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Fennessy JR, Donlevy GA, McKay MJ, Burns J, Cornett KMD, Menezes MP. Development of a functional outcome measure for riboflavin transporter deficiency. J Peripher Nerv Syst 2024; 29:185-192. [PMID: 38445790 DOI: 10.1111/jns.12619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2024] [Revised: 02/22/2024] [Accepted: 02/23/2024] [Indexed: 03/07/2024]
Abstract
BACKGROUND AND AIMS Riboflavin transporter deficiency (RTD) is a progressive inherited neuropathy of childhood onset, characterised clinically by pontobulbar palsy, sensory ataxia, sensorineural deafness, muscle weakness, optic atrophy and respiratory failure. A robust and responsive functional outcome measure is essential for future clinical trials of disease-modifying therapies including genetic therapies. The Charcot-Marie-Tooth disease Pediatric Scale (CMTPedS) is a well-validated outcome measure for CMT and related neuropathies, and might have utility for measuring disease progression in individuals with RTD. However, the CMTPedS requires modifications to account for phenotypic differences between children with CMT and RTD. The aim of this study was to develop a functional outcome measure based on the CMTPedS for specific use in individuals with RTD. METHODS The CMTPedS data collected over the last 10 years in individuals with RTD attending the Peripheral Neuropathy Management Clinic at the Children's Hospital at Westmead (Sydney, Australia) were reviewed to evaluate each item within the CMTPedS. A literature review of articles published until September 2021 for functional outcome measures generated an item pool for pilot testing. The results of this pilot testing, alongside analysis of existing CMTPedS item scores in the RTD cohort, informed the modification of the CMTPedS. RESULTS CMTPedS data were reviewed for eight individuals over the past 10 years. Two items were identified as requiring modification or removal and additional items of proximal strength and function needed to be considered. Six studies were identified in the literature review, and five items were selected for pilot testing. 'Shoulder internal rotation' and the '30-s sit to stand test' were added as proximal measures of strength and function. The composite balance item comprising nine tasks in the CMTPedS showed a ceiling effect and was replaced with the single 'Feet apart on a line eyes open' balance item. 'Pinprick sensation' was removed due to a floor effect. INTERPRETATION This study provides preliminary evidence that the Riboflavin Transporter Deficiency Pediatric Scale (RTDPedS) is a functional outcome measure covering strength, upper and lower limb function, balance and mobility for individuals with RTD to assess disease severity and progression in clinical trials and cohort studies.
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Affiliation(s)
- Jack R Fennessy
- Faculty of Medicine and Health, University of Sydney School of Health Sciences, Sydney, New South Wales, Australia
| | - Gabrielle A Donlevy
- Faculty of Medicine and Health, University of Sydney School of Health Sciences, Sydney, New South Wales, Australia
- Paediatric Gait Analysis Service of New South Wales, Sydney Children's Hospitals Network, Westmead, New South Wales, Australia
| | - Marnee J McKay
- Faculty of Medicine and Health, University of Sydney School of Health Sciences, Sydney, New South Wales, Australia
| | - Joshua Burns
- Faculty of Medicine and Health, University of Sydney School of Health Sciences, Sydney, New South Wales, Australia
- Paediatric Gait Analysis Service of New South Wales, Sydney Children's Hospitals Network, Westmead, New South Wales, Australia
| | - Kayla M D Cornett
- Faculty of Medicine and Health, University of Sydney School of Health Sciences, Sydney, New South Wales, Australia
- Paediatric Gait Analysis Service of New South Wales, Sydney Children's Hospitals Network, Westmead, New South Wales, Australia
| | - Manoj P Menezes
- Children's Hospital at Westmead Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia
- TY Nelson Department of Neurology and Neurosurgery, The Children's Hospital at Westmead, Sydney, New South Wales, Australia
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Kentab AY, Alsalloum Y, Labani M, Hudairi A, Hamad MH, Jamjoom DZ, Alwadei AH, Alhammad RM, Bashiri FA. Case Report: A rare treatable metabolic syndrome (Brown-Vialetto-Van Laere syndrome) masquerading as chronic inflammatory demyelinating polyneuropathy from Saudi Arabia. Front Pediatr 2024; 12:1377515. [PMID: 38745833 PMCID: PMC11091239 DOI: 10.3389/fped.2024.1377515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 04/12/2024] [Indexed: 05/16/2024] Open
Abstract
Background Brown-Vialetto-Van Laere (BVVL) syndrome is an extremely rare autosomal recessive progressive motoneuron disease that is caused by a defect in the riboflavin transporter genes SLC52A2 and SLC52A3. BVVL syndrome has a variable age of presentation, and it is characterized by progressive auditory neuropathy, bulbar palsy, stridor, muscle weakness, and respiratory compromise secondary to diaphragmatic and vocal cord paralysis. BVVL syndrome has a poor prognosis in the absence of treatment, including morbidity with quadriparesis and sensorineural hearing loss, with mortality in the younger age group. Early administration of riboflavin is associated with prolonged survival, low morbidity, and reversal of some clinical manifestations. Case presentation We describe an 18-month-old male infant with progressive pontobulbar palsy, loss of developmental milestones, and a clinical picture suggestive of chronic inflammatory demyelinating neuropathy. A nerve conduction study revealed axonal neuropathy, while molecular analysis revealed a homozygous mutation in one of the riboflavin transporter genes, SLC52A3, confirming BVVL syndrome. The patient needed long-term respiratory support and a gastrostomy tube to support feeding. With high-dose riboflavin supplementation, he experienced moderate recovery of motor function. Conclusion This report highlights the importance of considering BVVL syndrome in any patient who presents with the clinical phenotype of pontobulbar palsy and peripheral axonal neuropathy, as early riboflavin treatment may improve or halt disease progression, thus reducing the associated mortality and morbidity.
