Biotinidase deficiency: a reversible metabolic encephalopathy. Neuroimaging and MR spectroscopic findings in a series of four patients

Biotinidase Deficiency in the Second Decade with Atypical Neuroimaging Findings

Biotinidase deficiency is a rare autosomal recessive neurometabolic disorder resulting in biotin deficiency. Our patient presented with seizures and developmental delay since infancy and was started on megavitamin supplements. At 14 years, she presented with motor regression with encephalopathy after discontinuation of vitamins. There were no skin and hair changes. Magnetic resonance imaging (MRI) of the brain showed bilateral symmetrical posterior putamen signal changes. Tandem mass spectroscopy showed increased methyl malonyl carnitine and 3-OH isovaleryl carnitine. There was a low biotinidase level, and a pathogenic variant in the BTD gene in the next-generation sequencing was identified. Special importance is placed on the unusual symmetric posterior putamen involvement seen in MRI of the brain.

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.

Neuroimaging Features of Biotinidase Deficiency

Biotinidase deficiency is an autosomal recessive condition caused by pathogenic variants in the BTD gene. Resultant deficiency of free biotin leads to impaired activity of the enzyme carboxylase and related neurologic, dermatologic, and ocular symptoms. Many of these are reversible on treatment, but early recognition and commencement of biotin supplementation are critical. This practice is especially important in countries where routine neonatal screening for biotinidase deficiency is not performed. In this report comprising 14 patients from multiple centers, we demonstrate the MR imaging patterns of this disorder at various age groups. Knowledge of these patterns in the appropriate clinical context will help guide early diagnosis of this treatable metabolic disorder.

Main nutritional deficiencies

Nutrition is the source of energy that is required to carry out all the processes of human body. A balanced diet is a combination of both macro- and micronutrients. "Nutritional inadequacy" involves an intake of nutrients that is lower than the estimated average requirement, whereas "nutritional deficiency" consists of severely reduced levels of one or more nutrients, making the body unable to normally perform its functions and thus leading to an increased risk of several diseases like cancer, diabetes, and heart disease. Malnutrition could be caused by environmental factors, like food scarcity, as well as disease conditions, like anorexia nervosa, fasting, swallowing inability, persistent vomiting, impaired digestion, intestinal malabsorption, or other chronic diseases. Nutritional biomarkers - like serum or plasma levels of nutrients such as folate, vitamin C, B vitamins, vitamin D, selenium, copper, zinc - could be used for the evaluation of nutrient intake and dietary exposure. Macronutrients deficiencies could cause kwashiorkor, marasmus, ketosis, growth retardation, wound healing, and increased infection susceptibility, whereas micronutrient - like iron, folate, zinc, iodine, and vitamin A - deficiencies lead to intellectual impairment, poor growth, perinatal complications, degenerative diseases associated with aging and higher morbidity and mortality. Preventing macro- and micronutrient deficiency is crucial and this could be achieved through supplementation and food-based approaches.

Adult-Onset Genetic Central Nervous System Disorders Masquerading as Acquired Neuroinflammatory Disorders: A Review

Importance

Adult-onset genetic disorders may present with clinical and magnetic resonance imaging (MRI) features suggestive of acquired inflammatory diseases. An ever-growing number of potentially treatable adult-onset genetic neuroinflammatory disorders have been described in the past few years that need to be rapidly identified.

Observations

Adult-onset acquired neuroinflammatory disorders encompass a large group of central nervous system (CNS) diseases with varying presentation, MRI characteristics, and course, among which the most common is multiple sclerosis. Despite recent progress, including the discovery of specific autoantibodies, a significant number of adult-onset neuroinflammatory disorders with progressive or relapsing course still remain without a definite diagnosis. In addition, some patients with genetic disorders such as leukodystrophies, hemophagocytic lymphohistiocytosis, or genetic vasculopathies can mimic acquired neuroinflammatory disorders. These genetic disorders, initially described in pediatric populations, are increasingly detected in adulthood thanks to recent progress in molecular genetics and the larger availability of high-throughput sequencing technologies.

Conclusions and Relevance

Genetic adult-onset neuroinflammatory diseases are at the border between primary CNS inflammatory diseases and systemic disorders with multiorgan involvement and predominantly neurologic manifestations. Neurologists must be aware of the main clues and red flags so they can confirm a diagnosis early, when some of these genetic disorders can be successfully treated.

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.

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.

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.

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.

Congenital biotinidase deficiency – MRI findings in two cases

Congenital biotinidase deficiency is a rare inborn error of metabolism that most commonly presents in infantile age group. Diffusion changes on magnetic resonance imaging (MRI) are sparsely described in the literature. We are presenting diffusion-weighted MRI findings in two confirmed cases of congenital biotinidase deficiency in infantile age group with review of literature.

