Fatal coma in a young adult due to late-onset urea cycle deficiency presenting with a prolonged seizure: a case report

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.

Effect of Ornithine Transcarbamylase (OTC) Deficiency on Pregnancy and Puerperium

Ornithine transcarbamylase (OTC) deficiency is the most common inherited metabolic disorder in urea cycles with an incidence of 1:14,000 live births. Pregnancy, childbirth and the postpartum period are considered challenging for women with this hereditary metabolic disorder, with a risk of hyperammonemia, especially in the first week after delivery. In our article, we discuss severe hepatic failure, a pregnancy complication in an OTC deficient patient that has not previously been published. Firstly, our aim is to highlight the need for a strict adherence to the recommendation of the gradual increase of protein intake during pregnancy and the importance of multidisciplinary monitoring of pregnant patients with OTC deficiency. Secondly, we refer to critical postpartum hyperammonemia in patients with this hereditary metabolic disorder.

Late-onset ornithine transcarbamylase deficiency mimicking a focal opercular syndrome

A previously healthy 27-year-old man was brought to hospital after been found late at night confused, agitated and talking incoherently. He represented 12 days later with focal seizures, progressing to anarthria and encephalopathy. MR scan of brain showed diffuse cerebral oedema and his plasma ammonia was >2000 µmol/L (12-55 µmol/L). He developed refractory status epilepticus and subsequently died. Genetic analysis identified an ornithine transcarbamylase (OTC) gene mutation on the X chromosome. We discuss this atypical presentation of OTC deficiency as a rare but treatable cause of hyperammonaemic encephalopathy.

Fifteen years of urea cycle disorders brain research: Looking back, looking forward

Urea cycle disorders (UCD) are inherited diseases resulting from deficiency in one of six enzymes or two carriers that are required to remove ammonia from the body. UCD may be associated with neurological damage encompassing a spectrum from asymptomatic/mild to severe encephalopathy, which results in most cases from Hyperammonemia (HA) and elevation of other neurotoxic intermediates of metabolism. Electroencephalography (EEG), Magnetic resonance imaging (MRI) and Proton Magnetic resonance spectroscopy (MRS) are noninvasive measures of brain function and structure that can be used during HA to guide management and provide prognostic information, in addition to being research tools to understand the pathophysiology of UCD associated brain injury. The Urea Cycle Rare disorders Consortium (UCDC) has been invested in research to understand the immediate and downstream effects of hyperammonemia (HA) on brain using electroencephalogram (EEG) and multimodal brain MRI to establish early patterns of brain injury and to track recovery and prognosis. This review highlights the evolving knowledge about the impact of UCD and HA in particular on neurological injury and recovery and use of EEG and MRI to study and evaluate prognostic factors for risk and recovery. It recognizes the work of others and discusses the UCDC's prior work and future research priorities.

Review of Multi-Modal Imaging in Urea Cycle Disorders: The Old, the New, the Borrowed, and the Blue

The urea cycle disorders (UCD) are rare genetic disorder due to a deficiency of one of six enzymes or two transport proteins that act to remove waste nitrogen in form of ammonia from the body. In this review, we focus on neuroimaging studies in OTCD and Arginase deficiency, two of the UCD we have extensively studied. Ornithine transcarbamylase deficiency (OTCD) is the most common of these, and X-linked. Hyperammonemia (HA) in OTCD is due to deficient protein handling. Cognitive impairments and neurobehavioral disorders have emerged as the major sequelae in Arginase deficiency and OTCD, especially in relation to executive function and working memory, impacting pre-frontal cortex (PFC). Clinical management focuses on neuroprotection from HA, as well as neurotoxicity from other known and yet unclassified metabolites. Prevention and mitigation of neurological injury is a major challenge and research focus. Given the impact of HA on neurocognitive function of UCD, neuroimaging modalities, especially multi-modality imaging platforms, can bring a wealth of information to understand the neurocognitive function and biomarkers. Such information can further improve clinical decision making, and result in better therapeutic interventions. In vivo investigations of the affected brain using multimodal neuroimaging combined with clinical and behavioral phenotyping hold promise. MR Spectroscopy has already proven as a tool to study biochemical aberrations such as elevated glutamine surrounding HA as well as to diagnose partial UCD. Functional Near Infrared Spectroscopy (fNIRS), which assesses local changes in cerebral hemodynamic levels of cortical regions, is emerging as a non-invasive technique and will serve as a surrogate to fMRI with better portability. Here we review two decades of our research using non-invasive imaging and how it has contributed to an understanding of the cognitive effects of this group of genetic conditions.

Management of late onset urea cycle disorders-a remaining challenge for the intensivist?

Background

Hyperammonemia caused by a disorder of the urea cycle is a rare cause of metabolic encephalopathy that may be underdiagnosed by the adult intensivists because of its rarity. Urea cycle disorders are autosomal recessive diseases except for ornithine transcarbamylase deficiency (OTCD) that is X-linked. Optimal treatment is crucial to improve prognosis.

