Severe non-hepatic hyperammonaemic encephalopathy in an immunocompromised adolescent with enterocolitis.

Non-hepatic causes of hyperammonaemia are uncommon relative to hepatic aetiologies. An adolescent female was admitted to the hospital with a diagnosis of very severe aplastic anaemia. During her treatment with immunosuppressive therapy, she developed neutropenic enterocolitis, pseudomonal bacteraemia and hyperammonaemia. A combination of intermittent haemodialysis and high-volume continuous veno-venous haemodiafiltration (CVVHDF) was required to manage the hyperammonaemia. Despite a thorough investigation, there were no hepatic, metabolic or genetic aetiologies identified that explained the hyperammonaemia. The hyperammonaemia resolved only after the surgical resection of her inflamed colon, following which she was successfully weaned off from the renal support. This is a novel case report of hyperammonaemia of non-hepatic origin secondary to widespread inflammation of the colon requiring surgical resection in an immunocompromised patient. This case also highlights the role of high-volume CVVHDF in augmenting haemodialysis in the management of severe refractory hyperammonaemia.

Cerebral Aspects of Portal Hypertension: Hepatic Encephalopathy.

Portal hypertension has cerebral consequences via its causes and complications, namely hepatic encephalopathy (HE), a common and devastating brain disturbance caused by liver insufficiency and portosystemic shunting. The pathogenesis involves hyperammonemia and systemic inflammation. Symptoms are disturbed personality and reduced attention. HE is minimal or grades I to IV (coma). Bouts of HE are episodic and often recurrent. Initial treatment is of events that precipitated the episode and exclusion of nonhepatic causes. Specific anti-HE treatment is lactulose. By recurrence, rifaximin is add-on. Anti-HE treatment is efficacious also for prophylaxis, but emergence of HE marks advanced liver disease and a dismal prognosis.

Host and fungal factors both contribute to cryptococcosis-associated hyperammonemia (cryptammonia).

Cryptococcus neoformans and Cryptococcus gattii are both known urease producers and have the potential to cause hyperammonemia. We hypothesized that the risk of hyperammonemia is increased by renal failure, burden of cryptococcal infection, and fungal strain characteristics. We performed a retrospective review of plasma ammonia levels in patients with cryptococcal infections. Risk factors for hyperammonemia were statistically compared between patients with and without hyperammonemia (>53 µmol/L). Cryptococcal cells from three patients included in the study were recovered from our biorepository. Strain characteristics including urease activity, ammonia production, growth curves, microscopy, melanin production, and M13 molecular typing were analyzed and compared with a wild-type (WT) C. neoformans strain. We included 29 patients, of whom 37.9% had hyperammonemia, 59% had disseminated cryptococcal infection (DCI), and 41% had isolated central nervous system infection. Thirty-eight percent of patients had renal failure and 28% had liver disease. Renal failure was associated with 4.4 times (95% confidence interval [CI] 1.5, 13.0) higher risk of hyperammonemia. This risk was higher in DCIs (RR 6.2, 95% CI 1.0, 40.2) versus isolated cryptococcal meningitis (RR 2.5, 95% CI, 0.40, 16.0). Liver disease and cryptococcal titers were not associated with hyperammonemia. C. neoformans from one patient with extreme hyperammonemia demonstrated a 4- to 5-fold increase in extracellular urease activity, slow growth, enlarged cell size phenotypes, and diminished virulence factors. Hyperammonemia was strongly associated with renal failure in individuals with DCI, surpassing associations with liver failure or cryptococcal titers. However, profound hyperammonemia in one patient was attributable to high levels of urease secretion unique to that cryptococcal strain. Prospective studies are crucial to exploring the significance of this association.IMPORTANCECryptococcus produces and secretes the urease enzyme to facilitate its colonization of the host. Urease breaks down urea into ammonia, overwhelming the liver's detoxification process and leading to hyperammonemia in some hosts. This underrecognized complication exacerbates organ dysfunction alongside the infection. Our study investigated this intricate relationship, uncovering a strong association between the development of hyperammonemia and renal failure in patients with cryptococcal infections, particularly those with disseminated infections. We also explore mechanisms underlying increased urease activity, specifically in strains associated with extreme hyperammonemia. Our discoveries provide a foundation for advancing research into cryptococcal metabolism and identifying therapeutic targets to enhance patient outcomes.