Status of Newborn Screening and Inborn Errors of Metabolism in India

Inborn errors of metabolism (IEM) are a heterogeneous group of genetic disorders that cause significant neonatal and infant mortality. Expanded newborn screening which detects these disorders at birth is the standard preventive strategy in most countries. Prospective studies to evaluate the impact of these in the Indian population are lacking. The imminent need to address this lacuna warrants a review of available pan India data, as well as efforts for a carefully conducted prospective assessment of the burden of IEM. Published data on IEM in the Indian population comprising universal prospective screening and screening in selected subgroups (patients admitted to pediatric/neonatal ICUs, patients with developmental delay/mental retardation) was collected through a systematic search. The primary focus was to get an estimate of the disease burden in the Indian population. A true prevalence of IEM in India is not available. The systematic review identifies and stratifies the various situations where IEM are found. Data collected by universal screening of the low risk population is essential to identify the true prevalence of IEM in India.

Neuroimaging Findings of Organic Acidemias and Aminoacidopathies

Although individual cases of inherited metabolic disorders are rare, overall they account for a substantial number of disorders affecting the central nervous system. Organic acidemias and aminoacidopathies include a variety of inborn errors of metabolism that are caused by defects in the intermediary metabolic pathways of carbohydrates, amino acids, and fatty acid oxidation. These defects can lead to the abnormal accumulation of organic acids and amino acids in multiple organs, including the brain. Early diagnosis is mandatory to initiate therapy and prevent permanent long-term neurologic impairments or death. Neuroimaging findings can be nonspecific, and metabolism- and genetics-based laboratory investigations are needed to confirm the diagnosis. However, neuroimaging has a key role in guiding the diagnostic workup. The findings at conventional and advanced magnetic resonance imaging may suggest the correct diagnosis, help narrow the differential diagnosis, and consequently facilitate early initiation of targeted metabolism- and genetics-based laboratory investigations and treatment. Neuroimaging may be especially helpful for distinguishing organic acidemias and aminoacidopathies from other more common diseases with similar manifestations, such as hypoxic-ischemic injury and neonatal sepsis. Therefore, it is important that radiologists, neuroradiologists, pediatric neuroradiologists, and clinicians are familiar with the neuroimaging findings of organic acidemias and aminoacidopathies. ^©RSNA, 2018.

Subcortical DNET in a Patient With an Enzymatic Deficiency: A Rare Case and Review of the Literature

PURPOSE

This case report describes a toddler with a medical history of biotinidase deficiency who presented with atypical seizures due to a brain tumor.

METHODS

This is a case report.

RESULTS

Electroencephalogram revealed a frontal lobe mass, with magnetic resonance imaging confirmation of a mass extending from the frontal lobe into the genu and anterior corpus callosum. She underwent a near-total resection, and pathology identified a dysembryoplastic neuroepithelial tumor. The patient is now seizure free and clinically doing well.

CONCLUSIONS

Children with biotinidase deficiency and atypical seizures should receive a full electroencephalogram evaluation, as brain tumors continue to be on the differential for seizures in this patient population.

Amenable Treatable Severe Pediatric Epilepsies

Vitamin-dependent epilepsies and multiple metabolic epilepsies are amenable to treatment that markedly improves the disease course. Knowledge of these amenably treatable severe pediatric epilepsies allows for early identification, testing, and treatment. These disorders present with various phenotypes, including early onset epileptic encephalopathy (refractory neonatal seizures, early myoclonic encephalopathy, and early infantile epileptic encephalopathy), infantile spasms, or mixed generalized seizure types in infancy, childhood, or even adolescence and adulthood. The disorders are presented as vitamin responsive epilepsies such as pyridoxine, pyridoxal-5-phosphate, folinic acid, and biotin; transportopathies like GLUT-1, cerebral folate deficiency, and biotin thiamine responsive disorder; amino and organic acidopathies including serine synthesis defects, creatine synthesis disorders, molybdenum cofactor deficiency, and cobalamin deficiencies; mitochondrial disorders; urea cycle disorders; neurotransmitter defects; and disorders of glucose homeostasis. In each case, targeted intervention directed toward the underlying metabolic pathophysiology affords for the opportunity to significantly effect the outcome and prognosis of an otherwise severe pediatric epilepsy.

