Rare disorders of metabolism with elevated butyryl- and isobutyryl-carnitine detected by tandem mass spectrometry newborn screening

Tandem mass spectrometry was adopted for newborn screening by North Carolina in April 1999. Since then, three infants with short-chain acyl-CoA dehydrogenase (SCAD) and one with isobutyryl-CoA dehydrogenase deficiency were detected on the basis of elevated butyrylcarnitine/isobutyrylcarnitine (C4-carnitine) concentrations in newborn blood spots analyzed by tandem mass spectrometry. For three SCAD-deficient infants, biochemical evaluation included a plasma acylcarnitine profile with markedly elevated C4-carnitine, urine organic acid analysis with markedly elevated ethylmalonic and 2-methylsuccinic acids, and markedly elevated [U-13C]butyrylcarnitine concentrations in medium from fibroblasts incubated with [U-13C]palmitic acid and excess l-carnitine, consistent with classic SCAD deficiency. Two of three infants diagnosed with classic SCAD deficiency remained asymptomatic; however, the third infant presented with seizures and a cerebral infarct at 10 wk of age. All three infants had putatively inactivating mutations in both alleles of the SCAD gene. The highly elevated plasma C4-carnitine levels in the three infants detected by newborn screening tandem mass spectrometry differentiated them from infants and children who were homozygous or compound heterozygous for one of two SCAD gene susceptibility variations; for the latter group the C4-carnitine levels were normal. Isobutyryl-CoA dehydrogenase deficiency in a fourth infant was confirmed after isolated elevation of C4-carnitine in the acylcarnitine profile.     

Multiple acyl-coenzyme A dehydrogenase deficiency: diagnosis by acyl-carnitine analysis of a 12-year-old newborn screening card.

We report a family who experienced an unexplained neonatal death. Twelve years after the death, we retrospectively diagnosed multiple acyl-coenzyme A dehydrogenase deficiency by demonstrating an abnormal acyl-carnitine profile in the child's archived newborn screening card, using tandem mass spectrometry.     

Recent developments and new applications of tandem mass spectrometry in newborn screening

PURPOSE OF REVIEW: To summarize recent developments in the field of newborn screening related to the use of tandem mass spectrometry as an analytic platform. RECENT FINDINGS: Novel inborn errors of metabolism with informative amino acid and/or acylcarnitine profiles have been characterized, increasing the complexity of the differential diagnosis of abnormal results. In addition, methods have been developed for the analysis in dried blood spots of steroids and lysosomal enzymes. Previously unrecognized genotype/phenotype correlations have been found among cohorts of patients whose conditions were diagnosed by screening rather than clinically. Several government entities and professional organizations have issued position statements on newborn screening, and worldwide outcome studies continue to underscore the clinical and financial benefits of expanded newborn screening. SUMMARY: Although it is done inconsistently, newborn screening in the United States is undergoing a rapid expansion driven by the introduction of tandem mass spectrometry in at least 34 state programs. This technology is also used to detect disease markers beyond acylcarnitines and amino acids, as both primary and second-tier tests. In addition to analytic improvements, there is a trend toward the development of joint programs not limited to contiguous geographic areas, often based upon public-private partnerships. This review will summarize several new developments in the field that have occurred since early 2003 and will mention others likely to occur in the near future.     

Detection of neonatal carnitine palmitoyltransferase II deficiency by expanded newborn screening with tandem mass spectrometry

The introduction of tandem mass spectrometry to newborn screening has substantially expanded our ability to diagnose metabolic diseases in the newborn period. We report the first case of neonatal carnitine palmitoyltransferase deficiency II detected by expanded newborn screening with tandem mass spectrometry. The neonate presented with dysmorphic facial features, structural malformations, renal failure, seizures, and cardiac arrythmias and died on the third day of life. This experience illustrates the importance of expanded newborn screening to avoid missing a metabolic diagnosis in early infantile death.     

The current revolution in newborn screening: new technology, old controversies

Newborn screening has provided a model of a successful public health screening program for the past 40 years. However, the history of newborn screening is not without controversy. Many of these controversies have been rekindled with the introduction of tandem mass spectrometry, a technology that has greatly increased our ability to detect potential disease in asymptomatic newborns. This review highlights the challenges raised by this and future technological advances as we strive to maintain the success of newborn screening in the 21st century.     