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Affiliation(s)
- Amal Y. Kentab
- Division of Pediatric Neurology, Department of Pediatrics, College of Medicine, King Saud University, Riyadh, Saudi Arabia
- Department of Pediatrics, King Saud University Medical City, Riyadh, Saudi Arabia
| | - Yara Alsalloum
- Department of Pediatrics, King Saud University Medical City, Riyadh, Saudi Arabia
| | - Mai Labani
- Pediatric Intensive Care Unit, Department of Pediatrics, King Khalid University Hospital, King Saud University Medical City, Riyadh, Saudi Arabia
| | - Abrar Hudairi
- Department of Pediatrics, King Saud University Medical City, Riyadh, Saudi Arabia
| | - Muddathir H. Hamad
- Department of Pediatrics, King Saud University Medical City, Riyadh, Saudi Arabia
| | - Dima Z. Jamjoom
- Department of Radiology and Medical Imaging, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Ali H. Alwadei
- Department of Pediatrics, King Saud University Medical City, Riyadh, Saudi Arabia
- Pediatric Neurology Department, National Neuroscience Institute, King Fahd Medical City, Riyadh, Saudi Arabia
| | - Reem M. Alhammad
- Department of Internal Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Fahad A. Bashiri
- Division of Pediatric Neurology, Department of Pediatrics, College of Medicine, King Saud University, Riyadh, Saudi Arabia
- Department of Pediatrics, King Saud University Medical City, Riyadh, Saudi Arabia
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Cheng J, Yao J, Zhao S, Fu L, Zhang L, Jiang J. A riboflavin transporter deficiency presenting as pure red cell aplasia: a pediatric case report. Front Pediatr 2024; 12:1391245. [PMID: 38694724 PMCID: PMC11061399 DOI: 10.3389/fped.2024.1391245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2024] [Accepted: 04/04/2024] [Indexed: 05/04/2024] Open
Abstract
Introduction Riboflavin transporter deficiency (RTD) is a rare genetic disorder that affects riboflavin transport, leading to impaired red blood cell production and resulting in pure red cell aplasia. Recognizing and understanding its clinical manifestations, diagnosis, and management is important. Case presentation A 2-year-old patient presented with pure red cell aplasia as the primary symptom of RTD. After confirming the diagnosis, rapid reversal of anemia was achieved after high-dose riboflavin treatment. Conclusion RTD often has an insidious onset, and neurological symptoms appear gradually as the disease progresses, making it prone to misdiagnosis. Genetic testing and bone marrow biopsy can confirm the diagnosis.
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Affiliation(s)
| | | | | | | | | | - Jin Jiang
- Department of Hematology, National Center for Children’s Health, Beijing Children’s Hospital, Capital Medical University, Beijing, China
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4
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Ramirez EL, Gibson JB, Jülich K. Vitamin-Dependent Genetic Disorders of Childhood. Pediatr Rev 2023; 44:618-631. [PMID: 37907415 DOI: 10.1542/pir.2022-005637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Affiliation(s)
| | - James B Gibson
- Department of Pediatrics, The University of Texas at Austin, Dell Medical School, Austin, TX
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Fennessy JR, Cornett KMD, Burns J, Menezes MP. Benefit of high-dose oral riboflavin therapy in riboflavin transporter deficiency. J Peripher Nerv Syst 2023; 28:308-316. [PMID: 37537696 DOI: 10.1111/jns.12587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 07/28/2023] [Accepted: 08/02/2023] [Indexed: 08/05/2023]
Abstract
Riboflavin transporter deficiency (RTD) is a progressive inherited neuropathy of childhood onset, characterised by pontobulbar palsy, sensorineural deafness, sensory ataxia, muscle weakness, optic atrophy and respiratory failure. Riboflavin supplementation is beneficial in short-term reports, but the quantum of benefit in various clinical domains is not well understood. A PubMed search was conducted, which identified 94 genetically confirmed cases of RTD who received riboflavin supplementation and had follow-up assessments. Information on the clinical and functional status before and after riboflavin supplementation was collected and analysed. Seventy-six of the 94 patients (80.9%) showed an overall improvement after riboflavin supplementation, and the remaining (19.1%) were stable, though some patients had deteriorations in individual domains with no reported deaths. The domains that had the highest rates of response to riboflavin supplementation were gross motor function (93.3% improved), bulbar palsy (91.3%) and ataxia (90.0%). Improvements were also seen in limb muscle weakness, audiology, facial nerve palsy and respiratory function. Despite treatment, many patients required assistance to ambulate and had severe or profound hearing loss and some remained gastrostomy or tracheostomy dependent. Riboflavin supplementation is a lifesaving intervention for patients with RTD and results in a profound improvement in several functional domains, with early diagnosis and treatment further improving outcomes. Despite treatment, patients are left with residual disability. There is a need to accurately measure functional outcomes in children with RTD and develop additional disease-modifying therapies.
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Affiliation(s)
- Jack R Fennessy
- Sydney School of Health Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia
| | - Kayla M D Cornett
- Sydney School of Health Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia
- Paediatric Gait Analysis Service of New South Wales, Sydney Children's Hospitals Network, Sydney, New South Wales, Australia
| | - Joshua Burns
- Sydney School of Health Sciences, Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia
- Paediatric Gait Analysis Service of New South Wales, Sydney Children's Hospitals Network, Sydney, New South Wales, Australia
| | - Manoj P Menezes
- Children's Hospital at Westmead Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, New South Wales, Australia
- TY Nelson Department of Neurology and Neurosurgery, The Children's Hospital at Westmead, Sydney, New South Wales, Australia
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Elks N, Wilmshurst JM, Raga SV. Normal Outcome With Prenatal Intervention for Riboflavin Transporter Defect. Pediatr Neurol 2023; 144:16-18. [PMID: 37116404 DOI: 10.1016/j.pediatrneurol.2023.04.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 03/22/2023] [Accepted: 04/02/2023] [Indexed: 04/30/2023]
Abstract
BACKGROUND Riboflavin transporter deficiency is a rare but severe neurometabolic disorder. METHODS We report two siblings with pathogenic variants in SLC52A3 gene, resulting in riboflavin transporter 3 deficiency. RESULTS The first sibling was diagnosed at age 11 months with severe respiratory compromise and regression of developmental milestones. His symptoms significantly improved with riboflavin supplementation therapy. The younger sibling was diagnosed by antenatal genetic analysis; riboflavin supplementation was initiated in utero and continued from birth. Now at age two years, he remains clinically asymptomatic despite genetic confirmation of riboflavin transporter deficiency. CONCLUSIONS Antenatal riboflavin supplementation is a safe and effective treatment for the prevention of symptomatic manifestations of riboflavin transporter deficiency.
