Myopathy with MTCYB mutation mimicking Multiple Acyl-CoA Dehydrogenase Deficiency.

We describe two patients with mitochondrial DNA mutations in the gene encoding cytochrome b (m.15579A>G, p.Tyr278Cys and m.15045G>A p.Arg100Gln), which presented as a pure myopathic form (exercise intolerance), with an onset in childhood. Diagnosis was delayed, because acylcarnitine profile showed an increase in medium and long-chain acylcarnitines, suggestive of multiple acyl-CoA dehydrogenase deficiency, riboflavin transporter deficiency or FAD metabolism disorder. Implication of cytochrome b in fatty acid oxidation, and physiopathology of the mutations are discussed.

Tyrosinemia type II: Mutation update, 11 novel mutations and description of 5 independent subjects with a novel founder mutation.

BACKGROUND: Tyrosinemia type II, also known as Richner-Hanhart Syndrome, is an extremely rare autosomal recessive disorder, caused by mutations in the gene encoding hepatic cytosolic tyrosine aminotransferase, leading to the accumulation of tyrosine and its metabolites which cause ocular and skin lesions, that may be accompanied by neurological manifestations, mostly intellectual disability. AIMS: To update disease-causing mutations and current clinical knowledge of the disease. MATERIALS AND METHODS: Genetic and clinical information were obtained from a collection of both unreported and previously reported cases. RESULTS: We report 106 families, represented by 143 individuals, carrying a total of 36 genetic variants, 11 of them not previously known to be associated with the disease. Variants include 3 large deletions, 21 non-synonymous and 5 nonsense amino-acid changes, 5 frameshifts and 2 splice variants. We also report 5 patients from Gran Canaria, representing the largest known group of unrelated families sharing the same P406L mutation. CONCLUSIONS: Data analysis did not reveal a genotype-phenotype correlation, but stressed the need of early diagnosis: All patients improved the oculocutaneous lesions after dietary treatment but neurological symptoms prevailed. The discovery of founder mutations in isolated populations, and the benefits of early intervention, should increase diagnostic awareness in newborns.

Multiple acyl-CoA dehydrogenase deficiency (MADD) as a cause of late-onset treatable metabolic disease.

INTRODUCTION: Late-onset multiple acyl-CoA dehydrogenase deficiency (MADD) is a rare, treatable, beta-oxidation disorder responsible for neuromuscular symptoms in adults. This case series describes the clinical and biochemical features of 13 French patients with late-onset MADD. METHODS AND RESULTS: Thirteen ambulant patients (eight women, five men), with a median age at onset of 27 years, initially experienced exercise intolerance (n=9), isolated muscle weakness (n=1) and a multisystemic pattern with either central nervous system or hepatic dysfunction (n=3). During the worsening period, moderate rhabdomyolysis (n=5), a pseudomyasthenic pattern (n=5) and acute respiratory failure (n=1) have been observed. Weakness typically affected the proximal limbs and axial muscles, and there was sometimes facial asymmetry (n=3). Moderate respiratory insufficiency was noted in one case. Median baseline creatine kinase was 190IU/L. Lactacidemia was sometimes moderately increased at rest (3/10) and after exercise (1/3). The acylcarnitine profile was characteristic, with increases in all chain-length acylcarnitine species. Electromyography revealed a myogenic pattern, while muscle biopsy showed lipidosis, sometimes with COX-negative fibers (n=2). The mitochondrial respiratory chain was impaired in five cases, with coenzyme Q10 decreased in two cases. All patients harbored mutations in the ETFDH gene (four homozygous, seven compound heterozygous, two single heterozygous), with nine previously unidentified mutations. All patients were good responders to medical treatment, but exercise intolerance and/or muscular weakness persisted in 11 of them. CONCLUSION: Late-onset forms of MADD may present as atypical beta-oxidation disorders. Acylcarnitine profiling and muscle biopsy remain the most decisive investigations for assessing the diagnosis. These tests should thus probably be performed more widely, particularly in unexplained cases of neuromuscular and multisystemic disorders.