Carnitine transporter defect diagnosed by newborn screening with electrospray tandem mass spectrometry

The carnitine transporter defect is a potentially fatal but treatable disorder. We used electrospray tandem mass spectrometry in the New South Wales (Australia) Newborn Screening Programme to measure free carnitine and acylcarnitine species in the newborn population. Free carnitine levels in dried blood samples from 149,000 neonates did not vary markedly between 2 and 8 days of age. Two of 4 babies subsequently diagnosed clinically with the carnitine transporter defect had a free carnitine level in the neonatal blood sample low enough to be detected by screening.     

Neugeborenenscreening im Spannungsfeld der Gesundheitsökonomie

The present article is intended as an introduction to health economic evaluation as well as a review of economic evaluations of medium-chain acyl-CoA dehydrogenase deficiency (MCADD) in newborn screening using tandem mass spectrometry (TMS). With the help of a systematic literature search, ten full health economic evaluations were identified. The primary measure of health outcome was life years gained or quality-adjusted life years gained. All evaluations were based on modelling studies. Due to methodological heterogeneity, the incremental cost-effectiveness ratios showed a wide variation. In addition, differences in various assumptions underlying the evaluations played an important role in this variation. In comparison to conventional screening methods or no screening, TMS in newborn screening was proven in many cases to be cost-effective. In order to make a more sound statement on newborn screening in Germany, a tailored model is required.     

Decline of acute encephalopathic crises in children with glutaryl-CoA dehydrogenase deficiency identified by newborn screening in Germany

Glutaryl-CoA dehydrogenase (GCDH) deficiency is a rare neurometabolic disorder that is considered treatable if patients are identified before the onset of acute encephalopathic crises. To allow early identification of affected individuals, tandem mass spectrometry-based newborn screening for GCDH deficiency has been started in Germany in 1999. We prospectively followed neonatally screened patients (n=38) and compared the neurologic outcome with patients from a historical cohort (n=62). In the majority of neonatally screened children, the onset of encephalopathic crises has been prevented (89%), whereas acute encephalopathic crises or progressive neurologic impairment was common in the historical cohort. Neonatal screening in combination with intensive management is effective--even assuming ascertainment bias in the historical cohort. Similar proportions of commonest mutations and biochemical phenotypes (high and low excretors) were found in neonatally screened and historical patients. However, potential predictor variables for mild clinical phenotypes are not yet known and thus a selection of these patients by newborn screening is not excluded. No patient was known to be missed by newborn screening from 1999 to 2005. In conclusion, this study confirms that newborn screening for GCDH deficiency in combination with intensive management is beneficial.     

Glutaric aciduria type I: Outcome of patients with early- versus late-diagnosis

Patients with Glutaric aciduria type 1 (GA-1) can be identified by newborn screening using tandem mass spectrometry. The clinical evolution of screened patients seems to be more favourable compared with those diagnosed later, although long-term evolution is still doubtful. We have evaluated the outcome in nine GA-1 patients diagnosed in our region during 12 years. Six were detected by newborn screening and 3 clinically. The birth prevalence was 1:35,027. High blood C5DC concentration, in 8/9 patients, was found, whereas all patients exhibited high concentration of this metabolite in urine. Therefore, urine C5DC was a good marker for the detection of this disease. Eight different mutations in the GCDH gene were identified, four of them were novel (p.R88H, p.Y398C, p.R372K, p.D220N); being p.R227P the mostcommon. Macrocephaly with enlarged frontotemporal subarachnoid space was present in 4/6 patients diagnosed by newborn screening, all these patients required high energy intake, and in two cases, enteral feeding during the first year of life was needed. One child had an intercurrent episode of feeding refuse with hypoglycemia at two years of age. The mean follow-up time of screened patients was 56 months, and patients still remain asymptomatic. However, after a mean follow-up of 97 months treatment efficacy was poor in unscreened patients, two of them showing a severe spastic tetraparesis. Plasma levels of lysine, tryptophan and carnitine, were the most useful biomarkers for the follow-up.Our data support that, early diagnosis and treatment strategies are essential measures for the good clinical evolution of GA-1 patients.     

