Biotinidase Deficiency Research Articles

Intractable or refractory epilepsy

The prognosis for those suffering from frequent seizures will be closely linked to their etiology (1). If there is extensive brain damage, whether this results from trauma, disease, or brain tumors, there is likely to be a poor response to whatever treatment is given. The more diffuse the lesions the worse this will be: and localisation is also a factor, for example mesial temporal sclerosis causing complex partial seizures. For these reasons patients who are mentally handicapped often have the additional handicap of epilepsy (2). The best chance of controlling the fits lies in making an accurate diagnosis and applying appropriate treatment, whether this is surgery to remove a tumor or the identification of a metabolic disorder which can be controlled, such as pyridoxine dependency or biotinidase deficiency (3). It is important to identify epileptic syndromes, often genetically determined, so that at least an accurate prognosis can be given, even if this does not effect treatment. For example the prognosis for infantile spasms and the Lennox-Gastaut syndrome are well known (4). Tuberous sclerosis is another diagnosis to be viewed with concern. Even within the field of epilepsy there are important diagnostic issues; for instance differentiating minor seizures from reflex anoxic seizures, and absence epilepsy and pseudoseizures from complex partial seizures (5). EDITORIAL

A microsphere-based assay for mutation analysis of the biotinidase gene using dried blood spots

Biotinidase deficiency is an autosomal recessive syndrome caused by defects in the biotinidase gene, the product of which affects biotin metabolism. Newborn screening (NBS) for biotinidase deficiency can identify affected infants prior to onset of symptoms; biotin supplementation can resolve or prevent the clinical features. In NBS, dry blood spots (DBS) are usually tested for biotinidase enzyme activity by colorimetric analysis. By taking advantage of the multiplexing capabilities of the Luminex platform, we have developed a microsphere-based array genotyping method for the simultaneous detection of six disease causing mutations in the biotinidase gene, thereby permitting a second tier of molecular analysis. Genomic DNA was extracted from 3.2 mm DBS. Biotinidase gene sequences, containing the mutations of interest, were amplified by multiplexed polymerase chain reaction, followed by multiplexed allele-specific primer extension using universally tagged genotyping primers. The products were then hybridized to anti-tag carrying xTAG microspheres and detected on the Luminex platform. Genotypes were verified by sequencing. Genotyping results of 22 known biotinidase deficient samples by our xTAG biotinidase assay was in concordance with the results obtained from DNA sequencing, for all 6 mutations used in our panel. These results indicate that genotyping by an xTAG microsphere-based array is accurate, flexible, and can be adapted for high-throughput. Since NBS for biotinidase deficiency is by enzymatic assay, less than optimal quality of the DBS itself can compromise enzyme activity, while the DNA from these samples mostly remains unaffected. This assay warrants evaluation as a viable complement to the biotinidase semi-quantitative colorimetric assay.

Cost-Effectiveness Analysis of a National Newborn Screening Program for Biotinidase Deficiency

Cost-Effectiveness Analysis of a National Newborn Screening Program for Biotinidase Deficiency

Improved Identification of Partial Biotinidase Deficiency by Newborn Screening Using Age-Related Enzyme Activity Cutoffs: Reduction of the False-Positive Rate

Background: Biotinidase deficiency is an inherited metabolic disorder that if untreated can result in neurological and cutaneous features. Profound biotinidase deficiency presents in early childhood with severe symptoms, whereas partial biotinidase deficiency can also present with symptoms under times of stress. Symptoms can be prevented by administering biotin. Newborn screening for the disorder is performed using dried blood spots. We examined the relationship between biotinidase activity and age at collection to determine how best to identify infants with partial biotinidase deficiency. Methods: Biotinidase activity in dried blood spots is determined using a quantitative fluorometric assay. Subsequent specimens with biotinidase activity ≤100 U were analyzed by mutation analysis to determine the range of activities expressed in infants with partial biotinidase deficiency. Results: Enzyme activity increased with age, beginning at about three days of age, and rose until plateauing at about 11 days of age. An increase of about 47.6% was observed. A total of 54 specimens had mutation analysis performed identifying 20 affected infants who would not have been identified using the original cutoff activity of 50 U. Conclusion: Biotinidase activity in infants increases with age. Age-related cutoffs assist in selectively identifying infants with partial biotinidase deficiency.

