Fatal ammonia toxicity in an adult due to an undiagnosed urea cycle defect: under-recognition of ornithine transcarbamylase deficiency

Diagnostic and Management Issues in Patients with Late-Onset Ornithine Transcarbamylase Deficiency

Ornithine transcarbamylase deficiency (OTCD) is the most common inherited disorder of the urea cycle and, in general, is transmitted as an X-linked recessive trait. Defects in the OTC gene cause an impairment in ureagenesis, resulting in hyperammonemia, which is a direct cause of brain damage and death. Patients with late-onset OTCD can develop symptoms from infancy to later childhood, adolescence or adulthood. Clinical manifestations of adults with OTCD vary in acuity. Clinical symptoms can be aggravated by metabolic stressors or the presence of a catabolic state, or due to increased demands upon the urea. A prompt diagnosis and relevant biochemical and genetic investigations allow the rapid introduction of the right treatment and prevent long-term complications and mortality. This narrative review outlines challenges in diagnosing and managing patients with late-onset OTCD.

UK National audit of the measurement of ammonia

BACKGROUND

Severe hyperammonaemia is associated with significant morbidity and mortality. Rapid analysis and reporting of ammonia results is essential to prevent patient harm. The aim was to investigate the laboratory sample acceptance criteria, ammonia analysis and the reporting of ammonia results.

METHODS

A questionnaire was distributed to clinical biochemistry laboratories in the United Kingdom. The results were collated and compared to updated best practice guidelines on hyperammonaemia issued by the Metabolic Biochemistry Network (MetBio.net).

RESULTS

Seventy-six laboratories responded to the audit questionnaire. Although 83% laboratories are aware of the updated MetBio.net hyperammonaemia guidelines, most laboratories continue to reject samples for ammonia that are 'too old' for analysis (64%), haemolysed (72%) or not sent on ice (24%). Rapid ammonia analysis is available in 96% laboratories and all laboratories offer ammonia analysis on a 24/7 basis. Nearly all laboratories had implemented critical phoning limits for ammonia.

CONCLUSIONS

Laboratories are rejecting samples for ammonia analysis that have not been collected/transported in an optimal manner. Laboratories should review their sample acceptance criteria for ammonia and accept all samples in order to avoid delaying the diagnosis and management of hyperammonaemia.

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.

Adult Presentation of Ornithine Transcarbamylase Deficiency: 2 Illustrative Cases of Phenotypic Variability and Literature Review

Ornithine transcarbamylase (OTC) deficiency is an X-linked recessive disorder that usually presents in the neonatal period. Late-onset presentation of OTC can cause mild to severe symptoms. We describe laboratory and clinical findings of late-onset presentations of OTC deficiency. We conducted a literature search using search terms "ornithine transcarbamylase deficiency," "late onset presentation," and "hyperammonemia" from January 1, 1987, to December 31, 2016, was performed. Only papers published in English were included. We searched on PubMed, MEDLINE, and Google Scholar. We also present 2 OTC deficiency cases. A total of 30 adult cases had late-onset presentation of OTC deficiency reported. The majority were women (57%) with a median age of 37 years. The median level of ammonia was 308 mmol/L and the mortality rate was 30%. Our case 1 was a 40-year-old woman who succumbed to neurologic complications after a hyperammonemia crisis following an increased protein intake. Our case 2 was a 43-year-old woman with seizures associated with increased ammonia levels. Our 2 case reports show the wide phenotypic variability and severity in late-onset presentation of OTC ranging from seizures to cerebral herniation. Our literature review is the first to detail published laboratory and neurologic sequelae of late-onset OTC deficiency.

Psychiatric Disorders Secondary to Neurometabolic Disorders

Some diseases secondary to inborn errors of metabolism are associated with psychiatric disorders or minor neurological symptoms. The existence of some cases with exclusively psychiatric symptoms represents a diagnostic and therapeutic challenge. The aim of this article is to describe seven treatable neurometabolic disorders that should be taken into account in the psychiatric consultation as they manifest with psychiatric symptoms that mask the organic origin of the disorder. Homocysteine metabolism and urea cycle disorders, Wilson's disease, Niemann-Pick disease Type C, acute porphyria and cerebrotendinous xanthomatosis are described. Following an analysis of the literature, a list of psychiatric symptoms associated with these disorders are proposed, ranging from insidious changes in affective state and thought to atypical symptoms such as visual hallucinations, as well as paradoxical effects of antipsychotics or behavioural disorders in children and adolescents associated with loss of autonomy. The most frequently associated neurological signs, such as alterations in the state of consciousness, motor behaviour and balance disorders, catatonia or progressive cognitive deficit are also listed. Emphasis is placed on the importance of considering resistance to antipsychotic treatment as a warning sign to suspect organicity, as well as the significant improvement in psychiatric impairment when effective and early treatment is established.