Main body

We systematically reviewed cases reported in the literature on hyperammonemia in adulthood. We used the US National Library of Medicine Pubmed search engine since 2009. The two main causes are ornithine transcarbamylase deficiency followed by type II citrullinemia. Diagnosis by the intensivist remains very challenging therefore delaying treatment and putting patients at risk of fatal cerebral edema. Treatment consists in adapted nutrition, scavenging agents and dialysis. As adults are more susceptible to hyperammonemia, emergent hemodialysis is mandatory before referral to a reference center if ammonia levels are above 200 µmol/l as the risk of cerebral edema is then above 55%. Definitive therapy in urea cycle abnormalities is liver transplantation.

Conclusion

Awareness of urea cycle disorders in adults intensive care units can optimize early management and accordingly dramatically improve prognosis. By preventing hyperammonemia to induce brain edema and herniation leading to death.

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.

A Mysterious Case of Recurrent Acute Hyperammonemic Encephalopathy

Ammonia is a well-recognized neurotoxin. Awareness about hyperammonemia, in the absence of liver cirrhosis, may help in lifesaving, prompt diagnosis, and treatment. We present a case of a 53-year-old male who presented to the emergency department (ED) with altered mental status (AMS). He was unresponsive with occasional eye opening. Initial labs were normal except for mildly elevated blood alcohol level. Serum ammonia levels were very high (305 umol/L). He improved with lactulose. He had similar admissions later on. Urine orotic acid levels were high confirming ornithine transcarbamylase (OTC) deficiency. Noncirrhotic hyperammonemia as a cause of AMS remains a diagnosis of exclusion requiring high index suspicion. Very few cases of late inborn errors of urea cycle disorders (UCDs) have been reported in the literature. Our case highlights the importance of early diagnosis of UCDs and that outcome can be excellent if treated aggressively. Once identified, adult-onset forms of the UCDs have a good prognosis-largely due to the initiation of preventative measures and earlier recognition of exacerbations.

Clinical and cranial MRI features of female patients with ornithine transcarbamylase deficiency: Two case reports

INTRODUCTION

Ornithine transcarbamylase deficiency (OTCD) is a common metabolic disease of urea circulation disorder. We reported the clinical, brain imaging and genetic characteristics of 2 cases with OTCD. The patients' clinical features, novel gene mutations, cranial MR specific imaging changes and blood tandem mass spectrometry, and urine gas chromatography-mass spectrometry were, retrospectively, analyzed.

PATIENT CONCERNS

Patient 1 was a 1.6-year-old female. She was admitted to the hospital with 2-months history of general irritability and disturbance of consciousness for a day. Patient 2 was a 3.7-year-old female. She was admitted to the hospital due to decline of language ability and irritability for 5 days. Blood tandem mass spectrometry and urine gas chromatography-mass spectrometry showed uracil and orotate increased significantly in urine while amino acids in the urea cycle ring were in the normal range. The features of brain MRI are consistent with those of urea circulatory disorders. Gene detection showed 1 novel mutation in the OTC gene (c.658C>T) in patient 1 and, 1 novel mutation (c.298+2T>G) in the OTC gene in patient 2.

DIAGNOSIS

Combined with metabolic screening and gene detection, both patients were diagnosed with OTCD.

INTERVENTIONS

The patients' condition improved after following a low protein diet and receiving treatments for decreasing blood ammonia, energy supplement, correcting acid-base imbalance, and other symptomatic treatments.

OUTCOMES

After prompt symptomatic treatment, the consciousness and cognition of the children improved. Besides, liver function also improved significantly.

CONCLUSIONS

For patients with neurological symptoms and unexplained increase in transaminase and ammonia, OTCD should be considered as a possible diagnosis. Brain MRI can help the diagnosis of genetic metabolic encephalopathy and reflect the level of brain injury. Metabolic screening and genetic detection are helpful to make a confirmed diagnosis.

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.

Testing for Inborn Errors of Metabolism

PURPOSE OF REVIEW

This article provides an overview of genetic metabolic disorders that can be identified by metabolic tests readily available to neurologists, such as tests for ammonia, plasma amino acids, and urine organic acids. The limitations of these tests are also discussed, as they only screen for a subset of the many inborn errors of metabolism that exist.

RECENT FINDINGS

Advances in next-generation sequencing and the emerging use of advanced metabolomic screening have made it possible to diagnose treatable inborn errors of metabolism that are not included in current newborn screening programs. Some of these inborn errors of metabolism are especially likely to present with nonspecific neurologic phenotypes, such as epilepsy, ataxia, or intellectual disability. However, cost may be a barrier to obtaining these newer tests. It is important to keep in mind that common metabolic testing may lead to treatable diagnoses. Resources are available to guide neurologists in diagnosing genetic metabolic conditions.

SUMMARY

This article introduces the clinical presentations of treatable inborn errors of metabolism that are important for neurologists to consider in patients of all ages. Inborn errors of metabolism are rare, but they can present with neurologic symptoms. Newborns are now screened for many treatable metabolic disorders, but these screening tests may miss milder presentations of treatable inborn errors of metabolism that present later in life. These patients may present to adult neurologists who may be less likely to consider metabolic genetic testing.

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.