Next-generation sequencing based newborn screening and comparative analysis with MS/MS

BACKGROUND

Newborn screening (NBS), such as tandem mass spectrometry (MS/MS), may yield false positive/negative results. Next-generation sequencing (NGS) has the potential to provide increased data output, efficiencies, and applications. This study aimed to analyze the types and distribution of pathogenic gene mutations in newborns in Huzhou, Zhejiang province, China and explore the applicability of NGS and MS/MS in NBS.

METHODS

Blood spot samples from 1263 newborns were collected. NGS was employed to screen for pathogenic variants in 542 disease-causing genes, and detected variants were validated using Sanger sequencing. Simultaneously, 26 inherited metabolic diseases (IMD) were screened using MS/MS. Positive or suspicious samples identified through MS/MS were cross-referenced with the results of NGS.

RESULTS

Among all newborns, 328 had no gene mutations detected. NGS revealed at least one gene mutation in 935 newborns, with a mutation rate of 74.0%. The top 5 genes were FLG, GJB2, UGT1A1, USH2A, and DUOX2. According to American College of Medical Genetics guidelines, gene mutations in 260 cases were classified as pathogenic or likely pathogenic mutation, with a positive rate of 20.6%. The top 5 genes were UGT1A1, FLG, GJB2, MEFV, and G6PD. MS/MS identified 18 positive or suspicious samples for IMD and 1245 negative samples. Verification of these cases by NGS results showed no pathogenic mutations, resulting in a false positive rate of 1.4% (18/1263).

CONCLUSION

NBS using NGS technology broadened the range of diseases screened, and enhanced the accuracy of diagnoses in comparison to MS/MS for screening IMD. Combining NGS and biochemical screening would improve the efficiency of current NBS.

UPLC-Orbitrap-HRMS application for analysis of plasma sterols

Correct identification and quantification of different sterol biomarkers can be used as a first-line diagnostic approach for inherited metabolic disorders (IMD). The main drawbacks of current methodologies are related to lack of selectivity and sensitivity for some of these compounds. To address this, we developed and validated two sensitive and selective assays for quantification of six cholesterol biosynthesis pathway intermediates (total amount (free and esterified form) of 7-dehydrocholesterol (7-DHC), 8-dehydrocholesterol (8-DHC), desmosterol, lathosterol, lanosterol and cholestanol), two phytosterols (total amount (free and esterified form) of campesterol and sitosterol) and free form of two oxysterols (7-ketocholesterol (7-KC) and 3β,5α,6β-cholestane-triol (C-triol). For quantification of four cholesterol intermediates we based our analytical approach on sterol derivatization with 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD). Quantification of all analytes is performed using UPLC coupled to an Orbitrap high resolution mass spectrometry (HRMS) system, with detection of target ions through full scan acquisition using positive atmospheric pressure chemical ionization (APCI) mode. UPLC and MS parameters were optimized to achieve high sensitivity and selectivity. Analog stable isotope labeled for each compound was used for proper quantification and correction for recovery, matrix effects and process efficiency. Precision (2.4%-12.3% inter-assay variation), lower limit of quantification (0.027 nM-50.5 nM) and linearity (5.5 μM (R2 0.999) - 72.3 μM (R2 0.997)) for phyto- and oxysterols were determined. The diagnostic potential of these two assays in a cohort of patients (n = 31, 50 samples) diagnosed with IMD affecting cholesterol and lysosomal/peroxisomal homeostasis is demonstrated.

Clinical and Molecular Characteristics of Neuronal Ceroid Lipofuscinosis in Saudi Arabia

BACKGROUND

Neuronal ceroid lipofuscinoses (NCLs) represent a heterogeneous group of inherited metabolic lysosomal disorders characterized by neurodegeneration. This study sought to describe the clinical and molecular characteristics of NCLs in Saudi Arabia and determine the most common types in that population.

METHODS

A retrospective review of electronic medical records was conducted for 63 patients with NCL (55 families) from six tertiary and referral centers in Saudi Arabia between 2008 and 2022. Clinical, radiological, and neurophysiological data as well as genetic diagnoses were reviewed.

RESULTS

CLN6 was the predominant type, accounting for 45% of cases in 25 families. The most common initial symptoms were speech delay (53%), cognitive decline (50%) and/or gait abnormalities (48%), and seizure (40%). Behavioral symptomatology was observed in 20%, whereas visual impairment was less frequently (9.3%) encountered. Diffuse cerebral and cerebellar atrophy was the predominant finding on brain magnetic resonance imaging. Electroencephalography generally revealed background slowing in all patients with generalized epileptiform discharges in 60%. The most common genotype detected was the p.Ser265del variant found in 36% (20 of 55 families). The most rapidly progressive subtypes were CLN2 and CLN6. Two patients with each died at age five years. The earliest age at which a patient was nonambulatory was two years in a patient with CLN14.

CONCLUSIONS

This is the largest molecularly confirmed NCL cohort study from Saudi Arabia. Characterizing the natural history of specific NLC types can increase understanding of the underlying pathophysiology and distinctive genotype-phenotype characteristics, facilitating early diagnosis and treatment initiation as well as genetic counseling for families.

Blood cytopenias as manifestations of inherited metabolic diseases: a narrative review

Inherited Metabolic Diseases (IMD) encompass a diverse group of rare genetic conditions that, despite their individual rarity, collectively affect a substantial proportion, estimated at as much as 1 in 784 live births. Among their wide-ranging clinical manifestations, cytopenia stands out as a prominent feature. Consequently, IMD should be considered a potential diagnosis when evaluating patients presenting with cytopenia. However, it is essential to note that the existing scientific literature pertaining to the link between IMD and cytopenia is limited, primarily comprising case reports and case series. This paucity of data may contribute to the inadequate recognition of the association between IMD and cytopenia, potentially leading to underdiagnosis. In this review, we synthesize our findings from a literature analysis along with our clinical expertise to offer a comprehensive insight into the clinical presentation of IMD cases associated with cytopenia. Furthermore, we introduce a structured diagnostic approach underpinned by decision-making algorithms, with the aim of enhancing the early identification and management of IMD-related cytopenia.

Implementation of a "hypoglycemia kit" in a pediatric emergency room: A retrospective study during 2011-2019

INTRODUCTION

Hypoglycemia is a common symptom in pediatrics that can lead to neurological sequelae. The etiologies are mostly benign, but hypoglycemia can be a symptom of severe underlying disease. To streamline the etiological investigations, a "hypoglycemia kit," containing supplies needed to perform specific analyses quickly, was made available in the pediatric emergency department of the Rouen University Hospital in 2011. Since its introduction, this kit has been used to explore all cases of hypoglycemia regardless of the context. However, although very useful, these analyses are expensive. The objective of our study was to examine the cost-effectiveness of this kit and to refine its indications if necessary.

METHODS

This was a non-interventional and retrospective single-center study. Digital records of patients for whom a hypoglycemia kit was used from September 2011 to August 2019 at the pediatric emergency department of Rouen University Hospital were used to retrieve clinical characteristics, laboratory results, and the causes of hypoglycemia.

RESULTS

The study included 82 patients. The etiologic investigation concluded that 74 patients had functional hypoglycemia, and eight cases were attributed to other etiologies. In two cases, the kit led to a diagnosis, i.e., 2.4 % efficiency. A history of congenital malformations or previous hypoglycemia was significantly associated with severe etiologies. However, there was no significant association between hypoglycemia severity, age, sex, and these etiologies.