Defekt der langkettigen 3-Hydroxy-Acyl-CoA-Dehydrogenase—LCHAD-Defekt

Long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency is a rare inborn disorder of mitochondrial fatty acid β-oxidation. Clinical manifestations include acute symptoms such as hypoketotic hypoglycemia with hepatopathy and encephalopathy and chronic symptoms such as myopathy, cardiomyopathy, neuropathy, and retinopathy. More than 80% of patients with acute manifestations of LCHAD deficiency will die during the first 2 years of life. Fatty acid oxidation defects can now be diagnosed during the initial days of life in the presymptomatic state by newborn screening with tandem mass spectrometry. Screening of 630,000 newborns detected 9 patients with LCHAD defect (a high incidence of 1:30,000 in the north-western part of Germany). We report on the clinical course of two patients with LCHAD defect who were diagnosed by newborn screening during their first 2 years of life. The development of characteristic symptoms in both patients could not be prevented. However, with early and specific therapy both patients showed normal development at the age of 24 months. The hope is that early identification of such patients through newborn screening may improve the prognosis of patients with this disorder.     

The impact of screening for propionic and methylmalonic acidaemia

The outcome of the severe variants of propionic and methylmalonic acidaemia is not good. Patients with these disorders have increased concentrations of propionylcarnitine and using tandem mass spectrometry to detect this compound, it is possible to screen in the newborn period. Various criteria have been used to identify the patients but only a small number of patients have been diagnosed so far and some have been missed. Furthermore many will have already presented before the result of the screening test is available. CONCLUSION: It is not yet clear whether the outcome is better for those identified in screening programmes.     

尿素循环障碍的新生儿筛查

尿素循环障碍（urea cycle disorders,UCDs）是一类遗传代谢病,由于尿素循环代谢过程中酶或转运体缺陷引起氨解毒或精氨酸合成障碍,以血氨增高为最显著的临床表现,50%的患者表现为新生儿高氨血症,病死率高达 25%~50%,临床发作之前及早诊断可减缓甚至避免高氨血症并发症的发生。新生儿筛查是实现早期诊治、改善预后的最佳方法。串联质谱技术引入新生儿筛查以来更多的病种得到早期诊断,UCDs一直没有完全被纳入新生儿筛查项目,且在疾病种类选择、筛查时机以及随访、监测方案方面一直存在争议。     

Brain injury in glutaric aciduria type I: The value of functional techniques in magnetic resonance imaging

BackgroundAcute striatal necrosis is a devastating consequence of encephalopathic crisis in patients with glutaric aciduria type I (GA-I), but the mechanisms underlying brain injury are not completely understood.ObjectiveTo approach pathophysiological aspects of brain injury in GA-I by means of functional techniques in magnetic resonance imaging (MRI).Patients and methodsFour patients during an acute encephalopathic crisis and three asymptomatic siblings with GA-I underwent single-voxel hydrogen magnetic resonance spectroscopy (MRS) and brain MRI including gradient echo T1-weighted, FLAIR, T2-weighted and diffusion-weighted imaging.ResultsThe study was performed between three and eight days after the onset of acute encephalopathic crisis. Isotropic diffusion images showed high signal changes with corresponding low apparent diffusion coefficient values within the putamen, caudate nuclei and globus pallidus (four patients), and the cerebral peduncles including the substantia nigra (one patient). The study disclosed normal findings in asymptomatic siblings. MRS showed decreased N-acetyl-aspartate/creatine ratio at the basal ganglia in encephalopathic patients when compared to a group of sex- and age-matched controls.ConclusionsBrain injury in GA-I is characterizied by the presence of cytotoxic edema and reduced neuronal integrity by functional imaging techniques. Involvement of the basal ganglia may be asymmetrical in patients with unilateral motor disorder and may extent to the cerebral peduncles and substantia nigra, which may be responsible for the acute onset dystonia in some patients. Functional techniques failed to demonstrate any abnormalities in asymptomatic patients, which is in agreement with the integrity of basal ganglia structures observed by conventional MRI sequences.     

