Management and emergency treatments of neonates with a suspicion of inborn errors of metabolism

Inherited metabolic disorders in the neonatal intensive care unit: Red flags to look out for

BACKGROUND

We aimed to assess symptoms, laboratory findings, and radiological abnormalities in patients diagnosed with inherited metabolic disorders (IMDs) in the neonatal intensive care unit.

METHODS

A total of 6,150 newborns treated in a third-level neonatal intensive care unit between 2012 and 2020 in Turkey were screened, of which 195 consulted with a suspicion of metabolic disease based on their clinical, laboratory, or radiological findings were included in the present study.

RESULTS

The prevalence of IMDs in the patients was 1:94.6. Those consulted in the department of pediatric metabolism were divided into two groups, with the 65 diagnosed with IMDs assigned as Group I, and the 130 patients who were not diagnosed with IMDs as Group II. The most common IMDs were organic acidemias (29.23%) and urea cycle disorders (UCDs) (26.15%). The rates of consanguinity marriage (75.3% vs 37.6%, P < 0.001), siblings diagnosed with an IMD (27.6% vs 3.8%, P < 0.001), and sibling death (56.9% vs 14.6%, P < 0.001) were higher in Group I than in Group II. Hyperammonemia (61.5% vs 18.4%, P < 0.001) was the most common laboratory finding in Group I, and anemia (Group I 60.0% vs 43.0% P = 0.033), metabolic acidosis (53.8% vs 36.9%, P = 0.028) and respiratory alkalosis (16.9% vs 1.5%, P < 0.001) were all higher in Group I.

CONCLUSIONS

This retrospective study found that the results of clinical findings and basic laboratory tests could be strong indicators of IMDs, although extensive newborn screening tests and advanced biochemical and genetic tests should be carried out for the diagnosis of IMDs in newborns.

Univariate Analysis of Short-Chain Fatty Acids Related to Sudden Infant Death Syndrome

Sudden infant death syndrome (SIDS) is defined as the death of a child under one year of age, during sleep, without apparent cause, after exhaustive investigation, so it is a diagnosis of exclusion. SIDS is the principal cause of death in industrialized countries. Inborn errors of metabolism (IEM) have been related to SIDS. These errors are a group of conditions characterized by the accumulation of toxic substances usually produced by an enzyme defect and there are thousands of them and included are the disorders of the β-oxidation cycle, similarly to what can affect the metabolism of different types of fatty acid chain (within these, short chain fatty acids (SCFAs)). In this work, an analysis of postmortem SCFAs profiles of children who died due to SIDS is proposed. Initially, a set of features containing SCFAs information, obtained from the NIH Common Fund's National Metabolomics Data Repository (NMDR) is submitted to an univariate analysis, developing a model based on the relationship between each feature and the binary output (death due to SIDS or not), obtaining 11 univariate models. Then, each model is validated, calculating their receiver operating characteristic curve (ROC curve) and area under the ROC curve (AUC) value. For those features whose models presented an AUC value higher than 0.650, a new multivariate model is constructed, in order to validate its behavior in comparison to the univariate models. In addition, a comparison between this multivariate model and a model developed based on the whole set of features is finally performed. From the results, it can be observed that each SCFA which comprises of the SFCAs profile, has a relationship with SIDS and could help in risk identification.

Laboratory diagnostic approaches in metabolic disorders

The diagnosis of inborn errors of metabolism (IEM) takes many forms. Due to the implementation and advances in newborn screening (NBS), the diagnosis of many IEM has become relatively easy utilizing laboratory biomarkers. For the majority of IEM, early diagnosis prevents the onset of severe clinical symptoms, thus reducing morbidity and mortality. However, due to molecular, biochemical, and clinical variability of IEM, not all disorders included in NBS programs will be detected and diagnosed by screening alone. This article provides a general overview and simplified guidelines for the diagnosis of IEM in patients with and without an acute metabolic decompensation, with early or late onset of clinical symptoms. The proper use of routine laboratory results in the initial patient assessment is also discussed, which can help guide efficient ordering of specialized laboratory tests to confirm a potential diagnosis and initiate treatment as soon as possible.

Acute Presentation and Management of the Encephalopathic Child With an Undiagnosed Inborn Error of Metabolism

BACKGROUND

Inborn errors of metabolism (IEM) commonly present in infancy and, less commonly, later in life.