Hepatic Encephalopathy Secondary to Non-cirrhotic Portosystemic Shunt.

Hepatic encephalopathy is uncommon in the absence of cirrhosis. We report a 71-year-old woman who presented with altered mental status in the setting of hyperammonemia for the second time in 6 months. Magnetic resonance imaging of the abdomen revealed an uncommon portosystemic shunt involving an enlarged posterior branch of the right portal vein and an accessory right hepatic vein, with no features of cirrhosis. Appropriate management of these patients with ammonia-lowering therapy can reduce repeat episodes and improve quality of life. This case demonstrates the importance of diagnosing non-cirrhotic hepatic encephalopathy in patients with altered mental status.

Are asymptomatic carriers of OTC deficiency always asymptomatic? A multicentric retrospective study of risk using the UCDC longitudinal study database.

BACKGROUND: Ornithine transcarbamylase deficiency (OTCD) due to an X-linked OTC mutation, is responsible for moderate to severe hyperammonemia (HA) with substantial morbidity and mortality. About 80% of females with OTCD remain apparently "asymptomatic" with limited studies of their clinical characteristics and long-term health vulnerabilities. Multimodal neuroimaging studies and executive function testing have shown that asymptomatic females exhibit limitations when stressed to perform at higher cognitive load and had reduced activation of the prefrontal cortex. This retrospective study aims to improve understanding of factors that might predict development of defined complications and serious illness in apparent asymptomatic females. A proband and her daughter are presented to highlight the utility of multimodal neuroimaging studies and to underscore that asymptomatic females with OTCD are not always asymptomatic. METHODS: We review data from 302 heterozygote females with OTCD enrolled in the Urea Cycle Disorders Consortium (UCDC) longitudinal natural history database. We apply multiple neuroimaging modalities in the workup of a proband and her daughter. RESULTS: Among the females in the database, 143 were noted as symptomatic at baseline (Sym). We focused on females who were asymptomatic (Asx, n = 111) and those who were asymptomatic initially upon enrollment in study but who later became symptomatic sometime during follow-up (Asx/Sym, n = 22). The majority of Asx (86%) and Asx/Sym (75%) subjects did not restrict protein at baseline, and ~38% of Asx and 33% of Asx/Sym subjects suffered from mild to severe neuropsychiatric conditions such as mood disorder and sleep problems. The risk of mild to severe HA sometime later in life for the Asx and Asx/Sym subjects as a combined group was ~4% (5/133), with ammonia ranging from 77 to 470 µM and at least half (2/4) of subjects requiring hospital admission and nitrogen scavenger therapy. For this combined group, the median age of first HA crisis was 50 years, whereas the median age of first symptom which included neuropsychiatric and/or behavioral symptoms was 17 years. The multimodal neuroimaging studies in female heterozygotes with OTCD also underscore that asymptomatic female heterozygotes with OTCD (e.g., proband) are not always asymptomatic. CONCLUSIONS: Analysis of Asx and Asx/Sym females with OTCD in this study suggests that future evidence-based management guidelines and/or a clinical risk score calculator for this cohort could be useful management tools to reduce morbidity and improve long-term quality of life.

Hepatic veno-occlusive disease complicated with extreme hyperammonaemia (920 µmol/L) treated with defibrotide, lactulose, rifampin and haemodialysis.

Hepatic veno-occlusive disease (VOD)/sinusoidal obstructive syndrome (SOS) is a severe complication that can occur following haematopoietic stem cell transplant (HSCT) with high-intensity conditioning chemotherapy regimens. Severe VOD/SOS, often characterised by multiorgan failure, is associated with a high mortality rate. This case report details the complex clinical course of a male patient in his mid-20s, recently diagnosed with B cell acute lymphoblastic leukaemia, who underwent allogeneic HSCT. Based on the 2023 European Society for Blood and Marrow Transplantation (EBMT) criteria, the patient developed very severe VOD/SOS, prompting immediate treatment with defibrotide. Unexpectedly, he developed profound hyperammonaemia exceeding 900 µmol/L, leading to encephalopathy and cerebral oedema. Despite aggressive interventions including defibrotide, lactulose, rifampin and haemodialysis, the patient passed away due to cerebral oedema and pulseless electrical activity arrest. We theorise the hyperammonaemia is disproportionate to his hepatic dysfunction and is possibly secondary to an acquired defect of the urea synthesis consistent with idiopathic hyperammonaemia, a rare complication in patients receiving intense conditioning chemotherapy.