Comprehensive cDNA study and quantitative analysis of mutant HADHA and HADHB transcripts in a French cohort of 52 patients with mitochondrial trifunctional protein deficiency.

BACKGROUND: Deficiency of mitochondrial trifunctional protein (MTP) is caused by mutations in the HADHA and HADHB genes, which have been mostly delineated at the genomic DNA level and have not been always elucidated. AIM: To identify mutations in a French cohort of 52 MTP deficient patients and the susceptibility of mutations generating premature termination codons (PTCs) to the nonsense mRNA mediated decay (NMD). METHODS: Mutation screening in fibroblasts was performed at the cDNA level and real-time RT-PCR was used to compare the levels of the different PTC-bearing mRNAs before and after a treatment of fibroblasts by emetine, a translation inhibitor. RESULTS: A mutation detection rate of 100% was achieved. A total of 22 novel mutations were identified, including a large-sized genomic deletion in HADHB gene. A high proportion of all identified mutations were non-sense, frameshift and splicing mutations, generating (PTCs), distributed essentially on HADHA coding regions. We could demonstrate that the majority of mutations resulting in PTCs conform to the established rules governing the susceptibility to NMD. CONCLUSION: Our results emphasize the value of cDNA analysis in the characterization of HADHA and HADHB mutations and further strengthen the model of haploinsufficiency as a major pathomechanism in MTP defects.

[Multiple acyl-CoA dehydrogenase deficiency (MADD): a curable cause of genetic muscular lipidosis]. / Déficit multiple en acyl-CoA déshydrogénases : une cause traitable de lipidose musculaire d'origine génétique.

INTRODUCTION: Multiple acyl-CoA dehydrogenase deficiency (MADD) is a rare genetic disease involving fatty acid oxidation. It is due to the deficiency of one of the two electron transporters: electron transfer flavoprotein (ETF) or electron transfer flavoprotein ubiquinone oxydoreductase (ETF-QO). Symptoms begin more often in childhood or in young adulthood with a multisystemic disease with encephalopathy or muscular weakness. CASE REPORTS: We report here two adult cases with ETF-QO deficiency, confirmed by mutation analysis (ETFDH gene), revealed by a muscular weakness associated with muscle lipidosis. One of our patients presented an acute encephalopathy with vomiting ten years before the onset of muscular symptoms. The second patient exhibited a slowly progressive pelvic girdle muscle weakness. Diagnosis was established by characteristic abnormalities of acylcarnitine profile by tandem mass spectrometry. For both patients, a dramatic clinical improvement was observed under treatment with riboflavine and L-carnitine. CONCLUSION: Since it is a treatable disorder, this diagnosis must be considered by performing an acylcarnitine profile in all patients presenting with an unexplained muscular weakness.

Development and implementation of a novel assay for L-2-hydroxyglutarate dehydrogenase (L-2-HGDH) in cell lysates: L-2-HGDH deficiency in 15 patients with L-2-hydroxyglutaric aciduria.

L-2-hydroxyglutaric aciduria (L-2-HGA) is a rare inherited autosomal recessive neurometabolic disorder caused by mutations in the gene encoding L-2-hydroxyglutarate dehydrogenase. An assay to evaluate L-2-hydroxyglutarate dehydrogenase (L-2-HGDH) activity in fibroblast, lymphoblast and/or lymphocyte lysates has hitherto been unavailable. We developed an L-2-HGDH enzyme assay in cell lysates based on the conversion of stable-isotope-labelled L-2-hydroxyglutarate to 2-ketoglutarate, which is converted into L-glutamate in situ. The formation of stable isotope labelled L-glutamate is therefore a direct measure of L-2-HGDH activity, and this product is detected by liquid chromatography-tandem mass spectrometry. A deficiency of L-2-HGDH activity was detected in cell lysates from 15 out of 15 L-2-HGA patients. Therefore, this specific assay confirmed the diagnosis unambiguously affirming the relationship between molecular and biochemical observations. Residual activity was detected in cells derived from one L-2-HGA patient. The L-2-HGDH assay will be valuable for examining in vitro riboflavin/FAD therapy to rescue L-2-HGDH activity.

