Successful outcomes of older adolescents and adults with profound biotinidase deficiency identified by newborn screening

Newborn Screening Conditions: Early Intervention and Probability of Developmental Delay

OBJECTIVES

The purpose of this study is to explore which newborn screening (NBS) conditions are automatically eligible for early intervention (EI) across states and to determine the extent to which each disorder should automatically qualify for EI because of a high probability of developmental delay.

METHODS

We examined each state's EI eligibility policy and reviewed the literature documenting developmental outcomes for each NBS condition. Using a novel matrix, we assessed the risk of developmental delay, medical complexity, and risk of episodic decompensation, revising the matrix iteratively until reaching consensus. Three NBS conditions (biotinidase deficiency, severe combined immunodeficiency, and propionic acidemia) are presented in detail as examples.

RESULTS

Most states (88%) had Established Conditions lists to autoqualify children to EI. The average number of NBS conditions listed was 7.8 (range 0-34). Each condition appeared on average in 11.7 Established Conditions lists (range 2-29). After the literature review and consensus process, 29 conditions were likely to meet national criteria for an Established Condition.

CONCLUSION

Despite benefiting from NBS and timely treatment, many children diagnosed with NBS conditions are at risk for developmental delays and significant medical complexity. The results demonstrate a need for more clarity and guidance regarding which children should qualify for EI. We suggest that most NBS conditions should automatically qualify based on the probability of resulting in a developmental delay. These findings suggest a future opportunity for collaboration between NBS and EI programs to create a consistent set of Established Conditions, potentially expediate referrals of eligible children, and streamline children's access to EI services.

Successful pregnancy and childbirth without metabolic abnormality in a patient with holocarboxylase synthetase deficiency

Holocarboxylase synthetase deficiency (HSD), an autosomal recessive biotin cycle disorder, is caused by holocarboxylase synthetase (HLCS) genetic variants, resulting in multiple carboxylase deficiency. Catabolic stress can induce metabolic crises in patients with HSD. Although pharmacological doses of biotin have improved HLCS enzyme activity and HSD prognosis, the prolonged life expectancy has gradually highlighted novel issues in adult patients with HSD. To the best of our knowledge, there is only one report on a case of HSD during pregnancy and childbirth, and the metabolic profile was not well defined. In this report, we present the history and metabolic profile of a woman with HSD who had an uncomplicated pregnancy and childbirth. A high pharmacological dose of biotin, 100 mg/day, had no effect on the fetus. Even during the emergency cesarean section, the detailed metabolic assessments revealed no significant laboratory findings, such as ketolactic acidosis, hyperammonemia, and remarkable acylcarnitine change. This report suggests that a woman with HSD who regularly takes biotin can conceive and give birth safely, and biotin doses of 100 mg/day may not influence the growth and development of the fetus. Further research and case studies on pregnant women with HSD are required to determine an acceptable maximum dosage of biotin for human fetuses.

Revisiting the administration of biotin to children with biotin-responsive disorders

There continues to be questions and misconceptions about the administration of the vitamin, biotin, to children with the inherited biotin-responsive disorder, especially infants. Therefore, this commentary is intended to address the issues of biotin administration for healthcare workers, parents of children with the biotin-responsive disorders and the individuals with the disorders.

New and emerging pharmacologic treatments for developmental and epileptic encephalopathies

PURPOSE OF REVIEW

Summarize evidence on Developmental and Epileptic Encephalopathies (DEEs) treatments focusing on new and emerging pharmacologic therapies (see Video, http://links.lww.com/CONR/A61, Supplementary Digital Content 1, which provides an overview of the review).

RECENT FINDINGS

Advances in the fields of molecular genetics and neurobiology have led to the recognition of underlying pathophysiologic mechanisms involved in an increasing number of DEEs that could be targeted with precision therapies or repurposed drugs, some of which are currently being evaluated in clinical trials. Prompt, optimal therapy is critical, and promising therapies approved or in clinical trials for tuberous sclerosis complex, Dravet and Lennox-Gastaut Syndromes including mammalian target of rapamycin inhibitors, selective membrane channel and antisense oligonucleotide modulation, and repurposed drugs such as fenfluramine, stiripentol and cannabidiol, among others, may improve seizure burden and neurological outcomes. There is an urgent need for collaborative efforts to evaluate the efficacy and safety of emerging DEEs therapies.

SUMMARY

Development of new therapies promise to address unmet needs for patients with DEEs, including improvement of neurocognitive function and quality of life.