CONCLUSION

Our study reveals that the cost-effectiveness of the hypoglycemia kit is low in pediatric emergencies (2.4 %) at Rouen University Hospital, where functional hypoglycemia remains the leading cause of hypoglycemia. However, our results allow us to suggest a decision tree for refining the usability of this kit, which would considerably increase its efficiency.

Metabolic kidney diseases

Kidney disease is a global health burden with high morbidity and mortality. Causes of kidney disease are numerous, extending from common disease groups like diabetes and arterial hypertension to rare conditions including inherited metabolic diseases (IMDs). Given its unique anatomy and function, the kidney is a target organ in about 10% of known IMDs, emphasizing the relevant contribution of IMDs to kidney disease. The pattern of injury affects all segments of the nephron including glomerular disease, proximal and distal tubular damage, kidney cyst formation, built-up of nephrocalcinosis and stones as well as severe malformations. We revised and updated the list of known metabolic etiologies associated with kidney involvement and found 190 relevant IMDs. This represents the 14th of a series of educational articles providing a comprehensive and revised list of metabolic differential diagnoses according to system involvement.

Respiratory manifestations

At any age, respiratory manifestations are a major cause of increased morbidity and mortality of inherited metabolic diseases (IMDs). Type and severity are extremely variable, this depending on the type of the underlying disorder. Symptoms and signs originating from upper or lower airways and/or thoracic wall and/or respiratory muscles involvement can occur either at presentation or in the late clinical course. Acute respiratory symptoms can trigger metabolic decompensation which, in turn, makes airway symptoms worse, creating a vicious circle. We have identified 181 IMDs associated with various types of respiratory symptoms which were classified into seven groups according to the type of clinical manifestations affecting the respiratory system: (i) respiratory failure, (ii) restrictive lung disease, (iii) interstitial lung disease, (iv) lower airway disease, (v) upper airway obstruction, (vi) apnea, and (vii) other. We also provided a list of investigations to be performed based on the respiratory phenotypes and indicated the therapeutic strategies currently available for IMD-associated airway disease. This represents the thirteenth issue in a series of educational summaries providing a comprehensive and updated list of metabolic differential diagnoses according to system involvement.

Palliative Care in Children with Inherited Metabolic Diseases: Why does it matter?

BACKGROUND

Inherited metabolic diseases (IMD) bring considerable burden on the child and family. Challenging areas for health care include the identification of distressing symptoms, prognostic uncertainty, and bereavement. Literature regarding the impact of paediatric palliative care (PPC) is scarce.

OBJECTIVE

This study aims to evaluate children with IMD referred to a PPC team (PPCT) and to analyse its impact on home care, decision to limit treatment (DLT), use of hospital resources (emergency department admissions - EDA, hospital admissions - HA, intensive care admissions - ICA) and end of life support.

METHODS

Retrospective cohort study of children with IMD referred to a specialized PPCT (2016-2022). We assessed clinical data: symptoms control, time of referral and length of the follow-up period, DLT, device dependency, use of hospital resources prior to and after referral, place of death and end-of-life support.

RESULTS

Fifteen children with IMD were referred to PPCT (8% of total referrals), with median age of 7 years (4 months - 17 years); 53% female. All children were non or pre-verbal. Most prevalent symptoms were neurologic and motor impairment (100%), respiratory and gastrointestinal (75%). 80% had tube feeding, 90% had some respiratory device (non-invasive ventilation in 23%). All children had multidrug use, with a mean of 6 drugs per child (2-9). 73% had home PPC and 80% had DLT planned. Nine children died (78% in hospital), after a mean of 17 months of follow-up (2 months to 4 years), all with DLT planned. 67% had support from PPCT at the end of life. All these families received emotional support. Decrease in EDA (10 vs 2) was noticed before and after PPCT. No impact was seen in HA and ICA (6 vs 5 and 1 vs 1, respectively) and there was a longer mean of hospitalisation stay (15 vs 32 days).

CONCLUSION

Our cohort includes a group of children with severe, complex and neurodegenerative IMD. They need multiple medications for symptoms control, are highly dependent on medical devices and consume significant healthcare resources. Communication impairment adds complexity being a major barrier to symptom assessment. PPCT referral allowed home support, anticipated care plans development with end of life and bereavement support, as well as a tendency towards a reduction in EDA. These findings reinforce the need for holistic approach to identify and address the PPC needs of children with IMD.

Symptoms of SARS-CoV-2 infection and vaccine status of sixty-seven adult patients affected by inherited metabolic diseases: a phone survey

BACKGROUND

The Covid pandemic seems to have had several detrimental effects on managing patients affected by inherited metabolic diseases (IMD), although published data about the impact of COVID-19 on patients suffering from IMD are very scarce. The scope of our work was to evaluate adherence to the vaccination plan, the side effects experienced by our adult IMD patients, and the symptoms of the SARS-CoV-2 infection.

RESULTS

Sixty-seven patients agreed to respond to a phone interview. The mean age was 36.5 (± 11.6 SD). Regarding the vaccination campaign, fifty-five patients (82%) joined it, of whom ten had received two doses and the remaining forty-five, three. Forty-two patients (76%) reported adverse events following vaccination, the most frequent being local reaction, fever, and asthenia, which lasted an average of two days and resolved without sequelae. Regarding SARS-CoV-2 infection, twenty-seven out of sixty-seven patients (40%) tested positive for the virus; seven of them were not vaccinated at the time of infection; on the other hand, twenty had already had at least two doses. Regarding the prevalence of long-Covid, as many as 12 patients (44%) reported symptoms that persisted after the nasopharyngeal swab tested negative and lasted an average of 81 (± 74 SD) days. There were no statistically significant differences in BMI of patients who contracted the infection and patients who did not (25.15 vs. 25.20, p = .861), between those who had adverse reactions to the vaccine and those who did not (24.40 vs. 25.75, p = .223), between those who had long-Covid and those who did not (25.9 vs. 27.7, p = .183). No relation was observed between metabolic inherited disease, SARS-CoV-2 infection symptoms and adverse vaccine reactions.

CONCLUSIONS

The data indicate that IMD patients adhered to the vaccination campaign comparably to the general Italian population. Adverse events to the vaccine were negligible. SARS-CoV-2 infection, which occurred in most cases after receiving at least two doses of the vaccine, did not cause serious symptoms and never required hospitalisation. A non-negligible share of patients suffered from long-Covid symptoms.

COVID-19 in inherited metabolic disorders: Clinical features and risk factors for disease severity

BACKGROUND

Old age, obesity, and certain chronic conditions are among the risk factors for severe COVID-19. More information is needed on whether inherited metabolic disorders (IMD) confer risk of more severe COVID-19. We aimed to establish COVID-19 severity and associated risk factors in patients with IMD currently followed at a single metabolic center.

METHODS

Among all IMD patients followed at a single metabolic referral center who had at least one clinic visit since 2018, those with accessible medical records were reviewed for SARS-CoV-2 tests. COVID-19 severity was classified according to the WHO recommendations, and IMD as per the international classification of IMD.

RESULTS

Among the 1841 patients with IMD, 248 (13.5%) had tested positive for COVID-19, 223 of whom gave consent for inclusion in the study (131 children and 92 adults). Phenylalanine hydroxylase (48.4%) and biotinidase (12.1%) deficiencies were the most common diagnoses, followed by mucopolysaccharidoses (7.2%). 38.1% had comorbidities, such as neurologic disabilities (22%) or obesity (9.4%). The majority of COVID-19 episodes were asymptomatic (16.1%) or mild (77.6%), but 6 patients (2.7%) each had moderate and severe COVID-19, and two (0.9%) had critical COVID-19, both of whom died. 3 patients had an acute metabolic decompensation during the infection. Two children developed multisystem inflammatory syndrome (MIS-C). Long COVID symptoms were present in 25.2%. Presence of comorbidities was significantly associated with more severe COVID-19 in adults with IMD (p < 0.01), but not in children (p = 0.45). Compared to other categories of IMD, complex molecule degradation disorders were significantly associated with more severe COVID-19 in children (p < 0.01); such a significant IMD category distinction was not found in adults.

