Organic Acidemias.

After completing this article, readers should be able to: 1. List the major categories of diseases detectable by expanded newborn screening. 2. Give examples of the benefits and limitations of screening by tandem mass spectrometry. 3. Describe the appropriate follow-up for an abnormal screening result. The screening of newborns for inherited metabolic disorders is a well-established public health activity, first implemented in the early 1960s for the presymptomatic identification of patients who have phenylketonuria (PKU). Since then, significant technological advances, most importantly the development of tandem mass spectrometry (MS/MS), have enabled the detection of an increasing number of metabolic disorders in newborn blood. This article reviews the basic technology of MS/MS and its application to newborn screening, with the aim of highlighting the benefits and pointing out some limitations of this powerful technology. Early screening for PKU used the bacterial inhibition assay of Guthrie, in which inhibition of bacterial growth on an agar medium, introduced by the addition of a phenylalanine analog, was overcome by the presence of dried blood discs containing high levels of phenylalanine (such as from a PKU patient). This approach later was adapted for the detection of leucine in patients who have maple syrup urine disease (MSUD), methionine in patients who have classic homocystinuria, and tyrosine in patients who have tyrosinemia. Over the years, other techniques have been implemented to screen for additional disorders, including congenital hypothyroidism, biotinidase deficiency, galactosemia, hemoglobinopathies, and congenital adrenal hyperplasia. The classic criteria used to determine whether a disorder is suitable for screening include: 1) the disorder is clinically and biochemically well defined, 2) it is associated with significant morbidity or mortality, 3) an effective treatment is available, and 4) there is a simple and safe screening test. (1) By the early 1990s, all states offered screening for at least PKU and congenital hypothyroidism, …

Newborn Screening Program for Oman: The Time is Here and Now

To investigate the effects of tandem mass spectrometry (MS/MS) combined with gas chromatography mass spectrometry (GC-MS) in the diagnosis of inborn errors of metabolism in children. Amino acids and acylcarnitines in the dry blood filter papers were tested by MS/MS, and the organic acid profiles in urea were tested by GC-MS among 4981 children suspected to be with inborn errors of metabolism from more than 100 hospitals in China. A few pediatric patients underwent analysis of activity of enzyme and gene mutation analysis too. 319 of the 4981 children (6.4%) were diagnosed as with 24 kinds of diseases: 155 of the 319 cases (48.6%) with 8 kinds of amino acid diseases (97 with hyperphenylalaninemia, 14 with maple syrup urine disease 13 with ornithine transcarbamylase deficiency, 13 with citrullinemia type II, 10 with tyrosinemia type I, 5 with citrullinemia type I, 2 with homocystinuria, and 1 with arginasemia); 150 of the 319 cases (47.0%) were diagnosed as with 10 kinds of organic acidemias (81 with methylmalonic acidemia, 17 with propionic acidemia, 17 with multiple CoA carboxylase deficiency, 11 with glutaric acidemia type II, 8 with isovaleric acidemia, 6 with beta-keto thiolase deficiency, 5 with 3-methylcrotonyl-CoA carboxylase deficiency, and 3 with 3-hydroxy-3-methylglutaryl-CoA lyase deficiency); 14 cases (4.4%) were diagnosed as with 6 kinds of fatty acid disorders (5 with medium chain acyl-CoA dehydrogenase deficiency, 3 with very long chain acyl CoA dehydrogenase deficiency, 2 with short chain acyl-CoA dehydrogenase deficiency, 2 with multiple acyl-CoA dehydrogenase deficiency, 1 with carnitine palmitoyl transferase type II, and 1 with carnitine palmitoyl transferase type I). MS/MS is specific for amino acid diseases and fatty acid disorders. GC-MS is specific for detect organic acidemias. And the diagnoses of part of amino acid diseases need the combination of both methods.