Newborn Screening for Biotinidase Deficiency. The Experience of a Regional Center in Italy

Introduction: Biotinidase deficiency (BD) is an autosomal recessive disease causing a defect in the biotin-releasing enzyme. Newborn screening (NBS) allows early diagnosis and treatment, ensuring excellent prognosis. The aim of this study was to describe our experience in the diagnosis, treatment, and follow-up showing key strategies and unsolved questions of the management of BD patients. Methods: We analyzed data of patients identified by the Regional Centre for Newborn Screening of Verona and followed by the Inherited Metabolic Disease Unit of Verona and Neonatal Intensive Care Unit of Bolzano, Italy, from 2014 to 2020. Results: Thirty-seven patients were diagnosed by NBS (five profound and 32 partial BD), with a total incidence of 1:5,996. All were started on biotin at diagnosis and presented no symptoms at follow-up. Analysis of parents and siblings led to identification of five asymptomatic patients with partial BD: one asymptomatic parent and four young siblings. Genetic analysis of the BTD gene identified 17 different genotypes and one mutation not previously known. Discussion: Our data confirm that NBS introduction had a dramatic impact on BD diagnosis, and the incidence has increased significantly compared to other areas. Partial defects are more common than profound and have a distinctive genotype. Partial BD treatment is still controversial even at what dose of biotin and for how long. At the end, BD treatment is very easy and inexpensive and prevents severe neurological damage. Sharing experiences is essential to achieving guidelines for treatment and follow-up and a better genotype-phenotype correlation.

Developmental and behavioral outcomes of preschool-aged children with biotinidase deficiency identified by newborn screening

Biotinidase deficiency (BD) may cause neurological symptoms and developmental problems. However, newborn screening of BD and early biotin treatment prevent the manifestation of the majority of symptoms. This study intended to examine the developmental and behavioral outcomes as well as maternal anxiety and depressive symptoms of preschool-aged children with BD and to compare these with the outcomes of healthy preschool-aged children. In total, 49 children with BD and 23 healthy children are included. All children were screened for developmental and behavioral problems. Moreover anxiety and depressive symptomatology of their mothers were evaluated. Despite the high percentage of developmental delay in BD group, the numbers of children screened positive for a developmental delay were statistically similar in children with BD and healthy children. Among patients with BD, children with risk of developmental delay had more unfavorable socio-demographic features compared to typically developing ones. Behavioral problem scores, maternal anxiety, and depressive symptoms scores of children with BD were not higher than the healthy children.Conclusion: Children with BD were not different from their healthy peers in terms of developmental and behavioral outcomes. Developmental problems of children with BD may be related to the unfavorable socio-demographic features, not the BD itself. What is known: • Biotinidase deficiency (BD) may result in neurological symptoms and developmental problems. • Newborn screening and early biotin supplementation prevent the manifestation of the majority of symptoms. What is new: • Preschool-aged children with BD identified by newborn screening are not different from their healthy peers in terms of developmental and behavioral outcomes. • Maternal anxiety and depressive symptoms scores of children with BD are similar to scores of healthy children.

Biotinidase deficiency is a rare, potentially treatable cause of peripheral neuropathy with or without optic neuropathy in adults

Background

We describe two adult brothers with lower limb neuropathy and one with progressive optic neuropathy. One brother was found to have profound biotinidase deficiency by identifying biallelic pathogenic variants of the BTD gene by whole exome sequencing, which was confirmed by markedly decreased serum biotinidase activity.

Case report and methods

The first brother had progressive optic atrophy and vision loss over 10 years and progressive peripheral neuropathy with weakness, pain, and fatigue for 20 years. Profound biotinidase deficiency was also identified in an older brother, who exhibited peripheral neuropathy since four years of age, but had no vision loss.

Results

The first brother's vision loss and neuropathy improved markedly with biotin in six months. However, the neuropathy of the other brother did not improve with 16 months of biotin therapy.

Conclusions

The first brother's neurological issues partially reversed with biotin. However, the longer-term symptoms of the other brother were irreversible. These cases emphasize the importance of considering biotinidase deficiency in the differential diagnosis of adolescents and adults with peripheral neuropathy with or without optic neuropathy/atrophy before symptoms become irreversible. Although WES initially identified the disorder in this family, measuring serum biotinidase activity was a necessary confirmatory step after WES and is less expensive than performing whole exome sequencing.

One Year of Newborn Screening for SMA - Results of a German Pilot Project

Objective:

Spinal muscular atrophy (SMA) is the most common neurodegenerative disease in childhood. The study was conducted to assess the impact of early detection of SMA by newborn screening (NBS) on the clinical course of the disease.