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Affiliation(s)
- Natasha Elks
- University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Jo M Wilmshurst
- Paediatric Neurology Department, Red Cross War Memorial Children's Hospital, Rondebosch, Cape Town, South Africa; Neuroscience Institute, University of Cape Town, Cape Town, South Africa
| | - Sharika V Raga
- Paediatric Neurology Department, Red Cross War Memorial Children's Hospital, Rondebosch, Cape Town, South Africa; Neuroscience Institute, University of Cape Town, Cape Town, South Africa; International Centre for Genomic Medicine in Neuromuscular Diseases Study, University College London, London, United Kingdom.
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Zhao S, Che F, Yang L, Zheng Y, Wang D, Yang Y, Wang Y. First report of paternal uniparental disomy of chromosome 8 with SLC52A2 mutation in Brown-vialetto-van laere syndrome type 2 and an analysis of genotype-phenotype correlations. Front Genet 2022; 13:977914. [PMID: 36186484 PMCID: PMC9520306 DOI: 10.3389/fgene.2022.977914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2022] [Accepted: 08/23/2022] [Indexed: 11/17/2022] Open
Abstract
Purpose: This study reports the clinical and genetic features of Brown-Vialetto-Van Laere syndrome (BVVL) type 2 in a case of uniparental disomy of chromosome 8 in mainland China and analyzes the genotype-phenotype correlation through a review of the literature of BVVL type 2 cases. Methods: The clinical characteristics, treatment, and follow-up data of the patient were summarized, and the etiology was identified by whole-exome sequencing and gene chip analysis. Correlations between the genotype and phenotype were analyzed by collecting clinical and genetic data of published cases and our patient. Results: We identified a homozygous mutation in SLC52A2 (NM_001253815.2 c.1255G>A) by trio-WES. Sanger sequencing confirmed that his father was heterozygous and his mother was wild type. Subsequently, paternal uniparental disomy of chromosome 8 [UPD (8)pat] was confirmed by chromosomal microarray analysis.The patient received long-term oral riboflavin treatment (7 mg/kg.d) and was followed up for 40 months by which time the child’s bulbar palsy, ataxia, and motor function had improved. A review of the literature and statistical analysis found that the symptoms of BVVL type 2 appear at the earliest shortly after birth and at the latest at 10 years of age. The median age of onset was 2.5 years, but the overall delay in diagnosis was a median of 5.6 years. The most common symptoms were hearing loss (83.9%), followed by muscle weakness (80.6%), visual impairment (64.5%), and ataxia (61.3%). To date, a total of 32 mutations in the SLC52A2 gene have been reported, with the most common being a missense mutation. Mutations occur throughout the length of the gene apart from at the N-terminus. In patients with missense mutations, homozygous pattern was more likely to present with ataxia as the first symptom (p < 0.05), while compound heterozygous pattern was more likely to develop respiratory insufficiency during the course of disease (p < 0.001). Moreover, patients with one missense mutation located in inside the transmembrane domain were more likely to have respiratory insufficiency than those with mutations both inside and outside the domain (p < 0.05). Riboflavin supplementation was an important factor in determining prognosis (p < 0.001). Conclusion: We report the first UPD(8)pat with SLC52A2 homozygous pathogenic mutation case in BVVL type 2, which expand the mutation spectrum of gene.
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Affiliation(s)
- Siyu Zhao
- Department of Pediatric neurology, Xi’an Children’s hospital, Xi’an, China
| | - Fengyu Che
- Shaanxi Institute of Pediatric Diseases, Xi’an Children’s Hospital, Xi’an, China
| | - Le Yang
- Department of Pediatric neurology, Xi’an Children’s hospital, Xi’an, China
| | - Yanyan Zheng
- Department of Pediatric neurology, Xi’an Children’s hospital, Xi’an, China
| | - Dong Wang
- Department of Pediatric neurology, Xi’an Children’s hospital, Xi’an, China
| | - Ying Yang
- Shaanxi Institute of Pediatric Diseases, Xi’an Children’s Hospital, Xi’an, China
- *Correspondence: Ying Yang, Yan Wang,
| | - Yan Wang
- Department of Pediatric neurology, Xi’an Children’s hospital, Xi’an, China
- *Correspondence: Ying Yang, Yan Wang,
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Silksmith B, Munot P, Starling L, Pujar S, Matthews E. Accelerating the genetic diagnosis of neurological disorders presenting with episodic apnoea in infancy. THE LANCET. CHILD & ADOLESCENT HEALTH 2022; 6:495-508. [PMID: 35525254 DOI: 10.1016/s2352-4642(22)00091-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 02/25/2022] [Accepted: 03/03/2022] [Indexed: 11/26/2022]
Abstract
Unexplained episodic apnoea in infants (aged ≤1 year), including recurrent brief (<1 min) resolved unexplained events (known as BRUE), can be a diagnostic challenge. Recurrent unexplained apnoea might suggest a persistent, debilitating, and potentially fatal disorder. Genetic diseases are prevalent among this group, particularly in those who present with paroxysmal or episodic neurological symptoms. These disorders are individually rare and challenging for a general paediatrician to recognise, and there is often a delayed or even posthumous diagnosis (sometimes only made in retrospect when a second sibling becomes unwell). The disorders can be debilitating if untreated but pharmacotherapies are available for the vast majority. That any child should suffer from unnecessary morbidity or die from one of these disorders without a diagnosis or treatment having been offered is a tragedy; therefore, there is an urgent need to simplify and expedite the diagnostic journey. We propose an apnoea gene panel for hospital specialists caring for any infant who has recurrent apnoea without an obvious cause. This approach could remove the need to identify individual rare conditions, speed up diagnosis, and improve access to therapy, with the ultimate aim of reducing morbidity and mortality.