Breastfeeding has been recommended for the dietary treatment of infants with phenylketonuria, but studies documenting clinical experience in other inborn errors of metabolism are very few. Seven infants diagnosed with methylmalonyl-CoA mutase deficiency (n=2), ornithine carbamoyltransferase deficiency (n=1), propionic acidaemia (n=1), isovaleric acidaemia (n=1), maple syrup urine disease (n=1) and glutaric acidemia type I (n=1) were tried with breastfeeding over two years. After the control of acute metabolic problems, an initial feeding period with a measured volume of expressed breast milk plus a special essential amino acid mixture was continued with breastfeeding on demand and with the addition of a special essential amino acid mixture. Two patients with methylmalonic acidaemia and one patient with glutaric acidaemia type I tolerated breastfeeding on demand very well, with good growth and metabolic control for periods of 18, 8 and 5 months, respectively. In the patient with propionic acidaemia, on-demand breastfeeding continued for 3 months but was terminated after two acute metabolic episodes. The patient with isovaleric acidaemia had insufficiency of breast milk and formula supplementation ended with breast milk cessation. In the patient with severe ornithine carbamoyltransferase deficiency, breastfeeding was stopped owing to poor metabolic control. The patient with maple syrup urine disease also experienced problems, both in metabolic control and in insufficiency of breast milk, resulting in termination of breastfeeding. Breastfeeding of infants with inborn errors of protein catabolism is feasible, but it needs close monitoring with attention to such clinical parameters as growth, development and biochemistry, including amino acids, organic acids and ammonia.

After completing this article, readers should be able to: 1. List examples of disorders for which tandem mass spectrometry (MS/MS) can screen. 2. Delineate potential difficulties with MS/MS newborn screening. Tandem mass spectrometry (MS/MS) technology has shown tremendous promise in newborn screening pilot programs worldwide with its capacity to measure numerous metabolites from a dried blood spot virtually simultaneously with an extremely rapid throughput per sample (approximately 2 min). The expansion of newborn screening programs by inclusion of an additional 15 to 30 metabolic disorders has the potential to decrease significantly the morbidity and mortality associated with inborn errors of metabolism and could offer the clinician critical diagnostic information when caring for an acutely ill neonate. Newborn screening for metabolic disorders began in 1962 in the United States, with the introduction of the Guthrie bacterial inhibition assay for phenylketonuria (PKU) in a Massachusetts voluntary program. Child health advocates, including the National Association for Retarded Citizens and the March of Dimes Birth Defects Foundation, developed model legislation and lobbied for passage of newborn screening laws at the state level. As a result of these efforts, newborn screening for PKU was legally mandated in most states in the early 1960s. The success of newborn screening for PKU led to development of tests for other conditions, including metabolic disorders (eg, galactosemia, maple syrup urine disease [MSUD], homocystinuria, and biotinidase deficiency), endocrinopathies (eg, congenital hypothyroidism and congenital adrenal hyperplasia), hemoglobinopathies (eg, sickle cell disease and thalassemias), and cystic fibrosis. Different states screen for a variable number of these disorders, with most screening for three to six conditions (Figure⇓ ). Such differences reflect state political and economic environments, technologic capabilities of public health departments, regional ethnic composition, and community expectations. All states screen for PKU and congenital hypothyroidism, and 48 states screen for galactosemia. Other inborn …