Inborn Errors of Metabolism with Hyperammonemia: Urea Cycle Defects and Related Disorders

The urea cycle disorders are a group of inherited biochemical diseases caused by a complete or partial deficiency of any one of the enzymes or transport proteins required to convert toxic ammonia into urea and to produce arginine and citrulline. The clinical manifestations of these disorders are mostly the result of acute or chronic hyperammonemia, which affects the central nervous system. Affected individuals can also develop hepatic dysfunction. These disorders can present at any age from the immediate newborn to later in life. Early diagnosis and treatment are key to improving outcomes.

[Treatable neurometabolic diseases. Association with schizophrenia spectrum disorders]

Schizophrenia spectrum disorders are presented on 1% of subjects over general population. Organic pathologies prevalence in schizophrenia spectrum patients is not well determined, and it is probably underestimated. In the present update review, we are going to highlight seven treatable neurometabolic diseases (NMD) associated to sub-clinic neurological symptoms. It is not infrequent to witness the absence of any clinical neurological signs going along with the NMD. Psychiatric symptoms may be the only clinical alarm that can guide physicians to an acute diagnosis. This is why it is a challenging pathology, defying our clinical accuracy as psychiatrist or any other practitioners confronted to this population. Hereby we are going to expose a literature review and comprehensive tables in order to present in a glance the essential clinical features of disorders of homocysteine metabolism, urea cycle disorders, Niemann-Pick disease type C, acute porphyria, cerebrotendinous-xanthomatosis. These conditions are sensible to major improvement strongly correlated to the accuracy of diagnosis. Literature analysis led us to propose a comprehensive list of atypical psychiatric symptoms including highly predominant visual hallucinations, compared to auditory ones, as well as confusion, catatonia or progressive cognitive decline. We highlight the importance of considering antipsychotic treatment resistance as a crucial sign leading to suspect an organic factor beneath the psychiatric features.

Genotype-Phenotype Correlations in Ornithine Transcarbamylase Deficiency: A Mutation Update

Ornithine transcarbamylase (OTC) deficiency is an X-linked trait that accounts for nearly half of all inherited disorders of the urea cycle. OTC is one of the enzymes common to both the urea cycle and the bacterial arginine biosynthesis pathway; however, the role of OTC has changed over evolution. For animals with a urea cycle, defects in OTC can trigger hyperammonemic episodes that can lead to brain damage and death. This is the fifth mutation update for human OTC with previous updates reported in 1993, 1995, 2002, and 2006. In the 2006 update, 341 mutations were reported. This current update contains 417 disease-causing mutations, and also is the first report of this series to incorporate information about natural variation of the OTC gene in the general population through examination of publicly available genomic data and examination of phenotype/genotype correlations from patients participating in the Urea Cycle Disorders Consortium Longitudinal Study and the first to evaluate the suitability of systematic computational approaches to predict severity of disease associated with different types of OTC mutations.

Secondary psychosis induced by metabolic disorders

Metabolic disorders are not well-recognized by psychiatrists as a possible source of secondary psychoses. Inborn errors of metabolism (IEMs) are not frequent. Although their prompt diagnosis may lead to suitable treatments. IEMs are well-known to pediatricians, in particular for their most serious forms, having an early expression most of the time. Recent years discoveries have unveiled later expression forms, and sometimes very discreet first physical signs. There is a growing body of evidence that supports the hypothesis that IEMs can manifest as atypical psychiatric symptoms, even in the absence of clear neurological symptoms. In the present review, we propose a detailed overview at schizophrenia-like and autism-like symptoms that can lead practitioners to bear in mind an IEM. Other psychiatric manifestations are also found, as behavioral, cognitive, learning, and mood disorders. However, they are less frequent. Ensuring an accurate IEM diagnosis, in front of these psychiatric symptoms should be a priority, in order to grant suitable and valuable treatment for these pathologies.

Sudden unexpected fatal encephalopathy in adults with OTC gene mutations-Clues for early diagnosis and timely treatment

Background

X-linked Ornithine Transcarbamylase deficiency (OTCD) is often unrecognized in adults, as clinical manifestations are non-specific, often episodic and unmasked by precipitants, and laboratory findings can be normal outside the acute phase. It may thus be associated with significant mortality if not promptly recognized and treated. The aim of this study was to provide clues for recognition of OTCD in adults and analyze the environmental factors that, interacting with OTC gene mutations, might have triggered acute clinical manifestations.