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Affiliation(s)
- Bryony Silksmith
- Department of Neurology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Pinki Munot
- Dubowitz Neuromuscular Centre, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Luke Starling
- Centre for Inherited Cardiovascular Diseases, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Suresh Pujar
- Department of Neurology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK
| | - Emma Matthews
- Atkinson-Morley Neuromuscular Centre, Department of Neurology, St George's University Hospitals NHS Foundation Trust, London, UK; Molecular and Clinical Sciences Research Institute, St George's University of London, London, UK.
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Liu Z, Peng Q, Li J, Rao C, Lu X. BVVLS2 overlooked for 3 years in a pediatric patient caused by novel compound heterozygous mutations in SLC52A2 gene. Clin Chim Acta 2021; 523:402-406. [PMID: 34737166 DOI: 10.1016/j.cca.2021.10.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 10/22/2021] [Accepted: 10/25/2021] [Indexed: 11/17/2022]
Abstract
BACKGROUND Brown-Vialetto-Van Laere syndrome-2 (BVVLS2) is a rare autosomal recessive neurological disorder caused by mutations in the SLC52A2 gene, which is characterized by early childhood onset of sensorineural hearing loss, bulbar palsy, peripheral neuropathy, and respiratory insufficiency. We aimed to investigate the genetic cause of a 4-year-old boy who suffered from BVVLS2 whose initial presentation was severe normocytic anemia and had been overlooked for three years in a local hospital. He was misdiagnosed with pure red cell aplasia (PRCA) and treated with hormones and chemotherapy drugs, but there was no obvious effect. METHODS The targeted capture of 927 genes associated with neuromuscular disorders and next-generation sequencing were performed. Sanger sequencing was employed to verify the variant mutations. RESULTS The proband was found to be heterozygous for c.350T > C (p.L117P) in exon 3 and c.1135_1137delTGG (p.W379del) in exon 5 of SLC52A2 gene. His anemia and neurological symptoms improved significantly after treatment with low dose oral riboflavin. CONCLUSIONS This study expands the mutational spectrum of SLC52A2 and phenotypic spectrum of BVVLS2, which provides a foundation for further investigations elucidating the SLC52A2 related mechanisms of BVVLS2. A low-dosage of riboflavin supplementation was used to obtain good curative effect, which provides further future references for the clinical treatments of BVVLS.
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Affiliation(s)
- Ziqiang Liu
- Child Healthcare Department, Dongguan Children's Hospital, Dongguan, Guangdong, China
| | - Qi Peng
- Laboratory Department, Dongguan Children's Hospital, Dongguan, Guangdong, China; Department of Medical and Molecular Genetics, Dongguan Institute of Pediatrics, Dongguan, Guangdong, China; Key Laboratory for Children's Genetics and Infectious Diseases of Dongguan, Dongguan, Guangdong, China
| | - Jianwei Li
- Department of Neurology, Dongguan Children's Hospital, Dongguan, Guangdong, China
| | - Chunbao Rao
- Laboratory Department, Dongguan Children's Hospital, Dongguan, Guangdong, China; Department of Medical and Molecular Genetics, Dongguan Institute of Pediatrics, Dongguan, Guangdong, China; Key Laboratory for Children's Genetics and Infectious Diseases of Dongguan, Dongguan, Guangdong, China
| | - Xiaomei Lu
- Laboratory Department, Dongguan Children's Hospital, Dongguan, Guangdong, China; Department of Medical and Molecular Genetics, Dongguan Institute of Pediatrics, Dongguan, Guangdong, China; Key Laboratory for Children's Genetics and Infectious Diseases of Dongguan, Dongguan, Guangdong, China.
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Jin C, Yonezawa A. Recent advances in riboflavin transporter RFVT and its genetic disease. Pharmacol Ther 2021; 233:108023. [PMID: 34662687 DOI: 10.1016/j.pharmthera.2021.108023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 09/30/2021] [Accepted: 10/12/2021] [Indexed: 12/20/2022]
Abstract
Riboflavin (vitamin B2) is essential for cellular growth and function. It is enzymatically converted to flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which participate in the metabolic oxidation-reduction reactions of carbohydrates, amino acids, and lipids. Human riboflavin transporters RFVT1, RFVT2, and RFVT3 have been identified and characterized since 2008. They are highly specific transporters of riboflavin. RFVT3 has functional characteristics different from those of RFVT1 and RFVT2. RFVT3 contributes to absorption in the small intestine, reabsorption in the kidney, and transport to the fetus in the placenta, while RFVT2 mediates the tissue distribution of riboflavin from the blood. Several mutations in the SLC52A2 gene encoding RFVT2 and the SLC52A3 gene encoding RFVT3 were found in patients with a rare neurological disorder known as Brown-Vialetto-Van Laere syndrome. These patients commonly present with bulbar palsy, hearing loss, muscle weakness, and respiratory symptoms in infancy or later in childhood. A decrease in plasma riboflavin levels has been observed in several cases. Recent studies on knockout mice and patient-derived cells have advanced the understanding of these mechanisms. Here, we summarize novel findings on RFVT1-3 and their genetic diseases and discuss their potential as therapeutic drugs.
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Affiliation(s)
- Congyun Jin
- Department of Clinical Pharmacology and Therapeutics, Kyoto University Hospital, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan; Graduate School of Pharmaceutical Sciences, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan
| | - Atsushi Yonezawa
- Department of Clinical Pharmacology and Therapeutics, Kyoto University Hospital, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan; Graduate School of Pharmaceutical Sciences, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.
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11
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The audiovestibular profile of Brown-Vialetto-Van Laere syndrome. The Journal of Laryngology & Otology 2021; 135:1000-1009. [PMID: 34496984 DOI: 10.1017/s0022215121002395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND Brown-Vialetto-Van Laere syndrome, a rare disorder associated with motor, sensory and cranial nerve neuropathy, is caused by mutations in riboflavin transporter genes SLC52A2 and SLC52A3. Hearing loss is a characteristic feature of Brown-Vialetto-Van Laere syndrome and has been shown in recent studies to be characterised by auditory neuropathy spectrum disorder. METHOD This study reports the detailed audiovestibular profiles of four cases of Brown-Vialetto-Van Laere syndrome with SLC52A2 and SLC52A3 mutations. All of these patients had auditory neuropathy spectrum disorder. RESULTS There was significant heterogeneity in vestibular function and in the benefit gained from cochlear implantation. The audiological response to riboflavin therapy was also variable, in contrast to generalised improvement in motor function. CONCLUSION We suggest that comprehensive testing of vestibular function should be conducted in Brown-Vialetto-Van Laere syndrome, in addition to serial behavioural audiometry as part of the systematic examination of the effects of riboflavin.
