Disease Information for Hyperglycinemia, nonketotic

An autosomal recessive metabolic disorder caused by deficiencies in the mitochondrial GLYCINE cleavage system; an enzyme system with four components: P-, T-, H-, and L-proteins; Deficiency of the P-protein is the most prevalent form; Neonatal and juvenile presentations have been ; Clinical features include SEIZURES; hypotonia; APNEA; and COMA; When the illness presents in childhood there tends to be an associated progressive DEMENTIA accompanied by extrapyramidal signs;

-----------(Menkes, Textbook of Child Neurology, 5th ed,)---Nonketotic Hyperglycinemia;Glycinemia, Nonketotic; Hyperglycinemia, Nonketotic;Nonketotic hyperglycinemia is an inborn error of metabolism characterized by the accumulation of large amounts of the amino acid glycine in blood, urine and, particularly, the cerebrospinal fluid (CSF); The metabolic block occurs in the conversion of glycine into smaller molecules; There are four forms of this disorder: a relatively common neonatal form, an infantile form, a mild-episodic form, and a late-onset form; [NORD 2005]---------------------------------

Non Ketotic hyperglycinemia synonyms: GLYCINE ENCEPHALOPATHY; GCE; HYPERGLYCINEMIA, NONKETOTIC; NKH; HYPERGLYCINEMIA, TRANSIENT NEONATAL, INCLUDED; TNH, INCLUDE

[Gene map locus 16q24, 9p22, 3p21.2-p21.1] mutations in several genes in the mitochondrial glycine cleavage system have been found to cause glycine encephalopathy (GCE), also known as nonketotic hyperglycinemia (NKH). These include the genes encoding P protein , T protein, and, in one case, the H protein; Most patients with GCE have a defect in the GLDC gene. [A]. Classic most severe Neonatal Form: Most patients with GCE have the neonatal phenotype, presenting in the first few days of life with lethargy, hypotonia, and myoclonic jerks, and progressing to apnea, and often to death. Those who regain spontaneous respiration develop intractable seizures and profound mental retardation.[ B] In the infantile form of GCE, patients present with seizures and have various degrees of mental retardation after a symptom-free interval and seemingly normal development for up to 6 months.[C] In the mild-episodic form, patients present in childhood with mild mental retardation and episodes of delirium, chorea, and vertical gaze palsy during febrile illness. [D] In the late-onset form, patients present in childhood with progressive spastic diplegia and optic atrophy, but intellectual function is preserved and seizures have not been reported ;. Unlike glycinemia with ketoacidosis and leukopenia, also known as propionic academia,, episodic ketoacidosis with vomiting, neutropenia, and thrombocytopenia does not occur in nonketotic hyperglycinemia----------------[OMIM 2005]----------

(Edit)