Mitochondrial targets in hyperammonemia: Addressing urea cycle function to improve drug therapies.

The urea cycle (UC) is a critically important metabolic process for the disposal of nitrogen (ammonia) produced by amino acids catabolism. The impairment of this liver-specific pathway induced either by primary genetic defects or by secondary causes, namely those associated with hepatic disease or drug administration, may result in serious clinical consequences. Urea cycle disorders (UCD) and certain organic acidurias are the major groups of inherited rare diseases manifested with hyperammonemia (HA) with UC dysregulation. Importantly, several commonly prescribed drugs, including antiepileptics in monotherapy or polytherapy from carbamazepine to valproic acid or specific antineoplastic agents such as asparaginase or 5-fluorouracil may be associated with HA by mechanisms not fully elucidated. HA, disclosing an imbalance between ammoniagenesis and ammonia disposal via the UC, can evolve to encephalopathy which may lead to significant morbidity and central nervous system damage. This review will focus on biochemical mechanisms related with HA emphasizing some poorly understood perspectives behind the disruption of the UC and mitochondrial energy metabolism, namely: i) changes in acetyl-CoA or NAD+ levels in subcellular compartments; ii) post-translational modifications of key UC-related enzymes, namely acetylation, potentially affecting their catalytic activity; iii) the mitochondrial sirtuins-mediated role in ureagenesis. Moreover, the main UCD associated with HA will be summarized to highlight the relevance of investigating possible genetic mutations to account for unexpected HA during certain pharmacological therapies. The ammonia-induced effects should be avoided or overcome as part of safer therapeutic strategies to protect patients under treatment with drugs that may be potentially associated with HA.

Urea cycle disorders in critically Ill adults.

PURPOSE OF REVIEW: Urea cycle disorders (UCDs) cause elevations in ammonia which, when severe, cause irreversible neurologic injury. Most patients with UCDs are diagnosed as neonates, though mild UCDs can present later - even into adulthood - during windows of high physiologic stress, like critical illness. It is crucial for clinicians to understand when to screen for UCDs and appreciate how to manage these disorders in order to prevent devastating neurologic injury or death. RECENT FINDINGS: Hyperammonemia, particularly if severe, causes time- and concentration-dependent neurologic injury. Mild UCDs presenting in adulthood are increasingly recognized, so broader screening in adults is recommended. For patients with UCDs, a comprehensive, multitiered approach to management is needed to prevent progression and irreversible injury. Earlier exogenous clearance is increasingly recognized as an important complement to other therapies. SUMMARY: UCDs alter the core pathway for ammonia metabolism. Screening for mild UCDs in adults with unexplained neurologic symptoms can direct care and prevent deterioration. Management of UCDs emphasizes decreasing ongoing ammonia production, avoiding catabolism, and supporting endogenous and exogenous ammonia clearance. Core neuroprotective and supportive critical care supplements this focused therapy.

Hepatic Encephalopathy in Children.

Hepatic encephalopathy, characterized by mental status changes and neuropsychiatric impairment, is associated with chronic liver disease as well as acute liver failure. In children, its clinical manifestations can be challenging to pinpoint. However, careful assessment for the development of hepatic encephalopathy is imperative when caring for these patients as progression of symptoms can indicate impending cerebral edema and systemic deterioration. Hepatic encephalopathy can present with hyperammonemia, but it is important to note that the degree of hyperammonemia is not indicative of severity of clinical manifestations. Newer forms of assessment are undergoing further research, and include imaging, EEG and neurobiomarkers. Mainstay of treatment currently includes management of underlying cause of liver disease, as well as reduction of hyperammonemia with either enteral medications such as lactulose and rifaximin, or even with extracorporeal liver support modalities.

Adult presentation of ornithine transcarbamylase deficiency: a possible cause of hyperammonemia after high-dose chemotherapy and stem cell transplantation.

