Ornithine transcarbamylase deficiency unmasked because of gastrointestinal bleeding

Drug-induced hyperammonaemia

Hyperammonaemia (HA) as a consequence of numerous primary or secondary causes, gives rise to clinical manifestations due to its toxic effects on the brain. The neurological consequences broadly reflect the ammonia level, duration and age, with paediatric patients being more susceptible. Drug-induced HA may arise due to either decreased ammonia elimination or increased production. This is associated most frequently with use of valproate and presents a dilemma between ongoing therapeutic need, toxicity and the possibility of an alternative cause. As there is no specific test for drug-induced HA, prompt discussion with a metabolic physician is recommended, as the neurotoxic effects are time-dependent. Specific guidelines for managing drug-induced HA have yet to be published and hence the treatment approach outlined in this review reflects that outlined in relevant urea cycle disorder guidelines.

Increasing serum ammonia level is a risk factor for the prognosis of critically ill patients: A multicenter retrospective cohort study

PURPOSE

To assess the association between serum ammonia level upon admission during the initial intensive care unit (ICU) stay and mortality.

MATERIALS AND METHODS

This retrospective cohort study included 2703 adult patients in eICU Collaborative Research Database. The ICU mortality within ammonia deciles were assessed. Logistic regression analyses were performed to analyze the relationship between ammonia and mortality.

RESULTS

We defined three ammonia categories: <47, 47-111, and ≥111 μg/dL, corresponding to low, intermediate, and high ICU mortality. Increased ammonia was significantly associated with increased ICU mortality (per 10 μg/dL increase: odds ratio, 1.070 [95% confidence intervals, 1.05-1.09]; intermediate vs. low: 1.90 [1.41-2.56]; high vs. low: 4.38 [2.99-6.41]) and in-hospital mortality (1.06 [1.04-1.08]; 1.45 [1.13-1.87]; 3.41 [2.43-4.79]). Adding ammonia to the Acute Physiology and Chronic Health Evaluation (APACHE) IV score improved the area under the curve from 0.826 to 0.839 (P < 0.001) and from 0.806 to 0.813 (P = 0.001) for ICU and in-hospital mortality, respectively. Interaction and subgroup analyses demonstrated consistent results in patients with different APACHE IV scores, with or without hepatic diseases.

CONCLUSIONS

Elevated serum ammonia level in critically ill patients upon admission was an early risk factor for higher ICU and in-hospital mortality.

Late Onset Ornithine Transcarbamylase Deficiency Triggered by an Acute Increase in Protein Intake: A Review of 10 Cases Reported in the Literature

While the urea cycle disorders (UCDs) classically present in the neonatal stage, they have become increasingly recognized as a rare cause of unexplained hyperammonemic encephalopathy in adults. Many metabolic triggers for late-onset UCDs have been described in the literature including excessive protein intake. In this case series, ten such documented cases are reviewed with analysis of patient demographic, protein load, treatment course, and patient outcome. Common delays in treatment include recognition of hyperammonemia as the cause of encephalopathy and initiation of hemodialysis. In only one case was a diet history used to raise suspicion for a metabolic derangement. Metabolic disorders remain an important consideration in adults presenting with encephalopathy not explained by more common etiologies, and recent and remote dietary history may provide valuable information.

Suggested guidelines for the diagnosis and management of urea cycle disorders: First revision