Inherited metabolic disorders in Turkish patients with autism spectrum disorders.

Autism spectrum disorders (ASDs) are a major health problem because of their high prevalence in the general population. The pathophysiology of ASD remains unclear, although genetic defects may be detected in 10-20% of affected patients. Among these cases, the prevalence of inherited metabolic disorders (IMD) has not been extensively evaluated. IMDs responsible for ASDs are usually identified via clinical manifestations such as microcephaly, dysmorphic features, convulsions, and hepatosplenomegaly. Infrequently, patients with no additional clinical symptoms suggestive of an IMD may be diagnosed as having an idiopathic ASD. High consanguinity rates have resulted in an increased prevalence of IMDs in the Turkish population. The aim of this study was to explore the benefits of systematic screening for IMD among Turkish patients with ASDs. In our study, data were retrospectively collected for 778 children with ASDs. In all cases, the metabolic investigations included an arterial blood gas analysis, serum ammonia and lactate levels, a quantitative plasma amino acid analysis, a whole blood acylcarnitine profile via tandem mass spectrometry and a urine organic acid profile. Urinary glycosaminoglycan levels and homocysteine levels were screened in selected cases; 300 of the 778 patients with ASDs whose physical and metabolic investigations were complete and met this study's criteria were enrolled. Among the 300 children with autism, IMD were diagnosed in nine patients as follows: two patients were diagnosed with phenylketonuria, and one patient was diagnosed with partial biotinidase deficiency; one patient was diagnosed with mucopolysaccharidosis type III, and one patient was diagnosed with classical homocystinuria; one patient was diagnosed with glutaric acidemia type 1, and one patient was diagnosed with short chain acyl-CoA dehydrogenase deficiency; one patient was diagnosed with argininemia, and one patient was diagnosed with L-2-hydroxyglutaric aciduria.

Secondary Hemophagocytosis in Propionic Acidemia.

Secondary Hemophagocytosis in Propionic Acidemia.

Neurometabolic Disorders-Related Early Childhood Epilepsy: A Single-Center Experience in Saudi Arabia

Data on the pattern of epilepsy caused by metabolic disorders in the first 2 years of life are limited in developing countries. We aimed to identify the metabolic causes of epilepsy presented in the first 2 years of life and to describe their clinical, radiological, molecular, and electroencephalographic characteristics. This retrospective study was conducted between January 2010 and December 2011 at Saad Specialist Hospital (Al Khobar, Saudi Arabia). All patients younger than 2 years at the onset of epilepsy caused by metabolic disorders were reviewed. The International League Against Epilepsy definition was used, and febrile convulsion was excluded. Of 221 children diagnosed with epilepsy in the first 2 years of life at our hospital, 24 had metabolic diseases. The characteristics of these 24 children included the following: consanguinity in 18 patients (75%), developmental delay in 13 (54%), generalized tonic-clonic seizures in 10 (42%), infantile spasms in four (17%), myoclonic in seven (29%), and focal seizures in three. The diagnosis was confirmed by DNA studies in 17 patients (71%) and enzyme assay in seven (29%). The main diagnoses were peroxisomal disorders (n=3), nonketotic hyperglycinemia (n=3), Menkes disease (n=2), neuronal ceroid lipofuscinosis (n=2), biotinidase deficiency (n=2), and mitochondrial disorder (n=2). The remaining patients had lysosomal storage disease, aminoacidopathy, fatty acid oxidation defects, and organic aciduria. Seizure freedom was achieved in one third of patients in this cohort. Different metabolic disorders were identified in this cohort, which caused different types of epilepsy, especially myoclonic seizures and infantile spasms.

