Analysis of OTC gene variants in four children with delayed onset Ornithine transcarbamylase deficiency / 中华医学遗传学杂志

OBJECTIVE@#To analyze the clinical manifestation and genetic basis for four children with delayed onset Ornithine transcarbamylase deficiency (OTCD).@*METHODS@#Clinical data of four children with OTCD admitted to the Children's Hospital of the First Affiliated Hospital of Zhengzhou University from January 2020 to April 2021 were reviewed. Peripheral blood samples of the children and their parents were collected and subjected to whole exome sequencing (WES). Bioinformatic analysis and Sanger sequencing verification were carried out to verify the candidate variants. Impact of the candidate variants on the protein structure was also predicted.@*RESULTS@#The clinical manifestations of the four children included vomiting, convulsion and disturbance of consciousness. WES revealed that the child 1 was heterozygous for a c.421C>T (p.R141X) variant in exon 5, children 2 and 3 were hemizygous for a c.119G>A (p.R40H) variant in exon 2, and child 4 was hemizygous for a c.607T>A (p.S203T) variant in exon 5 of the OTC gene. Among these, the c.607T>A variant was unreported previously and predicted to be pathogenic (PM1+PM2_Supporting+PP3+PP4). Bioinformatic analysis has predicted that the variant may result in breakage of hydrogen bonds and alter the protein structure and function. Sanger sequencing confirmed that the variants in children 2 to 4 have derived from their mothers.@*CONCLUSION@#The pathogenic variants of the OTC gene probably underlay the delayed OTCD in 4 children. The discovery of the c.607T>A variant has enriched the mutational spectrum of the OTC gene.

Neonate-onset ornithine transcarbamylase deficiency / 中国当代儿科杂志

The male neonate in this case study was admitted to the hospital at 15 hours of age due to respiratory distress for 15 hours and poor response for 3 hours after resuscitation from asphyxia. The neonate was highly unresponsive, with central respiratory failure and seizures. Serum ammonia was elevated (>1 000 μmol/L). Blood tandem mass spectrometry revealed a significant decrease in citrulline. Rapid familial whole genome sequencing revealed OTC gene mutations inherited from the mother. Continuous hemodialysis filtration and other treatments were given. Neurological assessment was performed by cranial magnetic resonance imaging and electroencephalogram. The neonate was diagnosed with ornithine transcarbamylase deficiency combined with brain injury. He died at 6 days of age after withdrawing care. This article focuses on the differential diagnosis of neonatal hyperammonemia and introduces the multidisciplinary management of inborn error of metabolism.

Consensus on diagnosis and treatment of ornithine trans-carbamylase deficiency / 浙江大学学报·医学版

Ornithine transcarbamylase deficiency(OTCD)is a most common ornithine cycle (urea cycle) disorder. It is a X-link inherited disorder caused by

Lethal Hyperammonemia due to Ornithine Transcarbamylase Deficiency in a Patient with Severe Septic Shock / 대한구급학회지

Severe hyperammonemia can occur as a result of inherited or acquired liver enzyme defects in the urea cycle, among which ornithine transcarbamylase deficiency (OTCD) is the most common form. We report a very rare case of a 45-year-old Korean male who was admitted to the intensive care unit (ICU) due to severe septic shock with acute respiratory failure caused by Pneumocystis jiroveci pneumonia. During his ICU stay with ventilator care, the patient suffered from marked hyperammonemia (>1,700 µg/dL) with abrupt mental change leading to life-threatening cerebral edema. Despite every effort including continuous renal replacement therapy and use of a molecular adsorbent recirculating system (extracorporeal liver support-albumin dialysis) to lower his serum ammonia level, the patient was not recovered. The lethal hyperammonemia in the patient was later proven to be a manifestation of acquired liver enzyme defect known as OTCD, which is triggered by serious catabolic conditions, such as severe septic shock with acute respiratory failure.

