Ten years of enzyme replacement therapy in paediatric onset mucopolysaccharidosis II in England.

The outcome of 110 patients with paediatric onset mucopolysaccharidosis II (MPS II) since the commercial introduction of enzyme replacement therapy (ERT) in England in 2007 is reported. Median length of follow up was 10 years 3 months (range = 1 y 2 m to 18 years 6 month). 78 patients were treated with ERT, 18 had no ERT or disease modifying treatment 7 had haematopoietic stem cell transplant, 4 experimental intrathecal therapy and 3 were lost to follow up. There is clear evidence of improved survival (median age of death of ERT treated (n = 16) = 15.13 years (range = 9.53 to 20.58 y), and untreated (n = 17) = 11.43 y (0.5 to 19.13 y) p = .0005). Early introduction of ERT improved respiratory outcome at 16 years, the median FVC (% predicted) of those in whom ERT initiated <8 years = 69% (range = 34-86%) and 48% (25-108) (p = .045) in those started >8 years. However, ERT appears to have minimal impact on hearing, carpal tunnel syndrome or progression of cardiac valvular disease. Cardiac valvular disease occurred in 18/46 (40%), with progression occurring most frequently in the aortic valve 13/46 (28%). The lack of requirement for neurosurgical intervention in the first 8 years of life suggests that targeted imaging based on clinical symptomology would be safe in this age group after baseline assessments. There is also emerging evidence that the neurological phenotype is more nuanced than the previously recognized dichotomy of severe and attenuated phenotypes in patients presenting in early childhood.

The utility of dried blood spot monitoring of branched-chain amino acids for maple syrup urine disease: A retrospective chart review study.

BACKGROUND: Branched-chain amino acid (BCAA) concentrations must be tracked and maintained within an optimal range to minimize disease phenotypes in patients with maple syrup urine disease (MSUD). In 2014, the Hospital for Sick Children (SickKids) implemented a dried blood spot (DBS) home monitoring system, allowing patients to track BCAA concentrations without the inconvenience of having to travel to the hospital. METHODS: We conducted a retrospective chart review study (n = 15) to assess the impacts of DBS monitoring implementation on biochemical control. Furthermore, we explored relationships among various MSUD patient parameters, including monitoring frequency, age, biochemical control, and hospitalizations. RESULTS: There was a 35% increase in the proportion of LEU concentrations that met recommended targets post-DBS monitoring implementation. Monitoring frequency was positively associated with better biochemical control in the newborn period (r = 0.68, p = 0.046). Frequency of hospital visits decreased steadily throughout life. CONCLUSION: DBS monitoring has resulted in a sharp increase in monitoring frequency, which is further correlated with biochemical control. Younger patients are more likely to visit the hospital and respond better to increased monitoring efforts. We recommend that DBS monitoring be adopted by other centers more broadly to improve metabolic control in MSUD patients.

How to use a controlled fast to investigate hypoglycaemia.

Controlled fasts can play a valuable role in the diagnosis and management of hypoglycaemia in paediatric clinical practice, but are no substitute for the collecting of appropriate critical samples at the time of hypoglycaemia for metabolic and endocrine studies. Fatty acid oxidation defects, hyperinsulinism and adrenal insufficiency should always be excluded prior to organising controlled fasts. Controlled fasts are safe if conducted in an experienced setting with strict protocols in place. Failure to adhere to protocol can defeat the purpose of the study and can potentially be dangerous. Proper planning in conjunction with the laboratory and close supervision by staff experienced in controlled fasts is crucial to ensure the best quality information is yielded from these procedures.

Pyruvate dehydrogenase phosphatase 1 (PDP1) null mutation produces a lethal infantile phenotype.

Pyruvate dehydrogenase phosphatase deficiency has previously only been confirmed at the molecular level in two brothers and two breeds of dog with exercise intolerance. A female patient, who died at 6 months, presented with lactic acidemia in the neonatal period with serum lactate levels ranging from 2.5 to 17 mM. Failure of dichloroacetate to activate the PDH complex in skin fibroblasts was evident, but not in early passages. A homozygous c.277G > T (p.E93X) nonsense mutation in the PDP1 gene was identified in genomic DNA and immunoblotting showed a complete absence of PDP1 protein in mitochondria. Native PDHC activity could be restored by the addition of either recombinant PDP1 or PDP2. This highlights the role of PDP2, the second phosphatase isoform, in PDP1-deficient patients for the first time. We conclude that the severity of the clinical course associated with PDP1 deficiency can be quite variable depending on the exact nature of the molecular defect.

Mitochondrial disorders and general anaesthesia: a case series and review.

Patients with mitochondrial disease are at risk of metabolic decompensation and often require general anaesthesia (GA) as part of their diagnostic work up and subsequent management. However, the evidence base for the use of GA is limited and inconclusive. We have documented the practice and outcome in the use of GA in paediatric patients with mitochondrial disease using a retrospective case review study of 38 mitochondrial patients who had undergone 58 anaesthetics within the regional metabolic service for the period 1989-2005. A variety of anaesthetic agents were used and the pattern of use reflects that seen in standard paediatric practice. There were no episodes of malignant hyperthermia and no documented intraoperative events attributable to the GA. Three postoperative adverse events were noted; one episode of hypovolaemia, one episode of acute on chronic renal failure, and one episode of metabolic decompensation 12 h post-muscle biopsy. Despite theoretical concern about this group of patients, adverse events after GA are rare and in most cases unrelated to the anaesthesia. Further prospective studies of GA in mitochondrial disease are required to create evidence-based clinical guidelines for safe practice.

Auxiliary liver transplantation for propionic acidemia: a 10-year follow-up.

