Biotin–thiamine–responsive basal ganglia disease: catastrophic consequences of delay in diagnosis and treatment

Biotin-Thiamine-Responsive Basal Ganglia Disease: A Case Report

Introduction

Biotin-thiamine responsive basal ganglia disease (BTBGD) is a rare autosomal recessive neurometabolic disorder characterized by diverse and variable phenotypic features, which can make diagnosis challenging. However, prompt treatment with thiamine and biotin can effectively manage the condition. Diagnosis relies on the identification of biallelic pathogenic variants in the SLC19A3 gene. This case report describes two novel variants of uncertain significance in the SLC19A3 gene, which may be correlated with the phenotypic manifestations of BTBGD.

Case Presentation

Our case is a 7-month-old female infant who presented with a 3-week history of irritability, altered behavior, and refusal of newly introduced solid foods. Symptoms started with an upper respiratory tract infection, followed by lethargy, floppiness, and abnormal movements. The patient was admitted to the pediatric ward with a broad differential diagnosis. Extensive laboratory evaluations revealed lactic acidosis. MRI brain showed symmetric restricted diffusion affecting the bilateral basal ganglia, thalami, and cortical regions. Whole genome sequencing identified biallelic variants of the SLC19A3: a c.1364T>G p.Met455Arg missense variant in the maternal allele and a 2.3 kb deletion of intron 3 of the paternal allele. Both variants were identified as variants of uncertain significance. However, given the clinical picture, MRI brain findings, resolution of symptoms with empiric biotin and thiamine supplementation, and biallelic SLC19A3 variants of unknown significance, the patient most likely suffers from BTBGD. Patient continues to show sustained developmental progress on biotin and thiamine supplementation.

Conclusion

This case highlights the fact that genetic testing remains a vital but improvable tool for the diagnosis of BTBGD. As of yet, genetic testing and diagnosis of BTBGD continues to be limited by the knowledge of which SLC19A3 variants are established to be pathogenic variants. Thus, further research is required to study other SCL19A3 variants of unknown significance to further improve genetic testing and diagnosis of BTBGD in the future.

Derivation of two iPSC lines (KAIMRCi004-A, KAIMRCi004-B) from a Saudi patient with Biotin-Thiamine-responsive Basal Ganglia Disease (BTBGD) carrying homozygous pathogenic missense variant in the SCL19A3 gene

The neurometabolic disorder known as biotin-thiamine-responsive basal ganglia disease (BTBGD) is a rare autosomal recessive condition linked to bi-allelic pathogenic mutations in the SLC19A3 gene. BTBGD is characterized by progressive encephalopathy, confusion, seizures, dysarthria, dystonia, and severe disabilities. Diagnosis is difficult due to the disease's rare nature and diverse clinical characteristics. The primary treatment for BTBGD at this time is thiamine and biotin supplementation, while its long-term effectiveness is still being investigated. In this study, we have generated two clones of induced pluripotent stem cells (iPSCs) from a 10-year-old female BTBGD patient carrying a homozygous mutation for the pathogenic variant in exon 5 of the SLC19A3 gene, c.1264A > G (p.Thr422Ala). We have confirmed the pluripotency of the generated iPS lines and successfully differentiated them to neural progenitors. Because our understanding of genotype-phenotype correlations in BTBGD is limited, the establishment of BTBGD-iPSC lines with a homozygous SLC19A3 mutation provides a valuable cellular model to explore the molecular mechanisms underlying SLC19A3-associated cellular dysfunction. This model holds potential for advancing the development of novel therapeutic strategies.