In 2012, we published guidelines summarizing and evaluating late 2011 evidence for diagnosis and therapy of urea cycle disorders (UCDs). With 1:35 000 estimated incidence, UCDs cause hyperammonemia of neonatal (~50%) or late onset that can lead to intellectual disability or death, even while effective therapies do exist. In the 7 years that have elapsed since the first guideline was published, abundant novel information has accumulated, experience on newborn screening for some UCDs has widened, a novel hyperammonemia-causing genetic disorder has been reported, glycerol phenylbutyrate has been introduced as a treatment, and novel promising therapeutic avenues (including gene therapy) have been opened. Several factors including the impact of the first edition of these guidelines (frequently read and quoted) may have increased awareness among health professionals and patient families. However, under-recognition and delayed diagnosis of UCDs still appear widespread. It was therefore necessary to revise the original guidelines to ensure an up-to-date frame of reference for professionals and patients as well as for awareness campaigns. This was accomplished by keeping the original spirit of providing a trans-European consensus based on robust evidence (scored with GRADE methodology), involving professionals on UCDs from nine countries in preparing this consensus. We believe this revised guideline, which has been reviewed by several societies that are involved in the management of UCDs, will have a positive impact on the outcomes of patients by establishing common standards, and spreading and harmonizing good practices. It may also promote the identification of knowledge voids to be filled by future research.

Split-graft liver transplantation from an adult donor with an unrecognized UCD to a pediatric and adult recipient

We report the outcomes of an adult and pediatric split liver transplant from an adult male donor who died due to an unrecognized UCD, OTC deficiency. Recognizing inborn errors of metabolism can be challenging, especially in adult centers where such disorders are rarely encountered. Shortage of donors for liver transplantation has led to procedures to maximize donor utilization, such as split and live donor grafts. The cause of death should be ascertained before accepting a cadaveric donor organ.

Liver involvement in urea cycle disorders: a review of the literature

Urea cycle disorders (UCDs) are inborn errors of metabolism of the nitrogen detoxification pathway and encompass six principal enzymatic deficiencies. The aging of UCD patients leads to a better knowledge of the long-term natural history of the condition and to the reporting of previously unnoticed manifestations. Despite historical evidence of liver involvement in UCDs, little attention has been paid to this organ until recently. Hence, we reviewed the available scientific evidence on acute and chronic liver dysfunction and liver carcinogenesis in UCDs and discuss their pathophysiology. Overall, liver involvement, such as acute liver failure or steatotic-like disease, which may evolve toward cirrhosis, has been reported in all six main UCDs. Excessive glycogen storage is also a prominent histologic feature, and hypoglycemia has been reported in citrin deficiency. Hepatocarcinomas seem frequent in some UCDs, such as in citrin deficiency, and can sometimes occur in non-cirrhotic patients. UCDs may differ in liver involvement according to the enzymatic deficiency. Ornithine transcarbamylase deficiency may be associated more with acute liver failure and argininosuccinic aciduria with chronic liver failure and cirrhosis. Direct toxicity of metabolites, downstream metabolic deficiencies, impaired tricarboxylic acid cycle, oxidative stress, mitochondrial dysfunction, energy deficit, and putative toxicity of therapies combine in various ways to cause the different liver diseases reported.

Hyperammonemia: What Urea-lly Need to Know: Case Report of Severe Noncirrhotic Hyperammonemic Encephalopathy and Review of the Literature

Purpose. A 66-year-old man who presented with coma was found to have isolated severe hyperammonemia and diagnosed with a late-onset urea-cycle disorder. He was treated successfully and had full recovery. Methods. We report a novel case of noncirrhotic hyperammonemia and review the literature on this topic. Selected literature for review included English-language articles concerning hyperammonemia using the search terms “hyperammonemic encephalopathy”, “non-cirrhotic encephalopathy”, “hepatic encephalopathy”, “urea-cycle disorders”, “ornithine transcarbamylase (OTC) deficiency”, and “fulminant hepatic failure”. Results. A unique case of isolated hyperammonemia diagnosed as late-onset OTC deficiency is presented. Existing evidence about hyperammonemia is organized to address pathophysiology, clinical presentation, diagnosis, and treatment. The case report is discussed in context of the reviewed literature. Conclusion. Late-onset OTC deficiency presenting with severe hyperammonemic encephalopathy and extensive imaging correlate can be fully reversible if recognized promptly and treated aggressively.