Methods

We carried out a clinical, biochemical and molecular study on five unrelated adult patients (one female and four males) with late onset OTCD, who presented to the Emergency Department (ED) with initial fatal encephalopathy. The molecular study consisted of OTC gene sequencing in the probands and family members and in silico characterization of the newly detected mutations.

Results

We identified two new, c.119G>T (p.Arg40Leu) and c.314G>A (p.Gly105Glu), and three known OTC mutations. Both new mutations were predicted to cause a structural destabilization, correlating with late onset OTCD. We also identified, among the family members, 8 heterozygous females and 2 hemizygous asymptomatic males. Patients' histories revealed potential environmental triggering factors, including steroid treatment, chemotherapy, diet changes and hormone therapy for in vitro fertilization.

Conclusions

This report raises awareness of the ED medical staff in considering OTCD in the differential diagnosis of sudden neurological and behavioural disorders associated with hyperammonemia at any age and in both genders. It also widens the knowledge about combined effect of genetic and environmental factors in determining the phenotypic expression of OTCD.

Diagnostic and treatment implications of psychosis secondary to treatable metabolic disorders in adults: a systematic review

Objective

It is important for psychiatrists to be aware of certain inborn errors of metabolism (IEMs) as these rare disorders can present as psychosis, and because definitive treatments may be available for treating the underlying metabolic cause. A systematic review was conducted to examine IEMs that often present with schizophrenia-like symptoms.

Data sources

Published literature on MEDLINE was assessed regarding diseases of homocysteine metabolism (DHM; cystathionine beta-synthase deficiency [CbS-D] and homocysteinemia due to methyltetrahydrofolate reductase deficiency [MTHFR-D]), urea cycle disorders (UCD), acute porphyria (POR), Wilson disease (WD), cerebrotendinous-xanthomatosis (CTX) and Niemann-Pick disease type C (NP-C).

Study selection

Case reports, case series or reviews with original data regarding psychiatric manifestations and cognitive impairment published between January 1967 and June 2012 were included based on a standardized four-step selection process.

Data extraction

All selected articles were evaluated for descriptions of psychiatric signs (type, severity, natural history and treatment) in addition to key disease features.

Results

A total of 611 records were identified. Information from CbS-D (n = 2), MTHFR-D (n = 3), UCD (n = 8), POR (n = 12), WD (n = 11), CTX (n = 14) and NP-C publications (n = 9) were evaluated. Six non-systematic literature review publications were also included. In general, published reports did not provide explicit descriptions of psychiatric symptoms. The literature search findings are presented with a didactic perspective, showing key features for each disease and psychiatric signs that should trigger psychiatrists to suspect that psychotic symptoms may be secondary to an IEM.

Conclusion

IEMs with a psychiatric presentation and a lack of, or sub-clinical, neurological signs are rare, but should be considered in patients with atypical psychiatric symptoms.

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.

Late-onset ornithine transcarbamylase deficiency: treatment and outcome of hyperammonemic crisis

Hyperammonemic crises in ornithine transcarbamylase deficiency (OTC) can be associated with devastating cerebral edema resulting in severe long-term neurologic impairment and death. We present an 8-year-old boy who had late-onset OTC deficiency in which early and aggressive management of hyperammonemia and associated cerebral edema, including therapeutic hypothermia and barbiturate-induced coma, resulted in favorable neurologic outcome. Our patient presented with vomiting and altered mental status, and was found to have a significantly elevated serum ammonia level of 1561 μmol/L. Hyperammonemia was managed with hemodialysis, 10% sodium phenylacetate, 10% sodium benzoate, L-arginine, intravenous 10% dextrose, intralipids, and protein restriction. He developed significant cerebral edema with intracranial pressures >20 mm Hg, requiring treatment with 3% saline and mannitol. Despite this treatment our patient continued to have elevated intracranial pressures, which were treated aggressively with non-conventional modalities including therapeutic hypothermia, barbiturate-induced coma, and external ventricular drainage. This therapy resulted in stabilization of hyperammonemia and resolution of cerebral edema. Molecular testing later revealed a hemizygous mutation within the OTC gene. Neuropsychological testing 1 year after discharge showed normal intelligence with no visual-motor deficits, minor deficits in working memory and processing speed, and slightly below average processing speed and executive functioning.

