Sensory neuropathy as a manifestation of multiple acyl-coenzyme A dehydrogenase deficiency.

Multiple acyl-coenzyme A dehydrogenase deficiency (MADD) is a rare metabolic disorder which typically manifests with muscle weakness. However, despite late-onset MADD being treatable, it is often misdiagnosed, due in part to the heterogeneity of presentations. We report a case of late-onset MADD manifesting first as a sensory neuropathy before progressing to myopathic symptoms and acute metabolic decompensation. Early diagnostic workup with acylcarnitine profiling and organic acid analysis was critical in patient outcome; metabolic decompensation and myopathic symptoms were completely reversed with riboflavin supplementation and dietary modification, although sensory neuropathy persisted. Clinical consideration of MADD as part of the differential diagnosis of neuropathy with myopathy is crucial for a timely diagnosis and treatment of MADD.

The presence of white cell Jordan's anomaly in multiple Acyl-CoA dehydrogenase deficiency: A case report and implications for clinical practice.

BACKGROUND: Multiple Acyl-CoA Dehydrogenase Deficiency (MADD), also known as Glutaric Aciduria Type II, is an exceptionally rare autosomal recessive genetic disorder that disrupts the metabolism of fatty acids, amino acids, and choline. It presents with a wide range of clinical manifestations, from severe neonatal-onset forms to milder late-onset cases, with symptoms including metabolic disturbances and muscle weakness. Jordan's anomaly is a distinctive morphological feature found in peripheral blood white cells and is typically associated with Neutral Lipid Storage Disease (NLSD). CASE REPORT: In our case report, the patient initially presented with symptoms of vomiting, abdominal pain, and altered consciousness. The presence of white cell Jordan's anomaly was detected in the blood smear. Subsequent serum tests revealed elevated levels of transaminases, creatine kinase, uric acid, and multiple acylcarnitines, while blood glucose and free carnitine levels were notably reduced. High-throughput sequencing confirmed heterozygous pathogenic variants in the electron-transferring flavoprotein dehydrogenase (ETFDH) gene, leading to the conclusive diagnosis of MADD. Following a three-month treatment regimen involving high-dose vitamin B2, coenzyme Q10, and other supportive interventions, the patient exhibited significant clinical improvement, ultimately resulting in discharge. CONCLUSION: The identification of Jordan's anomaly in a pediatric patient with late-onset MADD sheds light on its broader implications within the realm of lipid storage myopathies. The significance of this finding extends beyond its conventional association with NLSD, challenging the notion of its exclusivity. This novel observation serves as a compelling reminder of the diagnostic significance this morphological abnormality holds, potentially revolutionizing diagnostic practices within the field.

Clinical, biochemical, and genetic spectrum of MADD in a South African cohort: an ICGNMD study.