Case report: biotin-thiamine-responsive basal ganglia disease with severe subdural hematoma on magnetic resonance imaging

Background: Biotin-thiamine-responsive basal ganglia disease (BTBGD) is a rare, treatable autosomal recessive neurometabolic disorder. This condition eventually leads to severe disability and death if not treated correctly. The clinical features of BTBGD, especially those with unusual complications, are not widely known by neurologists or pediatricians.Case presentation: A 4-month-old male infant was admitted to the hospital with a history of cough for the past 7 days and convulsions of 6 h duration. Physical examination showed confusion, bilateral pupillary light reflex delays, hypertonia of limbs, and brisk tendon reflexes of the limbs. Brain magnetic resonance imaging (MRI) showed multiple abnormal signals in the bilateral basal ganglia, lobes, corpus callosum, brainstem, and brain atrophy. However, his condition continued to worsen. Computed tomography performed 3 months later showed severe subdural hematoma and effusion. Subsequently, he underwent puncture drainage; however, his condition did not improve postoperatively. Repeated MRIs showed increasing subdural hematoma and effusion, and brain atrophy. The patient was diagnosed with BTBGD following whole-genome sequencing, which identified a novel compound heterozygous mutation of SLC19A3 gene. He was treated with biotin and thiamine, and the symptoms gradually improved. Subsequent MRIs showed a decrease in the subdural hematoma and effusion and partial improvement in brain atrophy.Conclusion: To the best of our knowledge, this is the first reported case of BTBGD, complicated by severe subdural hematoma. These observations extend our understanding of the clinical features, neuroimaging spectrum, and gene mutation spectrum of BTBGD. The phenotypic spectrum and pathophysiology of BTBGD are not completely understood and need to be studied further.

Efficacy of high thiamine dosage in treating patients with biotin thiamine responsive basal ganglia disease: a two case reports

BACKGROUND

Biotin-thiamine-responsive basal ganglia disease (BTBGD) is a rare, autosomal recessive neurometabolic disorder caused by mutations in the SLC19A3 gene and characterized by recurrent sub-acute episodes of encephalopathy. Patients with BTBGD have classical neuroimaging findings and a dramatic response to high doses of thiamine.

OBJECTIVE

To highlight the advantages of administering a higher dose of thiamine for patients with BTBGD who have not shown improvement with the standard recommended dosage.

RESULTS

Herein, we report on two Saudi girls with classical clinical and radiological findings of BTBGD. Hallmark symptoms in these patients included an acute onset of ataxia, tremor, slurred speech, dystonia, and dysphagia. The initial routine laboratory workups were unremarkable. Brain magnetic resonance imaging revealed extensive hyperintense signals in the bilateral basal ganglia, which suggested the diagnosis of a BTBGD. Hence started empirically on biotin 10 mg/kg/day and thiamine 40 mg/kg/day, but there was no noticeable improvement. After increasing the thiamine to 75 mg/kg/day the patients started to improve significantly. Genetic testing was requested and came positive for the mutation of the SLC19A3 gene. After two months of initiating the management, thiamine was reduced to 30 mg/kg/day. Subsequent follow-ups showed complete improvement in their condition with no apparent long-term sequel or relapse.

CONCLUSION

we conclude that administration of thiamine at a dosage of up to 40 mg/kg/day may not be sufficient in treating certain patients with BTBGD. Thus, considering a significantly higher dosage could potentially contribute to achieving remission.