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Carey G, Kuchcinski G, Gauvrit F, Defebvre L, Nguyen S, Dhaenens CM, Dessein AF, Vianey-Saban C, Acquaviva C, Tard C. Three cases of adult-onset Brown-Vialetto-Van Laere syndrome: Novel variants in SLC52A3 gene and MRI abnormalities. Neuromuscul Disord 2021; 31:752-755. [PMID: 34384672 DOI: 10.1016/j.nmd.2021.06.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 06/15/2021] [Accepted: 06/21/2021] [Indexed: 11/24/2022]
Abstract
Brown-Vialetto-Van Laere syndrome is a rare, autosomal, recessive neurological condition caused by variants in the riboflavin transporter genes SLC52A2 and SLC52A3. Here, we report on three cases. Case 1 was a 35-year-old woman from a consanguineous family who presented with progressive deafness, subacute multiple cranial nerve impairments (III, VII, IX, XII), and MRI abnormalities (including as hypersignal from the cranial nerves). The patient was homozygous for a novel SLC52A3variant. Case 2 was the woman's brother, who presented similar symptoms. Case 3 was an 18-year-old woman experiencing progressive hearing loss, bilateral steppage gait and a cranial nerves impairment (VII and XII). MRI revealed hypersignal in the root nerves and cauda equina. A novel heterozygous variant in SLC52A3 was identified. A subacute history of polyradiculoneuropathy along with progressive deafness, cranial nerve impairment, and MRI abnormalities should raise suspicion for Brown-Vialetto-Van Laere syndrome.
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Affiliation(s)
- Guillaume Carey
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, F-59000 Lille, France; Neurology Department, Lille University Medical Center, Lille, France.
| | - Gregory Kuchcinski
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, F-59000 Lille, France; Neuroradiology Department, Lille University Medical Center, Lille, France
| | - Fanny Gauvrit
- ENT Department, Lille University Medical Center, Lille, France
| | - Luc Defebvre
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, F-59000 Lille, France; Neurology Department, Lille University Medical Center, Lille, France
| | - Sylvie Nguyen
- Centre de référence des maladies neuromusculaires Nord Est Ile de France, Lille University Medical Centre, Lille, France; Neuropediatric Department, Lille University Medical Center, Lille, France
| | - Claire-Marie Dhaenens
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, F-59000 Lille, France
| | - Anne Frédérique Dessein
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, F-59000 Lille, France
| | - Christine Vianey-Saban
- Service de Biochimie et Biologie Moléculaire, UF Maladies Héréditaires du Métabolisme, Hospices Civils de Lyon, Bron, France
| | - Cécile Acquaviva
- Service de Biochimie et Biologie Moléculaire, UF Maladies Héréditaires du Métabolisme, Hospices Civils de Lyon, Bron, France
| | - Céline Tard
- Univ. Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, F-59000 Lille, France; Centre de référence des maladies neuromusculaires Nord Est Ile de France, Lille University Medical Centre, Lille, France; Neurology Department, Lille University Medical Center, Lille, France
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13
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Naz S. Molecular genetic landscape of hereditary hearing loss in Pakistan. Hum Genet 2021; 141:633-648. [PMID: 34308486 DOI: 10.1007/s00439-021-02320-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 07/17/2021] [Indexed: 01/13/2023]
Abstract
Approximately 14.5 million Pakistani individuals have a hearing loss and half of these cases may be due to genetic causes. Though significant progress has been made in uncovering genetic variants for recessively inherited nonsyndromic deafness, Pendred syndrome, and Usher syndromes, the same is not true for dominantly inherited hearing loss, most syndromic cases and deafness with complex inheritance patterns. Variants of 57 genes have been reported to cause nonsyndromic recessive deafness in Pakistan, though most are rare. Variants of just five genes GJB2, HGF, MYO7A, SLC26A4, and TMC1 together explain 57% of profound deafness while those of GJB2, MYO15A, OTOF, SLC26A4, TMC1, and TMPRSS3 account for 47% of moderate to severe hearing loss. In contrast, although variants of at least 39 genes have been implicated in different deafness syndromes, their prevalence in the population and the spectrum of mutations have not been explored. Furthermore, research on genetics of deafness has mostly focused on individuals from the Punjab province and needs to be extended to other regions of Pakistan. Identifying the genes and their variants causing deafness in all ethnic groups is important as it will pinpoint rare as well as recurrent mutations. This information may ultimately help in offering genetic counseling and future treatments.
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Affiliation(s)
- Sadaf Naz
- School of Biological Sciences, University of the Punjab, Quaid-e-Azam Campus, Lahore, 54590, Pakistan.
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14
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Pająk R, Mendela E, Będkowska N, Paprocka J. Update on Neuropathies in Inborn Errors of Metabolism. Brain Sci 2021; 11:brainsci11060763. [PMID: 34201281 PMCID: PMC8227217 DOI: 10.3390/brainsci11060763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 05/31/2021] [Accepted: 06/02/2021] [Indexed: 11/16/2022] Open
Abstract
Neuropathies are relatively common in inborn errors of metabolism (IEMs); however, due to the early onset and severe, progressive course of many IEMs, they have not been very well researched yet. This article aims to review and compare neuropathies in inborn errors of metabolism, mostly with childhood and juvenile onset. Some of these diseases are treatable if diagnosed early and in many cases, the therapy can not only slow down disease progression, but can also reverse the changes already made by the condition.