Novel imaging findings in two cases of biotinidase deficiency-a treatable metabolic disorder

Biotinidase deficiency is one of the few treatable inborn errors of metabolism. We describe unique MRI features in two patients with biotinidase deficiency. Brain MRI in case one demonstrated symmetrical diffusion restriction in bilateral hippocampi, parahippocampal gyri, central tegmental tracts, and cerebellar white matter besides other structures that have been reported previously. The second patient was noted to have bilateral symmetrical T2 hyperintensities involving the anterior, lateral and posterior columns of the entire spinal cord on MRI. Knowledge of the varied MRI features of biotinidase deficiency will aid the prompt diagnosis and treatment of a potentially disabling illness, especially in countries where newborn screening is not routinely performed.

Stress-induced upregulation of SLC19A3 is impaired in biotin-thiamine-responsive basal ganglia disease

Biotin-thiamine-responsive basal ganglia disease (BTBGD) is a potentially treatable disorder caused by mutations in the SLC19A3 gene, encoding the human thiamine transporter 2. Manifestation of BTBGD as acute encephalopathy triggered by a febrile infection has been frequently reported, but the underlying mechanisms are not clear. We investigated a family with two brothers being compound heterozygous for the SLC19A3 mutations p.W94R and p.Q393*fs. Post-mortem analysis of the brain of one brother showed a mixture of acute, subacute and chronic changes with cystic and necrotic lesions and hemorrhage in the putamen, and hemorrhagic lesions in the caudate nucleus and cortical layers. SLC19A3 expression was substantially reduced in the cortex, basal ganglia and cerebellum compared with an age-matched control. Importantly, exposure of fibroblasts to stress factors such as acidosis or hypoxia markedly upregulated SLC19A3 in control cells, but failed to elevate SLC19A3 expression in the patient's fibroblasts. These results demonstrate ubiquitously reduced thiamine transporter function in the cerebral gray matter, and neuropathological alterations similar to Wernicke's disease in BTBGD. They also suggest that episodes of encephalopathy are caused by a substantially reduced capacity of mutant neuronal cells to increase SLC19A3 expression, necessary to adapt to stress conditions.

Vitamin-responsive epileptic encephalopathies in children

Untreated epileptic encephalopathies in children may potentially have disastrous outcomes. Treatment with antiepileptic drugs (AEDs) often may not control the seizures, and even if they do, this measure is only symptomatic and not specific. It is especially valuable to identify potential underlying conditions that have specific treatments. Only a few conditions have definitive treatments that can potentially modify the natural course of disease. In this paper, we discuss the few such conditions that are responsive to vitamin or vitamin derivatives.

Epilepsy in biotinidase deficiency after biotin treatment

Patients with severe biotinidase deficiency (BD), if untreated, may exhibit seizures, psychomotor delay, deafness, ataxia, visual pathology, conjunctivitis, alopecia, and dermatitis. Clinical features normally appear within the first months of life, between two and five. Seizures are one of the most common symptoms in these patients (55%), usually presented as generalized tonic-clonic, and improving within 24 h of biotin treatment. Treatment delay has been associated with irreversible neurological damage, mental retardation, ataxia, paraparesis, deafness, and epilepsy exceptionally.We report the case of a girl who was admitted at 2.5 months because of vomiting, failure to thrive, flexor spasms, dermatitis, and neurological depression for 1 month. BD was identified and was treated with biotin, stopping seizures and improving symptoms. Developmental delay, paraparesis, optic atrophy, and seizures during febrile illness were observed at follow-up. At the age of 8, she suffered hemigeneralized seizures despite appropriate biotin treatment, so levetiracetam was administered, and epilepsy was controlled. Organic acid measurement was performed to determine whether the child was receiving enough or no biotin.Even though BD is a rare condition, because the biotinidase screening is a reliable procedure and the disorder is readily treatable, the implementation of extended biotinidase screening will effectively help to prevent any acute and long-term neurological problems as well as the significant morbidity associated with untreated disease. In addition, neonatal screening and early treatment with biotin prevents severe neurological sequelae, such as epilepsy, which has not been thoroughly described in the literature.

The neurology of biotinidase deficiency

Biotinidase deficiency is an autosomal recessively inherited metabolic disorder in which the enzyme, biotinidase, is defective and the vitamin, biotin, is not recycled. Individuals with biotinidase deficiency, if not treated with biotin, usually exhibit neurological and cutaneous abnormalities. Biotin treatment can ameliorate or prevent symptoms. Biotinidase deficiency meets the major criteria for inclusion in newborn screening programs. With the advent of universal newborn screening for the disorder, the "window-of-opportunity" to characterize the consequences of the untreated disease is essentially gone. To understand the neurology of biotinidase deficiency, we must depend on what is already known about symptomatic individuals with the disorder. Therefore, in this review, the neurological findings of symptomatic individuals with profound biotinidase deficiency have been compiled to catalog the characteristic features of the disorder and the consequences of biotin treatment on these findings. In addition, based on the available evidence, I have speculated on the cause of neurological problems associated with the disorder. Future studies in biotinidase-deficient animals should allow us to demonstrate more definitively if these speculations are correct.