Prospect of genetic disorders in Saudi Arabia

Introduction: Rare diseases (RDs) create a massive burden for governments and families because sufferers of these diseases are required to undergo long-term treatment or rehabilitation to maintain a normal life. In Saudi Arabia (SA), the prevalence of RDs is high as a result of cultural and socio-economic factors. This study, however, aims to shed light on the genetic component of the prevalence of RDs in SA. Methodology: A retrospective study was conducted between September 2020 and December 2021 at King Saud Medical City, a tertiary hospital of the Ministry of Health (MOH), SA. A total of 1080 individuals with 544 potentially relevant variants were included. The index was 738, and the samples were tested in a commercialized laboratory using different molecular techniques, including next-generation sequencing. Result: A total of 867 molecular genetics tests were conducted on 738 probands. These tests included 610 exome sequencing (ES) tests, four genome sequencing (GS) tests, 82 molecular panels, 106 single nucleotide polymorphism (SNP) array, four methylation studies, 58 single-gene studies and three mitochondrial genome sequencing tests. The diagnostic yield among molecular genetics studies was 41.8% in ES, 24% in panels, 12% in SNP array and 24% in single gene studies. The majority of the identified potential variants (68%) were single nucleotide variants (SNV). Other ascertained variants included frameshift (11%), deletion (10%), duplication (5%), splicing (9%), in-frame deletion (3%) and indels (1%). The rate of positive consanguinity was 56%, and the autosomal recessive accounted for 54%. We found a significant correlation between the ES detection rate and positive consanguinity. We illustrated the presence of rare treatable conditions in DNAJC12, SLC19A3, and ALDH7A1, and the presence of the founder effect variant in SKIC2. Neurodevelopmental disorders were the main phenotype for which genetics studies were required (35.7%). Conclusion: This is the sixth-largest local study reporting next-generation sequencing. The results indicate the influence of consanguineous marriages on genetic disease and the burden it causes for the Kingdom of SA. This study highlights the need to enrich our society's knowledge of genetic disorders. We recommend utilising ES as a first-tier test to establish genetic diagnosis in a highly consanguineous population.

Biotin-thiamine-responsive basal ganglia disease: A case report

Biotin-Thiamine-Responsive Basal Ganglia Disease is an extremely rare autosomal recessive neurometabolic disorder characterized by recurrent waxing and waning episodes of subacute encephalopathy and seizures. High dose biotin and thiamine administration has been shown to improve symptoms within days, and the symptoms may reappear rapidly if supplementation is discontinued. Here we present a case of a 20-year-old male with classical clinical and imaging findings of Biotin-Thiamine-Responsive Basal Ganglia Disease, with a 12-year delay in diagnosis, finally diagnosed after presenting at our institution based on imaging and subsequent reexamination of exome sequencing. In this report, we review the classic imaging findings in this disease and examine why making the diagnosis can be extremely challenging due to its wide differential. Both clinically and radiographically, this condition demonstrates significant overlap with a vast array of disease entities, ranging from viral or autoimmune encephalitis to metabolic disorders. Finally, we discuss the various negative prognostic predictors described in the literature, several of which were observed in this patient's clinical course.

Early treatment of biotin-thiamine-responsive basal ganglia disease improves the prognosis

Background

Biotin–thiamine–responsive basal ganglia disease (BTBGD) is an autosomal recessive neurometabolic disorder associated with pathogenic variants in SLC19A3 gene. The clinical picture includes symptoms of subacute encephalopathy (e.g. confusion, dysphagia, dysarthria, and seizures), which respond very well to early treatment with thiamine and biotin.

Method

A retrospective review of clinical characteristics, magnetic resonance imaging and molecular findings in 3 patients with BTBGD.

Results

The first symptoms in all patients occurred at 12–24 months of age and they had subacute encephalopathy, ataxia and dystonia. The baseline magnetic resonance imaging demonstrated abnormal signal intensity in the basal ganglia with atrophy and necrosis of the basal ganglia during follow-up in two patients. One patient was diagnosed and the treatment was initiated after a long period from symptoms onset and he is currently severely affected, with dystonia, quadriparesis and seizures. The other two patients were diagnosed early in life and are currently stable on treatment, without the clinical symptoms. Genetic testing demonstrated pathogenic variants in SLC19A3 gene.

Conclusion

To avoid diagnostic errors and delayed or incorrect treatment, BTBGD must be recognized early. Adequate prompt treatment gives the chance of significant clinical improvement. Unexplained encephalopathy and MRI abnormalities including bilateral abnormal signal in the basal ganglia should alert the clinician to consider BTBGD in the differential, and the treatment with biotin and thiamine should be introduced immediately.