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Affiliation(s)
- Renata Pająk
- Students’ Scientific Society, Department of Pediatric Neurology, Faculty of Medical Sciences in Katowice, Medical University of Silesia, 40-752 Katowice, Poland; (R.P.); (E.M.); (N.B.)
| | - Ewelina Mendela
- Students’ Scientific Society, Department of Pediatric Neurology, Faculty of Medical Sciences in Katowice, Medical University of Silesia, 40-752 Katowice, Poland; (R.P.); (E.M.); (N.B.)
| | - Natalia Będkowska
- Students’ Scientific Society, Department of Pediatric Neurology, Faculty of Medical Sciences in Katowice, Medical University of Silesia, 40-752 Katowice, Poland; (R.P.); (E.M.); (N.B.)
| | - Justyna Paprocka
- Department of Pediatric Neurology, Faculty of Medical Sciences in Katowice, Medical University of Silesia, 40-752 Katowice, Poland
- Correspondence:
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15
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Console L, Tolomeo M, Indiveri C. Functional Study of the Human Riboflavin Transporter 2 Using Proteoliposomes System. Methods Mol Biol 2021; 2280:45-54. [PMID: 33751428 DOI: 10.1007/978-1-0716-1286-6_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Riboflavin is essential for cell viability. The biologically active forms of riboflavin, FMN and FAD, participate in many biochemical redox reactions including the metabolism of carbohydrates, amino acids, and lipids. Differently from bacteria, fungi, and plants which synthesize riboflavin, higher organisms have lost the ability to synthesize the vitamin and must absorb it from food and intestinal microflora production. The riboflavin flux through cell membranes occurs via specific transporters belonging to the SLC52 family. Three members of this family have been identified so far which show poor homology with the riboflavin transporters of Saccharomyces cerevisiae or bacteria. Alterations of RFVTs are causative of severe diseases. Indeed, under pathological stress, humans are susceptible of developing riboflavin deficiency. Such a deficiency in pregnancy induces fetus abnormalities, and has been indicated as a risk factor for anemia, cancer, cardiovascular diseases, and neurodegeneration. Moreover, inherited diseases are also of interest; the most well-described is the Brown-Vialetto-van Laere syndrome, a rare neurological disorder characterized by infancy onset sensorineural deafness and pontobulbar palsy. Numerous polymorphisms of Slc52a2 and Slc52a3 genes associated with this syndrome have been discovered. In spite of their important metabolic role and their relevance to human health, the riboflavin transporters are still poorly characterized. Bacterial overexpression, purification, and protein reconstitution in liposomes represent an up-to-date methodology for obtaining functional data information. The methodology for reconstituting the RFVT2 into proteoliposomes and performing transport assay is described. These methods will be suitable for investigating the functional defects of the variants of RFVTs associated with human pathologies.
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Affiliation(s)
- Lara Console
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy
| | - Maria Tolomeo
- Department of Biosciences, Biotechnology and Biopharmaceutics, University of Bari, Bari, Italy
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria, Arcavacata di Rende, Italy.
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16
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Wongworawat YC, Liu YA, Raghavan R, White CL, Dietz R, Zuppan C, Rosenfeld J. Aggressive FUS-Mutant Motor Neuron Disease Without Profound Spinal Cord Pathology. J Neuropathol Exp Neurol 2020; 79:365-369. [PMID: 32142142 DOI: 10.1093/jnen/nlaa011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 08/07/2019] [Indexed: 12/11/2022] Open
Abstract
A 29-year-old man presented with rapidly progressive severe neck weakness, asymmetrical bilateral upper extremity weakness, bulbar dysfunction, profound muscle wasting, and weight loss. Within 1 year, his speech became unintelligible, he became gastrostomy- and tracheostomy/ventilator-dependent, and wheelchair bound. Electrophysiology suggested motor neuron disease. Whole exome sequencing revealed a heterozygous pathogenic variant in the fused in sarcoma gene (FUS), c.1574C>T,p. R525L, consistent with autosomal dominant amyotrophic lateral sclerosis. Autopsy revealed extensive denervation atrophy of skeletal musculature. Surprisingly, there was only minimal patchy depletion of motor neurons within the cervico-thoracic spinal cord anterior horn cells, and the tracts were largely preserved. TDP-43 inclusions were absent. Abnormal expression of FUS mutation product (cytoplasmic inclusions) was demonstrated by immunohistochemistry within anterior horn motor neurons. The most prominent finding was a disparity between profound neck weakness and relatively low-grade anterior horn cell loss or tract degeneration in the cervico-thoracic cord.
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Affiliation(s)
- Yan Chen Wongworawat
- Department of Pathology and Laboratory Medicine, Loma Linda University Medical Center
| | - Yin Allison Liu
- Department of Pediatrics/Child Neurology, Loma Linda University Children's Hospital, Loma Linda, California
| | - Ravi Raghavan
- Department of Pathology and Laboratory Medicine, Loma Linda University Medical Center
| | - Charles L White
- Department of Pathology/Neuropathology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Robin Dietz
- Department of Pathology and Laboratory Medicine, Loma Linda University Medical Center
| | - Craig Zuppan
- Department of Pathology and Laboratory Medicine, Loma Linda University Medical Center
| | - Jeffrey Rosenfeld
- Department of Neurology, Loma Linda University Medical Center, Loma Linda, California
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17
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Effect of riboflavin deficiency on development of the cerebral cortex in Slc52a3 knockout mice. Sci Rep 2020; 10:18443. [PMID: 33116204 PMCID: PMC7595085 DOI: 10.1038/s41598-020-75601-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 10/19/2020] [Indexed: 12/13/2022] Open
Abstract
Riboflavin transporter 3 (RFVT3), encoded by the SLC52A3 gene, is important for riboflavin homeostasis in the small intestine, kidney, and placenta. Our previous study demonstrated that Slc52a3 knockout (Slc52a3−/−) mice exhibited neonatal lethality and metabolic disorder due to riboflavin deficiency. Here, we investigated the influence of Slc52a3 gene disruption on brain development using Slc52a3−/− embryos. Slc52a3−/− mice at postnatal day 0 showed hypoplasia of the brain and reduced thickness of cortical layers. At embryonic day 13.5, the formation of Tuj1+ neurons and Tbr2+ intermediate neural progenitors was significantly decreased; no significant difference was observed in the total number and proliferative rate of Pax6+ radial glia. Importantly, the hypoplastic phenotype was rescued upon riboflavin supplementation. Thus, it can be concluded that RFVT3 contributes to riboflavin homeostasis in embryos and that riboflavin itself is required during embryonic development of the cerebral cortex in mice.