Orthotopic liver transplantation (OLT) is an established treatment for patients with liver-based metabolic disorders that produce structural and functional impairment. Auxiliary liver transplantation (ALT) has been proposed as an alternative approach due to the potential advantage of preserving the native liver that could be used for future gene therapy and also serves as a back-up should the graft fail. The aim of our study was to determine if ALT has the long-term potential to correct the underlying abnormality in propionic acidemia (PA). A retrospective analysis was performed on graft function, metabolic parameters and effects on development in a child who underwent ALT for PA at our institute. The clinical and biochemical parameters are near normal with no diet restrictions and with good graft survival. A normal growth and an acceptable neurological and psychomotor development were achieved in the child. ALT is feasible and provides adequate liver mass to prevent metabolic decompensation in PA.

Clinical, enzymatic and molecular characterization of nine new patients with malonyl-coenzyme A decarboxylase deficiency.

We report nine new patients with malonic aciduria associated with enzyme-confirmed malonyl-CoA decarboxylase (MCD) deficiency in eight. Clinical details were available on eight, and molecular genetic characterization was obtained for nine. As for 15 previously described patients, cardinal clinical manifestations included developmental delay and cardiomyopathy; metabolic perturbations (e.g. acidosis) and seizures, however, were infrequent or not observed in our patients. For all, detection of elevated malonic acid in urine (+/- increased C3DC acylcarnitine by analysis employing tandem mass spectrometry) led to pursuit of enzyme studies. MCD activities (nmol/h PER mg protein) revealed: control (n = 22), 16.2 +/- 1.8 (SEM; range 5.7-46.2); patients (n = 8, assayed in duplicate), 1.7 +/- 0.3 (10% of parallel control; range 0.6-2.8). Molecular characterization by DNA sequence analysis and multiplex ligation-dependent probe amplification revealed nine novel mutations (c.796C>T; p.Gln266X, c.481delC; p.Leu161CysfsX18, c.1367A>C; p.Tyr456Ser, c.1319G>T; p.Ser440Ile, c.1430C>T; p.Ser477Phe, c.899G>T; p.Gly300Val, c.799-1683_949-1293del3128, and two other large genomic deletions comprising exons 1 or the complete gene) and two known mutations in the MLYCD gene. Our findings increase the number of enzyme-confirmed MCD-deficient patients by >50%, and expand our understanding of the phenotypic and molecular heterogeneity of this rare disorder.

Pyruvate dehydrogenase E3 binding protein (protein X) deficiency.

Pyruvate dehydrogenase (PDH) deficiency is a major cause of neurological dysfunction and lactic acidosis in infancy and early childhood. The great majority of cases (>80%) result from mutations in the X-linked gene for the E1alpha subunit of the complex (PDHA1). Mutations in the genes for the other subunits have all been described, but only dihydrolipoamide dehydrogenase (E3) and E3 binding protein (E3BP) defects contribute significantly to the total number of patients with PDH deficiency. Although previously considered rare, with only 13 reported cases, we have found that mutations in PDX1, the gene for the E3 binding protein, are in fact relatively common. Clinical, biochemical, and genetic features of six new patients (four males, two females; age range 15mo-6y) with mutations in this gene are compared with previously reported cases. All patients with E3BP deficiency identified to date have mutations which completely prevent synthesis of the protein product. However, they are generally less severely affected than patients with PDHA1 mutations, although there is considerable overlap in clinical and neuroradiological features.

Effects of calcium and lipophilicity on transport of clodronate and its esters through Caco-2 cells.

Clodronate, like other bisphosphonates, is poorly absorbed from the gastrointestinal tract, mainly due to its high hydrophilicity and ability to form complexes with divalent cations in the gastrointestinal tract. One strategy for improving oral absorption of these types of molecules is to develop more lipophilic derivatives. The importance of lipophilicity and calcium chelation in the absorption of clodronate was evaluated by studying the penetration of clodronate and its mono-, di-, and triphenyl esters through human intestinal Caco-2 cells. The transport rates of [(14)C]-clodronate and its mono-, di-, and triphenyl esters were quantified by calculating their apparent permeability coefficients (P(app)) both in normal (1.3 mM) calcium concentration and in 'minimum-calcium model'. The transport rate of 1 mM clodronate was very low (0.25 x 10(-7) cm/s), while the removal of calcium from the apical side increased this transport rate 6-fold. The transport rate of clodronate was increased with increasing dose. Mono- and diphenyl esters did not significantly enhance the transport of clodronate. Triphenyl ester, however, increased the transport rate 17-fold compared with parent clodronate. Removal of calcium did not affect the transport rates of di- or triphenyl esters, which indicated that the esterification of hydroxyl groups of clodronate decreased calcium complex formation. These results indicate that clodronate is transported paracellularly through Caco-2 cells and that calcium decreases strongly its absorption. They further suggest that at least three phosphate hydroxyl groups need to be substituted until the permeation route is changed from paracellular to transcellular.

Process analysis of fluidized bed granulation.

This study assesses the fluidized bed granulation process for the optimization of a model formulation using in-line near-infrared (NIR) spectroscopy for moisture determination. The granulation process was analyzed using an automated granulator and optimization of the verapamil hydrochloride formulation was performed using a mixture design. The NIR setup with a fixed wavelength detector was applied for moisture measurement. Information from other process measurements, temperature difference between process inlet air and granules (T(diff)), and water content of process air (AH), was also analyzed. The application of in-line NIR provided information related to the amount of water throughout the whole granulation process. This information combined with trend charts of T(diff) and AH enabled the analysis of the different process phases. By this means, we can obtain in-line documentation from all the steps of the processing. The choice of the excipient affected the nature of the solid-water interactions; this resulted in varying process times. NIR moisture measurement combined with temperature and humidity measurements provides a tool for the control of water during fluid bed granulation.