Report of the Largest Chinese Cohort With SLC19A3 Gene Defect and Literature Review

Thiamine metabolism dysfunction syndrome 2 (THMD2) is a rare metabolic disorder caused by SLC19A3 mutations, inherited in autosomal recessive pattern. As a treatable disease, early diagnosis and therapy with vitamin supplementation is important to improve the prognosis. So far, the reported cases were mainly from Saudi Arab regions, and presented with relatively simple clinical course because of the hot spot mutation (T422A). Rare Chinese cases were described until now. In this study, we investigated 18 Chinese THMD2 patients with variable phenotypes, and identified 23 novel SLC19A3 mutations, which expanded the genetic and clinical spectrum of the disorder. Meanwhile, we reviewed all 146 reported patients from different countries. Approximately 2/3 of patients presented with classical BTBGD, while 1/3 of patients manifested as much earlier onset and poor prognosis, including infantile Leigh-like syndrome, infantile spasms, neonatal lactic acidosis and infantile BTBGD. Literature review showed that elevated lactate in blood and CSF, as well as abnormal OXPHOS activities of muscle or skin usually correlated with infantile phenotypes, which indicated poor outcome. Brainstem involvement on MRI was more common in deceased cases. Thiamine supplementation is indispensable in the treatment of THMD2, whereas combination of biotin and thiamine is not superior to thiamine alone. But biotin supplementation does work in some patients. Genotypic-phenotypic correlation remains unclear which needs further investigation, and biallelic truncated mutations usually led to more severe phenotype.

Adolescent-Onset and Adult-Onset Vitamin-Responsive Neurogenetic Diseases: A Review

Importance

Vitamin-responsive inherited diseases are among the rare genetic disorders with a specific pharmacological treatment. Many of these conditions have a prominent neurological phenotype that is mainly reported in children. Being rare and often strikingly different in adult-onset forms, they are still poorly known in the medical fields specific to adults.

Observation

This article reviews all articles reporting cases of patients with a genetically confirmed inherited vitamin-responsive neurological disease and neurological onset after the age of 10 years. On this basis, 24 different diseases are described, involving vitamins A, B1, B2, B3, B6, B8, B9, B12, E, and tetrahydrobiopterin (BH4). Information such as clinical symptoms, disease course, imaging studies, biochemical alterations, and response to treatment present an overall picture of these patients.

Conclusions and Relevance

Vitamin-responsive neurogenetic diseases represent a group of rare conditions that are probably underdiagnosed in adults and may have a dramatic response to treatment when started early in the course of the disease. In this review, main features of the adult-onset forms are defined and simple key messages are provided to help identify clinical situations when specific diagnostic tests should be performed and/or vitamins should be promptly administered.

Mitochondrial medicine therapies: rationale, evidence, and dosing guidelines

PURPOSE OF REVIEW

Primary mitochondrial disease is a highly heterogeneous but collectively common inherited metabolic disorder, affecting at least one in 4300 individuals. Therapeutic management of mitochondrial disease typically involves empiric prescription of enzymatic cofactors, antioxidants, and amino acid and other nutrient supplements, based on biochemical reasoning, historical experience, and consensus expert opinion. As the field continues to rapidly advance, we review here the preclinical and clinical evidence, and specific dosing guidelines, for common mitochondrial medicine therapies to guide practitioners in their prescribing practices.

RECENT FINDINGS

Since publication of Mitochondrial Medicine Society guidelines for mitochondrial medicine therapies management in 2009, data has emerged to support consideration for using additional therapeutic agents and discontinuation of several previously used agents. Preclinical animal modeling data have indicated a lack of efficacy for vitamin C as an antioxidant for primary mitochondrial disease, but provided strong evidence for vitamin E and N-acetylcysteine. Clinical data have suggested L-carnitine may accelerate atherosclerotic disease. Long-term follow up on L-arginine use as prophylaxis against or acute treatment for metabolic strokes has provided more data supporting its clinical use in individuals with mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome and Leigh syndrome. Further, several precision therapies have been developed for specific molecular causes and/or shared clinical phenotypes of primary mitochondrial disease.

