Biotinidase deficiency: “if you have to have an inherited metabolic disease, this is the one to have”

Oxford nanopore sequencing-based assay for BTD gene screening: Design, clinical validation, and variant frequency assessment in the Turkish population

Biotinidase deficiency (BTD) is an autosomal recessive disorder characterized by impaired recycling of the water-soluble vitamin biotin which leads to a spectrum of clinical manifestations ranging from mild to severe, including mainly neurological and cutaneous symptoms. Biotin supplementation is a cornerstone of treatment, but diagnosis often relies on measuring serum enzyme activity, which needs to be confirmed by genetic analysis. Thus, molecular methods become necessary in the differential diagnosis of BTD. Accordingly, countries with a high-incidence have implemented next-generation sequencing (NGS) techniques to newborn screening programs for BT. Nevertheless, NGS platforms, while well-established, present challenges in cost, labor, accessibility, and duration for newborn screening programs targeting BTD, therefore these limitations necessitate the exploration of alternative systems to ensure efficient and widespread screening. Here, third-generation sequencing platforms, notably Oxford Nanopore Technology (ONT), present promising solutions to the associated challenges. Hence, in the present study, we aimed to develop an ONT-based assay for the screening of BTD gene. After designing and optimizing primers for long-PCR using reference DNA, we assessed the performance of the ONT assay in BTD patients previously diagnosed by enzyme assay and confirmed using Illumina-based sequencing. The results demonstrate a strong correlation between the two methods, indicating the reliability of the ONT-based assay. Moreover, this first in-house single gene testing specifically tailored for BTD successfully detected previously known genetic variants with high sequencing depths, affirming the effectiveness of ONT-based sequencing in human genetics.

Biallelic loss-of-function variations in BTD cause profound biotinidase deficiency in an Indian patient

BACKGROUND

Biotinidase deficiency (BD) is a rare, autosomal recessive metabolic disorder characterized by neurocutaneous symptoms. This study investigates a case of profound BD in an Indian infant and the underlying genetic basis.

METHODS

A 10-month-old male presenting with seizures, hypotonia, ataxia, visual impairments, and developmental delay underwent biochemical and genetic analysis. Biotinidase activity was measured using an ELISA kit. Sanger sequencing of the biotinidase (BTD) gene was performed to identify genetic variations. In silico analysis was employed to assess the potential impact of the identified variants.

RESULTS

The infant biotinidase activity was undetectable and its suggest profound biotinidase deficiency. Novel biallelic loss-of-function variations (c.903G > A and c.946 C > T) in the BTD gene were identified, leading to premature stop codons and truncated, non-functional protein fragments.

CONCLUSION

This case expands our knowledge of BD genetic diversity and underscores the critical role of early diagnosis and newborn screening programs in managing this treatable condition.

Exploiting urine-derived induced pluripotent stem cells for advancing precision medicine in cell therapy, disease modeling, and drug testing

The field of regenerative medicine has witnessed remarkable advancements with the emergence of induced pluripotent stem cells (iPSCs) derived from a variety of sources. Among these, urine-derived induced pluripotent stem cells (u-iPSCs) have garnered substantial attention due to their non-invasive and patient-friendly acquisition method. This review manuscript delves into the potential and application of u-iPSCs in advancing precision medicine, particularly in the realms of drug testing, disease modeling, and cell therapy. U-iPSCs are generated through the reprogramming of somatic cells found in urine samples, offering a unique and renewable source of patient-specific pluripotent cells. Their utility in drug testing has revolutionized the pharmaceutical industry by providing personalized platforms for drug screening, toxicity assessment, and efficacy evaluation. The availability of u-iPSCs with diverse genetic backgrounds facilitates the development of tailored therapeutic approaches, minimizing adverse effects and optimizing treatment outcomes. Furthermore, u-iPSCs have demonstrated remarkable efficacy in disease modeling, allowing researchers to recapitulate patient-specific pathologies in vitro. This not only enhances our understanding of disease mechanisms but also serves as a valuable tool for drug discovery and development. In addition, u-iPSC-based disease models offer a platform for studying rare and genetically complex diseases, often underserved by traditional research methods. The versatility of u-iPSCs extends to cell therapy applications, where they hold immense promise for regenerative medicine. Their potential to differentiate into various cell types, including neurons, cardiomyocytes, and hepatocytes, enables the development of patient-specific cell replacement therapies. This personalized approach can revolutionize the treatment of degenerative diseases, organ failure, and tissue damage by minimizing immune rejection and optimizing therapeutic outcomes. However, several challenges and considerations, such as standardization of reprogramming protocols, genomic stability, and scalability, must be addressed to fully exploit u-iPSCs' potential in precision medicine. In conclusion, this review underscores the transformative impact of u-iPSCs on advancing precision medicine and highlights the future prospects and challenges in harnessing this innovative technology for improved healthcare outcomes.

Ophthalmic manifestations of biotinidase deficiency: report of a case and review of literature

INTRODUCTION

Biotinidase deficiency (BD) is an inherited autosomal recessive metabolic disorder. BD has been associated with optic nerve atrophy, eye infections, and retinopathy. The most prevalent ophthalmic manifestation of BD is optic atrophy, which might be misdiagnosed as multiple sclerosis or neuromyelitis optica, especially in late-onset BD cases.

METHODS

In this article, we report a 9-year-old boy with gradual vision loss. Ophthalmologic examination, Brain MRI, and several laboratory tests such as Aquaporin-4 IgG level and biotinidase level were done on the patient.

RESULTS

Bilateral optic atrophy and impaired visual acuity were detected on examination. The patient had a biotin level of 1.25 U/min/ml (normal range 3-9 U/min/ml), favoring the BD.

CONCLUSION

In this study, we report a 9-year-old boy with vision loss diagnosed with BD. We also reviewed the literature to highlight the ophthalmic manifestations of BD. Ophthalmologists must consider BD in children with unexplained ophthalmologic complaints, especially when other characteristic signs of BD (e.g., developmental delay, seizure) are present. Also, patients with BD should undergo regular annual ophthalmologic examinations to be checked for any signs of eye involvement.