CASE REPORT

This case describes an IEM, specifically, ornithine transcarbamylase deficiency, in a previously healthy 7-year-old boy who presented to an emergency department with vomiting for approximately 24 h prior to admission. The child became progressively encephalopathic while in the emergency department, but an ammonia level was not obtained until several hours after admission. Irreversible brain damage with cerebral edema was already present at time of diagnosis, leading to death. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case emphasizes that acute hyperammonemia can rapidly cause irreversible neurological damage and, in the case of a newly encephalopathic pediatric patient, ammonia levels should be evaluated early to facilitate proper diagnostic tests and treatment.

An Introduction to Pharmacotherapy for Inborn Errors of Metabolism

Inborn errors of metabolism comprise a wide array of diseases and complications in the pediatric patient. The rarity of these disorders limits the ability to conduct and review robust literature regarding the disease states, mechanisms of dysfunction, treatments, and outcomes. Often, treatment plans will be based on the pathophysiology associated with the disorder and theoretical agents that may be involved in the metabolic process. Medication therapies usually consist of natural or herbal products. Established efficacious pediatric doses for these products are difficult to find in tertiary resources, and adverse effects are routinely limited to single case reports. This review article attempts to summarize some of the more common inborn errors of metabolism in a manner that is applicable to pharmacists who will provide care for these patients.

Inborn Errors of Metabolism in the Emergency Department (Undiagnosed and Management of the Known)

An inborn error of metabolism should be considered in any neonate who presents to the emergency department in extremis and in any young child who presents with altered mental status and vomiting. In children with unknown diagnoses, it is crucial to draw the appropriate laboratory studies before the institution of therapy, although treatment needs rapid institution to mitigate neurologic damage and avoid worsening metabolic crisis. Although there are hundreds of individual genetic disorders, they are roughly placed into groups that present similarly. This article reviews the approach to the patient with unknown metabolic diagnosis and up-to-date management pearls for children with known disorders.

Acute liver failure in neonates with undiagnosed hereditary fructose intolerance due to exposure from widely available infant formulas

Hereditary fructose intolerance (HFI) is an autosomal recessive disorder caused by aldolase B (ALDOB) deficiency resulting in an inability to metabolize fructose. The toxic accumulation of intermediate fructose-1-phosphate causes multiple metabolic disturbances, including postprandial hypoglycemia, lactic acidosis, electrolyte disturbance, and liver/kidney dysfunction. The clinical presentation varies depending on the age of exposure and the load of fructose. Some common infant formulas contain fructose in various forms, such as sucrose, a disaccharide of fructose and glucose. Exposure to formula containing fructogenic compounds is an important, but often overlooked trigger for severe metabolic disturbances in HFI. Here we report four neonates with undiagnosed HFI, all caused by the common, homozygous mutation c.448G>C (p.A150P) in ALDOB, who developed life-threatening acute liver failure due to fructose-containing formulas. These cases underscore the importance of dietary history and consideration of HFI in cases of neonatal or infantile acute liver failure for prompt diagnosis and treatment of HFI.

Aspects of Newborn Screening in Isovaleric Acidemia

Isovaleric acidemia (IVA), an inborn error of leucine catabolism, is caused by mutations in the isovaleryl-CoA dehydrogenase (IVD) gene, resulting in the accumulation of derivatives of isovaleryl-CoA including isovaleryl (C5)-carnitine, the marker metabolite used for newborn screening (NBS). The inclusion of IVA in NBS programs in many countries has broadened knowledge of the variability of the condition, whereas prior to NBS, two distinct clinical phenotypes were known, an "acute neonatal" and a "chronic intermittent" form. An additional biochemically mild and potentially asymptomatic form of IVA and its association with a common missense mutation, c.932C>T (p.A282V), was discovered in subjects identified through NBS. Deficiency of short/branched chain specific acyl-CoA dehydrogenase (2-methylbutyryl-CoA dehydrogenase), a defect of isoleucine degradation whose clinical significance remains unclear, also results in elevated C5-carnitine, and may therefore be detected by NBS for IVA. Treatment strategies for the long-term management of symptomatic IVA comprise the prevention of catabolism, dietary restriction of natural protein or leucine intake, and supplementation with l-carnitine and/or l-glycine. Recommendations on how to counsel and manage individuals with the mild phenotype detected by NBS are required.