BACKGROUND: Multiple acyl-CoA dehydrogenase deficiency (MADD) is an autosomal recessive disorder resulting from pathogenic variants in three distinct genes, with most of the variants occurring in the electron transfer flavoprotein-ubiquinone oxidoreductase gene (ETFDH). Recent evidence of potential founder variants for MADD in the South African (SA) population, initiated this extensive investigation. As part of the International Centre for Genomic Medicine in Neuromuscular Diseases study, we recruited a cohort of patients diagnosed with MADD from academic medical centres across SA over a three-year period. The aim was to extensively profile the clinical, biochemical, and genomic characteristics of MADD in this understudied population. METHODS: Clinical evaluations and whole exome sequencing were conducted on each patient. Metabolic profiling was performed before and after treatment, where possible. The recessive inheritance and phase of the variants were established via segregation analyses using Sanger sequencing. Lastly, the haplotype and allele frequencies were determined for the two main variants in the four largest SA populations. RESULTS: Twelve unrelated families (ten of White SA and two of mixed ethnicity) with clinically heterogeneous presentations in 14 affected individuals were observed, and five pathogenic ETFDH variants were identified. Based on disease severity and treatment response, three distinct groups emerged. The most severe and fatal presentations were associated with the homozygous c.[1067G > A];c.[1067G > A] and compound heterozygous c.[976G > C];c.[1067G > A] genotypes, causing MADD types I and I/II, respectively. These, along with three less severe compound heterozygous genotypes (c.[1067G > A];c.[1448C > T], c.[740G > T];c.[1448C > T], and c.[287dupA*];c.[1448C > T]), resulting in MADD types II/III, presented before the age of five years, depending on the time and maintenance of intervention. By contrast, the homozygous c.[1448C > T];c.[1448C > T] genotype, which causes MADD type III, presented later in life. Except for the type I, I/II and II cases, urinary metabolic markers for MADD improved/normalised following treatment with riboflavin and L-carnitine. Furthermore, genetic analyses of the most frequent variants (c.[1067G > A] and c.[1448C > T]) revealed a shared haplotype in the region of ETFDH, with SA population-specific allele frequencies of < 0.00067-0.00084%. CONCLUSIONS: This study reveals the first extensive genotype-phenotype profile of a MADD patient cohort from the diverse and understudied SA population. The pathogenic variants and associated variable phenotypes were characterised, which will enable early screening, genetic counselling, and patient-specific treatment of MADD in this population.

A comparative study on riboflavin responsive multiple acyl-CoA dehydrogenation deficiency due to variants in FLAD1 and ETFDH gene.

Lipid storage myopathy (LSM) is a heterogeneous group of lipid metabolism disorders predominantly affecting skeletal muscle by triglyceride accumulation in muscle fibers. Riboflavin therapy has been shown to ameliorate symptoms in some LSM patients who are essentially concerned with multiple acyl-CoA dehydrogenation deficiency (MADD). It is proved that riboflavin responsive LSM caused by MADD is mainly due to ETFDH gene variant (ETFDH-RRMADD). We described here a case with riboflavin responsive LSM and MADD resulting from FLAD1 gene variants (c.1588 C > T p.Arg530Cys and c.1589 G > C p.Arg530Pro, FLAD1-RRMADD). And we compared our patient together with 9 FLAD1-RRMADD cases from literature to 106 ETFDH-RRMADD cases in our neuromuscular center on clinical history, laboratory investigations and pathological features. Furthermore, the transcriptomics study on FLAD1-RRMADD and ETFDH-RRMADD were carried out. On muscle pathology, both FLAD1-RRMADD and ETFDH-RRMADD were proved with lipid storage myopathy in which atypical ragged red fibers were more frequent in ETFDH-RRMADD, while fibers with faint COX staining were more common in FLAD1-RRMADD. Molecular study revealed that the expression of GDF15 gene in muscle and GDF15 protein in both serum and muscle was significantly increased in FLAD1-RRMADD and ETFDH-RRMADD groups. Our data revealed that FLAD1-RRMADD (p.Arg530) has similar clinical, biochemical, and fatty acid metabolism changes to ETFDH-RRMADD except for muscle pathological features.

Riboflavin-responsive lipid-storage myopathy in elderly patients.

There are scarce reports of riboflavin-responsive lipid storage myopathy in elderly patients with onset in their sixties. We describe three elderly patients with riboflavin-responsive lipid-storage myopathy. All three patients (aged 67-71 years on first examination) had subacute onset of neck extensors and proximal limb weakness progressing to inability to rise from a sitting position or to walk. Muscle biopsies showed vacuoles with lipid content, mainly in type 1 fibers. Genetic analysis failed to identify any pathogenic variant in one patient, identified a heterozygous variant of uncertain significance c.812 A > G; p.Tyr271Cys in the ETFDH gene in the second patient, and revealed a heterozygote likely pathogenic variant c.1286-2 A > C in the ETFDH gene predicted to cause abnormal splicing in the third patient. All patients responded to treatment with riboflavin and carnitine, and regained normal strength. This report emphasizes the importance of muscle biopsy in revealing treatable lipid storage myopathy in elderly patients with progressive myopathy of unidentifiable cause.