Treatable inherited metabolic epilepsies

Inherited metabolic epilepsies (IMEs) represent inherited metabolic disorders predominately presenting with seizures. While most IMEs are currently managed with symptomatic and supportive therapies, some are amenable to disorder-specific targeted treatments. In most cases, these treatments are effective only if given in a narrow time window early in the lives of affected patients. Hence, prompt recognition of treatable inherited metabolic epilepsies at an early age and as soon as symptoms appear has paramount importance. Herein, we provide an overview of inherited metabolic epilepsies, which presently have established targeted treatments showing clinical efficacy in reducing seizure burden and improving neurodevelopmental outcomes. These therapeutic modalities range from specific diets, vitamins, and supplementation of organic compounds to synthetic pharmacological agents and novel genetic-based therapies that alter the biochemical pathways of these disorders at the cellular or molecular level, steering them to their normal function.

To B(enign) or Not to B: functionalisation of variant in a mild form of argininosuccinate lyase deficiency identified through newborn screening

Argininosuccinate lyase (ASL) deficiency is an autosomal recessive disorder of the urea cycle with a diverse spectrum of clinical presentation that is detectable in newborn screening. We report an 8-year-old girl with ASL deficiency who was detected through newborn screening and was confirmed using biochemical and functional assay. She is compound heterozygous for a likely pathogenic variant NM_000048.4(ASL):c.283C>T (p.Arg95Cys) and a likely benign variant NM_000048.4(ASL): c.1319T>C (p.Leu440Pro). Functional characterisation of the likely benign genetic variant in ASL was performed. Genomic sequencing was performed on the index patient presenting with non-specific symptoms of poor feeding and lethargy and shown to have increased serum and urine argininosuccinic acid. Functional assay using HEK293T cell model was performed. ASL enzymatic activity was reduced for Leu440Pro. This study highlights the role of functional testing of a variant that may appear benign in a patient with a phenotype consistent with ASL deficiency, and reclassifies NM_000048.4(ASL): c.1319T>C (p.Leu440Pro) variant as likely pathogenic.

A different approach to the evaluation of the genotype-phenotype relationship in biotinidase deficiency: repeated measurement of biotinidase enzyme activity

OBJECTIVES

In the present study, we aimed to evaluate the genotype-phenotype relation in patients with biotinidase enzyme deficiency based on repeated biotinidase enzyme measurements.

METHODS

The hospital file information of patients with biotinidase, enzyme deficiency was assessed retrospectively, and the relationship between the BTD gene mutations analysis results and biotinidase enzyme activity following the first and repeated enzyme activity assessments was analyzed.

RESULTS

One-hundred-ten patients were included. In the first enzyme evaluation, profound biotinidase enzyme deficiency was identified in 15 (13.6 %), partial biotinidase enzyme deficiency in 63 (57.3 %), and heterozygous biotinidase enzyme deficiency in 32 (29.1 %) of the patients. The BTD genetic analysis revealed 42 (38.2 %) homozygous, 42 (38.2 %) heterozygous, and 26 (23.6 %) compound heterozygous variants. The most common homozygous variant, p.Asp444His, was evaluated with 130 repeated enzyme measurements and was consistent with a partial biotinidase enzyme deficiency in 55.4 % of cases, heterozygous biotinidase enzyme deficiency in 43.8 % of cases, and profound biotinidase enzyme deficiency in one (0.8 %) case. Clinical symptoms developed in 17 patients during follow-up, of which 70.6 % were related to neurodevelopment. The most common variant was homozygous p.Asp444His (29.4 %) among the patients who developed symptoms.

CONCLUSIONS

This is the first study to date to evaluate the genotype-phenotype relationship in patients with biotinidase deficiency through repeated measurements of biotinidase enzyme activity. The study reveals that biotinidase enzyme activity alone is inadequate for diagnosing biotinidase enzyme deficiency or evaluating disease severity, as genetic investigations are also required for a definitive diagnosis of biotinidase enzyme deficiency.

Analysis of Biotinidase Activity in Serum by Digital Imaging Colorimetry Detection

Biotinidase deficiency (BD) is an autosomal recessive inherited disorder of biotin recycling that leads to neurological and cutaneous consequences if left untreated. The clinical features of BD can be ameliorated or prevented by the administration of pharmacological doses of the vitamin biotin. Since it is a treatable disorder, BD is included in the newborn screening program in Türkiye as in many other countries. Therefore, monitoring of biotinidase enzyme activity (BEA) is of vital importance, especially for patients. The aim of this study was to develop a simple and reliable colorimetric method based on digital imaging for the analysis of BEA in serum samples. To determine the optimum distance and LED light source in the analyzer box that we fabricated in the laboratory, images of the solutions in a 96-well microplate were taken with a mobile phone camera, and each color space was examined. The most reliable relationship was between blank subtracted intensities of green channel and analyte concentrations, which was in the range of 35-400 ng/mL p-aminobenzoic acid (r2 = 0.999). The limit of detection and limit of quantification were 11 and 35 ng/mL, respectively. The proposed method was successfully applied to serum samples of 60 patients with BD and 60 healthy controls. We claim that the method can be easily performed for determination of BEA anywhere without needing expensive instruments.

Delayed Biotin Therapy in a Child with Atypical Profound Biotinidase Deficiency: Late Arrival of the Truth and a Lesson Worth Thinking