Perioperative management of living-donor liver transplantation for methylmalonic acidemia

Methymalonic acidemia (MMA) is a hereditary metabolic disorder characterized by a defect of the methylmalonyl-CoA mutase that breaks down propionate. The efficacy of liver transplantation for MMA was recently reported. However, the anesthetic management of liver transplant for MMA is not clear. The aim of this article is to describe an anesthetic management algorithm of liver transplant for MMA by reviewing our cases of liver transplant for MMA. Fourteen patients received a liver transplant; three cases showed metabolic decompensation during the transplant and two of the patients died. In the two patients who expired, propofol was used for maintenance anesthesia and preoperative continuous hemodiafiltration was used to reduce plasma methylmalonic acid level in one case, and to control severe metabolic decompensation before transplant for the other case. Their renal function was also worse than others and they were already experiencing metabolic decompensation before induction of anesthesia. Based on our experience of these 14 cases, we have established an anesthetic algorithm for patients with MMA undergoing liver transplant or other procedures. There are three important points in our experience: propofol should be avoided, dextrose infusion therapy should be continued to prevent metabolic decompensation, and liver transplant or other procedures should be avoided during metabolic decompensation.

High glucose intake and glycaemic level in critically ill neonates with inherited metabolic disorders of intoxication

To investigate glycaemic levels in critically ill neonates with inherited metabolic disorders of intoxication. Thirty-nine neonates with a median age of 7 days (0-24) were retrospectively included (urea cycle disorders (n = 18), maple syrup disease (n = 13), organic acidemias (n = 8)). Twenty-seven neonates were intubated, 21 were haemodialysed and 6 died. During the first 3 days, median total and peak blood glucose (BG) levels were 7.1 mmol/L (0.9-50) and 10 mmol/L (5.1-50), respectively. The median glucose intake rate was 11 mg/kg/min (2.7-15.9). Fifteen and 23 neonates exhibited severe hyperglycaemia (≥2 BG levels >12 mmol/L) and mild hyperglycaemia (≥2 BG levels >7 and ≤12 mmol/L), respectively. Glycaemic levels and number of hyperglycaemic neonates decreased over the first 3 days (p < 0.001) while total glucose intake rate was stable (p = 0.11). Enteral route of glucose intake was associated with a lower number of hyperglycaemic neonates (p = 0.04) and glycaemic level (p = 0.02).

CONCLUSION

Hyperglycaemia is common in critically ill neonates receiving high glucose intake with inherited metabolic disorders of intoxication. Physicians should decrease the rate of total glucose intake and begin enteral feeding as quickly as possible in cases of persistent hyperglycaemia.

WHAT IS KNOWN

• The risk of hyperglycaemia in the acute phase of critical illness is high. What is New: • Hyperglycaemia is common in the initial management of critically ill neonates with inherited metabolic disorders of intoxication receiving high glucose intake.

Inborn Errors of Metabolism

Inborn errors of metabolism are single gene disorders resulting from the defects in the biochemical pathways of the body. Although these disorders are individually rare, collectively they account for a significant portion of childhood disability and deaths. Most of the disorders are inherited as autosomal recessive whereas autosomal dominant and X-linked disorders are also present. The clinical signs and symptoms arise from the accumulation of the toxic substrate, deficiency of the product, or both. Depending on the residual activity of the deficient enzyme, the initiation of the clinical picture may vary starting from the newborn period up until adulthood. Hundreds of disorders have been described until now and there has been a considerable clinical overlap between certain inborn errors. Resulting from this fact, the definite diagnosis of inborn errors depends on enzyme assays or genetic tests. Especially during the recent years, significant achievements have been gained for the biochemical and genetic diagnosis of inborn errors. Techniques such as tandem mass spectrometry and gas chromatography for biochemical diagnosis and microarrays and next-generation sequencing for the genetic diagnosis have enabled rapid and accurate diagnosis. The achievements for the diagnosis also enabled newborn screening and prenatal diagnosis. Parallel to the development the diagnostic methods; significant progress has also been obtained for the treatment. Treatment approaches such as special diets, enzyme replacement therapy, substrate inhibition, and organ transplantation have been widely used. It is obvious that by the help of the preclinical and clinical research carried out for inborn errors, better diagnostic methods and better treatment approaches will high likely be available.

Deconstructing Black Swans: An Introductory Approach to Inherited Metabolic Disorders in the Neonate

BACKGROUND

Inherited metabolic disorders (IMDs) are individually rare but collectively common disorders that frequently require rapid or urgent therapy.