Lethal Hyperammonemia due to Ornithine Transcarbamylase Deficiency in a Patient with Severe Septic Shock / 대한중환자의학회지

Severe hyperammonemia can occur as a result of inherited or acquired liver enzyme defects in the urea cycle, among which ornithine transcarbamylase deficiency (OTCD) is the most common form. We report a very rare case of a 45-year-old Korean male who was admitted to the intensive care unit (ICU) due to severe septic shock with acute respiratory failure caused by Pneumocystis jiroveci pneumonia. During his ICU stay with ventilator care, the patient suffered from marked hyperammonemia (>1,700 µg/dL) with abrupt mental change leading to life-threatening cerebral edema. Despite every effort including continuous renal replacement therapy and use of a molecular adsorbent recirculating system (extracorporeal liver support-albumin dialysis) to lower his serum ammonia level, the patient was not recovered. The lethal hyperammonemia in the patient was later proven to be a manifestation of acquired liver enzyme defect known as OTCD, which is triggered by serious catabolic conditions, such as severe septic shock with acute respiratory failure.

Déficit de ornitina transcarbamilasa: Caso clínico / Ornithine carbamoyltransferase deficiency: A clinical case

Los trastornos del ciclo de la urea suponen hasta el 60% de las hiperamoniernias graves neonatales. La base de los trastornos de este ciclo deriva en el déficit de una de sus enzimas. El déficit de la enzima ornitina transcarbamilasa es el más frecuente. Su pronóstico dependerá del grado de deficiencia enzimàtica, la edad, la precocidad del diagnóstico e inicio del tratamiento. Presentamos el caso de un adolescente que, a partir de un cuadro de parálisis facial periférica tratado con prednisona, presentó agravamiento de su estado general y falleció a los pocos días. Las cifras elevadas de amoniaco en sangre hicieron sospechar tardíamente de una alteración congénita del ciclo de la urea, que fue confirmada por su estudio genético post mortem. Se estudiaron los familiares y se asesoró a los afectos y portadores. Reflexionamos sobre la importancia de los programas de cribado neonatal y la posibilidad de aplicarlos en la detección de los errores congénitos del metabolismo.

Disorders of urea cycle account for up to 60% of severe neonatal hyperamoniemias. The base of this cycle disorders results in a deficit of its enzymes. Deficiency of the enzyme ornithine transcarbamylase is the most frequently detected. The prognosis depends on the degree of enzyme deficiency, age, early diagnosis and initiation of treatment. We report the case of a teenager who was treated with prednisone because of a peripheral facial palsy. He showed a progressive worsening and died a few days later. The high levels of ammonia made suspect a congenital disorder of urea cycle. The postmortem genetic study confirmed it. We studied the family and advised carriers. We reflect about the importance of the neonatal screening programs and their applicability for detection of inborn errors of metabolism.

Liver transplantation for the treatment of hyperammonemia due to urea cycle disorder: report of four cases / 中华儿科杂志

<p><b>OBJECTIVE</b>To analyze clinical efficacy and prognosis of liver transplantation in children with hyperammonemia caused by urea cycle disorders.</p><p><b>METHOD</b>A retrospective analysis was performed on the occurrence of disease, operation and the follow-up post liver transplantation in 4 patients with urea cycle disorders who underwent liver transplantation during June 2001 to May 2014.</p><p><b>RESULT</b>Four girls were diagnosed with ornithine carbamoyl transferase deficiency by genetic test. They had the clinical onset at the age of 1.5 to 3.0 years. Liver transplantation had been performed at their age of 53.9 months, 40.6 months, 40.3 months and 22.8 months, respectively. The grafts of case 1 and case 2 were from left lateral lobe of liver of cadaveric donor, the graft of case 3 was from left lateral lobe of liver of a living donor, the graft of case 4 was a whole liver of a dead child. The liver function of 4 patients gradually returned to normal, blood ammonia levels were normal and restored the normal diet, 4 children were discharged on postoperative 25-30 days. Regular follow-up was done, the liver function, biochemical features and growth status have been followed up for 162.2 months, 124.2 months, 12.0 months and 4.8 months after liver transplantation, respectively. Now, all the four cases are healthy and growth is normal.</p><p><b>CONCLUSION</b>Liver transplantation is an important way to the patients with severe hyperammonemia caused by urea cycle disorders. In this study, the patients with ornithine carbamoyl transferase defect got satisfactory long-term outcome after liver transplantation.</p>