SUMMARY

We provide a comprehensive update on mitochondrial medicine therapies based on current evidence and our single-center clinical experience to support or refute their use, and provide detailed dosing guidelines, for the clinical management of mitochondrial disease. The overarching goal of empiric mitochondrial medicines is to utilize therapies with favorable benefit-to-risk profiles that may stabilize and enhance residual metabolic function to improve cellular resiliency and slow clinical disease progression and/or prevent acute decompensation.

Neuroimaging of Basal Ganglia in Neurometabolic Diseases in Children

Diseases primarily affecting the basal ganglia in children result in characteristic disturbances of movement and muscle tone. Both experimental and clinical evidence indicates that the basal ganglia also play a role in higher mental states. The basal ganglia can be affected by neurometabolic, degenerative diseases or other conditions from which they must be differentiated. Neuroradiological findings in basal ganglia diseases are also known. However, they may be similar in different diseases. Their assessment in children may require repeated MRI examinations depending on the stage of brain development (mainly the level of myelination). A large spectrum of pathological changes in the basal ganglia in many diseases is caused by their vulnerability to metabolic abnormalities and chemical or ischemic trauma. The diagnosis is usually established by correlation of clinical and radiological findings. Neuroimaging of basal ganglia in neurometabolic diseases is helpful in early diagnosis and monitoring of changes for optimal therapy. This review focuses on neuroimaging of basal ganglia and its role in the differential diagnosis of inborn errors of metabolism.

Movement Disorders in Inherited Metabolic Diseases in Children

Movement disorders are one of the important neurological manifestations of inherited metabolic disorders. Important clues to the presence of an underlying inborn error of metabolism are early onset, presence of neuroregression or degeneration, parental consanguinity, sibling affection, paroxysmal events, waxing and waning course, skin or hair changes, absence of a perinatal insult or any structural cause, and presence of identifiable triggers. It is particularly important to recognize this class of movement disorders as several of them are eminently treatable and may often need disease-specific therapy besides symptomatic treatment. The current review focusses on the movement disorders associated with inherited metabolic defects in children, with emphasis on treatable disorders.

[Paroxysmal crying and motor regression for more than two months in an infant]

The patient was a male who was found to be abnormal at the age of 4.5 months. He presented with irritability, motor regression and opisthotonus. Brain MRI revealed bilateral abnormality in the lentiform nucleus, thalamus, deutocerebrum and cerebellar hemispheres. Novel compound heterozygous mutations of SLC19A3 gene, c.950G>A(p.G317E) and c.962C>T(p.A321V), were found in the patient. Further study showed that c.950G>A was inherited from his father and c.962C>T came from his mother. Using bioinformatics software analysis, both of the mutations were found to be harmful. His symptoms were improved remarkably after biotin, thiamine and "cocktail" therapy. One month later a brain MRI revealed that the lesions in basal ganglia and cerebellar hemispheres were improved. The patient was definitely diagnosed with biotin-thiamine responsive basal ganglia disease (BTBGD). BTBGD is a treatable autosomal recessive disease and early administration of biotin and thiamine may lead to clinical improvement.

A novel mutation in CACNA1A gene in a Saudi female with episodic ataxia type 2 with no response to acetazolamide or 4-aminopyridine

Episodic ataxia is a genetically heterogeneous neurological condition characterized by spells of incoordination and imbalance, often associated with progressive ataxia. Episodic ataxia type 2, caused by calcium voltage-gated channel subunit alpha1 A (CACNA1A MIM: 601011) mutation, is the most common form of episodic ataxia. It is characterized by recurrent attacks of imbalance associated with interictal nystagmus lasting hours to days and triggered by emotional stress or exercise. In this article, we report a novel heterozygous intronic variant c.5743+14A>G in the CACNA1A gene in a Saudi family. To the best of our knowledge, this variant has not been described in the literature or reported in public mutation databases. This report indicated that acetazolamide is not beneficial, and it may be even harmful to patients with episodic ataxia type 2 if used in later stages. In addition, treatment with 4-aminopyridine did not show any efficacy to improve walking or balance in our patient, which indicates the importance of early initiation of therapy before the later stages of the disease. Further research is needed to explore potential treatments for this challenging disease.