Clinical and prognostic role of ammonia in advanced decompensated heart failure. The cardio-abdominal syndrome?

BACKGROUND

Advanced heart failure is associated with end-organ damage. Recent literature suggested an intriguing crosstalk between failing heart, abdomen and kidneys. Venous ammonia, as a by-product of the gut, could be a marker of abdominal injury in heart failure patients. The aim of the study was to investigate the clinical and prognostic role of ammonia in patients with advanced decompensated heart failure (ADHF).

METHODS & RESULTS

90 patients admitted with ADHF were prospectively studied. The prognostic role of ammonia at admission was evaluated. Primary end-points were: a composite of cardiac death, urgent heart transplantation and mechanical circulatory support at 3 months and need for renal replacement therapies (RRT). In the study cohort (age 59.0 ± 12.0 years, FE 21.6 ± 9.0%, INTERMACS profile 3.7 ± 0.9, creatinine 1.71 ± 0.95 mg/dl) 27 patients (30%) underwent the cardiac composite endpoint, while 9 patients (10%) needed RRT. At ROC curve analysis ammonia ≥ 130 μg/dl (abdominal damage) showed the best diagnostic accuracy. At multivariate analysis abdominal damage predicted the cardiac composite endpoint. Abdominal damage further increased risk among patient with cold profile at admission (HR 2.7, 95% CI 1.1-7.0, p = 0.046). At multivariate analysis abdominal damage also predicted need for RRT (OR 10.8, 95% CI 1.5-75.8, p = 0.017). The combined use of estimated right atrial pressure and ammonia showed the highest diagnostic accuracy and a very high specificity in prediction of need for RRT.

CONCLUSION

In a selected population admitted for ADHF ammonia, as a marker of abdominal derangement, predicted adverse cardiac events and need for RRT.

Significant hepatic involvement in patients with ornithine transcarbamylase deficiency

OBJECTIVE

To determine the frequency of significant liver injury and acute liver failure (ALF) in patients with ornithine transcarbamylase deficiency (OTCD), the most common urea cycle defect.

STUDY DESIGN

In this historical cohort study, charts of 71 patients with OTCD at 2 centers were reviewed to assess the prevalence of ALF (international normalized ratio [INR] ≥2.0), liver dysfunction (INR 1.5-1.99), and hepatocellular injury (aspartate aminotransferase/alanine aminotransferase ≥250 IU/L).

RESULTS

More than one-half (57%) of the 49 patients with symptomatic OTCD had liver involvement; 29% met the criteria for ALF, 20% had liver dysfunction, and 8% had isolated hepatocellular injury. The prevalence of ALF was highest in the patients with more severe OTCD, including those with markedly elevated ammonia levels (>1000 μmol/L). Some patients with severe liver involvement (INR ≥2.0 and aspartate aminotransferase/alanine aminotransferase >1000 IU/L) had only moderate hyperammonemia (ammonia 100-400 μmol/L). ALF was the initial presenting symptom of OTCD in at least 3 of 49 symptomatic patients with OTCD.

CONCLUSION

Episodes of hepatocellular injury, liver dysfunction, and ALF were identified in a high proportion of children with symptomatic OTCD. The more severely affected patients had a higher likelihood of ALF. The diagnosis of a urea cycle defect should be considered in patients with unexplained ALF, liver dysfunction, or hepatocellular injury.

Hyperammonemic Coma in an Adult due to Ornithine Transcarbamylase Deficiency

Objective. To report an unusual cause of coma in an adult. Design. Case report. Setting. University teaching hospital. Patient. A previously healthy 53-year-old man initially presented with altered mental status and progressed to coma. He was found to be substantially hyperammonemic and did not improve with lactulose therapy and continuous venovenous hemodialysis. Results. Biochemical testing revealed previously undiagnosed ornithine transcarbamylase deficiency, and the patient responded to arginine, sodium phenylacetate, and sodium benzoate. Conclusion. Even in adult patients with no known history, inborn errors of metabolism must be considered in the differential diagnosis of unexplained coma. Defects of the urea cycle can present with an unprovoked hyperammonemic coma.

