Validation of plasma amino acid profile using UHPLC-mass spectrometer (QDa) as a screening method in a metabolic disorders reference centre: Performance and accreditation concerns.

INTRODUCTION: Amino acid (AA) analysis in plasma is essential for diagnosis and monitoring of inborn errors of metabolism (IEM). The efficacy of patient management is governed by the rapidity of AA profile availability, along with the robustness of the method. French quality guidelines and progress made in analytical techniques have led biologists to develop AA profile exploration via mass spectrometry (MS). OBJECTIVES: The aim of this study was to validate an analytical method with a single quadrupole mass spectrometer (MS) and to suggest reference values in regard to French quality and IEM society recommendations. DESIGN AND METHODS: Plasma samples from patients were deproteinised and derivatised with AccqTag™ reagent. Analysis was performed by reverse-phase chromatography coupled to QDA detector. We evaluated accuracy, intra-days and inter-days precision and limit of quantification by the ß-expectation tolerance interval method for 27 AA. Method comparison was performed with the standard method (ion exchange chromatography, IEC) on Jeol Aminotac® and to tandem MS. Reference values were established on AA concentrations of the cohort of patients who had no IEM. RESULTS: Our method allowed the separations of almost all amino acids with a total run time of 12 min. Separation of isoleucine and alloisoleucine was incomplete (R = 0.55) but without impact on biological interpretation. Precision, accuracy and quantification were satisfactory (intra-days coefficient of variation (CV) was <5%, inter-days precision CV <10% and accuracy <15%). The limits of quantification were validated between 1 and 900 µmol/L. Results were comparable between the new method and IEC. CONCLUSION: Ultimately, we validated a rapid method on plasma for quantifying 27 amino acids that can be used in routine practice, according to French quality laboratories and SFEIM (French Society of Inborn Error of Metabolism) recommendations. Furthermore, estimated reference values were similar to those found in published studies focusing on other methods. Despite a lower specificity compared to tandem MS, the simplicity and rapidity of our method are the main advantage of this technique and place it as a major tool in IEM diagnosis and management.

Transition from pediatric to adult care in adolescents with hereditary metabolic diseases: Specific guidelines from the French network for rare inherited metabolic diseases (G2M).

Inherited metabolic diseases (IMD) form a heterogeneous group of genetic disorders that surface primarily during childhood and result in significant morbidity and mortality. A prevalence of 1 in 2500-5000 live births is often reported. The transfer of adolescents from pediatric care to adult health facilities is often difficult for patients and their families and can lead to a breakdown in medical follow-up and therefore serious complications. Existing recommendations for the successful transition of patients with chronic disorders do not specifically address patients with IMDs associated with dietary treatment. Here, the French network for rare inherited metabolic diseases (G2M) presents its reflections and recommendations for a successful transition. Preparations for the transfer must be made well in advance. The transfer must aim for adolescents gaining autonomy by making them responsible and providing them with the knowledge that will enable them to manage their care themselves, know how to react appropriately if there is any change in their condition, and move comfortably within the adult healthcare system. This requires the active participation of the patient, his or her family, and pediatric and adult care teams. It involves multidisciplinary management plus the production and maintenance of an educational therapy program. Finally, the identification of physicians and dietitians trained in IMDs, relevant subspecialists, and even expert patients could improve the continuum of complete and appropriate care for these patients within adult medicine.

[Acute fatty liver of pregnancy and mitochondrial fatty acid oxidation. Consequences for the offspring]. / Stéatose hépatique aiguë gravidique et bêta-oxydation mitochondriale des acides gras : conséquences pour l'enfant.

Acute fatty liver of pregnancy (AFLP) is a rare liver disease unique to pregnancy that can lead to acute liver failure. The prognosis, initially often fatal for both mother and child, has been improved by prompt delivery. The diagnosis should be highly suspected if the mother presents epigastric pain, nausea and/or vomiting, or polyuria-polydipsia in the third trimester of pregnancy. AFLP has been found associated with a genetic deficiency of fatty acid beta-oxidation, which may cause sudden death in infancy. Consequently, the mother and her newborn should undergo screening for this deficiency.

A Multiplatform Metabolomics Approach to Characterize Plasma Levels of Phenylalanine and Tyrosine in Phenylketonuria.