Quality of analytical performance in inherited metabolic disorders: the role of ERNDIM.

External quality assurance (EQA) schemes are essential for improvement of accuracy, reliability and comparability of results of biochemical genetic tests. ERNDIM (European Research Network for evaluation and improvement of screening, Diagnosis and treatment of Inherited disorders of Metabolism), established in 1994, operates nine EQA schemes for biochemical genetic testing according to international norms and recommendations. These comprise qualitative schemes for amino acids, organic acids, purines and pyrimidines, special assays in serum and urine and white cell cystine, qualitative organic acid and acylcarnitine schemes, as well as diagnostic proficiency testing. The total number of participants has increased from 123 in 1994 to 268 in 2007. Additional activities include participation in the Eurogentest project, a laboratory directory, training, education and development of guidelines. Results from the quantitative amino acid scheme with 170 participants reveal good variation within and between laboratories of below 10% for 10 amino acids; good within-laboratory variation but intermediate inter-laboratory variation of 10-22% for 11 amino acids; and higher variation within and between laboratories for 8 amino acids. Results on samples from 51 inherited metabolic disorders from two of five centres organizing diagnostic proficiency testing indicate overall diagnostic efficiency above 80% and improved performance of individual laboratories. Comparison of results for 10 and 12 compounds in the serum and urine special assay schemes respectively for 2000 and 2007 reveal clear improvement of precision within laboratories and in inter-laboratory variation. There is considerable evidence that performance in biochemical genetic testing has improved since the introduction of ERNDIM schemes.

Chronic Diarrhea in L-Amino Acid Decarboxylase (AADC) Deficiency: A Prominent Clinical Finding Among a Series of Ten French Patients.

Aromatic L-amino acid decarboxylase (AADC) deficiency is an autosomal recessive inborn error of metabolism, affecting catecholamines and serotonin biosynthesis. Cardinal signs consist in psychomotor delay, hypotonia, oculogyric crises, dystonia, and extraneurological symptoms. PATIENTS AND METHODS: We present a retrospective descriptive multicentric study concerning ten French children with a biochemical and molecular confirmed diagnosis of AADC deficiency. RESULTS: Clinical presentation of most of our patients was consistent with the previous descriptions from the literature (hypotonia (nine children), autonomic signs (nine children), sleep disorders (eight children), oculogyric crises (eight children), motor disorders like hypertonia and involuntary movements (seven children)). We described however some phenotypic particularities. Two patients exhibited normal intellectual abilities (patients already described in the literature). We also underlined the importance of digestive symptoms like diarrhea, which occurred in five among the ten patients. We report in particular two children with chronic diarrhea, complicated by severe failure to thrive. Vanillactic acid (VLA) elevation in urines of one of these two patients led to suspect the diagnosis of AADC deficiency, as in two other patients from our population. CONCLUSION: Some symptoms like chronic diarrhea were atypical and have been poorly described in the literature up to now. Diagnosis of the AADC deficiency is sometimes difficult because of the phenotypic heterogeneity of the disease and VLA elevation in urines should suggest the diagnosis.

Homicide followed by freezing and burning: usefulness of measuring SCHAD (short-chain 3-hydroxyacyl-CoA dehydrogenase) activity.

An observation of homicide in which the victim was frozen, then burned, was reported. This confirmed the usefulness of measuring SCHAD (short-chain 3-hydroxyacyl-CoA dehydrogenase) activity in the freezing of a human corpse despite unusual circumstances.

Pilot Experience with an External Quality Assurance Scheme for Acylcarnitines in Plasma/Serum.