DISCUSSION

This is the largest study on COVID-19 in IMD patients relying on real-word data and objective definitions, and not on merely expert opinions or physician surveys. COVID-19 severity and long COVID incidence in IMD are probably similar to the general population, and the risk of acute metabolic decompensation is not likely to be greater than that in other acute infections. Disease category (complex molecule degradation) in children, and comorbidities in adults may be associated with COVID-19 severity in IMD. Additionally, the first documented accounts of COVID-19 in 27 different IMD are recorded. The high occurrence of MIS-C may be coincidental, but warrants further study.

PLA2G6-Associated Neurodegeneration: A Rare Case Report of Neurodegeneration with Brain Iron Accumulation in Children

This report aimed to describe and review the clinical features, neuroimaging findings, and PLA2G6 mutations identified in a 34-month-old girl with regression of developmental milestones. A 34 months old girl came to Dr.Soetomo Hospital's outpatient clinic, Surabaya, with a developmental regression for six months, and got worse until she could not do any activity and was followed by recurrent seizures. She had a sibling who had similar problems and symptoms and then died at five years of age. The head MRI revealed brain atrophy, the possibility of an early sign of metabolic disorder, and a white matter lesion at the globuspallidus bilateral that supports the encephalopathy metabolic view. The genetic test revealed a positive homozygous such as a pathogenic variant in the PLA2G6 gene, which confirmed the diagnosis. PLA2G6-Associated with Neurodegeneration (PLAN) should be considered as a diagnosis in children with developmental regression.

Metabolic ear disease

Damages to the ear are very diverse and can depend on the type of inherited metabolic diseases (IMD). Indeed, IMDs can affect all parts of the auditory system, from the outer ear to the central auditory process. We have identified 219 IMDs associated with various types of ear involvement which we classified into five groups according to the lesion site of the auditory system: congenital external ear abnormalities, acquired external ear abnormalities, middle ear involvement, inner ear or retrocochlear involvement, and unspecified hearing loss. This represents the ninth issue in a series of educational summaries providing a comprehensive and updated list of metabolic differential diagnoses according to system involvement.

Modeling Splicing Variants Amenable to Antisense Therapy by Use of CRISPR-Cas9-Based Gene Editing in HepG2 Cells

The field of splice modulating RNA therapy has gained new momentum with FDA approved antisense-based drugs for several rare diseases. In vitro splicing assays with minigenes or patient-derived cells are commonly employed for initial preclinical testing of antisense oligonucleotides aiming to modulate splicing. However, minigenes do not include the full genomic context of the exons under study and patients' samples are not always available, especially if the gene is expressed solely in certain tissues (e.g. liver or brain). This is the case for specific inherited metabolic diseases such as phenylketonuria (PKU) caused by mutations in the liver-expressed PAH gene.Herein we describe the generation of mutation-specific hepatic cellular models of PKU using CRISPR/Cas9 system, which is a versatile and easy-to-use gene editing tool. We describe in detail the selection of the appropriate cell line, guidelines for design of RNA guides and donor templates, transfection procedures and growth and selection of single-cell colonies with the desired variant , which should result in the accurate recapitulation of the splicing defect.

Using random forest to detect multiple inherited metabolic diseases simultaneously based on GC-MS urinary metabolomics

Inborn errors of metabolism, also known as inherited metabolic diseases (IMDs), are related to genetic mutations and cause corresponding biochemical metabolic disorder of newborns and even sudden infant death. Timely detection and diagnosis of IMDs are of great significance for improving survival of newborns. Here we propose a strategy for simultaneously detecting six types of IMDs via combining GC-MS technique with the random forest algorithm (RF). Clinical urine samples from IMD and healthy patients are analyzed using GC-MS for acquiring metabolomics data. Then, the RF model is established as a multi-classification tool for the GC-MS data. Compared with the models built by artificial neural network and support vector machine, the results demonstrated the RF model has superior performance of high specificity, sensitivity, precision, accuracy, and matthews correlation coefficients on identifying all six types of IMDs and normal samples. The proposed strategy can afford a useful method for reliable and effective identification of multiple IMDs in clinical diagnosis.

Neonatal sudden death caused by a novel heterozygous mutation in SLC25A20 gene: A case report and brief literature review

Carnitine-acylcarnitine translocase deficiency (CACTD) is a rare and life-threatening autosomal recessive disorder of fatty acid β-oxidation (FAO). Most patients with CACTD develop severe metabolic decompensation which deteriorates progressively and rapidly, causing death in infancy or childhood. As CACTD in some patients is asymptomatic or only with some nonspecific symptoms, the diagnosis is easy to be ignored, resulting in sudden death, which often triggers medical disputes. Herein, we report a case of neonatal sudden death with CACTD. The neonate showed a series of severe metabolic crisis, deteriorated rapidly and eventually died 3 days after delivery. Tandem mass spectrometry (MS-MS) screening of dry blood spots before death showed that the level of long-chain acylcarnitines, especially C12-C18 acylcarnitine, was increased significantly, and therefore a diagnosis of inherited metabolic disease (IMD) was suspected. Autopsy and histopathological results demonstrated that there were diffuse vacuoles in the heart and liver of the deceased. Mutation analysis revealed that the patient was a compound heterozygote with c.199-10 T > G and a novel c.1A > T mutation in the SLC25A20 gene. Pathological changes such as heart failure, arrhythmia and cardiac arrest related to mitochondrial FAO disorders are the direct cause of death, while gene mutation is the underlying cause of death.

Mitochondrial disease, mitophagy, and cellular distress in methylmalonic acidemia

Mitochondria—the intracellular powerhouse in which nutrients are converted into energy in the form of ATP or heat—are highly dynamic, double-membraned organelles that harness a plethora of cellular functions that sustain energy metabolism and homeostasis. Exciting new discoveries now indicate that the maintenance of this ever changing and functionally pleiotropic organelle is particularly relevant in terminally differentiated cells that are highly dependent on aerobic metabolism. Given the central role in maintaining metabolic and physiological homeostasis, dysregulation of the mitochondrial network might therefore confer a potentially devastating vulnerability to high-energy requiring cell types, contributing to a broad variety of hereditary and acquired diseases. In this Review, we highlight the biological functions of mitochondria-localized enzymes from the perspective of understanding—and potentially reversing—the pathophysiology of inherited disorders affecting the homeostasis of the mitochondrial network and cellular metabolism. Using methylmalonic acidemia as a paradigm of complex mitochondrial dysfunction, we discuss how mitochondrial directed-signaling circuitries govern the homeostasis and physiology of specialized cell types and how these may be disturbed in disease. This Review also provides a critical analysis of affected tissues, potential molecular mechanisms, and novel cellular and animal models of methylmalonic acidemia which are being used to develop new therapeutic options for this disease. These insights might ultimately lead to new therapeutics, not only for methylmalonic acidemia, but also for other currently intractable mitochondrial diseases, potentially transforming our ability to regulate homeostasis and health.