BACKGROUND: Different pathophysiological mechanisms have been described in phenylketonuria (PKU) but the indirect metabolic consequences of metabolic disorders caused by elevated Phe or low Tyr concentrations remain partially unknown. We used a multiplatform metabolomics approach to evaluate the metabolic signature associated with Phe and Tyr. MATERIAL AND METHODS: We prospectively included 10 PKU adult patients and matched controls. We analysed the metabolome profile using GC-MS (urine), amino-acid analyzer (urine and plasma) and nuclear magnetic resonance spectroscopy (urine). We performed a multivariate analysis from the metabolome (after exclusion of Phe, Tyr and directly derived metabolites) to explain plasma Phe and Tyr concentrations, and the clinical status. Finally, we performed a univariate analysis of the most discriminant metabolites and we identified the associated metabolic pathways. RESULTS: We obtained a metabolic pattern from 118 metabolites and we built excellent multivariate models to explain Phe, Tyr concentrations and PKU diagnosis. Common metabolites of these models were identified: Gln, Arg, succinate and alpha aminobutyric acid. Univariate analysis showed an inverse correlation between Arg, alpha aminobutyric acid and Phe and a positive correlation between Arg, succinate, Gln and Tyr (p < 0.0003). Thus, we highlighted the following pathways: Arg and Pro, Ala, Asp and Glu metabolism. DISCUSSION: We obtain a specific metabolic signature related to Tyr and Phe concentrations. We confirmed the involvement of different pathophysiological mechanisms previously described in PKU such as protein synthesis, energetic metabolism and oxidative stress. The metabolomics approach is relevant to explore PKU pathogenesis.

Validation of amino-acids measurement in dried blood spot by FIA-MS/MS for PKU management.

OBJECTIVES: Phenylketonuria (PKU) is a metabolic disorder leading to high concentrations of phenylalanine (Phe) and low concentrations of tyrosine (Tyr) in blood and brain that may be neurotoxic. This disease requires a regular monitoring of plasma Phe and Tyr as well as branched-chain amino-acids concentrations to adapt the Phe-restricted diet and other therapy that may be prescribed in PKU. We validated a Flow Injection Analysis tandem Mass Spectrometry (FIA-MS/MS) to replace the enzymatic method routinely used for neonatal screening in order to monitor in parallel to Phe, Tyr and branched-chain amino-acids not detected by the enzymatic method. DESIGN AND METHODS: We ascertained the performances of the method: linearity, detection and quantification limits, contamination index, accuracy. We cross validated the FIA-MS/MS and enzymatic methods and we evaluated our own reference ranges to monitor Phe, Tyr, Leu, Val on 59 dried blood spots of normal controls. We also evaluated Tyr, Leu and Val concentrations in PKU patients to detect some potential abnormalities, not evaluated by the enzymatic method. RESULTS: We developed a rapid method with excellent performances including precision and accuracy <15%. We noted an excellent correlation of Phe concentrations between FIA-MS/MS and enzymatic methods (p<0.0001) based on our database which are similar to references ranges published. We observed that 50% of PKU patients had lower concentrations of Tyr, Leu and/or Val that could not be detected by the enzymatic method. CONCLUSION: Based on laboratory accreditation recommendations, we validated a robust, rapid and reliable FIA-MS/MS method to monitor plasma Phe concentrations but also Tyr, Leu and Val concentrations, suitable for PKU management. We evaluated our own reference ranges of concentration for a routine application of this method.

[Cardiomyopathy induced by frequent premature ventricular contractions]. / Myocardiopathie rythmique induite par des extrasystoles ventriculaires chez un enfant.

We report on the rare case of 7-year-old child presenting with frequent and apparently benign premature ventricular complexes (VPC) and left ventricular dysfunction. No structural disease of the heart was seen at cardiological evaluation. Eighteen months after the introduction of an antiarrhythmic treatment with low-dose bisoprolol, Holter monitoring showed 70,000 VPC in 24h with left ventricular function remaining decreased. Six months after increasing the dose of bisoprolol, the VPC were less frequent and left ventricular function was completely normalized. This case was characteristic of a cardiomyopathy induced by frequent premature ventricular contractions.

[Malignant pertussis and exchange transfusion]. / Coqueluche maligne et exsanguino-transfusion.

CASE REPORT: Malignant pertussis is a critical clinical state associated with fatal outcome in 70% of cases. The severity criteria are a lung infection with pulmonary hypertension and hyperleukocytosis usually above 50 G/L. We report the case of a 2.5-month-old girl hospitalized with critical pertussis in a pediatric intensive care unit. She had acute respiratory distress syndrome with pulmonary hypertension complicated by a bacterial secondary infection with Enterobacter cloacae managed by high-frequency oscillatory ventilation associated with pulmonary vasodilatation therapy. In the absence of clinical improvement and before considering extracorporeal life support, exchange transfusion was performed at day 9 to reduce hyperleukocytosis at 70 G/L. Exchange transfusion was successfully performed with a reduction of leukocytes to under 40 G/L followed by steady improvement of pulmonary function. Weaning from mechanical ventilation and discharge took place at day 23 and 38, respectively. COMMENTS: Exchange transfusion should be considered in infants suffering from malignant pertussis with extreme leukocytosis before hemodynamic failure to improve the survival prognosis.