In most developed countries, neonatal mass screening programs for the early diagnosis of inborn errors of metabolism (IEM) have been implemented and have been found to be effective for the prevention or significant reduction of clinical symptoms such as mental retardation. These programs rely primarily on simple bacterial inhibition assays (the "Guthrie tests"). We developed a new method for screening IEM using GC/MS, which enables accurate chemical diagnoses through urinary analyses with a simple practical procedure. The urine sample preparation for GC/MS takes one hour for one sample or three hours for a batch of 30 samples (will be fully automated shortly), and the following GC/MS measurement is completed within 15 min per sample. This method allows the simultaneous analyses of amino acids, organic acids, sugars, sugar alcohols, sugar acids, and nucleic acid bases. Therefore, a large number of metabolic disorders can be simultaneously tested by this chemical diagnostic procedure. This method is quite comprehensive and different from conventional GC/MS organic acidemia screening procedures, which are not well-suited to detect metabolic disorders except organic acidurias. Sample preparation includes urease treatment, deproteinization, and derivatization. The method has also been applied to neonate urine specimens that are absorbed into filter paper. The air-dried samples were mailed to the analytical laboratory and eluted with water. The eluate (0.1 mL) was incubated with urease, followed by deproteinization with alcohol, evaporation to dryness of the supernatant, and trimethylsilylation; the samples were applied to GC/MS. A pilot study of the application of this diagnostic procedure to the neonatal mass screening of 22 disorders was started in Japan on February 1, 1995 in cooperation with four medical institutes. This program is supported by the Japanese Society for Biomedical Mass Spectrometry and the Japanese Mass Screening Society. The initial twenty-two target metabolic diseases are: methylmalonic acidemia; propionic acidemia; isovaleric acidemia; maple syrup urine disease; β-ketothiolase deficiency; galactosemia; phenylketonuria; hyperphenylalaninemia; homocystinuria; alkaptonuria; multiple carboxylase deficiency; nonketotic hyperglycinemia; lysinuria; cystinuria; tyrosinemia; glutaric aciduria type I; β-hydroxy-β-methylglutaric acidemia; β-methylcrotonylglycinuria; α-aminoadipic-α-ketoadipic aciduria; ornitine transcarbamylase deficiency (four urea cycle disorders can be screened); glutaric aciduria type II; and neuroblastoma. Neuroblastoma is not an IEM, and is examined at ca. 6 months of age. The twenty-two target diseases will be reconsidered during the pilot study. An accurate chemical diagnosis and hence early treatment of not only organic acidemias but also amino acidemias, and sugar-, polyol-, and nucleic acid base-accumulating metabolic disorders can be made at a very early stage of life. This procedure is also applicable to metabolic profiling of other body fluids that are potentially informative for the study and characterization of a wide range of inherited and acquired metabolic disorders. © 1997 John Wiley & Sons, Inc.

BackgroundThis study provides a general overview on liver and/or kidney transplantation in patients with an amino and organic acid‐related disorder (AOA) with the aim to investigate patient characteristics and global outcome in Europe. This study was an initiative of the E‐IMD and the AOA subnetwork of MetabERN.MethodsA questionnaire was sent to all clinically active European Society for the Study of Inborn Errors of Metabolism (SSIEM) members. The questionnaire focused on transplanted individuals with methylmalonic acidemia (MMA), propionic acidemia (PA), maple syrup urine disease (MSUD), and urea‐cycle disorders (UCDs).ResultsWe identified 280 transplanted AOA patients (liver transplantation in 20 MMA, 37 PA, 47 MSUD, and 111 UCD patients, kidney or combined liver and kidney transplantation in 57 MMA patients and undefined transplantation type in 8 MMA patients), followed by 51 metabolic centers. At a median follow‐up of 3.5 years, posttransplant survival ranged between 78% and 100%, being the lowest in PA patients. Overall, the risk of mortality was highest within 14 days posttransplantation. Neurological complications were mainly reported in Mut0 type MMA (n = 8). Nonneurological complications occurred in MMA (n = 28), PA (n = 7), and UCD (n = 14) patients, while it was virtually absent in MSUD patients. Only 116/280 patients were psychologically tested. In all, except MSUD patients, the intelligence quotient (IQ) remained unchanged in the majority (76/94, 81%). Forty‐one percentage (9/22) of MSUD patient showed improved IQ.ConclusionThe survival in AOA individuals receiving liver and/or kidney transplantation seems satisfactory. Evidence‐based guidelines, systematic data collection, and improved cooperation between transplantation centers and European Reference Networks are indispensable to improve patient care and outcomes.