Social and medical needs of rare metabolic patients: results from a MetabERN survey

BACKGROUND

Many surveys have been performed over the years to assess the medical and social requirements of patients with a rare disease, but no studies have focused specifically on patients in Europe or with an inherited metabolic disease (IMD). To obtain a comprehensive overview of the social and psychological status and needs of IMD patients, especially in Europe, the European Reference Network for Hereditary Metabolic Disorders (MetabERN) has performed a dedicated survey among its metabolic patients.

RESULTS

A total of 924 patients and caregivers responded to the questionnaire. Most participants were from 25 European countries, with Spain, Italy, and Germany being the most represented; only eight participants were extra-European. The survey showed that most social assistance services, from free educational/development services for those with intellectual disability to transition from childhood to adult care and job placement support, are available for a limited number of patients or are unknown to the majority of patients or their parents/caregivers. Similarly, psychological assistance for the patient or the parent/caregiver is available for a small fraction of respondents, despite the fact that the majority considers this type of support necessary for both the patient and the caregiver. In addition, for most IMD patients local specialised or emergency medical assistance is lacking, although national clinical pathways are defined, and medical professionals of reference are readily available when needed. Lastly, while most national health services in Europe cover all or part of the expenses for medications, medical devices, food supplements, dietary integrators, physiotherapy, and speech therapy, significant gaps in the economic support for healthcare and other expenses still exist.

CONCLUSIONS

Overall, our survey reveals a widespread lack of social, psychological, and economic support for IMD patients in Europe. More needs to be done to provide daily assistance to IMD patients in order to alleviate the burden on caregivers and to allow patients to become independent and productive adults. Where support is actually available locally or nationally, most IMD patients are not aware of it, so an active dissemination of this information among the metabolic community is essential.

U-IMD: the first Unified European registry for inherited metabolic diseases

Background

Following the broad application of new analytical methods, more and more pathophysiological processes in previously unknown diseases have been elucidated. The spectrum of clinical presentation of rare inherited metabolic diseases (IMDs) is broad and ranges from single organ involvement to multisystemic diseases. With the aim of overcoming the limited knowledge about the natural course, current diagnostic and therapeutic approaches, the project has established the first unified patient registry for IMDs that fully meets the requirements of the European Infrastructure for Rare Diseases (ERDRI).

Results

In collaboration with the European Reference Network for Rare Hereditary Metabolic Disorders (MetabERN), the Unified European registry for Inherited Metabolic Diseases (U-IMD) was established to collect patient data as an observational, non-interventional natural history study. Following the recommendations of the ERDRI the U-IMD registry uses common data elements to define the IMDs, report the clinical phenotype, describe the biochemical markers and to capture the drug treatment. Until today, more than 1100 IMD patients have been registered.

Conclusion

The U-IMD registry is the first observational, non-interventional patient registry that encompasses all known IMDs. Full semantic interoperability for other registries has been achieved, as demonstrated by the use of a minimum common core data set for equivalent description of metabolic patients in U-IMD and in the patient registry of the European Rare Kidney Disease Reference Network (ERKNet). In conclusion, the U-IMD registry will contribute to a better understanding of the long-term course of IMDs and improved patients care by understanding the natural disease course and by enabling an optimization of diagnostic and therapeutic strategies.

[The Newborn Screening Program in Italy: Comparison with Europe and other Countries.]

In Italy, since 2016, extended neonatal screening has been mandatory throughout the country for about 40 inherited metabolic diseases. The law contains indications on: the list of pathologies, the information and consent, the methods of collecting and sending samples, the newborn screening system with the elements of its organization, appointed to guarantee the entire path of newborn screening, from the level I test to taking charge of the confirmed positive newborn, the communication and recall procedures for diagnostic confirmation and patient management, training and information initiatives, as well as the criteria for allocating the allocation. Extended neonatal screening has introduced new issues in diagnosis, choice of decision levels, and metabolic disease panels to screen. Of particular relevance in order to a strong reduction of false positives, was the introduction of the second-tier test for some diseases such as leucinosis, isovaleric acidemia, methylmalonic aciduria. As regards the diseases to be screened, the Italian situation differs greatly from what happens in Europe where in the majority of member states there is no legislation / law governing this preventive pediatric service; screening is almost always on a voluntary basis (with the collection of written informed consent from both parents) and applied on the basis of health guidelines or recommendations. In the world, the most complete panel is the US one (RUSP, Recommended Uniform Screening Panel) which currently contains 62 pathologies, 35 of which are defined as core panels and 27 as secondary panels. As the name implies, it is a panel that the US Health Resources and Services Administration -HRSA- recommends that it be applied by every State and that includes new screening in some areas including Pompe disease and MPS I, creatine deficiency. In conclusion, extended neonatal screening represents a real revolution in the metabolic field offering newborns an early diagnosis combined with effective therapeutic treatments capable of radically changing the course of these serious diseases.

[Impact of the inclusion of second-tier tests in the newborn screening program of Catalonia and in other international programs.]

OBJECTIVE

Newborn screening programmes (NBSP) have experienced a qualitative breakthrough due to the implementation of tandem mass spectrometry. However, the tests used give rise to false positives (FP) generating an excessive request for second samples with the consequent anxiety of the families. In order to avoid this problem several programmes have developed second-tier tests (2TT).

METHODS

This article presents our experience in the implementation of 2TT in the NBSP of Catalonia, as well as in other international programmes.

RESULTS

From 2004 to the present, 2TT tests have been developed for more than 30 diseases. The use of 2TT helps to decrease the FP rate and increase the positive predictive value (PPV). In the NBSP of Catalonia, the implementation of 2TT for the detection of methylmalonic and propionic acidemias, homocystinurias, maple syrup disease and citrulinaemia, has managed to increase the PPV to 95% and decrease the PF rate to less than 0.01%. In cystic fibrosis, the application of 2TT slightly increases PPV but with a significant decrease in the request for second samples and in the number of cases referred to clinical units.

CONCLUSIONS

The introduction of 2TT in the NBSP allows to reduce considerably the FP, decreases the number of requested samples, as well as both anxiety and stress of the families, at the same time that the hospital costs are reduced and the PPV is increased, improving notably the efficiency of the NBSP.

SARS CoV2 infection in a young subject affected by arginosuccinate synthase deficiency: A case report of epilepsy worsening

We describe a case of a 21 years old woman affected by Citrullinemia type 1- Arginosuccinate Synthase deficiency (ASSD)-who underwent a SARS CoV2 infection during the first phase of pandemic burst in Italy. She had no symptoms of infection nor a metabolic crisis. After recovery from SARS CoV2, she experienced a worsening in their epilepsy despite therapy, with one/two crisis a week.

The impact of COVID-19 on rare metabolic patients and healthcare providers: results from two MetabERN surveys

The ongoing coronavirus disease 2019 (COVID-19) pandemic has caused disruption in all aspects of daily life, including the management and treatment of rare inherited metabolic disorders (IMDs). To perform a preliminary assessment of the incidence of COVID-19 in IMD patients and the impact of the coronavirus emergency on the rare metabolic community between March and April 2020, the European Reference Network for Hereditary Metabolic Diseases (MetabERN) has performed two surveys: one directed to patients’ organizations (PO) and one directed to healthcare providers (HCPs). The COVID-19 incidence in the population of rare metabolic patients was lower than that of the general European population (72.9 × 100,000 vs. 117 × 100,000). However, patients experienced extensive disruption of care, with the majority of appointments and treatments cancelled, reduced, or postponed. Almost all HCPs (90%) were able to substitute face-to-face visits with telemedicine, about half of patients facing treatment changes switched from hospital to home therapy, and a quarter reported difficulties in getting their medicines. During the first weeks of emergency, when patients and families lacked relevant information, most HCPs contacted their patients to provide them with support and information. Since IMD patients require constant follow-up and treatment adjustments to control their disease and avoid degradation of their condition, the results of our surveys are relevant for national health systems in order to ensure appropriate care for IMD patients. They highlight strong links in an interconnected community of HCPs and PO, who are able to work quickly and effectively together to support and protect fragile persons during crisis. However, additional studies are needed to better appreciate the actual impact of COVID-19 on IMD patients’ health and the mid- and long-term effects of the pandemic on their wellbeing.