[Donohue syndrome or leprechaunism]. / Le syndrome de Donohue ou lepréchaunisme : à propos d'un cas.

Donohue syndrome or leprechaunism is a severe congenital insulin-resistance syndrome. It is characterized by intra-uterine and neonatal growth retardation, typical dysmorphic features, and metabolic abnormalities with hyperinsulinism and hyperandrogenism. Problems in energy metabolism and loss of glucose homeostasis are responsible for early death in the first year of life. We describe a case with a novel homozygote mutation in the insulin receptor gene. This patient had hypertrophic cardiomyopathy with heart failure and bronchial compression leading to clinical deterioration over 5 days and subsequently death. A treatment with recombinant IGF-1 was tried without efficacy.

Successful treatment with fumagillin of the first pediatric case of digestive microsporidiosis in a liver-kidney transplant.

We report the first successful use, to our knowledge, of fumagillin alone in a pediatric patient to cure intestinal microsporidiosis in a liver-kidney transplanted child. Detection of Enterocytozoon bieneusi in stool became negative from the first post-therapeutic control, while digestive symptoms disappeared in 4 days. During a 9-month follow-up, polymerase chain reaction and direct examinations remained negative for microsporidia in her feces. No major undesirable effects were noted during the anti-microsporidial therapy.

[Atrioventricular block after transcatheter atrial septal defect closure using the Amplatzer septal occluder(®)]. / Bloc auriculo-ventriculaire après fermeture d'une communication interauriculaire avec un système Amplatzer septal occluder(®)

Transcatheter closure of atrial septal defect (ASD) in children is now an accepted treatment as an alternative to surgery. We report a case of complete atrioventricular block (AVB) observed over several days after closure of an ASD with an Amplatzer Septal Occluder(®) in a 13-year-old child. The spontaneous outcome was good with regression of the complete AVB, but 1 year later, a first-degree AVB was still present. The use of large devices in young children and a small postero-inferior rim seem to be risk factors of AVB. Transcatheter closure of ASD requires close monitoring of cardiac rhythm.

[Clinical presentation of inborn metabolic diseases in the neonatal period]. / Signes néonatals des maladies héréditaires du métabolisme.

Inborn metabolic diseases (IMDs) that can start in the neonatal period include various defects in numerous metabolic pathways. Such diseases are due to the genetic deficiency of an enzyme or a transporter. From a physiopathological point of view, the metabolic disorders can be divided into 3 diagnostically useful groups of diseases. The first group is due to the accumulation of endogenous toxic metabolites and includes inborn errors of amino acid metabolism, organic acidemias, urea cycle disorders, and sugar intolerances. The second one includes IMDs of intermediary metabolism causing a disturbance in energy production or utilization resulting from a defect in the liver, the muscles, the myocardium, or the brain (fatty acid oxidation defects, congenital lactic acidosis, etc.). The third group includes diseases that disturb the synthesis or the catabolism of complex molecules (lysosomal or peroxisomal disorders, etc.). IMDs are individually rare, but collectively numerous. Therefore, it is difficult to acquire extensive experience in the management of these diseases. However, the neonate has a limited repertoire of responses to severe illness and, at first, presents with nonspecific symptoms that could be easily attributed to infection or some other common cause. An IMD must be suspected in all situations of neonatal distress for which there is no apparent reason and that does not respond to symptomatic therapy. The priority is given to IMDs that are amenable to treatment, and emergency management has to be scheduled as soon as the diagnosis is suspected, even if the precise diagnosis is still unknown. In fact, emergency treatment must be undertaken in parallel with metabolic investigations, to prevent any delay in the management of the disease. The neonatologist must be able to recognize the neonatal distresses that suggest the possibility of an IMD. In such situations, an adequate diagnostic approach can be based on the proper use of only a few screening tests, which will also be useful to schedule adequate emergency treatment.

[Benefits of continuous subcutaneous insulin infusion in children with type 1 diabetes mellitus]. / Bénéfices de l'insulinothérapie par pompe chez les enfants diabétiques de type 1.