Biotinidase (BTD) deficiency (OMIM 253260) is an autosomal recessively inherited metabolic disorder resulting from deficient activity of the BTD enzyme, which can cleave and release biotin from a variety of biotin-dependent carboxylases, and is therefore recognized as a tool to recycle biotin. Being a condition caused by variations on BTD gene with a consequence of free biotin shortage, BTD deficiency may impair the activity of biotin-dependent carboxylases, and thus bring about a buildup of potentially toxic compounds in the body, primarily 3-hydroxyisovaleryl-carnitine in plasma as well as 3-hydroxyisovaleric acid in urine. The phenotype of BTD deficiency may vary dramatically, from asymptomatic adults to severe neurological anomalies, even death in infancy. In the present study, we reported on a 5-month-old boy, whose parents sought for medical consultation in our clinic for their son due to his loss of consciousness, repeated tetany, and motor retardation. Detailed clinical features included severe psychomotor retardation, hypotonia, as well as failure to thrive. The brain MRI at 12 months showed cerebellar hypoplasia and multiple foci of leukodystrophy. The result of antiepileptic therapy was not satisfying. During hospitalization, BTD deficiency was suggested by elevated concentration of 3-hydroxyisovaleryl-carnitine in the blood spots and 3-hydroxyisovaleric acid in the urine. The child was then diagnosed with profound BTD deficiency based on the above findings and low BTD enzyme activity. Subsequent mutational analysis revealed a novel homozygous variant, c.637_637delC (p.H213Tfs*51) in exon 4 of BTD gene in the proband, which was recognized as a further support to the diagnosis. Therefore, biotin treatment was started immediately, eventually with satisfactory outcomes achieved in terms of prevention of epileptic seizure, performance in deep tendon reflexes, and improvement of muscular hypotonia, but unfortunately, the therapy failed to show any evident effects on poor feeding and intellectual disability. This painful lesson suggests that newborn screening for inherited metabolic diseases is essential for early identification and treatment, which should have been performed in this case to avoid this tragedy.

Evaluation of 700 patients referred with a preliminary diagnosis of biotinidase deficiency by the national newborn metabolic screening program: a single-center experience

OBJECTIVES

This study aimed to investigate the clinical, demographic and laboratory characteristics of the patients referred with a preliminary diagnosis of biotinidase deficiency through the national newborn metabolic screening program. We also attempted to determine the cut-off level of the fluorometric method used for screening biotinidase deficiency by the Ministry of Health.

METHODS

A total of 700 subjects who were referred to the Pediatric Metabolism Outpatient Clinic with a preliminary diagnosis of biotinidase deficiency through the national newborn metabolic screening program were retrospectively evaluated. Patients detected by family screening were excluded. Biotinidase enzyme activity was assessed and BTD gene analysis was performed in all patients.

RESULTS

Of 700 subjects who were referred by the screening program, 284 (40.5 %) had biotinidase deficiency (BD). The enzyme activity was 0-10, 10-30 and >30 % in 39 (5.5 %), 245 (35 %) and 416 (59.5 %) patients, respectively. The BD was partial in majority of patients (86.2 %). The cut-off level was 59.5 MRU for partial BD and 50.5 MRU for profound BD. The most common mutation detected was p.Arg157His (c.470G>A) among patients with profound BD, and p.D444H (c.1330G>C) among patients with partial BD.

CONCLUSIONS

Treatment should be initiated promptly in patients who are referred by the newborn screening program. Any mean activity under 59.5 MRU should be considered partial BD, while less than 50.5 MRU should be considered profound BD. It should be kept in mind that clinical manifestations may develop both in profound and partial BD.

Biotinidase deficiency: What have we learned in forty years?

BACKGROUND

Biotinidase deficiency (BD) is an autosomal recessively inherited disorder that was first described in 1982. Forty years after its first description, we compiled available clinical data on BD with the aim of generating a more comprehensive picture of this condition.

METHODS

A systematic search strategy was performed in relevant databases without limits for publication date or languages. We screened 3966 records and included 144 articles reporting individuals with BD and their clinical presentation as well as the outcomes, when available.

RESULTS

This study included 1113 individuals with BD. More than half (51.5%) of these individuals were diagnosed by newborn screening, 43.3% in presence of clinical symptoms and 5.2% due to family screening. We grouped symptomatic individuals into four main clinical presentations: neonatal-onset (<1 month; 7.9%), early childhood-onset (<2 years; 59.2%), juvenile-onset (2-16 years; 25.1%) and adult-onset (>16 years; 7.7%). BD affected five main organ systems: nervous system (67.2%), skin (53.7%), eye (34.4%), auditory (26.9%) and respiratory system (17.8%). Involvement was mainly multisystemic (82.2%) of individuals, whereas isolated system presentation was seen in only 17.2% of individuals. When reported, metabolic acidosis was present in 42.4% of symptomatic individuals and characteristic abnormal organic acid metabolites were found in 57.1%. Biotin treatment led to clinical stability or improvement in 89.2% of individuals. 1.6% of reported individuals with BD died due to non-availability of treatment or late diagnosis.

CONCLUSION

Newborn screening has had a major positive impact on the outcome of many individuals with BD. However, undiagnosed and non-treated BD remains a health concern. Given the risk of mortality or complications associated with late or missed diagnosis if newborn screening is not available, a trial of biotin should be considered in undiagnosed infants and adults exhibiting suspected clinical signs. Enzymatic activity and/or analysis of genetic variants can readily confirm the diagnosis of BD.

A Rare Biotinidase Deficiency in the Pediatrics Population: Genotype-Phenotype Analysis

Biotinidase (BTD) deficiency is a rare autosomal recessive metabolic disorder caused by insufficient biotin metabolism, where it cannot recycle the vitamin biotin. When this deficiency is not treated with supplements, it can lead to severe neurological conditions. Approximately 1 in 60,000 newborns are affected by BTD deficiency. The BTD deficiency causes late-onset biotin-responsive multiple carboxylase deficiency, which leads to acidosis or lactic acidosis, hypoglycemia, and abnormal catabolism. BTD deficiency is of two types based on the amount of BTD Enzyme present in the serum. A wide range of pathogenic mutations in the BTD gene are reported worldwide. Mutations in the BTD gene lead to profound and partial BTD deficiency. Profound BTD deficiency results in a severe pathogenic condition. A high frequency of newborns are affected with the partial deficiency worldwide. They are mostly asymptomatic, but symptoms may appear during stressful conditions such as fasting or viral infections. Several pathogenic mutations are significantly associated with neurological, ophthalmological, and skin problems along with several other clinical features. This review discusses the BTD gene mutation in multiple populations detected with phenotypic features. The molecular-based biomarker screening is necessary for the disease during pregnancy, as it could be helpful for the early identification of BTD deficiency, providing a better treatment strategy. Moreover, implementing newborn screening for the BTD deficiency helps patients prevent several diseases.