PURPOSE

This article provides a generalized approach to IMDs, as well as some investigations and safe therapies that may be initiated pending the metabolic consult.

METHODS/SEARCH STRATEGY

An overview of the research supporting management strategies is provided. In addition, the newborn metabolic screen is reviewed.

FINDINGS/RESULTS

Caring for infants with IMDs can seem difficult because each of the types is rarely seen; however, collectively the management can be seen as similar.

IMPLICATIONS FOR PRACTICE

When an IMD is suspected, a metabolic specialist should be consulted for expert advice regarding appropriate laboratory investigations and management. Because rapid intervention of IMDs before the onset of symptoms may prevent future irreversible sequelae, each abnormal newborn screen must be addressed promptly.

IMPLICATIONS FOR RESEARCH

Management can be difficult. Research in this area is limited and can be difficult without multisite coordination since sample sizes of any significance are difficult to achieve.

Intermediaries of branched chain amino acid metabolism induce fetal hemoglobin, and repress SOX6 and BCL11A, in definitive erythroid cells

High levels of fetal hemoglobin (HbF) can ameliorate human β-globin gene disorders. The short chain fatty acid butyrate is the paradigmatic metabolic intermediary that induces HbF. Inherited disorders of branched-chain amino acid (BCAA) metabolism have been associated with supranormal HbF levels beyond infancy, e.g., propionic acidemia (PA) and methylmalonic acidemia (MMA). We tested intermediaries of BCAA metabolism for their effects on definitive erythropoiesis. Like butyrate, the elevated BCAA intermediaries isovalerate, isobutyrate, and propionate, induce fetal globin gene expression in murine EryD in vitro, are associated with bulk histone H3 hyperacylation, and repress the transcription of key gamma globin regulatory factors, notably BCL11A and SOX6. Metabolic intermediaries that are elevated in Maple Syrup Urine Disease (MSUD) affect none of these processes. Percent HbF and gamma (γ) chain isoforms were also measured in non-anemic, therapeutically optimized subjects with MSUD (Group I, n=6) or with Isovaleric Acidemia (IVA), MMA, or PA (Group II, n=5). Mean HbF was 0.24 ± 0.15% in Group I and 0.87 ± 0.13% in Group II (p=.01); only the Gγ isoform was detected. We conclude that a family of biochemically related intermediaries of branched chain amino acid metabolism induces fetal hemoglobin during definitive erythropoiesis, with mechanisms that mirror those so far identified for butyrate.

Hyperammonemia in review: pathophysiology, diagnosis, and treatment

Ammonia is an important source of nitrogen and is required for amino acid synthesis. It is also necessary for normal acid-base balance. When present in high concentrations, ammonia is toxic. Endogenous ammonia intoxication can occur when there is impaired capacity of the body to excrete nitrogenous waste, as seen with congenital enzymatic deficiencies. A variety of environmental causes and medications may also lead to ammonia toxicity. Hyperammonemia refers to a clinical condition associated with elevated ammonia levels manifested by a variety of symptoms and signs, including significant central nervous system (CNS) abnormalities. Appropriate and timely management requires a solid understanding of the fundamental pathophysiology, differential diagnosis, and treatment approaches available. The following review discusses the etiology, pathogenesis, differential diagnosis, and treatment of hyperammonemia.

Acute management of sick infants with suspected inborn errors of metabolism

Diagnosis of inborn errors of metabolism (IEM) such as an organic acidemia or urea cycle defects requires high index of suspicion in a critically ill infant as these conditions mimic common pediatric illnesses. Prompt initiation of the treatment is mandatory even if a definitive diagnosis is not established immediately. Initial screening investigations may give clues and help to classify these disorders in broad categories. It is of utmost importance to preserve samples for testing.

[A guide to the clinical diagnosis and urgent treatment of neonatal hyperammonaemia]

Symptomatic hyperammonaemia in newborn is a medical emergency that should be recognised in its early stages, specifically diagnosed and aggressively treated to improve the immediate and long-term prognosis of these children. The paediatrician and the neonatal doctor should have a diagnosis-therapy scheme for its urgent management.