Suggested guidelines for the diagnosis and management of urea cycle disorders

Urea cycle disorders (UCDs) are inborn errors of ammonia detoxification/arginine synthesis due to defects affecting the catalysts of the Krebs-Henseleit cycle (five core enzymes, one activating enzyme and one mitochondrial ornithine/citrulline antiporter) with an estimated incidence of 1:8.000. Patients present with hyperammonemia either shortly after birth (~50%) or, later at any age, leading to death or to severe neurological handicap in many survivors. Despite the existence of effective therapy with alternative pathway therapy and liver transplantation, outcomes remain poor. This may be related to underrecognition and delayed diagnosis due to the nonspecific clinical presentation and insufficient awareness of health care professionals because of disease rarity. These guidelines aim at providing a trans-European consensus to: guide practitioners, set standards of care and help awareness campaigns. To achieve these goals, the guidelines were developed using a Delphi methodology, by having professionals on UCDs across seven European countries to gather all the existing evidence, score it according to the SIGN evidence level system and draw a series of statements supported by an associated level of evidence. The guidelines were revised by external specialist consultants, unrelated authorities in the field of UCDs and practicing pediatricians in training. Although the evidence degree did hardly ever exceed level C (evidence from non-analytical studies like case reports and series), it was sufficient to guide practice on both acute and chronic presentations, address diagnosis, management, monitoring, outcomes, and psychosocial and ethical issues. Also, it identified knowledge voids that must be filled by future research. We believe these guidelines will help to: harmonise practice, set common standards and spread good practices with a positive impact on the outcomes of UCD patients.

Noncirrhotic hyperammonaemic encephalopathy

Adult hyperammonaemia is associated with severe liver disease in 90% of cases. In the remainder, noncirrhotic causes should be considered. Measurements of serum ammonia level must be part of the basic work-up in all patients presenting with encephalopathy of unknown origin, even when liver function is normal. Clinician awareness of noncirrhotic hyperammonaemic encephalopathy can contribute to early diagnosis and the initiation of sometimes life-saving treatment. This review focuses on the physiology, aetiology and underlying mechanisms of noncirrhotic hyperammonaemic encephalopathy and discusses the available treatment modalities.

Adult nonhepatic hyperammonemia: a case report and differential diagnosis

This article presents a case report of nonhepatic hyperammonemia, i.e., elevated serum ammonia secondary to a nonhepatic etiology. It then discusses the importance of broadening one's differential diagnosis to include such nonhepatic causes of elevated ammonia levels, and provides a short review of rarer causes of hyperammonemia in the adult population. Treating the underlying condition is the best way to prevent recurrence of hyperammonemia. However, symptomatic treatment should not be delayed while investigating the underlying source.

Ammonia toxicity and its prevention in inherited defects of the urea cycle

The urea cycle is the final pathway for removal of surplus nitrogen from the body, and the major route in humans for detoxification of ammonia. The full complement of enzymes is expressed only in liver. Inherited deficiencies of urea cycle enzymes lead to hyperammonaemia, which causes brain damage. Severe defects present with hyperammonaemic crises in neonates. Equally devastating episodes may occur in previously asymptomatic adults with mild defects, most often X-linked ornithine transcarbamylase (OTC) deficiency. Several mechanisms probably contribute to pathogenesis. Treatment aims to reduce plasma ammonia quickly, reduce production of waste nitrogen, dispose of waste nitrogen using alternative pathways to the urea cycle and replace arginine. These therapies have increased survival and probably improve the neurological outcome. Arginine, sodium benzoate, sodium phenylbutyrate and, less often, sodium phenylacetate are used. Long-term correction is achieved by liver transplantation. Gene therapy for OTC deficiency is effective in animals, and work is ongoing to improve persistence and safety.