Retrograde response to mitochondrial dysfunctions associated to LOF variations in FLAD1 exon 2: unraveling the importance of RFVT2.

Flavin adenine dinucleotide (FAD) synthase (EC 2.7.7.2), encoded by human flavin adenine dinucleotide synthetase 1 (FLAD1), catalyzes the last step of the pathway converting riboflavin (Rf) into FAD. FLAD1 variations were identified as a cause of LSMFLAD (lipid storage myopathy due to FAD synthase deficiency, OMIM #255100), resembling Multiple Acyl-CoA Dehydrogenase Deficiency, sometimes treatable with high doses of Rf; no alternative therapeutic strategies are available. We describe here cell morphological and mitochondrial alterations in dermal fibroblasts derived from a LSMFLAD patient carrying a homozygous truncating FLAD1 variant (c.745C > T) in exon 2. Despite a severe decrease in FAD synthesis rate, the patient had decreased cellular levels of Rf and flavin mononucleotide and responded to Rf treatment. We hypothesized that disturbed flavin homeostasis and Rf-responsiveness could be due to a secondary impairment in the expression of the Rf transporter 2 (RFVT2), encoded by SLC52A2, in the frame of an adaptive retrograde signaling to mitochondrial dysfunction. Interestingly, an antioxidant response element (ARE) is found in the region upstream of the transcriptional start site of SLC52A2. Accordingly, we found that abnormal mitochondrial morphology and impairments in bioenergetics were accompanied by increased cellular reactive oxygen species content and mtDNA oxidative damage. Concomitantly, an active response to mitochondrial stress is suggested by increased levels of PPARγ-co-activator-1α and Peroxiredoxin III. In this scenario, the treatment with high doses of Rf might compensate for the secondary RFVT2 molecular defect, providing a molecular rationale for the Rf responsiveness in patients with loss of function variants in FLAD1 exon 2.HIGHLIGHTSFAD synthase deficiency alters mitochondrial morphology and bioenergetics;FAD synthase deficiency triggers a mitochondrial retrograde response;FAD synthase deficiency evokes nuclear signals that adapt the expression of RFVT2.

The clinical, pathological, and genetic characteristics of lipid storage myopathy in northern China.

BACKGROUND: The lipid storage myopathy (LSM) diagnosis is based on the patient's clinical manifestations and muscle pathology. However, when genetic testing is lacking, there is a high rate of misdiagnosis of the disease. This study aimed to investigate the clinical and pathological features of genetically diagnosed LSM in northern China, analyze genetic mutations' characteristics, and improve the LSM diagnostic rate. METHODS: Twenty patients with LSM diagnosed were collected; meanwhile, the clinical data, muscle samples, and routine pathological staining of muscle specimens were collected. The morphological changes of muscle fibers were observed under an optical microscope. RESULTS: Among the included patients, 18 cases had ETFDH (HGNC ID: 3483) mutations, and two had PNPLA2 mutations. Family pedigree verification was performed on three patients with heterozygous mutations in the ETFDH gene complex. Histopathological staining showed that all patients had fine vacuoles in the muscle fibers, and some of them merged to form fissures, and the lipid droplets increased in cells. After therapy, 18 patients were associated with a favorable prognosis, and two patients were ineffective with the treatment of neutral lipid storage myopathy (NLSDM) caused by PNPLA2 mutation. DISCUSSION: The clinical manifestations of LSM are complex and diverse, mainly manifested by proximal muscle weakness and exercise intolerance in the extremities. The pathological images of LSM muscles are abnormal storage of lipid droplets in muscle fibers, primarily involving type I fibers. The LSM patients were mainly multiple acyl-CoA dehydrogenase deficiency (MADD) caused by the ETFDH gene mutation. It is necessary to perform an accurate typing diagnosis of LSM.