The analysis of acylcarnitines (AC) in plasma/serum is established as a useful test for the biochemical diagnosis and the monitoring of treatment of organic acidurias and fatty acid oxidation defects. External quality assurance (EQA) for qualitative and quantitative AC is offered by ERNDIM and CDC in dried blood spots but not in plasma/serum samples. A pilot interlaboratory comparison between 14 European laboratories was performed over 3 years using serum/plasma samples from patients with an established diagnosis of an organic aciduria or fatty acid oxidation defect. Twenty-three different samples with a short clinical description were circulated. Participants were asked to specify the method used to analyze diagnostic AC, to give quantitative data for diagnostic AC with the corresponding reference values, possible diagnosis, and advice for further investigations.Although the reference and pathological concentrations of AC varied among laboratories, elevated marker AC for propionic acidemia, isovaleric acidemia, medium-chain acyl-CoA dehydrogenase, very long-chain acyl-CoA dehydrogenase, and multiple acyl-CoA dehydrogenase deficiencies were correctly identified by all participants allowing the diagnosis of these diseases. Conversely, the increased concentrations of dicarboxylic AC were not always identified, and therefore the correct diagnosis was not reach by some participants, as exemplified in cases of malonic aciduria and 3-hydroxy-3-methylglutaryl-CoA lyase deficiency. Misinterpretation occurred in those laboratories that used multiple-reaction monitoring acquisition mode, did not derivatize, or did not separate isomers. However, some of these laboratories suggested further analyses to clarify the diagnosis.This pilot experience highlights the importance of an EQA scheme for AC in plasma.

Very long chain acyl-CoA dehydrogenase deficiency: identification of a new inborn error of mitochondrial fatty acid oxidation in fibroblasts.

A patient highly suspected of long chain fatty acid oxidation defect was investigated for membrane-bound palmitoyl-CoA dehydrogenation in a membrane extract from skin fibroblasts, using 1% sodium cholate as detergent. The profoundly decreased activity observed is consistent with a deficiency of the newly identified mitochondrial 'very long chain acyl-CoA dehydrogenase'.

[Creatine deficiency syndromes]. / Les syndromes de déficit en créatine.

INTRODUCTION: Creatine deficiency syndromes are a newly described group of inborn errors of metabolism affecting creatine metabolism. Three diseases have been described: deficiency of arginine: glycine amidinotransferase (AGAT), deficiency of guanidinoacetate methyltransferase (GAMT) and creatine transporter defect (CRTR). STATE OF ART: These syndromes are characterized by a depletion of creatine/phosphocreatine in the brain. Clinically, most of the patients develop a variable mental retardation and a severe speech delay associated with epilepsy, extra-pyramidal syndrome and behavior disturbances. These diseases are often diagnosed during infancy but a few adult cases have been reported recently. Diagnosis is established by measurement of guanidinoacetate and creatine in biologic fluids and in vivo proton magnetic resonance spectroscopy by the total lack of intra-cerebral creatine/phosphocreatine demonstrating. GAMT and AGAT deficiencies are treatable by oral creatine supplementation whereas patients with CRTR do not respond to the treatment. CONCLUSION: Better knowledge of these syndromes is necessary to optimize diagnosis and patient management of these rare but potentially treatable disorders.

Adult presentation of MCAD deficiency revealed by coma and severe arrythmias.

We report the case of a 33-year-old man who presented with headaches and vomiting. Soon after admission he became drowsy and agitated, developed ventricular tachycardia and his neurological state worsened (Glasgow coma score 6). Blood analysis showed respiratory alkalosis, hyperlactacidemia (8 mmol/l), hyperammonemia (390 micro mol/l) and hypoglycaemia (2.4 mmol/l). Subsequently, he developed supraventricular tachycardia, ventricular tachycardia and ultimately ventricular fibrillation resulting in cardiac arrest, which was successfully treated. A CT scan of the head revealed cerebral oedema. Whilst in the intensive care unit, he developed renal failure and rhabdomyolysis. The metabolic abnormalities seen at the time of admission normalised within 48 h with IV glucose infusion. Biological investigations, including urinary organic acids and plasma acylcarnitines, showed results compatible with MCAD deficiency. Mutation analysis revealed the patient was homozygous for the classical mutation A985G. This is one of only a few reports of severe cardiac arrhythmia in an adult due to MCAD deficiency. This condition is probably under-diagnosed in adult patients with acute neurological and/or cardiac presentations.