Atopic Dermatitis-like Genodermatosis: Disease Diagnosis and Management

Eczema is a classical characteristic not only in atopic dermatitis but also in various genodermatosis. Patients suffering from primary immunodeficiency diseases such as hyper-immunoglobulin E syndromes, Wiskott-Aldrich syndrome, immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome, STAT5B deficiency, Omenn syndrome, atypical complete DiGeorge syndrome; metabolic disorders such as acrodermatitis enteropathy, multiple carboxylase deficiency, prolidase deficiency; and other rare syndromes like severe dermatitis, multiple allergies and metabolic wasting syndrome, Netherton syndrome, and peeling skin syndrome frequently perform with eczema-like lesions. These genodermatosis may be misguided in the context of eczematous phenotype. Misdiagnosis of severe disorders unavoidably affects appropriate treatment and leads to irreversible outcomes for patients, which underlines the importance of molecular diagnosis and genetic analysis. Here we conclude clinical manifestations, molecular mechanism, diagnosis and management of several eczema-related genodermatosis and provide accessible advice to physicians.

High Incidence of Partial Biotinidase Deficiency in the First 3 Years of a Regional Newborn Screening Program in Italy

Biotinidase deficiency (BD) is an autosomal recessive inherited disorder in which the enzyme biotinidase is totally or partially defective and the vitamin biotin is not recycled. BD meets the major criteria for a population screening program. Newborn bloodspot screening (NBS) allows early diagnosis of BD, thus preventing the high morbidity and mortality associated with untreated disease. Both profound and partial BD variant can be detected by NBS test, and serum enzyme activity and/or mutational analysis are required for definitive diagnosis. In Italy, BD is included in the screening panel for inborn errors of metabolism (IEMs) that has been declared mandatory in 2016. We analyzed the data of the first 3 years of the NBS for BD in our region (Abruzzo, Italy), with the aim to describe the outcomes of this recently introduced screening program. In over 26,393 newborns screened, we found 2 carriers and 16 cases with genotype associated with partial BD. Since the serum biotinidase assay has been recently introduced in our algorithm, only three of our newborns met the criteria of genetic and biochemical confirmation, with an incidence of 1:8797, which is in the high range of what has been reported in the literature. All affected infants carried the 1330G>C (D444H) variant in compound heterozygosis, with variants known to be associated with profound BD. A variant previously not described and likely pathogenic was found in one newborn. None of the infants had signs or symptoms. The study of the distribution of the enzyme activity in our population allowed us to validate the adopted cutoff with which the program has a positive predictive value of 18% and to analyze some preanalytical factors influencing biotinidase activity: A correlation of the enzyme activity with gestational age and time at specimen collection was found. Lower mean values of enzyme activity were found in infants born in the summer.

Late Onset Subacute Profound Biotinidase Deficiency Caused by a Novel Homozygous Variant c.466-3T>G in the BTD Gene

Biotinidase deficiency (BD) is an autosomal recessive disorder caused by bi-allelic mutation in the BTD gene. Clinical manifestations in BD mainly depends on residual biotinidase enzyme activity, although there are some exceptions. Broadly BD disorders are classified as profound BD and partial BD. Further profound BD can be early onset, late onset, and sometimes may be asymptomatic. Clinically late-onset profound BD can present with spectrum of manifestations ranging from single organ to multiple organ involvement, typically affecting function of brain, eye, ear, and skin. Here, a first-born child to consanguineous parents with late-onset profound BD presenting with hyperventilation secondary to lactic acidosis, hypotonia, evolving spasticity, and abnormal neuroimaging findings caused by novel homozygous variant, c.466-3T>G in the BTD gene is reported.

Rare Treatable Cause of Demyelinating Leukoencephalopathy That One Cannot Afford to Miss

Biotinidase deficiency is a treatable neurometabolic disorder. It usually presents during the first year of life with seizures, ataxia, hypotonia, vision and hearing disturbance, alopecia, and skin rashes. It can have various neuroimaging findings but demyelinating leukoencephalopathy is an unusual finding in children with biotinidase deficiency that can cause diagnostic challenge as it can radiologically mimic perinatal hypoxic–ischemic encephalopathy or other leukodystrophies. It reverses with early diagnosis and treatment with biotin supplementation and the outcome is rewarding.

Recovery of enzyme activity in biotinidase deficient individuals during early childhood

Deficiency of the biotinidase (BTD) enzyme is an inborn error of biotin metabolism caused by biallelic pathogenic variants in the BTD gene. There are two forms, partial and profound BTD deficiency, which both can be successfully treated with pharmacological doses of biotin, justifying the inclusion of this disorder in the newborn screening in numerous countries. We investigated the BTD deficiency cohort (N = 87) in our metabolic center, as it was detected upon newborn screening since 2005, and aimed to better understand the long-term course of BTD enzyme activity and how it may relate to the patients' genetic background. We observed that individuals with partial BTD deficiency display an elevation of BTD enzyme activity with increasing age in 48% of cases-a recovery which allowed adjustment or stop of biotin supplementation in 20% of all individuals. In addition, we were able to recruit 56 patients (64%) for genetic testing, revealing 19 different variants (2 novel), and constituting 22 different genotypes. Genotype-phenotype correlations revealed that the most abundant allele in our cohort p.(Asp444His) was also the most common variant in patients displaying recovery of BTD enzyme activity. Based on our results, we recommend to retest all patients with partial BTD deficiency at the age of 5 years, as this may result in an impact on therapy. Moreover, genetic testing of BTD deficient individuals can allow prediction of the severity of BTD deficiency and of the likelihood of BTD enzyme activity recovery with age.

Molecular Background and Disease Prevalence of Biotinidase Deficiency in a Polish Population—Data Based on the National Newborn Screening Programme

Biotinidase deficiency (BD) is a rare autosomal recessive metabolic disease. Previously the disease was identified only by clinical signs and symptoms, and since recently, it has been included in newborn screening programs (NBS) worldwide, though not commonly. In Europe, BD prevalence varies highly among different countries, e.g., from 1:7 116 in Turkey to 1:75 842 in Switzerland. This paper aimed to present the molecular spectrum of BD (profound and partial forms) in Polish patients diagnosed within the national NBS of 1,071,463 newborns. The initial suspicion of BD was based on an abnormal biotinidase activity result determined in a dry blood spot (DBS) by colorimetric and by fluorimetric methods while biochemical verification was determined by serum biotinidase activity (as quantitative analysis). The final diagnosis of BD was established by serum enzyme activity and the BTD gene direct sequencing. The obtained results allowed for the estimation of disease prevalence (1:66,966 births, while 1:178,577 for profound and 1:107,146 for partial forms), and gave novel data on the molecular etiology of BD.