Cystic renal dysplasia as a leading sign of inherited metabolic disease

Glutaric acidemia type II and carnitine palmitoyltransferase type II deficiency are rare, but potentially treatable, inherited metabolic diseases. Hallmarks of the early onset form of both conditions are renal abnormalities and neonatal metabolic crisis. In this article, we report on two newborns with cystic renal dysplasia as a leading sign of these metabolic diseases. We focus on the clinical presentation and discuss the diagnostic tests and the available therapeutic options. We conclude that prenatal diagnosis of cystic renal dysplasia should alert the physician to the possibility of these metabolic diseases. This knowledge should prompt careful observation and, where necessary, early intervention during the postnatal period of catabolism.

[Management of neonatal seizures]

The aim of this review is to focus on the nosological classification of neonatal "convulsions", to precise the underlying aetiologies and the prognosis, and to propose diagnostic and therapeutical approach. Seizures may be epileptic or not, they may be occasional, part of an epilepsy syndrome or associated to a metabolic disease. Electroencephalography plays a central role; it enables to confirm the epileptic nature of the ictal events, it allows to evaluate the prognosis and to guide the treatment decision, and sometimes may help in the etiological diagnosis. Work up should include cerebral imaging (MRI) completed by other exams according to the diagnostic hypothesis. It is essential to go as far as possible in the etiological work-up not to attribute convulsions to an occasional event as HIE in which criteria remain very strict, when convulsions could be due to genetic origin or to maternal pathology. Treatment decision should comprise different ways: treatment of the underlying cause, of the eventual associated pathologies, maintenance of vital functions and antiepileptic treatment. Phenobarbitone remains the first line drug in occasional seizures, and second line drugs for which further studies are needed both for immediate and long-term secondary effects. Besides occasional seizures epilepsy syndromes and metabolic diseases remain exceptional. Nevertheless recognition of these conditions allows to establish the prognosis and to start immediately with an appropriate and specific medication depending on the epilepsy syndrome and can contribute to a prenatal diagnosis. It is important to recognize the inborn errors of metabolism because emergency appropriate treatment is required. Prognosis which is generally bad is essentially related to the underlying aetiology and probably to the duration of the active period of seizures.

The Emergency Department Approach to Newborn and Childhood Metabolic Crisis

For most emergency medicine physicians, the phrases "newborn workup" and "metabolic disease" are, at best, uncomfortable. This article, however, provides a simple approach to the recognition,evaluation, and treatment of infants with all manners of metabolic issues, including hypoglycemia, inborn errors of metabolism, jaundice, and electrolyte abnormalities. The disorders are grouped based on symptomatology, and have simple guidelines for work-up and management, with an emergency department practitioner perspective in mind.

Metabolic evaluation of the sick neonate

Inherited metabolic diseases are rare causes of neonatal morbidity, but they are associated with significant recurrence risks for the parents. Prompt identification and treatment of an infant with an inherited metabolic disease can minimize morbidity, mortality, and lifelong developmental problems. Diagnosis often requires specialized laboratory testing, but common laboratory tests can help identify those infants needing further evaluation. This paper reviews the laboratory abnormalities which can be found in various inherited metabolic diseases and can guide selection of specialized metabolic testing. Consultation with a metabolic specialist is essential for timely diagnosis and treatment to ensure the best possible outcome.

Newborn screening and the pediatric practitioner

Since the beginning of newborn screening for metabolic and other disorders in 1964, advances in the understanding of the disorders identified and development of new methods of testing newborn screening blood spots have contributed to improved health in children. Pediatricians and others involved in the health care of infants must be able to participate in the assessment and confirmatory testing of infants who have an abnormal test result and in the care of infants identified with a disorder. Expansion in the technology and number of disorders identified has complicated this process. As more and a greater variety of disorders are tested for and identified, a crucial collaborative role has emerged for the newborn screening programs and their public health professionals, the tertiary care specialists in the disorders and the primary care clinicians who comprise the medical home of the infants identified. This collaboration needs to provide prompt results of the newborn screening tests, expeditious and expert confirmatory testing and an effective care plan for the affected infant to realize the benefits of treatment for children with otherwise devastating disorders.

La galactosémie congénitale : une révélation singulière

Congenital galactosaemia reveals usually in the second and third weeks of life with a severe liver dysfunction. We report on a case of congenital galactosaemia with, on the one hand, an early onset liver failure, without any free interval, and on the other hand, an hemophagocytic syndrome as a severe secondary outbreak with pulmonary haemorrhage. Appropriate diet led to normalisation of liver function. Hemophagocytosis, probably linked to an associated Klebsiella Pneumoniae sepsis, had a favourable outcome after antibiotic and corticosteroid therapy.