Metabolic screening in children: newborn screening for metabolic diseases past,present and future

Newborn screening began with the diagnosis of phenylketonuria using a simple test applicable to all newborn babies. Treatment could be given before the onset of brain damage with near normal outcomes. Methods became available to screen for and treat a variety of inborn errors of metabolism, but their application was patchy. Screening for hypothyroidism is now universal in the UK, and screening for cystic fibrosis and, more recently, haemoglobinopathies is being implemented nationally. Tandem mass spectrometry allows detection of more than 30 metabolic disorders using the neonatal screening blood spot. Considerable worldwide experience is now available and limited studies have shown favourable outcomes. Following a pilot study, the UK is to adopt tandem mass spectrometry screening for medium-chain acyl-CoA dehydrogenase deficiency. There is the potential to develop expanded newborn screening for aminoacidopathies, urea cycle disorders, organic acidaemias and fatty acid oxidation defects.     

Laboratory integration and utilization of tandem mass spectrometry in neonatal screening: a model for clinical mass spectrometry in the next millennium

Clinical and neonatal screening methods using a tandem mass spectrometer are clearly a model for modern laboratory testing in the new Millennium. By the year 2000, more than 1 million blood and plasma samples will have been tested in laboratories throughout the world for a battery of metabolic disorders using a tandem mass spectrometer as the primary analytical device. A tandem mass spectrometer is considered the "ultimate" analytical detector in a variety of biochemical and clinical methods because of its very high accuracy, selectivity, precision, versatility and robust nature. The ability to achieve very high and reproducible sample throughput (approximately 600 samples/instrument/24 h) has made this technology cost-effective for newborn screening. In order to reliably measure markers of inborn errors of metabolism while maintaining low costs and high efficiency, accuracy and quality, much attention needs to be placed on monitoring and maintenance of all components of the entire testing system. These components include specimen collection and sample preparation methods, analysis by LC tandem mass spectrometry, conversion of raw mass spectra (data) into clinically meaningful results (concentration), expert interpretation of these results so that the clinician can be provided with information to facilitate a diagnose, and follow-up and education so that the maximum benefits of newborn screening translate into prevention of disease symptoms or more effective treatments. Addressing each part of the whole system will produce a quality screening program that will detect a battery of disorders using tandem mass spectrometry with a disease frequency of nearly 1 in 4000 infants.     

Frequencies of inherited organic acidurias and disorders of mitochondrial fatty acid transport and oxidation in Germany

The lack of epidemiological data on the frequency and/or burden of organic acidurias (OA) and mitochondrial fatty acid transport and oxidation disorders (mtFATOD) is one reason for hesitation to expand newborn screening (NBS) by tandem mass spectrometry (MS-MS). From 1999 to 2000, the frequency of ten potentially treatable OA and mtFATOD was assessed by active nation-wide surveillance on cases presenting with clinical symptoms using the German Paediatric Surveillance Unit (ESPED) system. Case ascertainment was complemented by a second independent source: 3-monthly inquiries in the metabolic laboratories performing secondary selected screening for OA and mtFATOD. Frequency estimates for clinically symptomatic cases older than 7 days in a birth cohort of 844,575 conventionally screened children was compared to the frequency found in a cohort of 382,247 screened by MS-MS in Bavaria and Baden-Württemberg. The overall frequency of the ten conditions considered was 1:8,000 (95% CI 1:11,000–1:6,000) by MS-MS as compared to 1:23,000 (95% CI 1:36,000–1:17,000) in symptomatic cases presenting mainly with metabolic crisis. The contributions of medium-chain acyl-CoA dehydrogenase deficiency (MCADD), other mtFATOD and OA were 29, 4 and 13 among the 46 cases identified by MS-MS, and 19, 1 and 13 among the 33 clinically symptomatic cases, respectively. Acute metabolic crisis, with a lethal outcome in four patients, was reported for 22/33 clinically symptomatic cases. No clinically symptomatic cases were reported from cohorts with screened by MS-MS. Conclusion: ten potentially treatable organic acidurias and mitochondrial fatty acid transport and oxidations disorders were more common than phenylketonuria with organic acidurias accounting for 28% of the cases detected by newborn screening and 39% of the cases identified on high risk screening. These conditions were related to considerable morbidity and mortality. Considerations for their inclusion in expanded newborn screening programmes might be warranted.Abbreviations ESPED Erhebungseinheit für seltene pädiatrische Erkrankungen in Deutschland (German Paediatric Surveillance Unit) - MCADD medium-chain acyl-CoA dehydrogenase deficiency - MS-MS tandem mass spectrometry - mtFATOD mitochondrial fatty acid transport and oxidation disorders - NBS newborn screening - OA organic acidurias     