We present the results of our experience in the diagnosis of inborn errors of metabolism (IEM) since the Expanded Newborn Screening was implemented in our Region. Dried blood samples were collected 48 h after birth. Amino acids and acylcarnitines were quantitated by mass spectrometry (MS)/MS. Newborns with alterations were referred to the clinical centers for follow‐up. Biochemical and molecular genetic studies for confirmation of a disease were performed. In the period 2011 to 2019, 592 822 children were screened: 902 of them were referred for abnormal results. An IEM was confirmed in 222 (1/2670): aminoacidopathies: 89 hyperphenylalaninemia (HPA) (51 benign HPA, 32 phenylketonuria, 4 DNAJC12 defect, and 2 primapterinuria), 6 hypermethioninemia, 3 tyrosinemia type 1 (TYR‐1), 1 TYR‐3, 4 maple syrup urine disease (MSUD), 2 branched‐chain amino acid transferase 2 deficiency, 2 homocystinuria, 1 cystinuria, 2 ornithine transcarbamylase (OTC) deficiency, 2 citrullinemia type I (CTLN1); FAO defects: 43 medium‐chain acyl‐CoA dehydrogenase deficiency (MCADD), 13 very long‐chain acyl‐CoA dehydrogenase deficiency, 2 long‐chain 3‐hydroxyacyl‐CoA dehydrogenase deficiency (LCHADD), 1 multiple acyl‐coA dehydrogenation deficiency, 11 systemic primary carnitine deficiency, 2 carnitine palmitoyltransferase type 2 (CPT‐II) deficiency, 1 CPT‐I deficiency; organic acidurias: 12 glutaric aciduria type 1 (GA‐1), 4 methylmalonic acidemia (MMA), 7 MMA including combined cases with homocystinuria (MMAHC), 6 propionic acidemia (PA), 7 3‐methylcrotonyl‐CoA carboxylase, 1 3‐hydroxy‐3‐methylglutaryl‐CoA lyase deficiency lyase deficiency. Only 19 infants (8.5%) were symptomatic at newborn screening result (1 LCHADD, 5 PA, 1 CPT‐II deficiency, 1 MMA, 3 MMAHC, 2 MSUD, 2 OTC deficiency, 1 CTLN1, 1 MCADD, 2 TYR‐1). No false negative cases were identified. Genetic diagnosis was conclusive in all biochemically confirmed cases, except for two infants with HPA, identifying pathogenic variants in 32 different genes. The conditions with the highest incidence were HPA (1/6661) and MCAD deficiencies (1/13 787).

Background Inborn errors of metabolism (IEM) are a phenotypically and genetically variable group of diseases produced by a variety of disorders in the metabolic pathway. They are more common in countries with a high consanguinity rate, such as Egypt. This study aimed to explore the frequency of IEM among eighty children who attend the Metabolic Outpatient Clinic at Alexandria University Children’s Hospital (AUCH) for follow-up from September 2019 to February 2023. Those children has been diagnosed clinically, radiologically and biochemically by using extended metabolic screening including amino acid screen, urine organic acids measurement and tandem mass spectrometry (TMS). Data about age, sex, birth order, area of residence, age at onset, presenting complaints, and family history of the same disease were all collected from caregivers and hospital records. Results There was a male predominance of 46 cases (57.5%), and females accounted for 34 (42.5%). Twenty percent of the studied cases had a history of a similar condition in their family. Specifically, 21 cases (26.3%) had maple syrup urine disease (MSUD), 19 cases (23.8%) had glutaric acidemia (GA) type 1, 13 cases (16.3%) had methylmalonic acidemia (MMA), and 8 (10%) had isovaleric acidemia (IVA). Only 2 cases (2.5%) of the studied cases had fatty acid oxidation defects (FAOD), and there was only one case (1.3%) of 3-hydroxy-3-methylglutaryl-CoA lyase deficiency (HMG-CoA) and one cases (1.3%) of propionic acidemia (PA). Conclusion IEM are frequent among children, and further research studies are needed to gain a better understanding of their nature, highlighting the importance of neonatal screening and timely diagnosis to improve outcomes of affected children. As prevalence of some disorders seem to be more common, it is better to address on newborn screening program (NBS) to address them.

Acute nutrition management in the prevention of metabolic illness: A practical approach with glucose polymers

Inborn errors of amino acid metabolism such as phenylketonuria, maternal phenylketonuria, maple syrup urine disease, homocystinuria, methylmalonic acidemia, propionic acidemia, isovaleric acidemia and other disorders of leucine metabolism, glutaric acidemia type I and tyrosinemia types I and II, and urea cycle disorders are rare diseases that are treatable by diet. Treatment might include the restriction of one or more amino acids, the restriction of total nitrogen, or the supplementation of specific substances. Untreated, these diseases culminate in severe mental retardation or death. Once diagnosis is confirmed, treatment of amino acid and urea cycle disorders must be carefully monitored by a physician with expertise in metabolic diseases. Special medical foods, commercially available, are indispensable for the active, ongoing treatment of diagnosed amino acid and urea cycle disorders. Special medical foods would, if used as the sole dietary source, represent a hazard to affected and healthy children. US Public Law (Publ L) 100-290 defines the term medical food as ". . . a food which is formulated to be consumed or administered enterally under the supervision of a physician and which is intended for the specific dietary management of a disease or condition for which distinctive nutritional requirements, based on recognized scientific principles, are established by medical evaluation."1 After passage of Publ L 100-290, many states provided funding for these products through Medicaid, and most states offered assistance through Crippled Children's and Women, Infant, and Children's programs. Some states now have laws mandating private insurance coverage for special medical foods. It is the position of the American Academy of Pediatrics that special medical foods that are used in the treatment of amino acid and urea cycle disorders are medical expenses that should be reimbursed.