Purification of electron transfer flavoprotein from pig liver mitochondria and its application to the diagnosis of deficiencies of acyl-CoA dehydrogenases in human fibroblasts.

Medium chain acyl-CoA dehydrogenase (MCAD) and long chain acyl-CoA dehydrogenase (LCAD) deficiency are defects of mitochondrial beta-oxidation. The method of choice to measure specifically acyl-CoA dehydrogenase activity in human tissues uses purified electron transfer flavoprotein (ETF). We describe a simple and optimized method of purification allowing isolation of ETF with a degree of purity never reported so far. An assay for acyl-CoA dehydrogenase activity in cultured skin fibroblasts was developed using microquantities of electron transfer flavoprotein and substrate. MCAD deficiency was demonstrated in fibroblasts from nine patients and LCAD deficiency in fibroblasts from two patients.

Oxidation of unsaturated fatty acids by human fibroblasts with very-long-chain acyl-CoA dehydrogenase deficiency: aspects of substrate specificity and correlation with clinical phenotype.

The degradation of unsaturated fatty acids was examined in fibroblasts from 16 patients with very-long-chain acyl-CoA dehydrogenase (VLCAD) deficiency. Analysis of acylcarnitine intermediates following incubation of intact human cells with these compounds revealed that the milder clinical phenotypes could be distinguished from the severe cardiomyopathic phenotype. These findings may reflect more effective contributions of alternate pathways in the milder forms of the disease. Incubation of VLCAD-deficient cells with cis-9 or trans-9 unsaturated fatty acids indicate that VLCAD is largely responsible for the 2,3-dehydrogenation of cis-5 or trans-5 intermediates in fibroblasts. The first two cycles of beta-oxidation with oleic and linoleic acids occur in the absence of VLCAD activity suggesting the presence of an additional acyl-CoA dehydrogenase or alternate pathway for the oxidation of these unsaturated fatty acids. These observations have clinical relevance for determining diagnosis, prognosis and strategies for dietary treatment of these patients.

Mitochondrial very-long-chain acyl-coenzyme A dehydrogenase deficiency: clinical characteristics and diagnostic considerations in 30 patients.

Very-long-chain acyl-CoA dehydrogenase (VLCAD) is an enzyme catalyzing the dehydrogenation of long-chain fatty acids in the first step of mitochondrial fatty acid oxidation. Using an ETF (electron transfer flavoprotein, the physiological electron acceptor of VLCAD) reduction assay, we identified VLCAD deficiency in cultured skin fibroblasts or liver tissue from 30 patients in 27 families. They clinically presented two phenotypes: a 'severe' presentation characterized by an early onset of symptoms, with hypertrophic cardiomyopathy and a high incidence of death, and a 'mild' form with hypoketotic hypoglycaemia, resembling MCAD (medium-chain acyl-CoA dehydrogenase) deficiency. Cells isolated from patients who develop cardiomyopathy characteristically accumulate longer-chain length acylcarnitines (hexadecanoylcarnitine and tetradecanoylcarnitine) when incubated with palmitate. However, cells from patients with the hypoglycaemic presentation produced relatively shorter-chain-length intermediates (mainly dodecanoylcarnitine). Inhibition of carnitine palmitoyl transferase I, in vitro, eliminated these intermediates with cells from both phenotypes indicating their intramitochondrial origin. Although the explanation for these distinct biochemical findings is not obvious, the correlation with the two phenotypes provides an opportunity for accurate prognosis and early implementation of appropriate treatment. Prenatal diagnosis of this life-threatening disorder was successfully performed in seven pregnancies in six of those families by assay of trophoblasts or amniocytes. In an at risk family, diagnosis of an affected fetus by measurement of VLCAD activity in noncultured chorionic villi allowed termination of the pregnancy before 13 weeks of gestation.

Plasma free fatty acids in mitochondrial fatty acid oxidation defects.