Characterization of 31 Patients with Riboflavin-Responsive Multiple acyl-CoA Dehydrogenase Deficiency

Aims: To evaluate the clinical, pathological, and genetic features of patients with riboflavin-responsive multiple acyl-CoA dehydrogenase deficiency (RR-MADD). Methods: Thirty-one patients with RR-MADD admitted to our hospital from January 2005 to November 2020 were enrolled, and their clinical data were collected. Pathological characteristics of the muscle tissue and possible pathogenic gene mutations were analyzed. Results: The most common clinical features in all patients were symmetrical proximal muscle weakness. Laboratory examination revealed elevated levels of creatine kinase, homocysteine, and uric acid, acylcarnitines, and organic acid. The muscle biopsy revealed typical pathological changes like lipid deposition. Genetic analysis identified ETFDH mutations in 29 patients, among which one had homozygotes, 19 had compound heterozygotes, 7 had heterozygous mutations, and 2 had heterozygous mutations of both ETFDH and ETFA. Two patients had no pathogenic gene mutations. All patients were treated with riboflavin, and their symptoms improved, which was consistent with the diagnosis of RR-MADD. Conclusion: The clinical manifestations and genetic test results of patients with RR-MADD are heterogeneous. Therefore, a comprehensive analysis of clinical, pathological, and genetic testing is essential for the early diagnosis of RR-MADD.

Clinical, pathological and genetic features and follow-up of 110 patients with late-onset MADD: a single-center retrospective study.

To observe a long-term prognosis in late-onset multiple acyl-coenzyme-A dehydrogenation deficiency (MADD) patients and to determine whether riboflavin should be administrated in the long-term and high-dosage manner, we studied the clinical, pathological and genetic features of 110 patients with late-onset MADD in a single neuromuscular center. The plasma riboflavin levels and a long-term follow-up study were performed. We showed that fluctuating proximal muscle weakness, exercise intolerance and dramatic responsiveness to riboflavin treatment were essential clinical features for all 110 MADD patients. Among them, we identified 106 cases with ETFDH variants, 1 case with FLAD1 variants and 3 cases without causal variants. On muscle pathology, fibers with cracks, atypical ragged red fibers (aRRFs) and diffuse decrease of SDH activity were the distinctive features of these MADD patients. The plasma riboflavin levels before treatment were significantly decreased in these patients as compared to healthy controls. Among 48 MADD patients with a follow-up of 6.1 years on average, 31 patients were free of muscle weakness recurrence, while 17 patients had episodes of slight muscle weakness upon riboflavin withdrawal, but recovered after retaking a small-dose of riboflavin for a short-term. Multivariate Cox regression analysis showed vegetarian diet and masseter weakness were independent risk factors for muscle weakness recurrence. In conclusion, fibers with cracks, aRRFs and diffuse decreased SDH activity could distinguish MADD from other genotypes of lipid storage myopathy. For late-onset MADD, increased fatty acid oxidation and reduced riboflavin levels can induce episodes of muscle symptoms, which can be treated by short-term and small-dose of riboflavin therapy.

Infant with early onset bilateral facial and bulbar weakness: Successful treatment of riboflavin in multiple acyl-CoA dehydrogenase deficiency caused by biallelic nonsense FLAD1 variants.

Multiple acyl-CoA dehydrogenase deficiency (MADD) is a heterogeneous group of inborn error of metabolic disease affecting the oxidation of fatty acids and amino acids, and choline metabolism. Genes involved in electrons transfer to the mitochondrial respiratory chain typically induce MADD. Recently, FLAD1, which encodes flavin adenine dinucleotide synthase, has also been reported as a cause of MADD. Here, we present a case of a 28-month girl with progressive weakness in facial and bulbar muscle. She has been suffering from feeding difficulty and recurrent respiratory distress. Lipid storage myopathy was evident from muscle biopsy. Furthermore, whole exome sequencing identified homozygous variant of c.745C > T (p.Arg249*) in FLAD1, confirming the diagnosis of FLAD1-related MADD. The patient showed improvements in her symptoms and exhibited catch-up growth following the supplementation of riboflavin. Lipid storage myopathy with FLAD1-related MADD is potentially treatable. Therefore, we should have high clinical suspicion, even though the diagnosis is challenging.