Metabolomics analysis of post-traumatic stress disorder symptoms in World Trade Center responders

Metabolomics has yielded promising insights into the pathophysiology of post-traumatic stress disorder (PTSD). The current study expands understanding of the systems-level effects of metabolites by using global metabolomics and complex lipid profiling in plasma samples from 124 World Trade Center responders (56 PTSD, 68 control) on 1628 metabolites. Differential metabolomics analysis identified hexosylceramide HCER(26:1) associated with PTSD at FDR < 0.1. The multi-metabolite composite score achieved an AUC of 0.839 for PTSD versus unaffected control classification. Independent component analysis identified three metabolomic modules significantly associated with PTSD. These modules were significantly enriched in bile acid metabolism, fatty acid metabolism and pregnenolone steroids, which are involved in innate immunity, inflammatory process and neuronal excitability, respectively. Integrative analysis of metabolomics and our prior proteomics datasets on subsample of 96 responders identified seven proteomic modules significantly correlated with metabolic modules. Overall, our findings shed light on the molecular alterations and identify metabolomic-proteomic signatures associated with PTSD by using machine learning and network approaches to enhance understanding of the pathways implicated in PTSD. If present results are confirmed in follow-up studies, they may inform development of novel treatments.

Alterações auditivas e deficiência de biotinidase: revisão integrativa da literatura

ABSTRACT Purpose: to review the available literature on the relationship between hearing disorders and Biotinidase deficiency. Methods: a literature search carried out between October 2018 and August 2021, on the following databases: ELSEVIER, MEDLINE, SciELO, LILACS. Descriptors were used in English, Portuguese, and Spanish. PRISMA tools were used to select the articles and STROBE was used to analyze them. Literature Review: the selected articles were published between 1983 and 2020 and answered the guiding question of the research. Observational studies, case series studies, and case reports were included. Articles without a methodology description, or carried out by the same author and with the same sample were excluded. The initial search strategy identified 152 articles. After applying the inclusion and exclusion criteria, 14 articles were selected for this review. Conclusion: the presence of Biotin was often associated with auditory pathways origins. The literature suggested a relationship between Biotinidase deficiency and hearing disorders.

Hearing disorders and biotinidase deficiency: an integrative literature review

ABSTRACT Purpose: to review the available literature on the relationship between hearing disorders and Biotinidase deficiency. Methods: a literature search carried out between October 2018 and August 2021, on the following databases: ELSEVIER, MEDLINE, SciELO, LILACS. Descriptors were used in English, Portuguese, and Spanish. PRISMA tools were used to select the articles and STROBE was used to analyze them. Literature Review: the selected articles were published between 1983 and 2020 and answered the guiding question of the research. Observational studies, case series studies, and case reports were included. Articles without a methodology description, or carried out by the same author and with the same sample were excluded. The initial search strategy identified 152 articles. After applying the inclusion and exclusion criteria, 14 articles were selected for this review. Conclusion: the presence of Biotin was often associated with auditory pathways origins. The literature suggested a relationship between Biotinidase deficiency and hearing disorders.

Clinical, biochemical and genotypical characteristics in biotinidase deficiency

OBJECTIVES

Hypotonia, lethargy, eczema, alopecia, conjunctivitis, ataxia, hearing loss, optic atrophy, cognitive retardation, and seizures can occur in patients with biotinidase deficiency, and it is inherited as autosomal recessive. The aim of this study was to evaluate the cases followed up with the diagnosis of biotinidase deficiency in our unit, in terms of clinical, biochemical and genetic analyses.

METHODS

A total of 112 cases followed up in our centre with the diagnosis of biotinidase deficiency between August 2018-September 2020 were included in the study. Data were collected retrospectively.

RESULTS

A total of 112 cases (55.4% male, mean age: 2.2 ± 2.8 years) diagnosed with biotinidase deficiency were evaluated. Diagnoses were made by newborn screening in 90.2% of the cases, by family screening in 4.5%, and by investigating symptoms in 5.4%. The most frequently (27.5%) detected mutations were c.1330G>C (p.D444H)/c.1330G>C (p.D444H) homozygous mutation, followed by (13.0%) c.1330G>C (p.D444H)/c.470G>A (p.R157H) compound heterozygous mutation, and (13.0%) c.470G>A (p.R157H)/c.470G>A (p.R157H) homozygous mutation. Biotinidase enzyme levels were found to be higher in patients with the p.D444H homozygous mutation than patients with other mutations. Biotin treatment was started in all patients with enzyme deficiency.

CONCLUSIONS

Since the treatment is inexpensive and easily available, it is vital to detect this disease before symptom onset, especially findings related to the central nervous system, hearing and vision loss. In patients diagnosed with enzyme deficiency, the diagnosis should be definitively confirmed by genetic analysis.

Novel treatments in epilepsy guided by genetic diagnosis

In recent years, precision medicine has emerged as a new paradigm for improved and more individualized patient care. Its key objective is to provide the right treatment, to the right patient at the right time, by basing medical decisions on individual characteristics, including specific genetic biomarkers. In order to realize this objective researchers and physicians must first identify the underlying genetic cause; over the last 10 years, advances in genetics have made this possible for several monogenic epilepsies. Through next generation techniques, a precise genetic aetiology is attainable in 30-50% of genetic epilepsies beginning in the paediatric age. While committed in such search for novel genes carrying disease-causing variants, progress in the study of experimental models of epilepsy has also provided a better understanding of the mechanisms underlying the condition. Such advances are already being translated into improving care, management and treatment of some patients. Identification of a precise genetic aetiology can already direct physicians to prescribe treatments correcting specific metabolic defects, avoid antiseizure medicines that might aggravate functional consequences of the disease-causing variant or select the drugs that counteract the underlying, genetically determined, functional disturbance. Personalized, tailored treatments should not just focus on how to stop seizures but possibly prevent their onset and cure the disorder, often consisting of seizures and its comorbidities including cognitive, motor and behaviour deficiencies. This review discusses the therapeutic implications following a specific genetic diagnosis and the correlation between genetic findings, pathophysiological mechanisms and tailored seizure treatment, emphasizing the impact on current clinical practice.