Biotinidase deficiency due to a de novo mutation or gonadal mosaicism in a first child

Biotinidase deficiency (BD), which is caused by BTD genetic lesions, if untreated, can result in neurological and cutaneous manifestations. Biotin supplementation can improve or prevent symptoms.We herewith present a family, which we studied at biochemical and molecular level, after identifying the proband through a newborn screening programme. BTD gene molecular analysis showed the proband to be compound heterozygous for the c.1330G>C p.(Asp444His) mild known variant, and for the c.1475 C>T p.(Thr492Ile) new variant. Bioinformatic analysis allowed us to confirm the pathogenic role of the newly identified variant.The proband's father, who exhibited low biotinidase (BTD) enzyme activity, was homozygous for the mild variant, whereas the proband's mother, who exhibited borderline BTD values, the BTD mutation carrier status could not be detected.This is the first description of a patient with BD harbouring a variant whose origin is either de novo or the consequence of gonadal mosaicism.BTD molecular analysis and bioinformatic tools for the evaluation of pathogenicity of newly identified variants are necessary for diagnostic purposes (i.e., clarifying borderline enzyme assays and the carrier status of parents), and for genetic counselling.

Detection of biotinidase gene mutations in Turkish patients ascertained by newborn and family screening.

The incidence of biotinidase deficiency in Turkey is currently one of the highest in the world. To expand upon the information about the biotinidase gene (BTD) variations in Turkish patients, we conducted a mutation screening in a large series (n = 210) of probands with biotinidase deficiency, using denaturing high-performance liquid chromatography and direct DNA sequencing. The putative effects of novel mutations were predicted by computational program. Twenty-six mutations, including six novels (p.C143F, p.T244I, c.1212-1222del11, c.1320delG, p.V457L, p.G480R) were identified. Nine of the patients were symptomatic at the initial clinical assessment with presentations of seizures, encephalopathy, and lactic acidemia. The most common mutation in this group of symptomatic patients was c.98-104 del7ins3. Among the screened patients, 72 have partial and 134 have profound biotinidase deficiency (BD) of which 106 are homozygous for BTD mutations. The common mutations (p.R157H, p.D444H, c.98-104del7ins3, p.T532M) cumulatively accounted for 72.3% of all the mutant alleles in the Turkish population. The identification of common mutations and hot spot regions of the BTD gene in Turkish patients is important for mutation screening in the Turkish population and helps to ascertain carriers, may have impact on genetic counseling and implementing prevention programs.

The Story of Biotinidase Deficiency and Its Introduction into Newborn Screening: The Role of Serendipity

Today, all of the states in the United States and many countries screen their newborns for biotinidase deficiency. Biotinidase deficiency meets the major criteria for including a disorder into screening programs. However, rarely do we learn the actual story behind the discovery of a disorder where the underlying etiology was elusive or about the events leading to a disorder’s incorporation into a newborn screening program. This is the story of the role that serendipity played in the story of biotinidase deficiency and the newborn screening of the disorder.

First contiguous gene deletion causing biotinidase deficiency: The enzyme deficiency in three Sri Lankan children

We report three symptomatic children with profound biotinidase deficiency from Sri Lanka. All three children presented with typical clinical features of the disorder. The first is homozygous for a missense mutation in the BTD gene (c.98_104 del7insTCC; p.Cys33PhefsX36) that is commonly seen in the western countries, the second is homozygous for a novel missense mutation (p.Ala439Asp), and the third is the first reported instance of a contiguous gene deletion causing the enzyme deficiency. In addition, this latter finding exemplifies the importance of considering a deletion within the BTD gene for reconciling enzymatic activity with genotype, which can occur in asymptomatic children who are identified by newborn screening.

Why screen newborns for profound and partial biotinidase deficiency?