Riboflavin in Neurological Diseases: A Narrative Review.

Riboflavin is classified as one of the water-soluble B vitamins. It is part of the functional group of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) cofactors and is required for numerous flavoprotein-catalysed reactions. Riboflavin has important antioxidant properties, essential for correct cell functioning. It is required for the conversion of oxidised glutathione to the reduced form and for the mitochondrial respiratory chain as complexes I and II contain flavoprotein reductases and electron transferring flavoproteins. Riboflavin deficiency has been demonstrated to impair the oxidative state of the body, especially in relation to lipid peroxidation status, in both animal and human studies. In the nervous system, riboflavin is essential for the synthesis of myelin and its deficiency can determine the disruption of myelin lamellae. The inherited condition of restricted riboflavin absorption and utilisation, reported in about 10-15% of world population, warrants further investigation in relation to its association with the main neurodegenerative diseases. Several successful trials testing riboflavin for migraine prevention were performed, and this drug is currently classified as a Level B medication for migraine according to the American Academy of Neurology evidence-based rating, with evidence supporting its efficacy. Brown-Vialetto-Van Laere syndrome and Fazio-Londe diseases are now renamed as "riboflavin transporter deficiency" because these are autosomal recessive diseases caused by mutations of SLC52A2 and SLC52A3 genes that encode riboflavin transporters. High doses of riboflavin represent the mainstay of the therapy of these diseases and high doses of riboflavin should be rapidly started as soon as the diagnosis is suspected and continued lifelong. Remarkably, some mitochondrial diseases respond to supplementation with riboflavin. These include multiple acyl-CoA-dehydrogenase deficiency (which is caused by ETFDH gene mutations in the majority of the cases, or mutations in the ETFA and ETFB genes in a minority), mutations of ACAD9 gene, mutations of AIFM1 gene, mutations of the NDUFV1 and NDUFV2 genes. Therapeutic riboflavin administration has been tried in other neurological diseases, including stroke, multiple sclerosis, Friedreich's ataxia and Parkinson's disease. Unfortunately, the design of these clinical trials was not uniform, not allowing to accurately assess the real effects of this molecule on the disease course. In this review we analyse the properties of riboflavin and its possible effects on the pathogenesis of different neurological diseases, and we will review the current indications of this vitamin as a therapeutic intervention in neurology.

Targeted Therapies for Metabolic Myopathies Related to Glycogen Storage and Lipid Metabolism: a Systematic Review and Steps Towards a 'Treatabolome'.

BACKGROUND: Metabolic myopathies are a heterogenous group of muscle diseases typically characterized by exercise intolerance, myalgia and progressive muscle weakness. Effective treatments for some of these diseases are available, but while our understanding of the pathogenesis of metabolic myopathies related to glycogen storage, lipid metabolism and ß-oxidation is well established, evidence linking treatments with the precise causative genetic defect is lacking. OBJECTIVE: The objective of this study was to collate all published evidence on pharmacological therapies for the aforementioned metabolic myopathies and link this to the genetic mutation in a format amenable to databasing for further computational use in line with the principles of the "treatabolome" project. METHODS: A systematic literature review was conducted to retrieve all levels of evidence examining the therapeutic efficacy of pharmacological treatments on metabolic myopathies related to glycogen storage and lipid metabolism. A key inclusion criterion was the availability of the genetic variant of the treated patients in order to link treatment outcome with the genetic defect. RESULTS: Of the 1,085 articles initially identified, 268 full-text articles were assessed for eligibility, of which 87 were carried over into the final data extraction. The most studied metabolic myopathies were Pompe disease (45 articles), multiple acyl-CoA dehydrogenase deficiency related to mutations in the ETFDH gene (15 articles) and systemic primary carnitine deficiency (8 articles). The most studied therapeutic management strategies for these diseases were enzyme replacement therapy, riboflavin, and carnitine supplementation, respectively. CONCLUSIONS: This systematic review provides evidence for treatments of metabolic myopathies linked with the genetic defect in a computationally accessible format suitable for databasing in the treatabolome system, which will enable clinicians to acquire evidence on appropriate therapeutic options for their patient at the time of diagnosis.