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18
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Carreau C, Benoit C, Ahle G, Cauquil C, Roubertie A, Lenglet T, Cosgrove J, Meunier I, Veauville-Merllié A, Acquaviva-Bourdain C, Nadjar Y. Late-onset riboflavin transporter deficiency: a treatable mimic of various motor neuropathy aetiologies. J Neurol Neurosurg Psychiatry 2020; 92:jnnp-2020-323304. [PMID: 33087424 DOI: 10.1136/jnnp-2020-323304] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 07/27/2020] [Accepted: 08/18/2020] [Indexed: 11/03/2022]
Abstract
OBJECTIVE Riboflavin transporter deficiencies (RTDs), involving SLC52A3 and SLC52A2 genes, have recently been related to Brown-Vialetto-Van Laere (BVVL) syndrome, a hereditary paediatric condition associating motor neuropathy (MN) and deafness. BVVL/RTD has rarely been reported in adult patients, but is probably underdiagnosed due to poor knowledge and lack of awareness of this form of disease among neurologists. In this study, we aimed to investigate the phenotype and prognosis of RTD patients with late-onset MN. METHODS We retrospectively collected clinical, biological and electrophysiological data from all French RTD patients with MN onset after 10 years of age (n=6) and extracted data from 19 other similar RTD patients from the literature. RESULTS Adult RTD patients with MN had heterogeneous clinical presentations, potentially mimicking amyotrophic lateral sclerosis or distal hereditary motor neuropathy (56%), multinevritis with cranial nerve involvement (16%), Guillain-Barré syndrome (8%) and mixed motor and sensory neuronopathy syndromes (20%, only in SLC52A2 patients). Deafness was often diagnosed before MN (in 44%), but in some patients, onset began only with MN (16%). The pattern of weakness varied widely, and the classic pontobulbar palsy described in BVVL was not constant. Biochemical tests were often normal. The majority of patients improved under riboflavin supplementation (86%). INTERPRETATION Whereas late-onset RTD may mimic different acquired or genetic causes of motor neuropathies, it is a diagnosis not to be missed since high-dose riboflavin per oral supplementation is often highly efficient.
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Affiliation(s)
- Christophe Carreau
- Department of Neurology, Reference Center for Lysosomal Diseases, Neuro-Metabolism Unit, AP-HP, Hôpital Universitaire Pitié Salpêtrière, Paris, France
| | - Charline Benoit
- Department of Neurology, AP-HP, Hôpital Universitaire Pitié Salpêtrière, Paris, France
| | - Guido Ahle
- Neurology, Hôpital Louis Pasteur, Colmar, Alsace, France
| | - Cécile Cauquil
- Neurology, Hôpital Bicêtre, Le Kremlin-Bicêtre, Île-de-France, France
| | - Agathe Roubertie
- Neuropediatrie, Hôpital Gui de Chauliac Pôle Neurosciences tête et cou, Montpellier, Languedoc-Roussillon Midi, France
| | - Timothée Lenglet
- Department of Neurophysiology, AP-HP, Hôpital Universitaire Pitié Salpêtrière, Paris, France
| | | | - Isabelle Meunier
- Ophthalmology, Hôpital Gui de Chauliac, Montpellier, Languedoc-Roussillon, France
| | - Alice Veauville-Merllié
- Laboratory of Inborn Errors of Metabolism, Hospices Civils de Lyon, Lyon, Auvergne-Rhône-Alpes, France
| | - Cécile Acquaviva-Bourdain
- Laboratory of Inborn Errors of Metabolism, Hospices Civils de Lyon, Lyon, Auvergne-Rhône-Alpes, France
| | - Yann Nadjar
- Department of Neurology, Reference Center for Lysosomal Diseases, Neuro-Metabolism Unit, AP-HP, Hôpital Universitaire Pitié Salpêtrière, Paris, France
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19
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Lyles JL, Hellmann JA, Oliveira SB. Neurologic Complications due to Severe Micronutrient Deficiencies in an American Adolescent. Nutr Clin Pract 2020; 36:1059-1062. [PMID: 32946633 DOI: 10.1002/ncp.10573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 07/13/2020] [Accepted: 08/16/2020] [Indexed: 11/07/2022] Open
Abstract
Micronutrient deficiencies are a major global health problem but are less common in developed nations. If left unidentified and untreated, micronutrient deficiencies can lead to serious, sometimes irreversible, sequelae such as with vitamin A deficiency and vision loss. Providers should recognize these issues not only in chronically ill and hospitalized patients but in those with non-illness-related malnutrition due to parent/child-selected restricted diets. Herein, we present a case of unrecognized chronic, severe, malnutrition due to severe behavioral food selectivity with associated neurologic deficits due to hypovitaminosis (vitamins A and B2 ). With adequate enteral nutrition and vitamin repletion, our patient's neurologic deficits have partially recovered.
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Affiliation(s)
- John L Lyles
- Division of Gastroenterology, Hepatology, and Nutrition, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Jennifer A Hellmann
- Division of Gastroenterology, Hepatology, and Nutrition, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Stephanie B Oliveira
- Division of Gastroenterology, Hepatology, and Nutrition, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
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20
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Amir F, Atzinger C, Massey K, Greinwald J, Hunter LL, Ulm E, Kettler M. The Clinical Journey of Patients with Riboflavin Transporter Deficiency Type 2. J Child Neurol 2020; 35:283-290. [PMID: 31868069 DOI: 10.1177/0883073819893159] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
PURPOSE To identify symptoms and health care interactions with patients with riboflavin transporter deficiency (RTD) type 2 prior to diagnosis. METHODS Parents of children with riboflavin transporter deficiency type 2 (n = 10) were interviewed to collect data on the patient's clinical journey. RESULTS The average diagnostic delay was 27.6 months. Neurologists were the most commonly visited clinician (90%). Common symptoms during the first year of the patient's clinical journey included abnormal gait and/or ataxia (70%), nystagmus (50%), and upper body muscle weakness (40%). Prior to diagnosis, optic atrophy, sleep apnea, breath-holding spells, and dysphagia were commonly observed. Hearing loss was only reported in 40% of subjects prior to diagnosis. Riboflavin responsive megaloblastic anemia is reported for the first time. Mitochondrial disease was the most common suspected diagnosis (30%). CONCLUSION Despite clinical variability, common early symptoms of riboflavin transporter deficiency type 2 exist that can better allow clinicians to more rapidly identify riboflavin transporter deficiency type 2.