Incidence of inherited metabolic disorders in southern Israel: a comparison between consanguinity and non-consanguinity communities

Background

Inherited metabolic disorders (IMDs) are group of rare monogenic diseases, usually derived from reduced or absent activity in a single metabolic pathway. Most of the IMDs are inherited in an autosomal recessive manner. The incidence of IMDs varies from country to country and within different ethnic groups, but data is still scarce. Consanguinity rate among populations is highly contributor factor for IMDs incidence. There are no reports comparing the incidence of IMD in consanguineous and non-consanguineous populations from the same geographic region with the same diagnostic capabilities. Our study objective is to compare the incidence of IMDs between between the relatively low consanguineous Jewish population and the consanguineous Bedouin population, both living in the southern of Israel.

Results

During 1990–2017 there were 393,772 live births in the Negev district, of Southern of Israel. Among them 187,049 were of Jewish origin while 206,723 were of Bedouin-Muslim origin. A total of 223 children were diagnosed in this study period with IMDs. Among those 223 children with IMD, 33 were of Jewish origin while the other 190 children were of Bedouin-Muslim origin. The overall incidence for IMDs of the overall Negev population was 56.6/100,000 live birth. The incidence for IMD's among the Bedouin population was significantly higher than among Jewish population.

Conclusions

IMDs are extremely more common in the consanguineous Bedouin compared with the relatively non-consanguineous Jewish population of Southern Israel. Health policy makers should consider these data and prepare educational and genetic counselling problems accordingly.

The juvenile gangliosidoses: A timeline of clinical change

Background

The gangliosidoses are rare inherited diseases that result in pathologic accumulation of gangliosides in the central nervous system and other tissues, leading to severe and progressive neurological impairment and early death in the childhood forms. No treatments are currently approved for the gangliosidoses, and development of treatments is impaired by limited understanding of the natural history of these diseases.

Objective

The objective of this study is to improve understanding of the juvenile gangliosidoses phenotypes and the late-infantile phenotypic subtype.

Methods

Through a prospective natural history study of subjects with juvenile GM1- and GM2-gangliosidosis, a timeline of clinical changes was developed for the classic juvenile phenotypes and the late-infantile phenotypes and results of serial neurodevelopmental testing was analyzed.

Results

Several candidate ‘outcome measures’ were identified: changes in ambulation and verbalization skills, the communication domain from neurodevelopmental testing and the caregiver-reported socialization domain.

Conclusions

The most common symptoms leading caregivers to seek a genetic diagnosis were changes in ambulation and verbalization.

Update of a colorimetric method for quantitative determination of galactose in blood samples: A simple and rapid method for the early detection of inherited metabolic diseases

BACKGROUND

A colorimetric microassay for the quantitative determination of galactose in the blood was taken and updated. This method helps in diagnosis and follow-up of several inherited metabolic diseases connected to galactose metabolism deficiency such as galactosemia, glycogenosis, glycosylation, tyrosinemia and citrin deficiency. Galactose assay in the blood presents difficulties due to interference with glucose. In this study, we update a method to get around these difficulties.

METHOD

This procedure was based on the incubation of whole blood with orcinol in a strongly acidic solution to form a galactose and glucose complexes able to absorb at two different wavelengths.

RESULTS

The standard curve analysis for the individual solutions of these two sugars showed a wide range of linearity from 0 to 200 mg / l. Under optimal experimental conditions, the stirring time of the orcinol is 3 minutes, the heating time of the reaction is 20 minutes at 56 ° C, and the duration of the incubation in the dark is 40 minutes. The analysis is carried out on fresh blood. The maximum absorbance of galactose and glucose is respectively 569 nm and 421 nm. An adapted diagnosis algorithm was developed based on our results.

CONCLUSION

this method could help in screening and identifying patients with hypergalactosemia that need further investigations. It could represent a promising method for neonatal screening in countries with limited resources.

Clouds over IMD? Perspectives for inherited metabolic diseases in adults from a retrospective cohort study in two Swiss adult metabolic clinics

Background

Inherited metabolic diseases (IMD) are complex medical conditions. Thanks to improvements in diagnosis and treatment, a growing number of pediatric IMD patients reach adulthood. Thus, clinical care of adults with IMD has emerged as a new and challenging reality. This purpose of this study of adults with IMD in an adult metabolic clinic at two academic hospitals (Lausanne and Geneva) was to help inform decisions on the future organization of health care for this group of patients.

Methods

All adult patients with a biochemical and/or genetic diagnosis of IMD followed at the clinics were included in the study. Electronic patient records were reviewed for clinical features, diagnostic studies, treatment and long-term outcome. Data of undiagnosed patients referred for suspected IMD were analyzed separately.

Results

126 patients were included in the study. The most prevalent group of diseases was small molecules disorders with 82 (65%) patients, followed by energy defects disorders with 29 (23%) patients and complex molecules disorders with 15 (12%) patients. Overall, 64% of patients were diagnosed before, and 36% after the age 16 years. Among the 126 cases, 51% suffered from medical complications. 79% of the patients were receiving a specific treatment for their disease. Among the 138 undiagnosed patients referred for suspicion of IMD, investigations lead to a genetic diagnosis in 24 (17%) patients. 19 had confirmation of an IMD, 5 were found to have another genetic condition.

Conclusions

This retrospective study reveals significant features of adult IMD cohort. The disorders are heterogeneous, and there is no one-size-fits-all approach – treatment must be tailored to fit each specific disorder in each individual patient. Even patients who are followed at the dedicated clinic are not protected from metabolic decompensations and/or chronic organ-specific complications. While it is commonly assumed that patients with IMD are more stable once they become adults, our data show that the diseases continue to exact a lifelong toll. A coordinated monitoring of target organs by a multidisciplinary team is needed. To ensure that the success in diagnosis and treatment of individuals with IMD is sustained, there is a clear requirement for adequately staffed adult IMD clinics.

Evaluation of the quality of clinical data collection for a pan-Canadian cohort of children affected by inherited metabolic diseases: lessons learned from the Canadian Inherited Metabolic Diseases Research Network

BACKGROUND

The Canadian Inherited Metabolic Diseases Research Network (CIMDRN) is a pan-Canadian practice-based research network of 14 Hereditary Metabolic Disease Treatment Centres and over 50 investigators. CIMDRN aims to develop evidence to improve health outcomes for children with inherited metabolic diseases (IMD). We describe the development of our clinical data collection platform, discuss our data quality management plan, and present the findings to date from our data quality assessment, highlighting key lessons that can serve as a resource for future clinical research initiatives relating to rare diseases.

METHODS

At participating centres, children born from 2006 to 2015 who were diagnosed with one of 31 targeted IMD were eligible to participate in CIMDRN's clinical research stream. For all participants, we collected a minimum data set that includes information about demographics and diagnosis. For children with five prioritized IMD, we collected longitudinal data including interventions, clinical outcomes, and indicators of disease management. The data quality management plan included: design of user-friendly and intuitive clinical data collection forms; validation measures at point of data entry, designed to minimize data entry errors; regular communications with each CIMDRN site; and routine review of aggregate data.