Adult onset urea cycle disorder in a patient with presumed hepatic encephalopathy

Deficiency of any of the 5 enzymes in the urea cycle results in the accumulation of ammonia, leading to encephalopathy; which if untreated, can be lethal and produce devastating neurologic sequelae in long-term survivors. We hereby present an interesting case that presented with hyperammonemia and encephalopathy; later found to have an urea cycle defect.

Hyperammonemia in the ICU

Patients experiencing acute elevations of ammonia present to the ICU with encephalopathy, which may progress quickly to cerebral herniation. Patient survival requires immediate treatment of intracerebral hypertension and the reduction of ammonia levels. When hyperammonemia is not thought to be the result of liver failure, treatment for an occult disorder of metabolism must begin prior to the confirmation of an etiology. This article reviews ammonia metabolism, the effects of ammonia on the brain, the causes of hyperammonemia, and the diagnosis of inborn errors of metabolism in adult patients.

Anesthetic management of patients with ornithine transcarbamylase deficiency

Ornithine transcarbamylase deficiency (OTCD) is the most common inborn error of the urea cycle. Several specific factors require care during anesthesia in patients with this condition to avoid metabolic decompensation with acute hyperammonemia and encephalopathy. We report monozygous twins with severe neonatal-onset OTCD undergoing general anesthesia twice each, with midazolam, s-ketamine, fentanyl and isoflurane in combination with surgical field infiltration with ropivacaine. Alternative pathway medication and high-caloric diet with 10% glucose solutions were continuously administered during the perioperative course. Both children were extubated within 10 min of the final suture, and their neurological state remained unchanged. Perioperatively, blood ammonia levels remained within the normal range.

Unmasked adult-onset urea cycle disorders in the critical care setting

Most often, urea cycle disorders have been described as acute onset hyperammonemia in the newborn period; however, there is a growing awareness that urea cycle disorders can present at almost any age, frequently in the critical care setting. This article presents three cases of adult-onset hyperammonemia caused by inherited defects in nitrogen processing in the urea cycle, and reviews the diagnosis, management, and pathophysiology of adult-onset urea cycle disorders. Individuals who have milder molecular urea cycle defects can lead a relatively normal life until a severe environmental stress triggers a hyperammonemic crisis. Comorbid conditions such as physical trauma often delay the diagnosis of the urea cycle defect. Prompt recognition and treatment are essential in determining the outcome of these patients.

Der Patient mit Ornithintranscarbamylasemangel

Ornithine transcarbamylase deficiency (OTCD) is the most common inborn urea cycle disorder. Patients with OTCD are at risk of acute metabolic decompensation with hyperammonemia and subsequent encephalopathy, coma and death. Symptoms may be triggered by infections, drugs and stress, evoked by trauma, pain, fear, surgery and anaesthesia or by episodes of protein catabolism, i.e. fasting-induced, post partum or during gastrointestinal bleeding. Several specific considerations must be made for anaesthetic and intensive care management in patients with this disease in order to avoid metabolic decompensation. We report the intensive care management of the first manifestation of late-onset OTCD in a 16-year-old girl and a course of inconspicuous general anaesthesia with midazolam, s-ketamine, fentanyl and isoflurane in a 22-year-old girl with known OTCD.

Differential utilization of systemic and enteral ammonia for urea synthesis in control subjects and ornithine transcarbamylase deficiency carriers

BACKGROUND

Female carriers of ornithine transcarbamylase deficiency (OTCD) have nearly normal rates of total urea synthesis, but they derive less urea from systemic glutamine amide nitrogen than do healthy persons.

OBJECTIVE

The objective of the study was to investigate whether females with symptomatic OTCD rely on alternative pathways to compensate for the reduced urea synthesis activity observed in this disorder.