Newborn screening for biotinidase deficiency is currently performed throughout the United States and inmany countries of the world. However, there are still many countries that do not screen for the disorder. After learning howmany countries are still not screening for biotinidase deficiency, and after I received the comments on a recently submitted publication, I was compelled to address twomajor concerns about newborn screening for the disorder. The first is why should a country screen their newborns for profound biotinidase deficiency (less than 10% of mean normal serum enzyme activity)? The second is, if a country screens their newborns for profound biotinidase deficiency, why should they also screen for partial biotinidase deficiency (between10% and 30% of mean normal serum enzyme activity)? Before addressing these issues, Iwould like to state that over thepast 32 years, my research has focused on the study of the clinical, biochemical and molecular aspects of biotinidase deficiency. Even though my laboratory developed the colorimetric assay for biotinidase activity using blood-soaked filter paper cards, and we conducted the first newborn screening program in Virginia, I have not received, nor do I currently receive, any compensation for any aspect of newborn screening of the disorder. This being said, I would like to address the above questions. Why screen newborns for profound biotinidase deficiency? Since the discovery of biotinidase deficiency in our laboratory in 1982 [1,2], there has been a rapid transition from the development of a colorimetric method for determining biotinidase activity using blood-soaked filter paper spots [3] to the demonstration of the feasibility of performing

Clinical, Biochemical and Outcome Profile of Biotinidase Deficient Patients from Tertiary Centre in Northern India.

Biotinidase deficiency is an inherited metabolic disorder with estimated birth incidence of 1 in 61,000 for profound and partial deficiency. Estimated incidence of profound and partial biotinidase deficiency is 1 in 1, 37,000 and 1 in 1, 10,000 respectively. The carrier frequency in general population is 1 in 120. We attempt to study clinical, biochemical and outcome from 10 Biotinidase deficient patients. A retrospective case record study was conducted to record Clinical, biochemical and outcome profile from genetic records. Biotinidase level was measured using spectrophotometric method. Study group comprised of 8 males and 2 females with median age of presentation 6 (2-45.75) months. Median (interquartile range) Biotinidase level in study group 0.3 (0.08-1.5) nmol/ml/min. Study group was further divided in to early onset group (< 12 months, n-6) and late onset group (> 12 months, n-4). Seizure, alopecia and hearing loss were predominant phenotypes in study group. The other rare presentations were: hypotonia, ataxia, skin rash, seborrhoea. The most common seizure type was focal seizure. Control of seizure activity was important immediate outcome measured in study group. Median duration (interquartile range) of seizure control in early onset group was 3 (2-4)days against 13.5 (12.25-14.75) days in late onset group. This study highlights the need of early diagnosis for favourable outcome for a potentially treatable inherited metabolic disorder.

High Incidence of Biotinidase Deficiency from a Pilot Newborn Screening Study in Minas Gerais, Brazil.

To assess the incidence of biotinidase deficiency among newborns and their clinical outcome up to one year of age in a large pilot screening study in Minas Gerais, Brazil. A prospective cohort study was conducted from September 2007 to June 2008 with heel-prick blood samples collected on filter paper for the purpose of newborn screening. A qualitative colorimetric test was used as the primary screening method. Colorimetric-positive cases were further tested with a serum confirmatory assay. Gene sequencing was performed for eight children suspected with biotinidase deficiency and for some of their parents. Positive cases were daily supplemented with oral biotin and were followed up for approximately six years. Out of 182,891 newborns screened, 129 were suspected of having biotinidase deficiency. Partial deficiency was confirmed in seven children (one was homozygous for p.D543E) and profound deficiency in one child (homozygous p.H485Q). Thus the incidence was one in 22,861 live births (95% confidence interval 1:13,503 to 1:74,454) for profound and partial biotinidase deficiency combined. Two novel mutations were detected: p.A281V and p.E177K. In silico analysis and estimation of the enzyme activity in the children and their parents showed that p.A281V is pathogenic and p.E177K behaves like p.D444H. The incidence of biotinidase deficiency in newborn screening in Minas Gerais was higher than several international studies. The sample size should be larger for final conclusions. Oral daily biotin apparently precluded clinical symptoms, but it may have been unnecessary in some newborns.