Analysis of ornithine transcarbamylase gene mutations in three boys affected with late-onset ornithine transcarbamylase deficiency / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To identify the types of OTC gene mutations in three male patients with late onset ornithine transcarbamylase deficiency (OTCD, MIM #311250).</p><p><b>METHODS</b>Genomic DNA was extracted from peripheral blood leukocytes. The 10 exons and their flanking sequences of the OTC gene were amplified with polymerase chain reaction and subjected to direct DNA sequencing.</p><p><b>RESULTS</b>Based on DNA sequence analysis, all of the three patients have carried OTC gene mutations. Patients 1 and 2 were both hemizygous for mutation c.586G> A(p.D196N). A novel mutation c.800G> C(p.S267T) were confirmed in patient 3.</p><p><b>CONCLUSION</b>p.S267T mutation has affected the conserved amino acid motif of the OTC protein, and is therefore a pathogenic mutation.</p>

Analysis of clinical features, metabolic profiling and gene mutations of patients with ornithine transcarbamylase deficiency / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze the clinical features, metabolic profiling and gene mutations of patients with ornithine transcarbamylase deficiency (OTCD) and explore the molecular pathogenesis of OTCD in order to provide a solution for molecular diagnostics and genetic counseling.</p><p><b>METHODS</b>Clinical data of 3 neonates were analyzed. The amino acids level in blood was analyzed with mass spectrum technology. PCR was used to amplify all the 10 exons of OTC gene. The PCR products were directly sequenced to detect the mutations.</p><p><b>RESULTS</b>All of the 3 cases had neonatal onset and showed poor reaction, feeding difficulty, convulsion and neonatal infection. Citrulline levels were significantly decreased. Case 1 had a missense mutation of Y183C. Case 2 showed a missense mutation of V339G in exon 10. And a missense mutations of W332S in exon 9 was detected in case 3.</p><p><b>CONCLUSION</b>Analysis of OTC gene sequences can be used for the diagnosis of OTCD and screening of asymptomatic carriers. Mutation analysis is important for prenatal diagnosis of individuals with a positive family history and genetic counseling. The V339G and W332S mutations have been discovered for the first time. Patients with such mutations may have onset of the disease during neonatal period.</p>

Molecular diagnosis of OTC gene mutation in a Chinese family with ornithine transcarbamylase deficiency / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To detect potential mutations of OTC gene in a male infant affected with ornithine transcarbamylase deficiency.</p><p><b>METHODS</b>Genomic DNA were isolated from peripheral blood samples of family members and 100 healthy individuals. Potential mutations of the 10 exons of OTC gene were screened with PCR and Sanger sequencing.</p><p><b>RESULTS</b>A homozygous missense mutation c.917G>C in exon 9, which results in p.R306T, was identified in the infant. Sequencing of the mother and two female members of the family indicated a heterozygous status for the same mutation. The same mutation was not found in other members of the family and 100 healthy controls.</p><p><b>CONCLUSION</b>A missense mutation c.917G>C in the OTC gene is responsible for the pathogenesis of the disease. Identification of the mutation can facilitate prenatal diagnosis and genetic counseling for the family.</p>

Hyperammonemia in a Patient with Late-Onset Ornithine Carbamoyltransferase Deficiency

Ornithine carbamoyltransferase (OTC) deficiency is a urea cycle disorder that causes the accumulation of ammonia, which can lead to encephalopathy. Adults presenting with hyperammonemia who are subsequently diagnosed with urea cycle disorders are rare. Herein, we report a case of a late-onset OTC deficient patient who was successfully treated with arginine, benzoate and hemodialysis. A 59-yr-old man was admitted to our hospital with progressive lethargy and confusion. Although hyperammonemia was suspected as the cause of the patient's mental changes, there was no evidence of chronic liver disease. A plasma amino acid and urine organic acid analysis revealed OTC deficiency. Despite the administration of a lactulose enema, the patient's serum ammonia level increased and he remained confused, leading us to initiate acute hemodialysis. After treatment with arginine, sodium benzoate and hemodialysis, the patient's serum ammonia level stabilized and his mental status returned to normal.