Inborn errors of metabolism (IEMs) are inherited diseases causing significant morbidity and mortality, particularly in childhood. Liver transplantation (LT) can be curative or partially effective for these diseases. LT for IEMs has increased, making IEMs the second most common reason for pediatric LT after biliary atresia. Between 2001 and 2023, 50 pediatric patients with IEMs underwent LT at Başkent University, Ankara Hospital. Data collected retrospectively included diagnosis, gender, age of diagnosis, age of LT, LT indication, donor data, graft type, rejection episodes, post-transplant complications, and clinical findings of the IEMs before and after LT. Treatment methods, follow-up duration, and survival time were also recorded. Of the 332 pediatric LT patients, 50 (15.1%) had IEMs, with three requiring re-transplantations. Diagnoses included glycogen storage diseases (n = 11), tyrosinemia type 1 (n = 10), primary hyperoxaluria (n = 6), urea cycle disorders (n = 6), homozygous familial hypercholesterolemia (n = 4), propionic acidemia (n = 4), deoxyguanosine kinase deficiency (n = 3), maple syrup urine disease (n = 2), methylmalonic acidemia (n = 1), Niemann-Pick disease type B (n = 1), alkaptonuria with unknown neonatal cholestasis (n = 1), and bile acid synthesis disorder (n = 1). The parental consanguinity rate was 74%. Living-related donors provided organs for 48 (90.5%) patients. The mean age at LT was 75.3 ± 8.2 months (range: 5-218), with a follow-up period of 82.1 ± 10.2 months (range:1 day-229 months). Survival rates at 1, 5, 10, and 15 years were 83.7%, 81%, 81%, and 70.9%, respectively. LT is an effective solution for children with IEM causing chronic organ failure and difficult to manage with medical treatment, showing a good long-term prognosis.

Introduction: Modular diets (MDs) with low amount of offending amino acids have been developed using locally available food ingredients as alternatives to commercial formulas for the treatment of branched-chain organic acidurias (BCOAs). Herein, we conducted a clinical investigation of MDs in patients with BCOAs. Methods: Modular diet A (MDA), with low leucine was produced for maple syrup urine disease (MSUD), and modular diet B (MDB) products, MDB-1, -2, -3, and -4, with low leucine, valine, methionine and threonine were made for isovaleric aciduria (IVA)/methylmalonic aciduria (MMA)/propionic aciduria (PA). Children aged 4-18 years, with MSUD, IVA, PA or MMA were invited to participate in the study. The research subjects switched from metabolic formula protocol to modular diet protocol. They were followed-up at 0, 1, 2, 4, and 6 months. Clinical efficacies of MDs were determined by completion of study, compliance to MDs, clinical outcomes and complications, and parental satisfaction. Results: Six children (2 MSUD and 4 IVA) participated and completed the study. Compliance to MDA was 100% in MSUD subjects with G-tube feeding, while compliance to MDB varied among self-fed individuals with IVA. One subject with MSUD was clinically stable throughout the study, while the other experienced metabolic instability. All IVA individuals showed clinical and laboratory stability during the study. One MSUD and three IVA families preferred the metabolic formula, whereas the other IVA family reported no preference and the other MSUD subject preferred MDs. Conclusion: We provided a proof of concept in developing modular diets for BCOAs, and showed favourable outcomes when using MDs in IVA and varying clinical benefits in MSUD.

Selective screening for inborn errors of metabolism by tandem mass spectrometry at Sohag University Hospital, Egypt

Chapter 21 - Amino Acid-Related Diseases