Erratum to: Newborn screening for congenital hypothyroidism, galactosemia and biotinidase deficiency in Uttar Pradesh, India

Erratum to: Newborn screening for congenital hypothyroidism, galactosemia and biotinidase deficiency in Uttar Pradesh, India

ENT considerations in biotinidase deficiency

ENT considerations in biotinidase deficiency

Inborn Errors of Metabolism in the United Arab Emirates: Disorders Detected by Newborn Screening (2011-2014).

This study reports on the inborn errors of metabolism (IEM) detected by our national newborn screening between 2011 and 2014. One hundred fourteen patients (55 UAE citizens and 59 residents) were diagnosed during this period. The program was most comprehensive (tested 29 IEM) and universally applied in 2013, giving an incidence of 1 in 1,787 citizens. This relatively high prevalence resulted from the frequent consanguineous marriages (81.5%) among affected families. The following eight disorders accounted for 80% of the entities: biotinidase deficiency (14 of 55), phenylketonuria (11 of 55), 3-methylcrotonyl glycinuria (9 of 55), medium-chain acyl-CoA dehydrogenase deficiency (4 of 55), argininosuccinic aciduria, glutaric aciduria type 1, glutaric aciduria type 2, and methylmalonyl-CoA mutase deficiency (2 of 55 each). Mutation analysis was performed in 48 (87%) of the 55 patients, and 33 distinct mutations were identified. Twenty-nine (88%) mutations were clinically significant and, thus, could be included in our premarital screening. Most mutations were homozygous, except for the biotinidase deficiency. The BTD mutations c.1207T>G (found in citizens) and c.424C>A (found in Somalians) were associated with undetectable biotinidase activity. Thus, the high prevalence of IEM in our region is amenable to newborn and premarital screening, which is expected to halt most of these diseases.

Mutations in BTD gene causing biotinidase deficiency: a regional report.

Biotinidase deficiency is an autosomal recessive inborn error of biotin metabolism. Children with biotinidase deficiency cannot cleave biocytin and, therefore, cannot recycle biotin. Untreated individuals become secondarily biotin deficient, which in turn results in decreased activities of the biotin-dependent carboxylases and the subsequent accumulation of toxic metabolites causing clinical symptoms. Biotinidase deficiency is characterized by neurological, cutaneous manifestations and metabolic abnormalities. The worldwide incidence of profound biotinidase deficiency has been estimated at 1:112,271. The human biotinidase gene is located on chromosome 3p25 and consists of four exons with a total length of 1629 base pairs. To date, more than 100 mutations in the biotinidase gene known to cause biotinidase deficiency have been reported. The vast majority of mutations are homozygous or compound heterozygous. Finding known mutations can be correlated with the biochemical enzymatic results. This report summarizes the demographic features of patients identified as biotinidase deficient from August of 2012 through August of 2013 and mutation analysis results for 20 cases in the southeast region of Turkey.

Feasibility study of an outreach program of newborn screening in Uttar Pradesh.

To create awareness about newborn screening (NBS) in underprivileged population and establish the model of NBS as an outreach program in peripheral hospitals in and around Lucknow. During this project, social workers were trained in taking informed consent, demographic details of newborns, heel prick samples and transporting the filter papers to a central laboratory. These social workers were posted in seven hospitals, in and around Lucknow, catering to families with low socioeconomic strata. Assays were performed in a single laboratory and results were conveyed back to the social workers and the hospitals. A total of 13,426 newborns were screened for the three conditions namely congenital hypothyroidism (CH), biotinidase deficiency and galactosemia. Over all coverage rate was 73.5 % and average time of reporting of results was 8.8 + 2.4 days. More than 85 % (86.7 %) families with positive screening test could be contacted back and out of them, 83.6 % babies could be sampled for confirmatory tests. Eleven babies were diagnosed to have CH. The study has shown positive and enthusiastic responses of the lay persons. Questionnaire based survey among lay persons showed that almost 100 % individuals understood the advantages and method of NBS. This project has been successful in establishing a model of NBS as an outreach program in and around a district.

Biotinidase deficiency: Spectrum of molecular, enzymatic and clinical information—A pilot project

Biotinidase deficiency: Spectrum of molecular, enzymatic and clinical information—A pilot project