Metabolic Epilepsy

Inborn errors of metabolism have been considered as an infrequent cause of epilepsy. Improvement in diagnostics has improved the detection of a metabolic basis of recurrent seizures in neonates and children. The term 'metabolic epilepsy' is used to suggest inherited metabolic disorders with predominant epileptic manifestations as well as those where epilepsy is part of the overall neurological phenotype. Several of these disorders are treatable, and the physician should bear in mind the classical ages of presentation. As there are no specific clinical or electrographic features suggestive of metabolic epilepsies, an early suspicion is based on clinical and laboratory clues. Fortunately, with the advancement of gene sequencing technology, a diagnosis of these rare conditions is more straightforward and may not require invasive procedures such as biopsies, multiple metabolic stress-induced testing for abnormalities, and cerebrospinal fluid analysis. A gene panel may suffice in most cases and can be done from a blood sample. In many countries, many treatable metabolic disorders are now part of the neonatal screen. Early diagnosis and treatment of these disorders can result in the prevention of a full-scale metabolic crisis and improvement of neurological outcomes. Long-term neurological outcomes are variable and additional therapies may be required.

Juvenile progressive optic atrophy as the presenting feature of biotinidase deficiency, a treatable metabolic disorder

A 10-year-old girl initially diagnosed with functional visual loss was later diagnosed with progressive optic atrophy. Directed questioning at 13 years of age revealed difficulty hearing that had not been noted by the parents. Whole exome sequencing and subsequent metabolic testing confirmed biotinidase deficiency. Although biotinidase deficiency classically manifests in early childhood with multiple manifestations, such as seizures and failure to thrive, a delayed-onset form can present primarily as juvenile progressive optic atrophy. Early diagnosis is critical because biotin supplementation prevents disease and deterioration.

Toxicologic evaluation of a novel, highly soluble biotin salt, magnesium biotinate

A novel, highly soluble biotin salt, magnesium biotinate (MgB), was assessed for general and genetic toxicity using several toxicologic tests. This battery of tests included in vitro bacterial reverse mutation test, in vitro mammalian micronucleus assay, and oral acute, 14-day, and 90-day repeat-dose toxicity in Sprague-Dawley (SD) rats. The results of the in vitro studies indicate that MgB is not mutagenic, clastogenic, or aneugenic. The acute oral toxicity study established an LD50 ≥ 5000 mg MgB/kg. In the 14-day oral toxicity study, doses of MgB up to 2500 mg MgB/kg/day produced no clinical signs or mortality. In the 90-day oral toxicity study, administration of 600 mg MgB/kg/day resulted in no clinical signs and was determined to be the no-observed-adverse-effect-level (NOAEL), which equates to 39 g biotin/day for a 70 kg human. Since MgB is composed of 93% biotin, the 600 mg NOAEL equates to approximately 1.3 million times the current recommended daily allowance of 30 μg biotin/day and 3900 times supplement levels of 10 mg biotin/day. Based on the toxicologic profile and lack of findings in various in vitro and in vivo studies, MgB may be considered safe for long-term human use.

Gut microbiota-derived vitamins - underrated powers of a multipotent ally in psychiatric health and disease

Despite the well-established roles of B-vitamins and their deficiencies in health and disease, there is growing evidence indicating a key role of those nutrients in functions of the central nervous system and in psychopathology. Clinical data indicate the substantial role of B-vitamins in various psychiatric disorders, including major depression, bipolar disorder, schizophrenia, autism, and dementia, including Alzheimer's and Parkinson's diseases. As enzymatic cofactors, B-vitamins are involved in many physiological processes such as the metabolism of glucose, fatty acids and amino acids, metabolism of tryptophan in the kynurenine pathway, homocysteine metabolism, synthesis and metabolism of various neurotransmitters and neurohormones including serotonin, dopamine, adrenaline, acetylcholine, GABA, glutamate, D-serine, glycine, histamine and melatonin. Those vitamins are highly involved in brain energetic metabolism and respiration at the cellular level. They have a broad range of anti-inflammatory, immunomodulatory, antioxidant and neuroprotective properties. Furthermore, some of those vitamins are involved in the regulation of permeability of the intestinal and blood-brain barriers. Despite the fact that a substantial amount of the above vitamins is acquired from various dietary sources, deficiencies are not uncommon, and it is estimated that micronutrient deficiencies affect about two billion people worldwide. The majority of gut-resident microbes and the broad range of bacteria available in fermented food, express genetic machinery enabling the synthesis and metabolism of B-vitamins and, consequently, intestinal microbiota and fermented food rich in probiotic bacteria are essential sources of B-vitamins for humans. All in all, there is growing evidence that intestinal bacteria-derived vitamins play a significant role in physiology and that dysregulation of the "microbiota-vitamins frontier" is related to various disorders. In this review, we will discuss the role of vitamins in mental health and explore the perspectives and potential of how gut microbiota-derived vitamins could contribute to mental health and psychiatric treatment.

Partial Biotinidase Deficiency Revealed Imbalances in Acylcarnitines Profile at Tandem Mass Spectrometry Newborn Screening

Biotinidase (BTD) deficiency is an autosomal recessive inherited neurocutaneous disorder. BTD recycles the vitamin biotin, a coenzyme essential for the function of four biotin-dependent carboxylases, including propionyl-CoA carboxylase, 3-methylcrotonyl-CoA carboxylase, pyruvate carboxylase, and acetyl-CoA carboxylase. Due to deficient activities of the carboxylases, BTD deficiency is also recognized as late-onset multiple carboxylase deficiency and is associated with secondary alterations in the metabolism of amino acids, carbohydrates, and fatty acids. BTD deficiency can be classified as "profound", with less than 10% of mean normal activity, and as "partial" with 10-30% of mean normal activity. Newborn screening (NBS) of BTD deficiency is performed in most countries and is able to detect both variants. Moreover, mild metabolic alterations related to carboxylase deficiency in profound BTD deficiency could result and possibly be revealed in the metabolic profile by tandem mass spectrometry (MS/MS) NBS. Here, we report the case of a newborn female infant with an initial suspected BTD deficiency at the NBS test, finally confirmed as a partial variant by molecular testing. Although BTD deficiency was partial, interestingly her metabolic profile at birth and during the follow-up tests revealed, for the first time, alterations in specific acylcarnitines as a possible result of the deficient activity of biotin-dependent carboxylases.