Hyperammonemia is a rare and often fatal complication following the conditioning therapy in autologous and allogeneic stem cell transplant recipients. It is characterized by anorexia, vomiting, lethargy and coma without any other apparent cause. The diagnosis is often delayed because symptoms can be subtle and ammonia is usually not included among the routine analyzes. Previous reports have not identified the molecular mechanisms behind hyperammonemia in stem cell transplant recipients. Urea cycle disorders (UCDs) are inborn errors of metabolism leading to hyperammonemia that usually presents in early childhood, whereas first presentation in adults is less common. Here we describe an adult woman with hyperammonemia following autologous stem cell transplantation for multiple myeloma. No apparent cause of hyperammonemia was identified, including portosystemic shunting, liver dysfunction or recent hyperammonemia-inducing chemotherapy. Hyperammonemia, normal blood glucose as well as anion gap and a previous history of two male newborns that died early after birth, prompted biochemical and genetic investigations for a UCD. A heterozygous variant in the X-linked gene encoding ornithine transcarbamylase (OTC) was identified and was regarded as a cause of UCD. The patient improved after treatment with nitrogen scavengers and high caloric intake according to a UCD protocol. This case report suggests that UCD should be considered as a possible cause of hyperammonemia following stem cell transplantation.

Expanding the Spectrum of Extracorporeal Strategies in Small Infants with Hyperammonemia.

Hyperammonemia is a life-threatening condition mainly due to the neurotoxicity of ammonia. Ammonia scavengers may be insufficient, and extracorporeal treatment may be required. Continuous treatments are preferred, and a high-dose continuous renal replacement therapy (CRRT) must be prescribed to ensure a fast ammonia depletion. Many of the children with hyperammonemia are newborns, with lower blood volume than older children. The majority of the CRRT systems are adult-based, with large extracorporeal priming volumes and inadequate UF control. Recent strides have been made in the development of CRRT systems more suitable for young children with smaller sets to use in adult machines and dedicated monitors for neonates and infants. The main advantage of the machines for adults is the higher dialysis fluid flows, however with greater hemodynamic risks. Pediatric monitors have been designed to reduce the extracorporeal volume and to increase the precision of the treatment. However, they have substantial limitation in clearance performances. In this review, we discuss on current strategies to provide CRRT in newborns and small infants with hyperammonemia. We also presented our experience with the use of CARPEDIEM™ implemented in a CVVHDF modality, boosting the diffusive clearance with a post-replacement convective mechanism.

Closure of a distal splenorenal shunt as a therapy for refractory hyperammonaemia in setting of neuropsychiatric symptoms.

Before the widespread use of the transjugular intrahepatic portosystemic shunt, portal hypertension was addressed by the creation of an operative distal splenorenal shunt (DSRS). DSRS was largely regarded as a safe and effective therapy, though it did have a risk of precipitating hyperammonaemia and hepatic encephalopathy.A woman suffered a gunshot wound to the abdomen. This trauma led to portal vein thrombosis, cavernous transformation of the vein and eventually bleeding oesophageal varices from portal hypertension. A DSRS was created to decrease portal hypertension. Years later, she had profound depression with psychomotor slowing in the setting of hyperammonaemia. To reduce hepatic encephalopathy as a contributor to her neuropsychiatric condition, her shunt was closed. The hyperammonaemia resolved and neuropsychiatric symptoms improved.This case highlights several interesting clinical features, including portal hypertension due to chronic portal vein occlusion, cavernous transformation, a surgical DSRS causing hyperammonaemia and hepatic encephalopathy manifesting as neuropsychiatric symptoms.

Anesthesia management protocol for liver transplantation as treatment for ornithine transcarbamylase deficiency.

BACKGROUND: Ornithine transcarbamylase deficiency is an X-linked genetic disorder that induces accumulation of ammonia in the liver and is the most common urea cycle disorder. The clinical manifestation of ornithine transcarbamylase deficiency is hyperammonemia that causes irreversible neurological damage. Liver transplantation is a curative therapy for ornithine transcarbamylase deficiency. The aim of this study is to suggest, from our previous experience, an anesthesia management protocol of liver transplantation for ornithine transcarbamylase deficiency, particularly focused on liver transplantation for cases with uncontrolled hyperammonemia. METHOD: We retrospectively reviewed our anesthesia-related experience in all cases of liver transplantation for ornithine transcarbamylase deficiency in our center. RESULTS: Twenty-nine liver transplantation cases for ornithine transcarbamylase deficiency were found between November 2005 and March 2021 in our center. Of these, 25 cases were stable through the perioperative period. However, 2 cases with carrier donor graft had hyperammonemia after liver transplantation. Another two cases had uncontrolled hyperammonemia before liver transplantation, even with continuous hemodialysis. They underwent life-saving liver transplantation. Their metabolic status stabilized after the anhepatic phase. CONCLUSION: Liver transplantation for cases with uncontrolled hyperammonemia can be performed with proper management. Second, liver transplantation with carrier donors should be avoided because of the risk of postoperative recurrence.