Exacerbation of myopathy triggered by antiobesity drugs in a patient with multiple acyl-CoA dehydrogenase deficiency.

BACKGROUND: Multiple acyl-CoA dehydrogenase deficiency (MADD) is a treatable lipid metabolism disorder that presents as myopathy and episodic metabolic crisis. The metabolic crisis is typically associated with prolonged fasting or physical stress; however, the mechanism of metabolic crisis is not yet fully understood. CASE PRESENTATION: A 28-year-old Taiwanese woman presented with dyspnoea, poor appetite, and muscle weakness after using antiobesity drugs, including metformin, triiodothyronine, and topiramate. MADD was diagnosed, and her symptoms rapidly improved after treatment with riboflavin, carnitine, and ubiquinone. To date, antiobesity drugs have not been reported to be a provoking factor in fatty acid oxidation disorder. CONCLUSIONS: The increase of ß-oxidation activity due to antiobesity drugs supports the hypothetical substrate competition model for MADD metabolic crisis. Because the drugs our patient used are commonly prescribed, we report this case to increase the vigilance and proactivity of clinicians in recognising this treatable adult-onset myopathy.

Enantiomer-specific pharmacokinetics of D,L-3-hydroxybutyrate: Implications for the treatment of multiple acyl-CoA dehydrogenase deficiency.

D,L-3-hydroxybutyrate (D,L-3-HB, a ketone body) treatment has been described in several inborn errors of metabolism, including multiple acyl-CoA dehydrogenase deficiency (MADD; glutaric aciduria type II). We aimed to improve the understanding of enantiomer-specific pharmacokinetics of D,L-3-HB. Using UPLC-MS/MS, we analyzed D-3-HB and L-3-HB concentrations in blood samples from three MADD patients, and blood and tissue samples from healthy rats, upon D,L-3-HB salt administration (patients: 736-1123 mg/kg/day; rats: 1579-6317 mg/kg/day of salt-free D,L-3-HB). D,L-3-HB administration caused substantially higher L-3-HB concentrations than D-3-HB. In MADD patients, both enantiomers peaked at 30 to 60 minutes, and approached baseline after 3 hours. In rats, D,L-3-HB administration significantly increased Cmax and AUC of D-3-HB in a dose-dependent manner (controls vs ascending dose groups for Cmax : 0.10 vs 0.30-0.35-0.50 mmol/L, and AUC: 14 vs 58-71-106 minutes*mmol/L), whereas for L-3-HB the increases were significant compared to controls, but not dose proportional (Cmax : 0.01 vs 1.88-1.92-1.98 mmol/L, and AUC: 1 vs 380-454-479 minutes*mmol/L). L-3-HB concentrations increased extensively in brain, heart, liver, and muscle, whereas the most profound rise in D-3-HB was observed in heart and liver. Our study provides important knowledge on the absorption and distribution upon oral D,L-3-HB. The enantiomer-specific pharmacokinetics implies differential metabolic fates of D-3-HB and L-3-HB.

Late-onset multiple acyl-CoA dehydrogenase deficiency mimicking myositis in an elderly patient: a case report.