DESIGN

The 5-d study involved 6 control subjects (3 males, 3 females) and 6 female OTCD carriers who had a fixed energy intake of 133 kJ. kg(-)(1). d(-)(1) and a protein intake of 0.8 g. kg(-)(1). d(-)(1). They underwent two 12-h periods of isotopic tracer administration, separated by 2 d. On both occasions, [(18)O] or [(13)C]urea was infused intravenously, and the subjects consumed hourly meals. During the first period, [(15)N]NH(4)Cl was given intravenously; during the second period, the tracer was given as hourly oral doses.

RESULTS

OTCD carriers produced less urea (P < 0.05) but had a higher (P < 0.05) mean ammonia appearance rate and plasma ammonia concentration than did control subjects. OTCD carriers incorporated a lower (P < 0.001) mean (+/- SE) proportion of the intravenous [(15)N]NH(4)Cl dose into circulating urea than did control subjects (16 +/- 1% compared with 36 +/- 2%), but there was no genotypic difference in the incorporation of orally administered tracer (81 +/- 4% compared with 72 +/- 4%, respectively).

CONCLUSION

A good degree of dietary protein tolerance seemed to be retained in OTCD carriers by the maintenance of higher ammonia appearance rates, expansion of the plasma ammonia pool, and reliance on the ability of the perivenous hepatocytes to clear excess ammonia via glutamine synthesis.

Ornithine transcarbamylase deficiency: a urea cycle defect

The symptoms and signs of ornithine transcarbamylase deficiency are discussed. When the condition occurs among males in the neonatal period it is likely to be lethal. Pathological findings are non-specific. The diagnosis should be considered if coma with cerebral oedema and respiratory alkalosis occurs for no obvious reason. When hyperammonaemia is found, enzyme assay on a liver biopsy should be considered. A useful clue in an asymptomatic patient is a voluntary adoption of a vegetarian diet. Provocative tests, such as the allopurinol test can be used, but the method most frequently applied is mutation analysis. In the case of prenatal diagnosis this is possible on a chorionic villus sample. The prognosis of ornithine transcarbamylase deficiency is better for those with an onset after infancy, but morbidity from brain damage does not appear to be linked to the number of episodes of hyperammonaemia that have occurred. The syndrome results from a deficiency of the mitochondrial enzyme ornithine transcarbamylase which catalyses the conversion of ornithine and carbamoyl phosphate to citrulline. The gene responsible for this enzyme is located on Xp21.1, and is expressed in the liver and gut. Mutations can be divided into two groups: those with neonatal onset with all enzyme activity abolished, and those with later onset with partial and varying enzyme deficiency. There can be a variety of precipitating causes, for example sodium valproate. Treatment can be given with a low protein diet, and with alternate pathway drugs such as sodium benzoate and phenylbutyrate. Liver transplant can be considered when symptoms are life-threatening, although there may be severe complications.Gene replacement therapy is the hope of the future.

Late-onset presentation of ornithine transcarbamylase deficiency in a young woman with hyperammonemic coma

Ornithine transcarbamylase deficiency (OTCD) is an X-linked inherited disease and the most common inborn error in urea synthesis in human patients. In adult heterozygous patients, OTCD can be responsible for life-threatening hyperammonemic coma. We report the case of a 32-year-old woman admitted to our hospital with seizures after a recent high protein load. Her parents related a history of recurrent episodes of vomiting, meat refusal, lethargy, and convulsions since childhood, and measurement of plasma ammonemia levels was the key to early diagnosis of OTCD. We report the pathophysiologic characteristics, clinical features, clinical course, and differential diagnosis of OTCD and discuss the therapeutic options, including continuous venovenous hemodiafiltration and pharmacologic therapy for reduction of plasma ammonemia levels. A diagnosis of OTCD should be considered in adult nonhepatic patients with hyperammonemic coma, particularly if they have a history of protein avoidance and neurologic symptoms. Early recognition and appropriate treatment are critical to avoid severe brain damage and death.