Methods:

Screening was performed in two federal states of Germany, Bavaria and North Rhine Westphalia, between January 2018 and February 2019. The incidence in the screening population was calculated as number of detected patients with a homozygous deletion in the SMN1-gene per number of screened patients. To get an idea about the incidence of newly diagnosed SMA in the year prior to screening a survey covering all neuropediatric centers in the state of Bavaria was conducted, identifying all SMA-cases in 2017 and 2018. Following positive NBS and confirmatory diagnostic test, treatment was advised according to the recommendations of the “American SMA NBS Multidisciplinary Working Group”. Immediate treatment with Nusinersen was recommended in children with 2 and 3 SMN2 copies and a conservative strict follow-up strategy in children with ≥4 copies. All children underwent regular standardized neuropediatric examination, CHOP INTEND and HINE-2 testing as well as electrophysiological exams every 2-3 months.

Results:

165,525 children were screened. 22 cases of SMA were identified, meaning an incidence rate of 1:7524. SMN2 copy number analysis showed 2 SMN2 copies in 45% of patients, 3 SMN2 copies in 19 % and 4 SMN2 copies in 36%. These findings are confirmed in the most recent statistical data-cut from 31st August 2019 (incidence 1:7089, 2 SMN2 copies in 44%, 3 in 15% and 4 in 38%). Comparison with up-to-date German data on SMA incidence and the Bavarian survey give evidence that NBS did not lead to a relevant increase in incidence. 10 patients with 2 or 3 SMN2 copies were treated with Nusinersen, starting between 15– 39 days after birth, in 7/10 patients before onset of symptoms. Presymptomatically treated patients (age at last examination: 1– 12 months, median 8 months) showed no muscle weakness by the age of one month to one year. One child with 4 SMN2 copies became symptomatic at the age of 8 months.

Conclusions:

Newborn screening, resulting in presymptomatic treatment, improves outcome in children with genetically proven SMA. Newborn screening for SMA should be introduced in all countries where therapy is available. An immediate therapy in cases with 4 SMN2 copies should be considered.

An Overview of the Current State and the Future of Ataxia Treatments

Cerebellar ataxia can be caused by a variety of disorders, including degenerative processes, autoimmune and paraneoplastic illness as well as by gene mutations inherited in autosomal dominant, autosomal recessive, or X-linked fashions. In this review, we highlight the treatments for cerebellar ataxia in a systematic way, to provide guidance for clinicians who treat patients with cerebellar ataxia. In addition, we review therapies currently under development for ataxia, which we feel is currently one of the most exciting fields in neurology.

Integrated metabolome analysis reveals novel connections between maternal fecal metabolome and the neonatal blood metabolome in women with gestational diabetes mellitus

Gestational Diabetes Mellitus (GDM), which is correlated with changes in the gut microbiota, is a risk factor for neonatal inborn errors of metabolism (IEMs). Maternal hyperglycemia exerts epigenetic effects on genes that encode IEM-associated enzymes, resulting in changes in the neonatal blood metabolome. However, the relationship between maternal gut microbiota and the neonatal blood metabolome remains poorly understood. This study aimed at understanding the connections between maternal gut microbiota and the neonatal blood metabolome in GDM. 1H-NMR-based untargeted metabolomics was performed on maternal fecal samples and targeted metabolomics on the matched neonatal dry blood spots from a cohort of 40 pregnant women, including 22 with GDM and 18 controls. Multi-omic association methods (including Co-Inertia Analysis and Procrustes Analysis) were applied to investigate the relationship between maternal fecal metabolome and the neonatal blood metabolome. Both maternal fecal metabolome and the matched neonatal blood metabolome could be separated along the vector of maternal hyperglycemia. A close relationship between the maternal and neonatal metabolomes was observed by multi-omic association approaches. Twelve out of thirty-two maternal fecal metabolites with altered abundances from 872 1H- NMR features (Bonferroni-adjusted P < 0.05) in women with GDM and the controls were identified, among which 8 metabolites contribute (P < 0.05 in a 999-step permutation test) to the close connection between maternal and the neonatal metabolomes in GDM. Four of these eight maternal fecal metabolites, including lysine, putrescine, guanidinoacetate, and hexadecanedioate, were negatively associated (Spearman rank correlation, coefficient value < −0.6, P < 0.05) with maternal hyperglycemia. Biotin metabolism was enriched (Bonferroni-adjusted P < 0.05 in the hypergeometric test) with the four-hyperglycemia associated fecal metabolites. The results of this study suggested that maternal fecal metabolites contribute to the connections between maternal fecal metabolome and the neonatal blood metabolome and may further affect the risk of IEMs.