Biotin-Thiamine Responsive Encephalopathy: Report of an Egyptian Family with a Novel SLC19A3 Mutation and Review of the Literature

Biotin-thiamine responsive basal ganglia disease (BTRBGD) is an autosomal recessive neurometabolic disorder with poor genotype-phenotype correlation, caused by mutations in the SLC19A3 gene on chromosome 2q36.6. The disease is characterized by three stages: stage 1 is a sub-acute encephalopathy often triggered by febrile illness; stage 2 is an acute encephalopathy with seizures, loss of motor function, developmental regression, dystonia, external ophthalmoplegia, dysphagia, and dysarthria; stage 3 is represented by chronic or slowly progressive encephalopathy. Clinical and biochemical findings, as well as the magnetic resonance imaging (MRI) pattern, resemble those of Leigh's syndrome, so that BTRBGD can be misdiagnosed as a mitochondrial encephalopathy.Here we report the clinical and radiological phenotypes of two siblings diagnosed with BTRBGD in which a novel SLC19A3 mutation (NM_025243.3: c.548C > T; p.Ala183Val) was found by whole exome sequencing (WES) of the family members.

Ataxia with ocular apraxia type 2 not responding to 4-aminopyridine: A rare mutation in the SETX gene in a Saudi patient

Ataxia with ocular apraxia type 2 is an autosomal recessive disorder caused by a mutation in the senataxin (SETX) gene. The disease is characterized by early onset cerebellar ataxia, cerebellar atrophy, axonal sensorimotor neuropathy, oculomotor apraxia, and increased levels of α-fetoprotein. Reported here is a rare homozygous frameshift deletion c.5308_5311del, p.(Glu1770Ilefs*15) in the SETX gene in a Saudi family. Ataxia with ocular apraxia type 2 was diagnosed based on the patient's history, an examination, and genetic testing. Genetic testing remains the only definitive method with which to identify the gene responsible. This is the third case report of this rare mutation in the literature. Ataxia with ocular apraxia type 2 continues to be a challenging disease to manage with no therapeutic options available to date. In the current case, the medication 4-aminopyridine was inefficacious in improving walking or balance. Further research is needed to identify potential treatments for this challenging condition.

Compound heterozygous SLC19A3 mutations further refine the critical promoter region for biotin-thiamine-responsive basal ganglia disease

Mutations in the gene SLC19A3 result in thiamine metabolism dysfunction syndrome 2, also known as biotin-thiamine-responsive basal ganglia disease (BTBGD). This neurometabolic disease typically presents in early childhood with progressive neurodegeneration, including confusion, seizures, and dysphagia, advancing to coma and death. Treatment is possible via supplement of biotin and/or thiamine, with early treatment resulting in significant lifelong improvements. Here we report two siblings who received a refined diagnosis of BTBGD following whole-genome sequencing. Both children inherited compound heterozygous mutations from unaffected parents; a missense single-nucleotide variant (p.G23V) in the first transmembrane domain of the protein, and a 4808-bp deletion in exon 1 encompassing the 5′ UTR and minimal promoter region. This deletion is the smallest promoter deletion reported to date, further defining the minimal promoter region of SLC19A3. Unfortunately, one of the siblings died prior to diagnosis, but the other is showing significant improvement after commencement of therapy. This case demonstrates the power of whole-genome sequencing for the identification of structural variants and subsequent diagnosis of rare neurodevelopmental disorders.