Plasma free fatty acid profiles from patients suffering from various mitochondrial beta-oxidation deficiencies were analyzed by gas chromatography-mass spectrometry. cis-4-Decenoic acid (10:1n-6) in medium-chain acyl-CoA dehydrogenase deficiency and cis-5-tetradecenoic acid (14:1n-9) in very-long-chain and 3-hydroxy-long chain acyl-CoA dehydrogenase deficiencies are characteristic of these diseases. In addition, patients with 3-hydroxy-long chain acyl-CoA dehydrogenase deficiency showed a specific increase of 3-hydroxy-long chain fatty acids. The study of plasma free fatty acids is an easy and useful methodology for the diagnostic approach of some mitochondrial beta-oxidation deficiencies, allowing us to establish a quick differentiation between medium- and long-chain defects.

Metabolic studies in a patient with severe carnitine palmitoyltransferase type II deficiency.

Here we report on a patient with severe ("non-classic") carnitine palmitoyltransferase type II (CPT II) deficiency. Hypoglycemia prompted by an infectious episode and associated with non-ketotic dicarboxylic aciduria orientated diagnosis towards beta-oxidation deficiency disorders. Blood carnitine levels revealed a secondary carnitine deficiency that was responsive to oral L-carnitine supplementation. Blood acylcarnitine profiles were abnormal and included acetyl (C2:0), butyryl/isobutyryl (C4:0), isovaleryl/2-methylbutyryl (C5:0), hexanoyl (C6:0), myristoyl (C14:0), palmitoyl (C16:0), hexadecenoyl (C16:1), oleyl (C18:1) and stearoyl (C18:0) carnitine. In urine, excess excretion of dicarboxylylcarnitines, mainly dodecanedioylcarnitine, was noticed. Upon carnitine supplementation, C8 to C12 fatty acylcarnitines, with decanoylcarnitine as well as C10 to C14 dicarboxylylcarnitines being prominent, were observed in urine. Biochemical measurements disclosed a severe reduction of mitochondrial CPT II activity (7% of normal values). Correlations of metabolic findings in the patient and physiological roles of CPT II are briefly discussed.

Acylcarnitine removal in a patient with acyl-CoA beta-oxidation deficiency disorder: effect of L-carnitine therapy and starvation.

Carnitine levels and acylcarnitine profiles in a patient with mild multiple acyl-CoA dehydrogenase deficient beta-oxidation were compared with control results. Whereas blood and urine total carnitine levels were moderately decreased, blood esterified carnitine levels in the patient were about 2-fold higher than in controls. Urinary acylcarnitine profiles presented with a larger variety of carnitine esters than in controls and included propionylcarnitine, butyrylcarnitine, 2-methylbutyrylcarnitine, hexanoylcarnitine and octanolycarnitine. Total carnitine levels in body fluids were similarly affected by chronic oral L-carnitine administration in patient and controls. By contrast, esterified carnitine level increase was 2-fold more important in controls than in patient. Whereas no qualitative changes in urinary acylcarnitine profiles were induced by L-carnitine therapy in controls, several alterations of these profiles were observed in the patient. The effect of starvation on metabolites was also studied, especially beta-oxidation rates assessed by free fatty acids to 3-hydroxybutyric acid ratios in blood from the patient in the untreated and L-carnitine treated states. In the L-carnitine-supplemented patient, the effect of starvation on the time course of carnitine levels and acylcarnitine profiles could also be documented. The ability of chronic oral L-carnitine administration to remove relatively less important amounts of acylcarnitines in the patient than in controls is further discussed, as well as qualitative alterations of acylcarnitine profiles induced by this therapy in the pathological condition.

Mitochondrial very long chain acyl-CoA dehydrogenase deficiency--a new disorder of fatty acid oxidation.

Very long chain acyl-CoA dehydrogenase is a newly characterised enzyme in mitochondrial fatty acid oxidation. A girl who presented on the second day of life with a sudden and severe illness due to deficiency of this enzyme is reported. There is evidence that some children (and perhaps all) originally diagnosed with a deficiency of long-chain acyl-CoA dehydrogenase, in fact, have a defect involving very long chain acyl-CoA dehydrogenase.