RESULTS

As of June 2019, CIMDRN has enrolled 798 participants of whom 764 (96%) have complete minimum data set information. Results from our data quality assessment revealed that potential data quality issues were related to interpretation of definitions of some variables, participants who transferred care across institutions, and the organization of information within the patient charts (e.g., neuropsychological test results). Little information was missing regarding disease ascertainment and diagnosis (e.g., ascertainment method - 0% missing).

DISCUSSION

Using several data quality management strategies, we have established a comprehensive clinical database that provides information about care and outcomes for Canadian children affected by IMD. We describe quality issues and lessons for consideration in future clinical research initiatives for rare diseases, including accurately accommodating different clinic workflows and balancing comprehensiveness of data collection with available resources. Integrating data collection within clinical care, leveraging electronic medical records, and implementing core outcome sets will be essential for achieving sustainability.

Amino and organic acid analysis: Essential tools in the diagnosis of inborn errors of metabolism

Inborn errors of metabolism (IEMs) are a large class of genetic disorders that result from defects in enzymes involved in energy production and metabolism of nutrients. For every metabolic pathway, there are defects that can occur and potentially result in an IEM. While some defects can go undetected in one's lifetime, some have moderate to severe clinical consequences. In the latter case, the biochemical defect leads to accumulation of metabolites and byproducts that are toxic or interfere with normal biological function. Disorders of amino acid metabolism, organic acid metabolism and the urea cycle comprise a large portion of IEMs. Two essential tools required for the diagnosis of these categories of disorders are amino acid and organic acid profiling. Most all clinical laboratories offering metabolic testing perform amino acid analysis, while organic acid profiling is restricted to more specialized pediatric hospitals and reference laboratories. In this chapter, we will provide an overview of various methodologies employed for amino acid and organic acid profiling as well as specific examples to demonstrate how these techniques are applied in clinical laboratories for the diagnosis of IEMs.

Metabolic liver diseases

Inherited metabolic diseases account for about one third of pediatric patients with hepatomegaly, acute liver failure, cirrhosis or cholestasis. Specifically for pediatric acute liver failure, they account for 10-15% of cases, with a mortality of 22-65%. The percentage of acute liver failure caused by an inherited metabolic disease in children <2-3 years of age is even higher, ranging from a third to half of all cases. Metabolic liver disease accounts for 8-13% of all pediatric liver transplantations. Despite this high burden of disease, underdiagnosis remains common. We reviewed and updated the list of known metabolic etiologies associated with various types of metabolic liver involvement, and found 142 relevant inborn errors of metabolism. This represents the second of a series of articles attempting to create and maintain a comprehensive list of clinical and metabolic differential diagnoses according to system involvement.

Movement disorders

About a third of patients with inherited metabolic diseases with neurologic involvement suffer from a movement disorder, in the form of ataxia, hyperkinetic movements, or hypokinetic-rigid syndrome. We reviewed and updated the list of known metabolic etiologies associated with various types of movement disorders, and found approximately 200 relevant inborn errors of metabolism. This represents the first of a series of articles attempting to create and maintain a comprehensive list of clinical and metabolic differential diagnoses according to system involvement.

Health services use among children diagnosed with medium-chain acyl-CoA dehydrogenase deficiency through newborn screening: a cohort study in Ontario, Canada

BACKGROUND

We describe early health services utilization for children diagnosed with medium-chain acyl-CoA dehydrogenase (MCAD) deficiency through newborn screening in Ontario, Canada, relative to a screen negative comparison cohort.

METHODS

Eligible children were identified via newborn screening between April 1, 2006 and March 31, 2010. Age-stratified rates of physician encounters, emergency department (ED) visits and inpatient hospitalizations to March 31, 2012 were compared using incidence rate ratios (IRR) and incidence rate differences (IRD). We used negative binomial regression to adjust IRRs for sex, gestational age, birth weight, socioeconomic status and rural/urban residence.

RESULTS

Throughout the first few years of life, children with MCAD deficiency (n = 40) experienced statistically significantly higher rates of physician encounters, ED visits, and hospital stays compared with the screen negative cohort. The highest rates of ED visits and hospitalizations in the MCAD deficiency cohort occurred from 6 months to 2 years of age (ED use: 2.1-2.5 visits per child per year; hospitalization: 0.5-0.6 visits per child per year), after which rates gradually declined.

CONCLUSIONS

This study confirms that young children with MCAD deficiency use health services more frequently than the general population throughout the first few years of life. Rates of service use in this population gradually diminish after 24 months of age.

Inborn errors of metabolism

Inborn errors of metabolism, also known as inherited metabolic diseases, constitute an important group of conditions presenting with neurologic signs in newborns. They are individually rare but collectively common. Many are treatable through restoration of homeostasis of a disrupted metabolic pathway. Given their frequency and potential for treatment, the clinician should be aware of this group of conditions and learn to identify the typical manifestations of the different inborn errors of metabolism. In this review, we summarize the clinical, laboratory, electrophysiologic, and neuroimaging findings of the different inborn errors of metabolism that can present with florid neurologic signs and symptoms in the neonatal period.

Transplantation as disease modifying therapy in adults with inherited metabolic disorders

Transplantation is an established disease modifying therapy in selected children with certain inherited metabolic diseases (IMDs). Transplantation of hematopoietic stem cells or solid organs can be used to partially correct the underlying metabolic defect, address life threatening disease manifestations (such as neutropenia) or correct organ failure caused by the disease process. Much less information is available on the use of transplantation in adults with IMDs. Transplantation is indicated for the same IMDs in adults as in children. Despite similar disease specific indications, the actual spectrum of diseases for which transplantation is used differs between these age groups and this is partly related to the natural history of disease. There are diseases (such as urea cycle defects and X-linked adrenoleukodystrophy) for which transplantation is recommended for selected symptomatic patients as a treatment strategy in both adults and children. In those diseases, the frequency with which transplantation is used in adults is lower than in children and this may be related in part to a reduced awareness of transplantation as a treatment strategy amongst adult clinicians as well as limited donor availability and allocation policies which may disadvantage adult patients with IMDs. Risks of transplantation and disease-specific prognostic factors influencing outcomes also differ with age. We review the use of transplantation as a disease modifying strategy in adults focusing on how this differs from use in children to highlight areas for future research.

Metabolic causes of nonimmune hydrops fetalis: A next-generation sequencing panel as a first-line investigation

PURPOSES

Hydrops fetalis is a life-threatening fetal condition, and 85% of all cases are classified as nonimmune hydrops fetalis (NIHF). Up to 15% of NIHF cases may be due to inborn errors of metabolism (IEM), but a large proportion of cases linked to metabolic disorders remains undiagnosed. This lack of diagnosis may be related to the limitations of conventional biological procedures, which involve sequential investigations and require multiple samples and steps. In addition, this approach is time consuming. We have developed a next-generation sequencing (NGS) panel to investigate metabolic causes of NIHF, ascites, and polyhydramnios associated to another fetal abnormality.

METHODS

The hydrops fetalis (HydFet) panel was designed to cover the coding regions and flanking intronic sequences of 41 genes. A retrospective study of amniotic fluid samples from 40 subjects was conducted. A prospective study was subsequently initiated, and six samples were analyzed using the NGS panel.

RESULTS

Five IEM diagnoses were made using the HydFet panel (Niemann-Pick type C (NPC), Barth syndrome, HNF1Β deficiency, GM1 gangliosidosis, and Gaucher disease). This analysis also allowed the identification of 8p sequence triplication in an additional case.

