• Journal of The Korean Society of Inherited Metabolic disease
• /
• v.15 no.3
• /
• pp.165-170
• /
• 2015

Ornithine transcarbamylase (OTC) deficiency is a rare X-linked genetic disorder of urea synthesis in newborns. It is the most common urea cycle disorder and leads to elevated levels of ammonia in the blood. Excessive ammonia can cause various symptoms, including vomiting, lethargy, and coma. Boys have a more serious form of OTC deficiency than girls. If not treated immediately, severe OTC deficiency can lead to neurologic abnormalities, hyperammonemic coma, and death. Because late-onset OTC deficiency, which is more common in girls, presents mild symptoms, it is easy to miss diagnosis and prompt treatment. We describe an 11-month-old girl who presented periodic vomiting, intermittent lethargy, and seizure. She was diagnosed with OTC deficiency by elevated serum ammonia and urine orotic acid levels. Genetic analysis of the OTC gene revealed a missense mutation in exon 5 (c.418G>C). We reported an experience of exact diagnosis and successful treatment of late-onset OTC deficiency in our patient.

• Journal of The Korean Society of Inherited Metabolic disease
• /
• v.3 no.1
• /
• pp.32-37
• /
• 2003

Ornithine transcarbamylase(OTC) deficiency is the most common of all the urea cycle disorders. In this X-linked disorder, the hemizygote males are more severely affected than heterozygote females. The Heterozygote female may have mild episodic hyperammonemia symptoms in late infancy or childhood(late onset) or no clinical manifestations. Here we report a 6 year-old girl with late onset OTC deficiency who showed recurrent episodic lethargy, mental confusion and ataxia. On mutation analysis using DNA sequencing after PCR amplification of the 10 exons of OTC gene, G to T transversion in codon 221, causing substitution of asparagine for lysine was detected in exon 6.

• Journal of Yeungnam Medical Science
• /
• v.24 no.2
• /
• pp.322-328
• /
• 2007

Ornithine transcarbamylase (OTC) deficiency is the most common inborn error of urea cycle metabolism; it is inherited in an X-linked manner. The OTC catalyzes the third step of the urea cycle, the conversion of ornithine and carbamyl phosphate to citrulline. Deficiency of OTC leads to the accumulation of ammonia, causing neurological deficits. In most affected hemizygote males, OTC deficiency manifests as hyperammonemic coma that often leads to death in the newborn period, and those who recover from the coma may be neurologically impaired due to the sequelae of the hyperammonemic encephalopathy. In some, late-onset manifestations develop. We report a male neonate with early onset OT deficiency that had apnea and was comatous. On mutation analysis using DNA sequencing after polymerase chain reaction (PCR) amplification of the 10 exons, deletions of 10 bases in codon 285, causing a frame shift was detected in exon 8. The mother and a sister were diagnosed as female carriers. Therefore, genetic counseling and the risk assessment could be provided to the family.

• Journal of The Korean Society of Inherited Metabolic disease
• /
• v.2 no.1
• /
• pp.77-79
• /
• 2002

The urea cycle, consisting of a series of six enzymatic reactions, plays key roles to prevent the accumulation of toxic nitrogenous compound and synthesize arginine de novo. Five well characterized diseases have been described, resulting from an enzymatic defect in the biosynthesis of one of the normally expressed enzyme. This presentation will focus on two representative diseases; ornithine transcarbamylase(OTC) deficiency and citrullinemia(argininosuccinate synthetase deficiency). OTC deficiency is one of the most common inborn error of urea cycle, which is inherited in X-linked manner. We identified 17 different mutations in 20 unrelated Korean patients with OTC deficiency; L9X, R26P, R26X, T44I, R92X, G100R, R141Q, G195R, M205T, H214Y, D249G, R277W, F281S, 853 del C, R320X, V323M and 10 bp del at nt. 796-805. These mutations occur at well conserved nucleotide sequences across species or CpG hot spot. The L9X and R26X lead to the disruption of leader sequences, required for directing mitochondrial localization of the OTC precursor. Their phenotypes are severe, and neonatal onset. The G100R, R277W and V323M mutations were uniquely identified in patients with late onset OTC deficiency. The other genotypes are associated with neonatal onset. Out of 20 patients with OTC deficiency, only 6 patients are alive; two were liver transplanted, and normal in growth and development at 2, 4 years after transplantation respectively. Citrullinemia is an autosomal recessive disease, caused by the mutations in the argininosuccinate synthetase(ASS) gene. We identified in 3 major mutations in 11 unrelated Korean patients with citrullinemia; G324S, $IVS6^{-2}$ A to G, and 67 bp ins at nt 1125-1126. Among these, the 67 base pair insertion mutation is novel. The allele frequency of each mutation is; G324S(45%), IVS6-2 A to G(32%), and 67 base pair insertion(14%). All patients are diagnosed at neonatal or infantile age. Interestingly, two patients presented with stroke like episode. Out of 11 patients, 5 patients died. Among 6 patients alive, one patient was successfully liver transplanted.