Cross-sectional observational study of 208 patients with non-classical urea cycle disorders

Urea cycle disorders (UCDs) are inherited disorders of ammonia detoxification often regarded as mainly of relevance to pediatricians. Based on an increasing number of case studies it has become obvious that a significant number of UCD patients are affected by their disease in a non-classical way: presenting outside the newborn period, following a mild course, presenting with unusual clinical features, or asymptomatic patients with only biochemical signs of a UCD. These patients are surviving into adolescence and adulthood, rendering this group of diseases clinically relevant to adult physicians as well as pediatricians. In preparation for an international workshop we collected data on all patients with non-classical UCDs treated by the participants in 20 European metabolic centres. Information was collected on a cohort of 208 patients 50% of which were ≥ 16 years old. The largest subgroup (121 patients) had X-linked ornithine transcarbamylase deficiency (OTCD) of whom 83 were female and 29% of these were asymptomatic. In index patients, there was a mean delay from first symptoms to diagnosis of 1.6 years. Cognitive impairment was present in 36% of all patients including female OTCD patients (in 31%) and those 41 patients identified presymptomatically following positive newborn screening (in 12%). In conclusion, UCD patients with non-classical clinical presentations require the interest and care of adult physicians and have a high risk of neurological complications. To improve the outcome of UCDs, a greater awareness by health professionals of the importance of hyperammonemia and UCDs, and ultimately avoidance of the still long delay to correctly diagnose the patients, is crucial.

The neuropsychiatry of inborn errors of metabolism

A number of metabolic disorders that affect the central nervous system can present in childhood, adolescence or adulthood as a phenocopy of a major psychiatric syndrome such as psychosis, depression, anxiety or mania. An understanding and awareness of secondary syndromes in metabolic disorders is of great importance as it can lead to the early diagnosis of such disorders. Many of these metabolic disorders are progressive and may have illness-modifying treatments available. Earlier diagnosis may prevent or delay damage to the central nervous system and allow for the institution of appropriate treatment and family and genetic counselling. Metabolic disorders appear to result in neuropsychiatric illness either through disruption of late neurodevelopmental processes (metachromatic leukodystrophy, adrenoleukodystrophy, GM2 gangliosidosis, Niemann-Pick type C, cerebrotendinous xanthomatosis, neuronal ceroid lipofuscinosis, and alpha mannosidosis) or via chronic or acute disruption of excitatory/inhibitory or monoaminergic neurotransmitter systems (acute intermittent porphyria, maple syrup urine disease, urea cycle disorders, phenylketonuria and disorders of homocysteine metabolism). In this manuscript we review the evidence for neuropsychiatric illness in major metabolic disorders and discuss the possible models for how these disorders result in psychiatric symptoms. Treatment considerations are discussed, including treatment resistance, the increased propensity for side-effects and the possibility of some treatments worsening the underlying disorder.

Developmental and psychiatric presentations of inherited metabolic disorders

Pediatric neurologists and developmental pediatricians may evaluate patients with primary or associated behavioral and academic concerns. A critical element of the evaluation involves determining that the child's condition is not better explained by underlying inherited metabolic disorders. In this review, psychiatric and behavioral presentations of inherited metabolic disorders are discussed via several case studies. Key features of vignettes will illustrate when to consider these disorders in evaluating children referred for psychiatric and behavioral changes, after more common etiologies have been excluded. We seek to develop a better understanding of key clinical pearls to help identify children with an inherited metabolic disorder to account for behavioral or academic concerns.

Coagulopathy in patients with late-onset ornithine transcarbamylase deficiency in remission state: a previously unrecognized complication

The late-onset type of ornithine transcarbamylase (OTC) deficiency is almost asymptomatic before an abrupt onset of metabolic crisis in adolescence. This study focused on coagulopathy in OTC deficiency. We collected laboratory data regarding coagulation from OTC-deficient patients in Kyushu University Hospital in Japan or from cases reported from previous articles. Five patients with late-onset OTC deficiency, admitted to Kyushu University Hospital at the first metabolic attack or who presented at the outpatient clinic in the hospital, were analyzed, and 3 additional cases of OTC deficiency with coagulopathy in previous articles were included. As a result, the blood ammonia levels in these patients were remarkably high at the time of the metabolic attack, and prothrombin times were far below the normal level. The prothrombin times remained significantly abnormal on remission, despite almost normal levels of blood ammonia, serum aspartate aminotransferase, and alanine aminotransferase. Coagulation abnormality is a previously unidentified complication of OTC deficiency in remission state. This information will aid in the identification of patients with OTC deficiency before a lethal metabolic crisis occurs during adolescence.