CONCLUSION

NGS combined with robust bioinformatics analyses is a useful tool for identifying the causative variants of NIHF. Subsequent functional characterization of the protein encoded by the altered gene and morphological studies may confirm the diagnosis. This paradigm shift allows a significant improvement of IEM diagnosis in NIHF.

Biochemical signatures mimicking multiple carboxylase deficiency in children with mutations in MT-ATP6

Elevations of specific acylcarnitines in blood reflect carboxylase deficiencies, and have utility in newborn screening for life-threatening organic acidemias and other inherited metabolic diseases. In this report, we describe a newly-identified association of biochemical features of multiple carboxylase deficiency in individuals harboring mitochondrial DNA (mtDNA) mutations in MT-ATP6 and in whom organic acidemias and multiple carboxylase deficiencies were excluded. Using retrospective chart review, we identified eleven individuals with abnormally elevated propionylcarnitine (C3) or hydroxyisovalerylcarnitine (C5OH) with mutations in MT-ATP6, most commonly m.8993T>G in high heteroplasmy or homoplasmy. Most patients were ascertained on newborn screening; most had normal enzymatic or molecular genetic testing to exclude biotinidase and holocarboxylase synthetase deficiencies. MT-ATP6 is associated with some cases of Leigh disease; clinical outcomes in our cohort ranged from death from neurodegenerative disease in early childhood to clinically and developmentally normal after several years of follow-up. These cases expand the biochemical phenotype associated with MT-ATP6 mutations, especially m.8993T>G, to include acylcarnitine abnormalities mimicking carboxylase deficiency states. Clinicians should be aware of this association and its implications for newborn screening, and consider mtDNA sequencing in patients exhibiting similar acylcarnitine abnormalities that are biotin-unresponsive and in whom other enzymatic deficiencies have been excluded.

Establishing core outcome sets for phenylketonuria (PKU) and medium-chain Acyl-CoA dehydrogenase (MCAD) deficiency in children: study protocol for systematic reviews and Delphi surveys

BACKGROUND

Inherited metabolic diseases (IMD) are a large group of rare single-gene disorders that are typically diagnosed early in life. There are important evidence gaps related to the comparative effectiveness of therapies for IMD, which are in part due to challenges in conducting randomized controlled trials (RCTs) for rare diseases. Registry-based RCTs present a unique opportunity to address these challenges provided the registries implement standardized collection of outcomes that are important to patients and their caregivers and to clinical providers and healthcare systems. Currently there is no core outcome set (COS) for studies evaluating interventions for paediatric IMD. This protocol outlines a study that will establish COS for each of two relatively common IMD in children, phenylketonuria (PKU) and medium-chain acyl-CoA dehydrogenase (MCAD) deficiency.

METHODS

This two-part study is registered with the Core Outcome Measures in Effectiveness Trials (COMET) initiative. Part 1 includes a rapid review and development of an evidence map to identify a comprehensive listing of outcomes reported in past studies of PKU and MCAD deficiency. The review follows established methods for knowledge synthesis, including a comprehensive search strategy, two stages of screening citations against inclusion/exclusion criteria by two reviewers working independently, and extraction of important data elements from eligible studies, including details of the outcomes collected and outcome measurement instruments. The review findings will inform part 2 of our study, a set of Delphi surveys to establish consensus on the highest priority outcomes for each condition. Healthcare providers, families of children with PKU or MCAD deficiency, and health system decision-makers will be invited to participate in two to three rounds of Delphi surveys. The design of the surveys will involve parents of children with IMD who are part of a family advisory forum.

DISCUSSION

This protocol is a crucial step in developing the capacity to launch RCTs with meaningful outcomes that address comparative effectiveness questions in the field of paediatric IMD. Such trials will contribute high-quality evidence to inform decision-making by patients and their family members, clinicians, and policy-makers.

Experiences of caregivers of children with inherited metabolic diseases: a qualitative study

Background

We sought to understand the experiences of parents/caregivers of children with inherited metabolic diseases (IMD) in order to inform strategies for supporting patients and their families. We investigated their experiences regarding the management of disease, its impact on child and family life, and interactions with the health care system.

Methods

From four Canadian centres, we conducted semi-structured telephone interviews with parents/caregivers of children with an IMD who were born between 2006 and 2015 and who were participating in a larger cohort study. Participants were selected with the aim of achieving a diverse sample with respect to treatment centre, IMD, and age of the child. Interviews emphasized the impacts of the disease and its treatment on the child and family and explicitly queried perceptions of interactions with the health care system. We identified emergent themes from the interview data.

Results

We completed interviews with 21 parents/caregivers. The 21 children were aged <1 to 7 years old with IMD that included amino acid disorders, urea cycle disorders, fatty acid oxidation disorders, and organic acid disorders or ‘other’ IMD. Most parents reported that they and their families had adapted well to their child’s diagnosis. Parents used proactive coping strategies to integrate complex disease management protocols into routine family life. An important source of stress was concern about the social challenges faced by their children. Participants reported positive interactions with their most involved health care providers within the metabolic clinic. However, they reported challenges associated with the health care system outside of disease-specific metabolic care, when encountering systems and providers unfamiliar with the child’s disease.

Conclusions

The successful use of proactive coping strategies among parents of children with IMD in this study suggests the potential value of promoting positive coping and is an important direction for future study. Parents’ social concerns for their children were important stressors that warrant consideration by health care providers positioned to support families. Our results with respect to experiences with care highlight the important role of specialized metabolic clinics and point to a need for better coordination of the care that takes place outside the disease-specific management of IMD.

In vivo evidence of mitochondrial dysfunction and altered redox homeostasis in a genetic mouse model of propionic acidemia: Implications for the pathophysiology of this disorder

Accumulation of toxic metabolites has been described to inhibit mitochondrial enzymes, thereby inducing oxidative stress in propionic acidemia (PA), an autosomal recessive metabolic disorder caused by the deficiency of mitochondrial propionyl-CoA carboxylase. PA patients exhibit neurological deficits and multiorgan complications including cardiomyopathy. To investigate the role of mitochondrial dysfunction in the development of these alterations we have used a hypomorphic mouse model of PA that mimics the biochemical and clinical hallmarks of the disease. We have studied the tissue-specific bioenergetic signature by Reverse Phase Protein Microarrays and analysed OXPHOS complex activities, mtDNA copy number, oxidative damage, superoxide anion and hydrogen peroxide levels. The results show decreased levels and/or activity of several OXPHOS complexes in different tissues of PA mice. An increase in mitochondrial mass and OXPHOS complexes was observed in brain, possibly reflecting a compensatory mechanism including metabolic reprogramming. mtDNA depletion was present in most tissues analysed. Antioxidant enzymes were also found altered. Lipid peroxidation was present along with an increase in hydrogen peroxide and superoxide anion production. These data support the hypothesis that oxidative damage may contribute to the pathophysiology of PA, opening new avenues in the identification of therapeutic targets and paving the way for in vivo evaluation of compounds targeting mitochondrial biogenesis or reactive oxygen species production.

PHKA2 mutation spectrum in Korean patients with glycogen storage disease type IX: prevalence of deletion mutations

Background

Molecular diagnosis of glycogen storage diseases (GSDs) is important to enable accurate diagnoses and make appropriate therapeutic plans. The aim of this study was to evaluate the PHKA2 mutation spectrum in Korean patients with GSD type IX.

Methods

Thirteen Korean patients were tested for PHKA2 mutations using direct sequencing and a multiplex polymerase chain reaction method. A comprehensive review of the literature on previously reported PHKA2 mutations in other ethnic populations was conducted for comparison.