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Affiliation(s)
- Fatima Amir
- College of Medicine, University of Cincinnati, Cincinnati, OH, USA.,Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Carrie Atzinger
- College of Medicine, University of Cincinnati, Cincinnati, OH, USA.,Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | | | - John Greinwald
- Division of Pediatric Otolaryngology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Lisa L Hunter
- Cincinnati Children's Hospital Medical Center, Center for Professional Excel Rsch & EBP, Cincinnati, OH, USA
| | - Elizabeth Ulm
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Margaret Kettler
- Division of Audiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
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21
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Mutlu B, Topçu MT, Çiprut A. A Case with Brown-Vialetto-Van Laere Syndrome: A Sudden Onset Auditory Neuropathy Spectrum Disorder. Turk Arch Otorhinolaryngol 2019; 57:201-205. [PMID: 32128519 DOI: 10.5152/tao.2019.4639] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Accepted: 11/10/2019] [Indexed: 11/22/2022] Open
Abstract
The Brown-Vialetto-Van Laere syndrome (BVVLS) is a rare neurological disorder that may present at all ages with sensorineural hearing loss, bulbar palsy and respiratory compromise. We describe a 6-year-old male patient who suffered bilateral sudden onset severe hearing loss for two years. Audiological investigations revealed sudden onset auditory neuropathy spectrum disorder bilaterally. He also had neurological complaints. During riboflavin therapy an improvement in hearing loss and the benefit of hearing aids were observed. In BVVLS, it is difficult to plan and apply auditory rehabilitation interventions and the results vary from patient to patient. In audiological evaluation, it should be borne in mind that subjective and objective tests are complemental. Early medical intervention and regular audiological follow-up are very important for effective hearing rehabilitation in the patients with BVVLS.
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Affiliation(s)
- Başak Mutlu
- Department of Audiology, İstanbul Medeniyet University School of Health Sciences, İstanbul, Turkey
| | - Merve Torun Topçu
- Department of Audiology, İstanbul Medeniyet University School of Health Sciences, İstanbul, Turkey
| | - Ayça Çiprut
- Department of Audiology, Marmara University School of Medicine, İstanbul, Turkey
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22
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Reconstitution in Proteoliposomes of the Recombinant Human Riboflavin Transporter 2 (SLC52A2) Overexpressed in E. coli. Int J Mol Sci 2019; 20:ijms20184416. [PMID: 31500345 PMCID: PMC6769532 DOI: 10.3390/ijms20184416] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 09/03/2019] [Accepted: 09/06/2019] [Indexed: 11/30/2022] Open
Abstract
Background: the SLC52A2 gene encodes for the riboflavin transporter 2 (RFVT2). This transporter is ubiquitously expressed. It mediates the transport of Riboflavin across cell membranes. Riboflavin plays a crucial role in cells since its biologically active forms, FMN and FAD, are essential for the metabolism of carbohydrates, amino acids, and lipids. Mutation of the Riboflavin transporters is a risk factor for anemia, cancer, cardiovascular disease, neurodegeneration. Inborn mutations of SLC52A2 are associated with Brown-Vialetto-van Laere syndrome, a rare neurological disorder characterized by infancy onset. In spite of the important metabolic and physio/pathological role of this transporter few data are available on its function and regulation. Methods: the human recombinant RFVT2 has been overexpressed in E. coli, purified and reconstituted into proteoliposomes in order to characterize its activity following the [3H]Riboflavin transport. Results: the recombinant hRFVT2 showed a Km of 0.26 ± 0.07 µM and was inhibited by lumiflavin, FMN and Mg2+. The Riboflavin uptake was also regulated by Ca2+. The native protein extracted from fibroblast and reconstituted in proteoliposomes also showed inhibition by FMN and lumiflavin. Conclusions: proteoliposomes represent a suitable model to assay the RFVT2 function. It will be useful for screening the mutation of RFVT2.
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23
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O'Callaghan B, Bosch AM, Houlden H. An update on the genetics, clinical presentation, and pathomechanisms of human riboflavin transporter deficiency. J Inherit Metab Dis 2019; 42:598-607. [PMID: 30793323 DOI: 10.1002/jimd.12053] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 12/31/2018] [Indexed: 11/10/2022]
Abstract
Riboflavin transporter deficiency (RTD) is a rare neurological condition that encompasses the Brown-Vialetto-Van Laere and Fazio-Londe syndromes since the discovery of pathogenic mutations in the SLC52A2 and SLC52A3 genes that encode human riboflavin transporters RFVT2 and RFVT3. Patients present with a deteriorating progression of peripheral and cranial neuropathy that causes muscle weakness, vision loss, deafness, sensory ataxia, and respiratory compromise which when left untreated can be fatal. Considerable progress in the clinical and genetic diagnosis of RTDs has been made in recent years and has permitted the successful lifesaving treatment of many patients with high dose riboflavin supplementation. In this review, we first outline the importance of riboflavin and its efficient transmembrane transport in human physiology. Reports on 109 patients with a genetically confirmed diagnosis of RTD are then summarized in order to highlight commonly presenting clinical features and possible differences between patients with pathogenic SLC52A2 (RTD2) or SLC52A3 (RTD3) mutations. Finally, we focus attention on recent work with different models of RTD that have revealed possible pathomechanisms contributing to neurodegeneration in patients.
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Affiliation(s)
- Benjamin O'Callaghan
- MRC Centre for Neuromuscular Diseases, Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK
| | - Annet M Bosch
- Emma Children's Hospital, Amsterdam UMC, University of Amsterdam, Pediatric Metabolic Diseases, Amsterdam, The Netherlands
| | - Henry Houlden
- MRC Centre for Neuromuscular Diseases, Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and National Hospital for Neurology and Neurosurgery, London, UK
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