Clinical and gene mutation analyses of three patients with ornithine carbamoyltransferase deficiency / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze the clinical and genetic characteristics of three children with ornithine carbamoyltransferase deficiency(OTCD), and to provide a practical method for gene diagnosis and genetic counseling of the disease.</p><p><b>METHODS</b>All exons of the ornithine carbamoyltransferase (OTC) gene were screened by polymerase chain reaction-DNA direct sequencing in the three OTCD patients.</p><p><b>RESULTS</b>One patient firstly presented as vomiting at 6 month of age. A missense mutation of T262I was detected. His mother had the same mutation without any clinical symptoms. The second patient presented as restlessness, and had a missense mutation of R277W. Gene analysis of his parents was not available. The third patient presented as neonatal lethargy, harbored a missense mutation of I172M. His mother had the same mutation without any clinical symptoms.</p><p><b>CONCLUSION</b>Gene mutation analysis is a feasible way for diagnosing OTCD. Patients with I172M mutation present symptom early, while those with T262I and R277W mutations manifest symptoms later. Gene mutation analysis will be important for asymptomatic and prenatal diagnosis and genetic counseling.</p>

Analysis of clinical features, biochemical analysis and gene mutations in one Chinese pedigree with neonatal-onset ornithine transcarbamylase deficiency / 中华儿科杂志

<p><b>OBJECTIVE</b>This study aimed at understanding clinical features, biochemistry and gene mutation in one Chinese pedigree which had a neonatal-onset ornithine transcarbamylase deficiency (OTCD) boy, and exploring the significance of ornithine transcarbamylase analysis in prenatal diagnosis.</p><p><b>METHOD</b>The clinical and biochemical data of one case were analyzed. The amino acids in blood and organic acids in urine were analyzed by mass spectrum technology. The OTC gene mutation was detected using polymerase chain reaction (PCR) and DNA direct sequencing for the case, his parents and the fetus amniocyte and her blood after birth.</p><p><b>RESULT</b>The age of onset was 3 days after birth, he began to have poor reaction, difficulty to feed, high blood ammonia, infection, slight metabolic acidosis, which were consistent with the clinical diagnosis of urea cycle disorders. The boy died at the age of 9 days. Citrulline of blood was detected twice, and were 0.86 µm and 1.06 µm, respectively. The orotic acid was elevated (124 µm/M Creatinine), and urine lactic acid was significantly elevated. The citrulline and orotic acid in his parents and their second baby were normal in DBS and urine. One nonsense mutation in the OTC gene was found at the exon 9 (C. 958 C > T) and his mother was the heterozygote, which caused an arginine to terminate the code at position 320 of the protein (R320X). Two other mutations were also detected at intron 9 (C.1005 + 132 InsT) and intron 5 (C.542 + 134 G > G/A). But the analysis of his father's DNA, the fetus amniocyte and her blood was normal.</p><p><b>CONCLUSION</b>The mutation of C. 958 C > T in OTC gene may occur during neonatal period. This mutation would result in a very severe symptom, even die suddenly several days after birth, if it was a boy. It needs more researches to discuss whether the C.1005 + 132 InsT in intron 9 and C.542 + 134 G > G/A in intron 5 were associated with the neonatal-onset OTCD. The DNA analysis of OTC gene could be utilized for the prenatal diagnosis.</p>

Acute treatment of hyperammonemia by continuous renal replacement therapy in a newborn patient with ornithine transcarbamylase deficiency / 소아과

Ornithine transcarbamylase (OTC) deficiency is well known as the most common inherited disorder of the urea cycle, and 1 of the most common causes of hyperammonemia in newborns. We experienced a case of a 3-day-old boy with OTC deficiency who appeared healthy in the first 2 days of life but developed lethargy and seizure soon afterwards. His serum ammonia level was measured as >1700 microg/dL (range, 0 to 45 microg/dL). Continuous renal replacement therapy (CRRT) in the mode of continuous venovenous hemodiafiltration was immediately applied to correct the raised ammonia level. No seizure occurred after the elevated ammonia level was reduced. Therefore, CRRT should be included as 1 of the treatment modalities for newborns with inborn errors of metabolism, especially hyperammonemia. Here, we report 1 case of successful treatment of hyperammonemia by CRRT in a neonate with OTC deficiency.