Development and characterization of a mouse with profound biotinidase deficiency: a biotin-responsive neurocutaneous disorder

Biotinidase deficiency is the primary enzymatic defect in biotin-responsive, late-onset multiple carboxylase deficiency. Untreated children with profound biotinidase deficiency usually exhibit neurological symptoms including lethargy, hypotonia, seizures, developmental delay, sensorineural hearing loss and optic atrophy; and cutaneous symptoms including skin rash, conjunctivitis and alopecia. Although the clinical features of the disorder markedly improve or are prevented with biotin supplementation, some symptoms, once they occur, such as developmental delay, hearing loss and optic atrophy, are usually irreversible. To prevent development of symptoms, the disorder is screened for in the newborn period in essentially all states and in many countries. In order to better understand many aspects of the pathophysiology of the disorder, we have developed a transgenic biotinidase-deficient mouse. The mouse has a null mutation that results in no detectable serum biotinidase activity or cross-reacting material to antibody prepared against biotinidase. When fed a biotin-deficient diet these mice develop neurological and cutaneous symptoms, carboxylase deficiency, mild hyperammonemia, and exhibit increased urinary excretion of 3-hydroxyisovaleric acid and biotin and biotin metabolites. The clinical features are reversed with biotin supplementation. This biotinidase-deficient animal can be used to study systematically many aspects of the disorder and the role of biotinidase, biotin and biocytin in normal and in enzyme-deficient states.

Two unusual clinical and radiological presentations of biotinidase deficiency

Biotinidase deficiency is due to a defect in recycling of biotin and is a treatable autosomal recessive inherited disorder. We describe two cases with unusual presenting symptoms and rarely described MRI findings. We propose that the diagnosis of biotinidase deficiency should be considered when there are symmetrical MRI changes in the medial thalamus, dorsal brainstem, medulla and spinal cord as in our two cases. As long as there isn't newborn screening for biotinidase deficiency in the UK; increased awareness of this disorder and recognition of biotinidase deficiency as a cause of bilateral symmetrical MRI patterns similar to our patients, would facilitate early diagnosis and prevent many of the devastating neurological sequelae associated with missing the condition.

Pyruvate carboxylase deficiency: mechanisms, mimics and anaplerosis

Pyruvate carboxylase (PC) is a regulated mitochondrial enzyme that catalyzes the conversion of pyruvate to oxaloacetate, a critical transition that replenishes citric acid cycle intermediates and facilitates other biosynthetic reactions that drive anabolism. Its deficiency causes multiorgan metabolic imbalance that predominantly manifests with lactic acidemia and neurological dysfunction at an early age. Three clinical forms of PC deficiency have been identified: an infantile form (Type A), a severe neonatal form (Type B), and a benign form (Type C), all of which exhibit clinical or biochemical correlates of impaired anaplerosis. There is no effective treatment for these patients and most, except those affected by the benign form, die in early life. We review the physiology of this enzyme and dissect the major clinical, biochemical, and genetic aspects of its dysfunction, emphasizing features that distinguish PC deficiency from other causes of lactic acidemia that render PC deficiency potentially treatable using novel interventions capable of enhancing anaplerosis.

The identification of novel mutations in the biotinidase gene using denaturing high pressure liquid chromatography (dHPLC)

Biotinidase deficiency (BD) is an autosomal recessive disorder of biotin metabolism that causes incomplete recycling of free biotin. The resulting depletion of intracellular biotin leads to impaired activities of biotin-dependent carboxylases. The ensuing clinical phenotype includes progressive neurologic deterioration with epileptic seizures, muscular hypotonia as well as skin eczema. BD may be readily diagnosed by analysing enzyme activity in dried blood spots during newborn screening but typically requires molecular confirmation. More than 100 different mutations in the biotinidase gene have been reported to date. To simplify molecular testing we have developed a rapid and accurate denaturing high pressure liquid chromatography (dHPLC) method of the promoter, 3'UTR, all exons including exon/intron boundaries as a first line screen followed by direct sequencing of the respective PCR products. To validate this method we used DNA from 23 different, newly diagnosed patients with biochemically proven BD from Austria, India, Morocco and Spain. A total of 11 mutations, missense 7, frameshift 3 and 1 nonsense, were screened. Six mutations were novel to this study. All mutations revealed distinct dHPLC pattern thus enabling their accurate detection. This study revealed that dHPLC method is robust, automated, economical and above all highly sensitive for the molecular analysis of biotinidase gene and should be used as a pre-analytical tool followed by sequencing of aberrant heteroduplex forming amplicons.