BACKGROUND: The Diabetes Control and Complications Trial clearly demonstrated the benefits of blood glucose control, especially in children and adolescents, in the prevention of long-term complications of type 1 diabetes (T1D). This can be achieved with intensive insulin treatment with either multiple daily insulin injections (MDI) or continuous subcutaneous insulin infusion (CSII), also known as insulin pump. The aim of this study was to compare glycemic control of T1D children treated with either CSII or MDI. PATIENTS AND METHODS: Thirty-eight T1D children treated with CSII were compared to 38 children treated with MDI, matched for age, gender, and duration of diabetes. Collected data, including daily doses of insulin in IU/kg/d, HbA1c levels, body mass index expressed in standard deviation/age, number of severe hypoglycemia episodes and of admissions related to T1D expressed in events/patient/year, were retrospectively collected every 3 months. RESULTS: There was no difference between the 2 groups at baseline. During the 3 years of follow-up, patients treated with CSII had lower daily doses of insulin (0.78 ± 0.19 vs. 0.87 ± 0.22 IU/kg/d, p<0.05), significantly lower levels of HbA1c (7.5 ± 0.6 vs. 8.0 ± 1.3 %, p<0.05), and a decreased number of admissions related to T1D (0.07 ± 0.14 vs. 0.17 ± 0.22 events/patient/year, p<0.05) than children treated with MDI. In contrast, body mass index and number of severe hypoglycemic episodes did not differ between the two groups. No diabetic ketoacidosis episode was recorded in either group. CONCLUSION: The results from this study suggest that treatment with CSII provided better metabolic control than treatment with MDI, in spite of lower daily doses of insulin and without increasing acute complications, in children with T1D.

[Medium-chain acyl-CoA-dehydrogenase (MCAD) deficiency: French consensus for neonatal screening, diagnosis, and management]. / Déficit en acyl-CoA-déshydrogénase des acides gras à chaîne moyenne (MCAD): consensus français pour le dépistage, le diagnostic, et la prise en charge.

MCAD deficiency is the most common fatty acid oxidation disorder, with the prevalence varying from 1/10,000 to 1/27,000 in the countries adjacent to France. As the High Authority for Health has recently proposed including MCAD deficiency in the panel of diseases neonatally screened for in France, a consensus was written for the management of MCAD deficiency diagnosed either clinically or by neonatal screening. Patients may present acutely with hyperammonemia, hypoglycemia, encephalopathy, and hepatomegaly, mainly after a prolonged fast of intercurrent infection. Sudden death related to heartbeat disorders may also occur. The diagnosis of MCAD deficiency is suspected on the plasma acylcarnitine and/or the urinary organic acid profile. The diagnosis is confirmed by molecular biology and the enzymatic activity for patients who are not homozygous for the main mutation c.985A>G. However, some MCAD-deficient individuals may remain asymptomatic throughout life. The mainstay of treatment consists in avoiding prolonged fast and prescribing l-carnitine for patients who exhibit a deficiency in plasma carnitine. This management has radically modified the natural history of MCAD deficiency. This consensus will allow homogeneous management of these patients once the neonatal screening of MCAD deficiency has been introduced in France.

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.

[Hypercarotenaemia in an infant]. / Hypercaroténémie chez un nourrisson.

BACKGROUND: Hypercarotenaemia is the consequence of high serum carotenoid levels, which are deposited in the stratum corneum and give a yellowish coloration to the skin. It can be distinguished from jaundice by the absence of colouring of the conjunctivae as well as orange discolouration of the palms and soles. CASE REPORT: We report a rare case of hypercarotenaemia in a child that began at the age of three months. Clinical signs and symptoms included yellowish discolouration of the skin, orange palms and soles, xerosis and pruritus. Hypercarotenaemia was confirmed by high levels of serum carotenoids. Serum vitamin A was normal. Dietary and drug-induced causes of hypercarotenaemia were excluded in this case, as well as other classical metabolic causes (renal insufficiency, malabsorption syndrome, diabetes, hypothyroidism). The child was placed on a low-carotenoids diet for six months, resulting in decreased serum carotenoid levels and regression of cutaneous signs and symptoms, especially pruritus. DISCUSSION: Although pruritus has never been reported in isolated hypercarotenaemia it is a classical sign of hypervitaminosis A. The mechanism of pruritus is not understood in this instance since vitamin A levels were normal. This case report is also unusual in that no classical cause of hypercarotenaemia was found, as a result of which we concluded on a likely defect in beta-carotene 15, 15'oxygenase, an enzyme involved in vitamin A production.