A Case of Molecular Diagnosis of Ornithine Transcarbamylase Deficiency / 영남의대학술지

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.

Deficiencia de ornitina transcarbamilasa: presentación de un caso clínico / Ornithine transcarbamylase deficiency: presentation of clinical case

Se presenta el caso clínico de una preescolar de dos años y tres meses con antecedentes de sintomatología neurológica y digestiva recurrentes en la cual el perfil bioquímico es consistente con hiperamoniemia primaria por deficiencia de ornitina transcarbamilasa. La evolución clínica y bioquímica fue satisfactoria al iniciarse el tratamiento. Si bien los síntomas aislados son totalmente inespecíficos, es nuestro interés subrayar la importancia que el pediatra sospeche la posibilidad de una hiperamoniemia primaria ante síntomas episódicos de la esfera digestiva, neurológica o psiquiátrica. El diagnóstico precoz permite instituir rápidamente el tratamiento, evitando el coma hiperamoniémico con su alta morbimortalidad.

Intermittent hyperammonemic encephalopathy in a child with ornithine transcarbamylase deficiency.

Ornithine transcarbamylase (OTC) deficiency is an X-linked disorder and the most common inherited cause of hyperammonemia. Clinical manifestations are more severe in hemizygous males who often present in neonatal period. Heterozygous females may be asymptomatic until juvenile or adulthood. Fluctuating concentration of ammonia, glutamine and other excitotoxic amino acids result in a chronic or episodically recurring encephalopathy. The authors report a heterozygous female with OTC deficiency who presented with recurrent encephalopathy.

Successful Preimplantation Genetic Diagnosis for Ornithine Transcarbamylase Deficiency, Junctional Epidermolysis Bullosa and Lactic Acidosis Using Duplex Nested PCR: Delivery of Healthy Baby by Specific Preimplantation Genetic Diagnosis for Ornithine Tran / 대한산부인과학회잡지

OBJECTIVE: Preimplantation genetic diagnosis (PGD) is reserved for couples with a risk of transmitting a serious and incurable disease, and hence avoids the undesirable therapeutic abortion. Herein, we report the result of PGD to carriers at risk of transmitting ornithine transcarbamylase (OTC) deficiency, junctional epidermolysis bullosa (EB) and lactic acidosis (LA) due to defect of pyruvate dehydrogenase alpha1 gene, respectively. METHODS: The ovarian stimulation, oocyte retrieval and ICSI procedure were undergone by conventional protocols. PGD for single gene disorders was carried out after biopsy of one or two blastomeres from the embryos on the third day. We performed the duplex nested PCR of the simultaneous amplification for the causative mutation loci as well as the SRY gene on Y chromosome in case of OTC deficiency and LA. Two different mutation loci of ITGB4 gene in EB case were amplified by the same protocol. The PCR products were analyzed by agarose gel electrophoresis, restriction fragment length polymorphism analysis or direct DNA sequencing. RESULTS: A total of 26 embryos were analyzed by duplex nested PCR. One or two blastomeres were biopsied, and successful diagnosis rate of PGD with PCR was 92.3% (24/26). There was no contamination in all PCR samples of negative controls (n=67). Five embryos (19.2%) were diagnosed as normal embryos, which were transferred to the mothers' uterus in each cases. In OTC deficiency case, singleton pregnancy was established. At 17 weeks of gestation, genetic normality of OTC gene in fetus was confirmed by amniocentesis. A healthy baby was successfully delivered at 36 weeks of gestation in OTC deficiency case. Unfortunately, pregnancies were not achievement in cases of EB and LA. CONCLUSION: This is the first report in Korea that healthy baby was born after specific PGD for OTC deficiency. Our results demonstrate that duplex nested PCR for single cell is an efficient method in identifying the gender and single gene mutation or two different mutation loci, simultaneously. This PGD procedure could provide normal healthy baby to the couple with a high risk of transmitting genetic diseases.