  has an estimated incidence of 1 in 60,000, making it the second most common disorder of amino acid metabolism, after phenylketonuria. It is caused by a defect in the<unk>  cleavage system (GCS), which is made up of four protein subunits. Each of these four subunits is encoded by a separate gene. Defects in three of these four genes have been linked to<unk> . Gene Name Percent GLDC encodes the<unk>  dehydrogenase" subunit, also called<unk>  decarboxylase" About 70-75% of cases of<unk>  result from mutations in the GLDC gene. GCST or AMT encoding the "aminomethyltransferase" subunit About 20% of cases are caused by mutations in the AMT gene. GCSH encoding the subunit<unk>  cleavage system protein H" Mutations in the GCSH gene account for less than 1% of cases. There is a fourth unit in the complex, dihydrolipoamide dehydrogenase or GCSL. However, to date there have been no mutations in GCSL found to be associated with<unk> . A small percentage of affected individuals do not have detectable mutations in any of the three genes (listed above) that are typically associated with the disease. However, they still show defective<unk> -cleavage enzymatic activity. It is thought that these patients may have mutations in the genes encoding one of the cofactors associated with the GCS complex. Defects in the GCS proteins can prevent the complex from functioning properly or can prevent the GCS complex from forming entirely. When the complex is unable to metabolize<unk>  properly, this causes excess<unk>  to build up to toxic levels in the body's organs and tissues. Damage caused by elevated levels of<unk>  in the brain and cerebrospinal fluid is responsible for the characteristic seizures, breathing difficulties, movement disorders, and intellectual disability. This disorder is inherited in an autosomal recessive pattern. The term "autosomal" signifies that the gene associated with the disorder is located on an autosome. In an autosomal recessive inheritance pattern, two defective copies of the gene (one inherited from each parent) are required in order for a child to be born with the disorder. Therefore, each parent of an individual with an autosomal recessive disorder has at least one defective copy of the gene. With autosomal recessive disorders, individuals with only one copy of a defective gene (heterozygotes) are considered "carriers" for the disorder. Carriers usually do not show signs or symptoms of the disorder.
Glycine encephalopathy
Toxic encephalopathy
Ethylmalonic encephalopathy
Wernicke encephalopathy
Post-encephalitic parkinsonism
Early myoclonic encephalopathy
Carbamate poisoning
Viral encephalitis