BACKGROUND: Late-onset multiple acyl-CoA dehydrogenase deficiency (MADD) is a rare and treatable inherited lipid storage myopathy. Here, we report an elderly patient with MADD mimicking myositis. CASE PRESENTATION: An 80-year-old woman had progressive weakness in her limbs, exercise intolerance, and no muscle pain for 3 months. The patient's serum creatine kinase level was slightly elevated. The initial diagnosis was myositis. However, muscle biopsy showed many cytoplasmic vacuoles stained with oil red O, indicating the presence of lipid storage myopathy. The plasma acylcarnitine profile showed increased medium-chain and long-chain acylcarnitine species, consistent with the diagnosis of MADD. Riboflavin treatment dramatically improved muscle weakness. CONCLUSIONS: MADD should be considered when evaluating elderly patients with subacute muscle weakness.

Skin damage in a patient with lipid storage myopathy with a novel ETFDH mutation responsive to riboflavin.

Background: Recessive mutations in ETFDH gene have been associated with Multiple Acyl-CoA dehydrogenase deficiency (MADD). The late-onset MADD is often muscle involved, presenting with lipid storage myopathy (LSM). The symptoms of LSM were heterogeneous and definite diagnosis of this disease depends on the pathology and gene test.Methods: Neurological examination, muscle biopsy, and MRI examinations were performed in a patient with a novel missense ETFDH mutation.Results: We describe a patient with lipid storage myopathy complicated with skin damage. In addition, the next generation revealed a novel missense mutation (c.970G > T, p.Val324Leu) in exon 8, which was predicted to be a disease-causing mutation by Mutation-taster, and destroy the function of the protein by Sift.Conclusion: These findings expand the known mutational spectrum of ETFDH and phenotype of MADD.

Efficacy and safety of D,L-3-hydroxybutyrate (D,L-3-HB) treatment in multiple acyl-CoA dehydrogenase deficiency.

PURPOSE: Multiple acyl-CoA dehydrogenase deficiency (MADD) is a life-threatening, ultrarare inborn error of metabolism. Case reports described successful D,L-3-hydroxybutyrate (D,L-3-HB) treatment in severely affected MADD patients, but systematic data on efficacy and safety is lacking. METHODS: A systematic literature review and an international, retrospective cohort study on clinical presentation, D,L-3-HB treatment method, and outcome in MADD(-like) patients. RESULTS: Our study summarizes 23 MADD(-like) patients, including 14 new cases. Median age at clinical onset was two months (interquartile range [IQR]: 8 months). Median age at starting D,L-3-HB was seven months (IQR: 4.5 years). D,L-3-HB doses ranged between 100 and 2600 mg/kg/day. Clinical improvement was reported in 16 patients (70%) for cardiomyopathy, leukodystrophy, liver symptoms, muscle symptoms, and/or respiratory failure. D,L-3-HB appeared not effective for neuropathy. Survival appeared longer upon D,L-3-HB compared with historical controls. Median time until first clinical improvement was one month, and ranged up to six months. Reported side effects included abdominal pain, constipation, dehydration, diarrhea, and vomiting/nausea. Median D,L-3-HB treatment duration was two years (IQR: 6 years). D,L-3-HB treatment was discontinued in 12 patients (52%). CONCLUSION: The strength of the current study is the international pooling of data demonstrating that D,L-3-HB treatment can be effective and safe in MADD(-like) patients.

Needle EMG, a Jigsaw to Disclose Lipid Storage Myopathy Due to Multiple Acyl-CoA Dehydrogenase Deficiency.

Multiple acyl-CoA dehydrogenase deficiency is a rare autosomal recessive inborn error of metabolism. The late-onset multiple acyl-CoA dehydrogenase deficiency is frequently caused by mutations in ETFDH gene. Because of its clinical heterogeneity, diagnosis and treatment of late-onset multiple acyl-CoA dehydrogenase deficiency are often delayed. The authors described a previously healthy 40-yr-old Thai woman presenting with subacute severe weakness of bulbar-limb muscles and elevated serum creatine kinase. The authors emphasized the importance of needle EMG and prompt muscle histopathological evaluation, which rapidly led to the diagnosis and riboflavin therapy, resulting in a dramatic and rapid improvement before genetic study disclosed mutation in ETFDH gene.