Female and male perspectives on male partner roles in expanded carrier screening

PURPOSE

To explore facilitators and barriers for male partner follow through carrier screening (CS) after their female partners were identified as carriers, from both male and female perspectives.

METHODS

Participants were either females identified as a carrier through CS (512 participants) or males who had CS (125 participants). Participants were recruited via e-mails with survey links. The survey explored factors surrounding decisions to pursue CS or not.

RESULTS

Males who attended the females' CS appointment were more likely to have CS (OR: 2.07). More male partners of females identified as carriers of severe or profound conditions pursued CS (82.0%) than male partners of females who were carriers for moderate conditions (50.0%). Logistic factors were more impactful for males who pursued CS. Females whose male partners did not test endorsed personal belief factors as most impactful, reporting the perceived low risk (75.0%) and his low concern for the specific condition (65.5%) were the top reasons their partners did not test.

CONCLUSION

Many factors impact how male partners appraise reproductive risk from CS and make decisions regarding their own screening. Advising that male partners attend CS appointments may increase the likelihood of follow through CS. Thorough and repeated risk counseling is indicated.

Evaluation of the efficiency of serum biotinidase activity as a newborn screening test in Turkey

OBJECTIVES

Biotinidase Deficiency (BD) is an autosomal recessive metabolic disorder. However, the relationship between genotype and biochemical phenotype has not been completely elucidated yet. But still, some mutations are accepted to be associated with profound or partial deficiency. We aimed to evaluate the results of biochemical enzyme activity in accordance with the presence of genetic mutations and investigate the correlation between genotype and biochemical phenotype together in the study.

METHODS

This retrospective study was carried out using data from medical records of 133 infants detected by the newborn screening followed by serum biotinidase activity (BA) detection with semi-quantitative colorimetric method. Mutation analysis was performed to confirm the diagnosis. In addition, the expected biochemical phenotype based on the known mutant alleles were compared with the observed biochemical phenotype.

RESULTS

When confirmed with mutation analysis results, the diagnostic sensitivity and specificity of serum BA with spectrophotometric method was 93.1% and 95.1%, respectively. In 93.98% of the cases conformity was observed between the biochemical phenotype and the genotype. The c.1330 G>C(p.D444H) and c.470 G>A (p.Arg157His) were the most common allelic variants with frequencies of 63.69% and 33.75%, respectively.

CONCLUSIONS

The diagnostic test is supposed to have a high sensitivity to identify asymptomatic BD patients. Apparently healthy cases with almost normal enzyme activity and a variant allele in the genetic analysis were reported to present symptoms under stress conditions, which should be kept in mind. This study can be accepted as an informative report as it may contribute to the literature in terms of the allelic frequency and determination of the relation between genotype and biochemical phenotype. Also, method verification including the assessment of possible effects of non-genetic factors on BA according to the certain mutation types is warranted.

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.

Delayed Diagnosis of Congenital Hypothyroidism in a Child with Trisomy 21 and Biotinidase Deficiency and Successful Use of Levothyroxine Sodium Oral Solution

Endocrine disorders are more common and appear earlier in people with trisomy 21 (T21) than in the general population, with thyroid dysfunction being the most common, including both congenital and acquired hypothyroidism. The treatment for biotinidase deficiency, a condition that occurs in approximately 1 : 110,000 people, is with biotin (vitamin B7) supplementation. However, biotin can interfere with endocrine laboratory assays and cause falsely low thyroid-stimulating hormone (TSH) and elevated free thyroxine (FT4) levels. This can interfere with the timely diagnosis and subsequent treatment of congenital hypothyroidism (CH). This case report describes an infant with partial biotinidase deficiency that was confirmed on day 10 of life. Routine screening erroneously reported "normal" TSH that caused delayed diagnosis of CH due to interference with the TSH assay from concurrent biotin use. Once the biotin treatment was withheld for 4 days and the thyroid function tests repeated, an elevated TSH became apparent. Treatment with tablet levothyroxine (L-T4) was started and subsequently changed to L-T4 oral solution (Tirosint®-SOL) to overcome treatment administration difficulties encountered with the tablet form. This resulted in improved TSH control due to more accurate and consistent dosing compared with the tablet formulation. This is the first report of the use of L-T4 oral solution in an infant with T21 and biotinidase deficiency.

Severe Distal Motor Involvement in a Non-compliant Adult With Biotinidase Deficiency: The Necessity of Life-Long Biotin Therapy

Biotinidase deficiency is an autosomal recessive disorder in which affected individuals are unable to recycle biotin. Untreated, children usually exhibit hypotonia, seizures, ataxia, developmental delay, and/or hearing loss. Individuals diagnosed by newborn screening have an excellent prognosis with life-long biotin supplementation. We report a young adult diagnosed with profound biotinidase deficiency by newborn screening who was asymptomatic while on therapy. At 18 years of age, 6 months after voluntarily discontinuation of biotin, he developed a progressive distal muscle weakness. Molecular analysis of the BTD gene showed a pathogenic homozygous duplication c.1372_1373dupT p.(Cys458LeufsTer26) (1). Despite 16 months since reintroduction of biotin, muscle strength only partially recovered. Transition to adulthood in chronic metabolic diseases is known to be associated with an increased risk for non-compliance. Neurological findings in this adult are similar to those described in others with adult-onset biotinidase deficiency. Long-term prognosis in non-compliant symptomatic adult with biotinidase deficiency likely depends on the delay and/or severity of intervening symptoms until reintroduction of biotin.