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Neonatal hyperammonemia is a disorder of ammonia metabolism that occurs in the neonatal period. It is a clinical syndrome characterized by abnormal accumulation of ammonia in the blood and dysfunction of the central nervous system. Due to its low incidence and lack of specificity in clinical manifestations, it is easy to cause misdiagnosis and missed diagnosis. In order to further standardize the diagnosis and treatment of neonatal hyperammonemia, the Youth Commission, Subspecialty Group of Neonatology, Society of Pediatrics, Chinese Medical Association formulated the expert consensus based on clinical evidence in China and overseas and combined with clinical practice experience,and put forward 18 recommendations for the diagnosis and treatment of neonatal hyperaminemia.

Feline hyperammonemia associated with functional cobalamin deficiency: A case report.

Ammonia is a major neurotoxic substance associated with the complex pathogenesis of hepatic encephalopathy. Although several primary and secondary conditions have been reported to cause hyperammonemia, in veterinary medicine this condition is considered primarily associated with hepatic disease or portosystemic shunting. Only a few cases of inherited urea cycle enzyme deficiency and organic acid metabolic disorders have been reported in cats with hyperammonemia. To the best of our knowledge, this is the first report of hyperammonemia in a cat caused by accumulation of methylmalonic acid (MMA) secondary to functional cobalamin deficiency. A 2-year-old spayed female Turkish Angora cat exhibited postprandial depression with a 3-month history of hyperammonemia. Serum protein C and bile acid concentrations were normal. Plasma amino acid analysis revealed a deficiency of urea cycle amino acids. Although the serum cobalamin concentration was markedly high, there was no evidence of inflammatory, hepatic, or renal disease or neoplasia on blood, ultrasonographic, and computed tomographic examination. Gas chromatography-mass spectrometry revealed a high MMA concentration in the urine. Based on the results, functional cobalamin deficiency was diagnosed. Following oral amino acid supplementation and initiation of a low-protein diet, the serum ammonia level returned to normal and the postprandial depression improved. Urea cycle amino acid deficiency secondary to functional cobalamin deficiency presumably caused hyperammonemia due to MMA accumulation in this case.

Hyperammoniémie féline associée à un déficit fonctionnel en cobalamine : rapport de cas. L'ammoniac est une substance neurotoxique majeure associée à la pathogenèse complexe de l'encéphalopathie hépatique. Bien que plusieurs affections primaires et secondaires aient été signalées comme étant à l'origine d'une hyperammoniémie, en médecine vétérinaire, cette affection est considérée comme principalement associée à une maladie hépatique ou à un shunt porto-systémique. Seuls quelques cas de déficit héréditaire en enzymes du cycle de l'urée et de troubles métaboliques des acides organiques ont été signalés chez des chats atteints d'hyperammoniémie. À notre connaissance, il s'agit du premier rapport d'hyperammoniémie chez un chat causée par une accumulation d'acide méthylmalonique (MMA) secondaire à un déficit fonctionnel en cobalamine.Une chatte angora turque stérilisée âgée de 2 ans a présenté une dépression postprandiale avec une histoire d'hyperammoniémie depuis 3 mois. Les concentrations sériques de protéine C et d'acides biliaires étaient normales. L'analyse plasmatique des acides aminés a révélé une déficience en acides aminés du cycle de l'urée. Bien que la concentration sérique de cobalamine ait été nettement élevée, il n'y avait aucun signe de maladie inflammatoire, hépatique ou rénale ou de néoplasie à l'examen sanguin, échographique et tomodensitométrique. La chromatographie en phase gazeuse-spectrométrie de masse a révélé une forte concentration de MMA dans l'urine. Sur la base des résultats, un déficit fonctionnel en cobalamine a été diagnostiqué. Après une supplémentation orale en acides aminés et la mise en place d'un régime pauvre en protéines, le taux sérique d'ammoniac est revenu à la normale et la dépression postprandiale s'est améliorée. Une carence en acides aminés du cycle de l'urée secondaire à une carence en cobalamine fonctionnelle a vraisemblablement causé une hyperammoniémie due à l'accumulation de MMA dans ce cas.(Traduit par Dr Serge Messier).