Results

Among 13 patients tested, six unrelated male patients with GSD IX aged 2 to 6 years at the first diagnostic work-up for hepatomegaly with elevated aspartate transaminase (AST) and alanine transaminase (ALT) were found to have PHKA2 mutations. These patients had different PHKA2 mutations: five were known mutations (c.537 + 5G > A, c.884G > A [p.Arg295His], c.3210_3212delGAG [p.Arg1072del], exon 8 deletion, and exons 27–33 deletion) and one was a novel mutation (exons 18–33 deletion). Notably, the most common type of mutation was gross deletion, in contrast to other ethnic populations in which the most common mutation type was sequence variant.

Conclusions

This study expands our knowledge of the PHKA2 mutation spectrum of GSD IX. Considering the PHKA2 mutation spectrum in Korean patients with GSD IX, molecular diagnostic methods for deletions should be conducted in conjunction with direct sequence analysis to enable accurate molecular diagnosis of this disease in the Korean population.

Metabolic Diet App Suite for inborn errors of amino acid metabolism

BACKGROUND

An increasing number of rare inborn errors of metabolism (IEMs) are amenable to targeted metabolic nutrition therapy. Daily adherence is important to attain metabolic control and prevent organ damage. This is challenging however, given the lack of information of disorder specific nutrient content of foods, the limited availability and cost of specialty products as well as difficulties in reliable calculation and tracking of dietary intake and targets.

OBJECTIVES

To develop apps for all inborn errors of amino acid metabolism for which the mainstay of treatment is a medical diet, and obtain patient and family feedback throughout the process to incorporate this into subsequent versions.

METHODS & RESULTS

The Metabolic Diet App Suite was created with input from health care professionals as a free, user-friendly, online tool for both mobile devices and desktop computers (http://www.metabolicdietapp.org) for 15 different IEMs. General information is provided for each IEM with links to useful online resources. Nutrient information is based on the MetabolicPro™, a North American food database compiled by the Genetic Metabolic Dietitians International (GMDI) Technology committee. After user registration, a personalized dashboard and management plan including specific nutrient goals are created. Each Diet App has a user-friendly interface and the functions include: nutrient intake counts, adding your own foods and homemade recipes and, managing a daily food diary. Patient and family feedback was overall positive and specific suggestions were used to further improve the App Suite.

DISCUSSION

The Metabolic Diet App Suite aids individuals affected by IEMs to track and plan their meals. Future research should evaluate its impact on patient adherence, metabolic control, quality of life and health-related outcomes. The Suite will be updated and expanded to Apps for other categories of IEMs. Finally, this Suite is a support tool only, and does not replace medical/metabolic nutrition professional advice.

Vaccination coverage of patients with inborn errors of metabolism and the attitudes of their parents towards vaccines

To evaluate vaccination coverage of children and adolescents with inborn errors of metabolism (IEMs) and the attitudes of their parents towards vaccination, the vaccination status of 128 patients with IEM and 128 age- and gender-matched healthy controls was established by consulting the official vaccination chart. In children with IEMs, compared with healthy controls, low vaccination rates and/or delays in administration were observed for pneumococcal conjugate, meningococcus C, measles, mumps, rubella, diphtheria-tetanus-pertussis-inactivated polio, Bacillus Calmette-Guerin, and influenza vaccines. Among the parents of IEM patients, vaccine schedule compliance was primarily driven by the doctors at the hospital's reference centres; among the parents of the healthy controls, compliance was driven by the primary care paediatricians. These results show that IEM patients demonstrate sub-optimal vaccination coverage. Further studies of the different vaccines in each IEM disorder and educational programmes aimed at physicians and parents to increase immunization coverage in these patients are urgently needed.

Application of whole exome sequencing to a rare inherited metabolic disease with neurological and gastrointestinal manifestations: a congenital disorder of glycosylation mimicking glycogen storage disease

BACKGROUND

Rare inherited metabolic diseases with neurological and gastrointestinal manifestations can be misdiagnosed as other diseases or remain as disorders with indeterminate etiologies. This study aims to provide evidence to recommend the utility of whole exome sequencing in clinical diagnosis of a rare inherited metabolic disease.

METHODS AND RESULTS

A 4-month-old female baby visited an outpatient clinic due to poor weight gain, repeated seizure-like episodes, developmental delay, and unexplained hepatomegaly with abnormal liver function test results. Although liver biopsy revealed moderate fibrosis with a suggested diagnosis of glycogen storage disease (GSD), no mutations were identified either by single gene approach for GSD (G6PC and GAA) or by next generation sequencing panels for GSD (including 21 genes). Whole exome sequencing of the patient revealed compound heterozygous mutations of PMM2: c.580C>T (p.Arg194*) and c.713G>C (p.Arg238Pro) which mutations were associated with congenital disorder of glycosylation Ia (CDG-Ia: PMM2-CDG).

CONCLUSIONS

We successfully applied exome sequencing to diagnose the first reported Korean patient with CDG-Ia, which was misdiagnosed as GSD. Whole exome sequencing may prove to be the preferred strategy for analysis of clinical features that do not readily suggest a specific diagnosis, such as those observed in inherited metabolic diseases, including CDG.

Inherited metabolic disease screening in etiological diagnosis of infantile hepatitis syndrome

AIM: To assess the significance of screening for inherited metabolic diseases in the etiological diagnosis of infantile hepatitis syndrome.

METHODS: A retrospective analysis was performed of patients with infantile hepatitis syndrome who received hereditary metabolic disease screening from October 2003 to March 2010.

RESULTS: Among 802 patients with infantile hepatitis syndrome, 35 were identified to have hereditary metabolic hepatopathy. The main causes were tyrosinemia (n = 9), citrullinemia (n = 4), neonatal intrahepatic cholestasis caused by citrin deficiency (n = 4), hyperlactacidemia (n = 3), Niemann-Pick disease (n = 5), glycogenic thesaurismosis (n = 2), dicarboxylic aciduria (n = 2), alagille syndrome (n = 3), and progressive familial intrahepatic cholestasis (n = 3).

CONCLUSION: The causes of infantile hepatitis syndrome are diverse. It is necessary to conduct routine screening of inherited metabolic diseases in infantile hepatitis syndrome, which will be helpful to early diagnosis and correct treatment.

Psychiatric manifestations of treatable hereditary metabolic disorders in adults

Detecting psychiatric disorders of secondary origin is a crucial concern for the psychiatrist. But how can this reliably be done among a large number of conditions, most of which have a very low prevalence? Metabolic screening undertaken in a population of subjects with psychosis demonstrated the presence of treatable metabolic disorders in a significant number of cases. The nature of the symptoms that should alert the clinician is also a fundamental issue and is not limited to psychosis. Hereditary metabolic disorders (HMD) are a rare but important cause of psychiatric disorders in adolescents and adults, the signs of which may remain isolated for years before other more specific organic signs appear. HMDs that present purely with psychiatric symptoms are very difficult to diagnose due to low awareness of these rare diseases among psychiatrists. However, it is important to identify HMDs in order to refer patients to specialist centres for appropriate management, disease-specific treatment and possible prevention of irreversible physical and neurological complications. Genetic counselling can also be provided. This review focuses on three HMD categories: acute, treatable HMDs (urea cycle abnormalities, remethylation disorders, acute intermittent porphyria); chronic, treatable HMDs (Wilson's disease, Niemann-Pick disease type C, homocystinuria due to cystathionine beta-synthase deficiency, cerebrotendinous xanthomatosis); and chronic HMDs that are difficult to treat (lysosomal storage diseases, X-linked adrenoleukodystrophy, creatine deficiency syndrome). We also propose an algorithm for the diagnosis of HMDs in patients with psychiatric symptoms.