Evaluation of newborn screening for medium chain acyl-CoA dehydrogenase deficiency in 275 000 babies

OBJECTIVE: To evaluate newborn screening by tandem mass spectrometry for detection of medium chain acyl-CoA dehydrogenase (MCAD) deficiency, a fatty acid oxidation disorder with significant mortality in undiagnosed patients. DESIGN: The following were studied: (a) 13 clinically detected MCAD deficient subjects, most homozygous for the common A985G mutation, whose newborn screening sample was available; (b) 275 653 consecutive neonates undergoing routine newborn screening. Screened infants with blood octanoylcarnitine levels > or = 1 micromol/l were analysed for the A985G mutation, had analysis of plasma and repeat blood spot acylcarnitines and urinary organic acids, and had fibroblast fatty acid oxidation or acylcarnitine studies. RESULT: Twelve of the 13 patients later diagnosed clinically had newborn octanoylcarnitine levels > 2.3 micromol/l. Twenty three screened babies had initial octanoylcarnitine levels > or = 1 micromol/l. Eleven of 12 babies with persistent abnormalities had metabolite and/or enzyme studies indicating MCAD deficiency. Only four were homozygous for the A985G mutation, the remainder carrying one copy. CONCLUSIONS: Most patients with symptomatic MCAD deficiency could be detected by newborn screening. Infants actually detected had a lower frequency of A985G alleles than clinically diagnosed cases and may have a lower risk of becoming symptomatic.     

Multiple acyl-CoA-dehydrogenase deficiency (MADD): use of acylcarnitines and fatty acids to monitor the response to dietary treatment.

The treatment of multiple acyl-CoA-dehydrogenase deficiency (MADD) includes a low-fat, low-protein, high-carbohydrate diet, avoiding long fasting periods. However, there is no useful biochemical marker to determine the response to different diets or fasting periods. The aims of this study are to report a patient with MADD, diagnosed through a newborn screening program using tandem mass spectrometry, to assess her response to different feedings, and to evaluate the usefulness of acylcarnitines and FFA to monitor the response to dietary changes. The patient was diagnosed at 6 d. Family history revealed three dead siblings. Five tests were performed, one with breast milk and the subsequent four after giving the patient a bottle of a low-fat, low-protein formula (F), F with glucose polymers (GP), F+GP plus uncooked corn starch (CS), or F+GP+CS preceded by amylase. The results showed that acylcarnitines, FFA, and total nonesterified fatty acids levels were greatly improved at 2 and 4 h on F+GP compared with breast milk. At 6 mo of age, the test with F+CS was repeated to assess the response to a longer fast. The results were similar at 2 and 4 h, but showed a marked increase of acylcarnitines, FFA, and total nonesterified fatty acids at 6 h. The increase of these metabolites could not be avoided by the use of F+GP+CS, but was prevented when amylase was used simultaneously. The patient is currently 3.9 y old and has normal growth and development. We conclude that diagnosis of MADD through a newborn screening program using tandem mass spectrometry is suitable; acylcarnitines and FFA are useful to monitor the response to treatment; and exogenous amylase allows the use of CS in small children with MADD. This therapeutic approach may be an alternative to the use of continuous overnight feedings used for young children with severe fatty acid oxidation defects. Early diagnosis and treatment may change the natural history of MADD.     

Cardiomyopathy and Hypotonia in a 5-Month-Old Infant with Malonyl-CoA Decarboxylase Deficiency: Potential for Preclinical Diagnosis with Expanded Newborn Screening

Malonyl-CoA decarboxylase deficiency is an inborn error of metabolism that may cause hypotonia and a fatal cardiomyopathy in infancy. Newborn metabolic screening programs do not include this disorder, although there is a possibility that presymptomatic treatment may attenuate the development of cardiomyopathy. We report a case of malonyl-CoA decarboxylase deficiency in a 5-month-old boy who presented with cardiomyopathy and hypotonia. Retrospective analysis of the newborn screening test showed an elevation in the concentration of malonylcarnitine at age 3 days. Unfortunately, this perturbation was missed because the screening test did not routinely measure malonylcarnitine in the newborn blood. Our experience confirms the possibility of screening for malonyl-CoA decarboxylase deficiency with tandem mass spectrometry. This finding should enable studies to determine if presymptomatic treatment could change the outcome in this often fatal disorder.