Frequency of biotinidase gene variants and incidence of biotinidase deficiency in the Newborn Screening Program in Minas Gerais, Brazil

OBJECTIVE

The prevalence of biotinidase deficiency and the frequency of biotinidase gene variants in Brazil are not documented. We aimed to determine the incidence of partial and profound biotinidase deficiency in the state of Minas Gerais, Brazil, and to calculate the frequency of biotinidase gene variants in the newborn screening program of Minas Gerais.

METHODS

Neonates (1,168,385) were screened from May 2013 to June 2018. Those detected with abnormal biotinidase activity based on semi-quantitative assays underwent confirmatory serum tests. The biotinidase gene was sequenced in all confirmed cases.

RESULTS

The combined incidence of partial and profound biotinidase deficiency was estimated at 1:13,909 live births (95% confidence limit 1:11,235-1:17,217), much higher than the incidence rates reported in other populations worldwide. The most frequent biotinidase gene variants were p.D444H (allele frequency, 0.016), haplotype c.1330G>C;c.511G>A (p.D444H;A171T), p.D543E, c.310-15delT (intronic), p.V199M, and p.H485Q. Together these accounted for 74.6% of the alleles analysed.

CONCLUSION

Newborn screening for biotinidase deficiency, which revealed a higher incidence in Minas Gerais, is feasible and plays a critical role in the early identification of affected neonates and prevention of symptoms and irreversible sequelae. Biotinidase gene sequencing is a useful tool to confirm the diagnosis, and also provides valuable information about genetic variability among different populations.

Autosomal Recessive Cerebellar Ataxias: Paving the Way toward Targeted Molecular Therapies

Autosomal-recessive cerebellar ataxias (ARCAs) comprise a heterogeneous group of rare degenerative and metabolic genetic diseases that share the hallmark of progressive damage of the cerebellum and its associated tracts. This Review focuses on recent translational research in ARCAs and illustrates the steps from genetic characterization to preclinical and clinical trials. The emerging common pathways underlying ARCAs include three main clusters: mitochondrial dysfunction, impaired DNA repair, and complex lipid homeostasis. Novel ARCA treatments might target common hubs in pathogenesis by modulation of gene expression, stem cell transplantation, viral gene transfer, or interventions in faulty pathways. All these translational steps are addressed in current ARCA research, leading to the expectation that novel treatments for ARCAs will be reached in the next decade.

Genetic mimics of cerebral palsy

The term "cerebral palsy mimic" is used to describe a number of neurogenetic disorders that may present with motor symptoms in early childhood, resulting in a misdiagnosis of cerebral palsy. Cerebral palsy describes a heterogeneous group of neurodevelopmental disorders characterized by onset in infancy or early childhood of motor symptoms (including hypotonia, spasticity, dystonia, and chorea), often accompanied by developmental delay. The primary etiology of a cerebral palsy syndrome should always be identified if possible. This is particularly important in the case of genetic or metabolic disorders that have specific disease-modifying treatment. In this article, we discuss clinical features that should alert the clinician to the possibility of a cerebral palsy mimic, provide a practical framework for selecting and interpreting neuroimaging, biochemical, and genetic investigations, and highlight selected conditions that may present with predominant spasticity, dystonia/chorea, and ataxia. Making a precise diagnosis of a genetic disorder has important implications for treatment, and for advising the family regarding prognosis and genetic counseling. © 2019 International Parkinson and Movement Disorder Society.

Current strategies for the treatment of inborn errors of metabolism

Inborn errors of metabolism (IEMs) are a large group of inherited disorders characterized by disruption of metabolic pathways due to deficient enzymes, cofactors, or transporters. The rapid advances in the understanding of the molecular pathophysiology of many IEMs, have led to significant progress in the development of many new treatments. The institution and continued expansion of newborn screening provide the opportunity for early treatment, leading to reduced morbidity and mortality. This review provides an overview of the diverse therapeutic approaches and recent advances in the treatment of IEMs that focus on the basic principles of reducing substrate accumulation, replacing or enhancing absent or reduced enzyme or cofactor, and supplementing product deficiency. In addition, the challenges and obstacles of current treatment modalities and future treatment perspectives are reviewed and discussed.