Biotinidase deficiency in differential diagnosis of neuromyelitis optica spectrum disorder

We present a case of biotinidase deficiency mimicking neuromyelitis optica spectrum disorder (NMOSD) with tetraparesis and transverse myelitis, who was diagnosed with profound biotinidase deficiency after developing optic atrophy and hearing loss before the age of one year, and was untreated for six months. Biotinidase deficiency should be considered in the differential diagnosis of seronegative NMOSD.

Spinal cord demyelination in children: A diagnostic challenge in neuropaediatrics for a good outcome

BACKGROUND

Biotinidase deficiency (BTD) is an autosomal recessive inborn error of metabolism provoking progressive biotin depletion, which causes, in turn, multiple carboxylase deficiency. Its infantile onset is characterized by intractable seizures associated with lethargy, psychomotor regression, hypotonia, feeding and respiratory problems, and cutaneous abnormalities.

CASE DESCRIPTION

We describe a 52-month-old female whose clinical and neuroradiological pictures were consistent with myelopathy, which is generally more frequent in older patients, as well as with symptoms of an infantile onset of biotinidase deficiency, revealed at 17 months.

RESULTS

A biochemical biotinidase test revealed a profound deficiency of biotinidase detecting a 10% residual enzymatic activity, which led to the diagnosis of BTD. Gene sequencing revealed a compound heterozigous mutation (c.454A > C/c.1612C > T).

CONCLUSION

Our findings suggest that even if myelopathy is uncommonly reported in BTD, and generally occurs in older children, its presence in childhood-onset floppiness should always be considered as a possible marker for an atypical presentation of BTD. Although, until recently, BTD myelopathy was believed to be prevalent in older children, a spinal cord involvement has also been described in at least nine cases in early infancy. Thus, another early diagnosis suggests that myelopathy may be more frequent than previously thought, and it is probably underdiagnosed because spinal MRI is not always routinely performed on these children. Early recognition of BTD disease is important as it would lead to prompt treatment, preventing irreversible brain damage and increasing the chances of complete recovery.

StanDep: Capturing transcriptomic variability improves context-specific metabolic models

Diverse algorithms can integrate transcriptomics with genome-scale metabolic models (GEMs) to build context-specific metabolic models. These algorithms require identification of a list of high confidence (core) reactions from transcriptomics, but parameters related to identification of core reactions, such as thresholding of expression profiles, can significantly change model content. Importantly, current thresholding approaches are burdened with setting singular arbitrary thresholds for all genes; thus, resulting in removal of enzymes needed in small amounts and even many housekeeping genes. Here, we describe StanDep, a novel heuristic method for using transcriptomics to identify core reactions prior to building context-specific metabolic models. StanDep clusters gene expression data based on their expression pattern across different contexts and determines thresholds for each cluster using data-dependent statistics, specifically standard deviation and mean. To demonstrate the use of StanDep, we built hundreds of models for the NCI-60 cancer cell lines. These models successfully increased the inclusion of housekeeping reactions, which are often lost in models built using standard thresholding approaches. Further, StanDep also provided a transcriptomic explanation for inclusion of lowly expressed reactions that were otherwise only supported by model extraction methods. Our study also provides novel insights into how cells may deal with context-specific and ubiquitous functions. StanDep, as a MATLAB toolbox, is available at https://github.com/LewisLabUCSD/StanDep.

Biotinidase Deficiency: Prevalence, Impact And Management Strategies

Biotinidase deficiency is an autosomal recessive inherited neurocutaneous disorder. Clinically untreated patients with BD can present with variable neurological and dermatological signs, such as seizures, hypotonia, feeding problems, developmental delay, hearing loss, optic atrophy ataxia, alopecia, and skin rash. Clinical findings of patients with partial BD reported in the literature show that it can occur from infancy to adulthood. Outcomes of newborn screening programs support the fact that biotin treatment started after birth prevents patients with biotinidase deficiency from developing symptoms. Presence of late-onset cases with different clinical findings indicates that there is still much to learn about BD.

Clinical, biochemical and mutational findings in biotinidase deficiency among Malaysian population

Introduction

Biotinidase deficiency (BD) is an autosomal recessively inherited disorder characterized by developmental delay, seizures, hypotonia, ataxia, skin rash/eczema, alopecia, conjunctivitis/visual problem/optic atrophy and metabolic acidosis. Delayed diagnosis may lead to irreversible neurological damage.

Methodology

Clinically suspected patients were screened for biotinidase level by a fluorometry method. Profound BD patients were confirmed by mutation analysis of BTD gene.

Results

9 patients had biotinidase activity of less than 77 U. 3 patients (33%) had profound BD while 6 patients (67%) had partial BD. Compound heterozygous mutations were detected at c.98_104delinsTCC p.(Cys33Phefs*36) in Exon 2 and c.833T>C p.(Leu278Pro) in Exon 4 in two patients and a homozygous mutation at c.98_104delinsTCC p.(Cys33Phefs*36) in Exon 2 in another patient.

Conclusion

Correct diagnosis lead to early treatment and accurate management of patient. Biochemical screening of BD in symptomatic child is prerequisite to determine enzyme status however molecular confirmation is vital in differentiating individuals with profound biotinidase deficiency from partial biotinidase deficiency and also individuals' carriers.

Identification and Characterization of BTD Gene Mutations in Jordanian Children with Biotinidase Deficiency

Biotinidase deficiency is an autosomal recessive metabolic disorder whose diagnosis currently depends on clinical symptoms and a biotinidase enzyme assay. This study aimed to investigate the mutational status and enzymatic activity of biotinidase deficiency in seven unrelated Jordanian families including 10 patients and 17 healthy family members. Amplified DNA was analyzed by the automated Sanger sequencing method, and the enzymatic assay was performed using a colorimetric assessment. Biotinidase level was significantly lower (p < 0.001) in BTD children compare to their non-affected family members. Genetic sequencing revealed six different mutations in Jordanian patients. One mutation was novel and located in exon 4, which could be a prevalent mutation for biotinidase deficiency in the Jordanian population. Identification of these common mutations and combing the enzymatic activity with genotypic data will help clinicians with regard to better genetic counseling and management through implementing prevention programs in the future.

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.