FLAD1-associated multiple acyl-CoA dehydrogenase deficiency identified by newborn screening.

BACKGROUND: Multiple acyl-CoA dehydrogenase deficiency (MADD), also known as glutaric aciduria type II, is a mitochondrial fatty acid oxidation disorder caused by variants in ETFA, ETFB, and ETFDH. Recently, riboflavin transporter genes and the mitochondrial FAD transporter gene have also been associated with MADD-like phenotype. METHODS: We present a case of MADD identified by newborn biochemical screening in a full-term infant suggestive of both medium-chain acyl-CoA dehydrogenase deficiency and MADD. Urine organic acid GC/MS analysis was also concerning for both disorders. However, panel sequencing of ETFA, ETFB, ETFDH, and ACADM was unrevealing. Ultimately, a variant in the FAD synthase gene, FLAD1 was found explaining the clinical presentation. RESULTS: Exome sequencing identified compound heterozygous variants in FLAD1: NM_025207.4: c.[442C>T];[1588C>T], p.[Arg148*];[Arg530Cys]. The protein damaging effects were confirmed by Western blot. The patient remained asymptomatic and there was no clinical decompensation during the first year of life. Plasma acylcarnitine and urinary organic acid analyses normalized without any treatment. Riboflavin supplementation was started at 15 months. CONCLUSION: Newborn screening, designed to screen for specific treatable congenital metabolic diseases, may also lead to the diagnosis of additional, very rare metabolic disorders such as FLAD1 deficiency. The case further illustrates that even milder forms of FLAD1 deficiency are detectable in the asymptomatic state by newborn screening.

Determinants of Riboflavin Responsiveness in Multiple Acyl-CoA Dehydrogenase Deficiency.

BACKGROUND: Multiple acyl-CoA dehydrogenase (MADD) deficiency, which is a rare metabolic disorder involving electron transport flavoproteins, has a wide array of clinical phenotypes. In this article, we describe 25 patients with MADD deficiency and present the clinical and laboratory characteristics and diagnostic challenges associated with riboflavin-responsive MADD deficiency. METHODS: Hospital records of patients with biallelic mutations in ETFA, ETFB, or ETFDH genes diagnosed in a single center were analyzed retrospectively. Demographic, clinical, and laboratory characteristics of patients with riboflavin-responsive and riboflavin-unresponsive MADD deficiency were compared using Mann-Whitney U and Fisher's exact tests. RESULTS: Respiratory distress and depressed consciousness were significantly more common in patients with riboflavin-unresponsive MADD deficiency (P = 0.015 and P < 0.001), who presented at a younger age (P < 0.001). Patients with riboflavin-responsive MADD deficiency had favorable outcomes but also had life-threatening complications, longer diagnostic delay (median of two years versus 30 days; P < 0.001), and multiple differential diagnoses, resulting in unnecessary investigations and maltreatment. Biopsies showed lipid storage, and complete autopsy was performed in one newborn with riboflavin-unresponsive MADD deficiency, revealing multiple abnormalities. Metabolic profiles were not distinguishable between riboflavin-responsive and riboflavin-unresponsive MADD deficiency (P > 0.05). Four novel variants were detected in ETFDH, one of which (c.1790C>T) may confer riboflavin responsiveness. Siblings with the common myopathic ETFDH c.1130T>C mutation presented with a new phenotype dominated by chronic fatigue without apparent myopathy. CONCLUSIONS: Symptoms and outcomes significantly differed between riboflavin-responsive and unresponsive MADD deficiency, but metabolic profiles did not. Functional studies are needed to better characterize the novel ETFDH variants. As treatment is available for riboflavin-responsive MADD deficiency, physicians should maintain a high index of suspicion for MADD deficiency in all age groups.