Laboratory diagnosis of biotinidase deficiency, 2017 update: a technical standard and guideline of the American College of Medical Genetics and Genomics

Disclaimer: These ACMG Standards and Guidelines are intended as an educational resource for clinical laboratory geneticists to help them provide quality clinical laboratory genetic services. Adherence to these Standards and Guidelines is voluntary and does not necessarily assure a successful medical outcome. These Standards and Guidelines should not be considered inclusive of all proper procedures and tests or exclusive of others that are reasonably directed to obtaining the same results. In determining the propriety of any specific procedure or test, clinical laboratory geneticists should apply their professional judgment to the specific circumstances presented by the patient or specimen. Clinical laboratory scientists and geneticists are encouraged to document in the patient's record the rationale for the use of a particular procedure or test, whether or not it is in conformance with these Standards and Guidelines. They also are advised to take notice of the date any particular guideline was adopted, and to consider other relevant medical and scientific information that becomes available after that date. It also would be prudent to consider whether intellectual property interests may restrict the performance of certain tests and other procedures.Biotinidase deficiency is an autosomal recessively inherited disorder of biotin recycling that is associated with neurologic and cutaneous consequences if untreated. Fortunately, the clinical features of the disorder can be ameliorated or prevented by administering pharmacological doses of the vitamin biotin. Newborn screening and confirmatory diagnosis of biotinidase deficiency encompasses both enzymatic and molecular testing approaches. These guidelines were developed to define and standardize laboratory procedures for enzymatic biotinidase testing, to delineate situations for which follow-up molecular testing is warranted, and to characterize variables that can influence test performance and interpretation of results.

Treatable inherited rare movement disorders

There are many rare movement disorders, and new ones are described every year. Because they are not well recognized, they often go undiagnosed for long periods of time. However, early diagnosis is becoming increasingly important. Rapid advances in our understanding of the biological mechanisms responsible for many rare disorders have enabled the development of specific treatments for some of them. Well-known historical examples include Wilson disease and dopa-responsive dystonia, for which specific and highly effective treatments have life-altering effects. In recent years, similarly specific and effective treatments have been developed for more than 30 rare inherited movement disorders. These treatments include specific medications, dietary changes, avoidance or management of certain triggers, enzyme replacement therapy, and others. This list of treatable rare movement disorders is likely to grow during the next few years because a number of additional promising treatments are actively being developed or evaluated in clinical trials. © 2017 International Parkinson and Movement Disorder Society.

"Think metabolic" in adults with diagnostic challenges: Biotinidase deficiency as a paradigm disorder

Neurologists should consider the possibility of an inherited metabolic disorder in adults with neurologic symptoms that may or may not mimic those seen in affected children, such as in the case of biotinidase deficiency. Because many of these disorders are treatable, they must be included in the differential diagnosis. Technologies, such as specific biochemical analysis and whole exomic sequencing, can assist the clinician by leading to the appropriate diagnosis and treatment. Whole exomic sequencing can identify known and putative mutations in a patient's genome. The neurologist must "think metabolic" in sorting out complex and difficult cases.

Carvalho MR, S. Fonseca PA, S. Camelo J, M. Ribeiro E, F. V. de Medeiros P, M. Lourenço C, F. M. de Souza C, Boy R, Félix TM, M. Bittar C, L. C. Pinto L, C. Neto E, J. Blom H, D. Schwartz IV. Biotinidase deficiency: Genotype-biochemical phenotype association in Brazilian patients

Introduction

The association between the BTD genotype and biochemical phenotype [profound biotinidase deficiency (BD), partial BD or heterozygous activity] is not always consistent. This study aimed to investigate the genotype-biochemical phenotype association in patients with low biotinidase activity.

Methods

All exons, the 5'UTR and the promoter of the BTD gene were sequenced in 72 Brazilian individuals who exhibited low biotinidase activity. For each patient, the expected biochemical phenotype based on the known genotype was compared with the observed biochemical phenotype. Additional non-genetic factors that could affect the biotinidase activity were also analysed.

Results

Most individuals were identified by neonatal screening (n = 66/72). When consecutive results for the same patient were compared, age, prematurity and neonatal jaundice appeared to affect the level of biotinidase activity. The biochemical phenotype at the time of the second blood collection changed in 11/22 patients compared to results from the first sample. Three novel variants were found: c.1337T>C (p.L446P), c.1466A>G (p.N489S) and c.962G>A (p.W321*). Some patients with the same genotype presented different biochemical phenotypes. The expected and observed biochemical phenotypes agreed in 68.5% of cases (concordant patients). The non-coding variants c.-183G>A, c.-315A>G and c.-514C>T were present in heterozygosis in 5/17 discordant patients. In addition, c.-183G>A and c.-514C>T were also present in 10/37 concordant patients.

Conclusions

The variants found in the promoter region do not appear to have a strong impact on biotinidase activity. Since there is a disparity between the BTD genotype and biochemical phenotype, and biotinidase activity may be affected by both genetic and non-genetic factors, we suggest that the diagnosis of BD should be based on more than one measurement of plasma biotinidase activity. DNA analysis can be of additional relevance to differentiate between partial BD and heterozygosity.