Enzyme Deficiency Disorders Research Articles

Best Practices for Development and Validation of Enzymatic Activity Assays to Support Drug Development for Inborn Errors of Metabolism and Biomarker Assessment.

Aberrant or dysfunctional cellular enzymes are responsible for a wide range of diseases including cancer, neurodegenerative conditions, and metabolic disorders. Deficiencies in enzyme level or biofunction may lead to intracellular accumulation of substrate to toxic levels and interfere with overall cellular function, ultimately leading to cell damage, disease, and death. Marketed therapeutic interventions for inherited monogenic enzyme deficiency disorders include enzyme replacement therapy and small molecule chaperones. Novel approaches of in vivo gene therapy and ex vivo cell therapy are under clinical evaluation and provide promising opportunities to expand the number of available disease-modifying treatments. To support the development of these different therapeutics, assays to quantify the functional activity of protein enzymes have gained importance in the diagnosis of disease, assessment of pharmacokinetics and pharmacodynamic response, and evaluation of drug efficacy. In this review, we discuss the technical aspects of enzyme activity assays in the bioanalytical context, including assay design and format as well as the unique challenges and considerations associated with assay development, validation, and life cycle management.

Georacial Epidemiological Estimates of Glucose-6-Phosphate Dehydrogenase Deficiency among Newborns in the United States.

Glucose-6-phosphate dehydrogenase deficiency (G6PDd) is the most common inherited enzyme deficiency disorder worldwide and a major risk factor for the development of severe hyperbilirubinemia. Racial diversity of phenotypes and genotypes in affected individuals is likely to exist in the United States because of changing population demographics. The aim of the present study was to predict an empirical estimate of annual prevalence of G6PDd in newborns adjusted for geography (state of birth), maternal racial identity, and sex of the infant. Birth statistics (2019) from National Center for Vital Statistics and CDC-WONDER data and race-specific prevalence of G6PDd in the United States were evaluated from published sources. We developed Simpson's diversity index (DI) for each State and correlated these to rates of G6PDd in neonates. Descriptive statistics including modeled prevalence and its association with DI were assessed using the Spearman's rho correlation test. We modeled state-specific prevalence for six states (California, Washington DC, Illinois, Massachusetts, New York, and Pennsylvania) using population-level allele frequencies and race, based on Hardy-Weinberg equilibrium. We estimated 78,010 (95% confidence interval: 76,768-79,252) newborns had G6PDd at birth in 2019 with cumulative median prevalence of 17.3 (interquartile range: 12.4-23.2) per 1,000 live births for United States. A strong association was noted for DI and prevalence of G6PDd (p < 0.0005). Five states (Washington DC, Mississippi, Louisiana, Georgia, and Maryland) have the highest projected G6PDd prevalence, with a range of 35 to 48 per 1,000 live births. The probability of G6PDd for female heterozygotes, based on male prevalence, ranged from 1.1 to 7.5% for each cohort in the select six states. States with diverse populations are likely to have higher rates of G6PDd. These prevalence estimates exceeded by several-fold when compared with disorders screened by existing state mandated newborn screening panels. These discrepancies are further confounded by known risk of severe neonatal hyperbilirubinemia that results with G6PDd and the life-long risk of hemolysis. Combined universal newborn predischarge screening for G6PDd and bilirubin could alert and guide a clinician's practices for parental education and closer medical surveillance during the vulnerable neonatal time period. · G6PDd is a common X-linked disorder that can present with varied phenotypes among newborns.. · Prevalence of G6PDd and genotype distribution varies with sex, race, and ethnicity.. · We present regional race- and sex-based estimates of G6PDd in the United States..

Clinical Significance of Diffusion Tensor Imaging in Metachromatic Leukodystrophy.

Metachromatic leukodystrophy (MLD) is a lysosomal enzyme deficiency disorder leading to progressive demyelination and, consecutively, to cognitive and motor decline. Brain magnetic resonance imaging (MRI) can detect affected white matter as T2 hyperintense areas but cannot quantify the gradual microstructural process of demyelination more accurately. Our study aimed to investigate the value of routine MR diffusion tensor imaging in assessing disease progression. MR diffusion parameters (apparent diffusion coefficient [ADC] and fractional anisotropy [FA]) were in the frontal white matter, central region (CR), and posterior limb of the internal capsule in 111 MR datasets from a natural history study of 83 patients (age: 0.5-39.9 years; 35 late-infantile, 45 juvenile, 3 adult, with clinical diffusion sequences of different scanner manufacturers) as well as 120 controls. Results were correlated with clinical parameters reflecting motor and cognitive function. ADC values increase and FA values decrease depending on disease stage/severity. They show region-specific correlations with clinical parameters of motor and cognitive symptoms, respectively. Higher ADC levels in CR at diagnosis predicted a disease course with more rapid motor deterioration in juvenile MLD patients. In highly organized tissues such as the corticospinal tract, in particular, diffusion MR parameters were highly sensitive to MLD-associated changes and did not correlate with the visual quantification of T2 hyperintensities. Our results show that diffusion MRI can deliver valuable, robust, clinically meaningful, and easily obtainable/accessible/available parameters in the assessment of prognosis and progression of MLD. Therefore, it provides additional quantifiable information to established methods such as T2 hyperintensity.

MR-spectroscopy in metachromatic leukodystrophy: A model free approach and clinical correlation

Background and purposeMetachromatic leukodystrophy (MLD) is a lysosomal enzyme deficiency disorder leading to demyelination and subsequently to a progressive decline in cognitive and motor function. It affects mainly white matter where changes during the course of the disease can be visualized on T2-weighted MRI as hyperintense areas. Associated changes in brain metabolism can be quantified by MR spectroscopy (MRS) and may give complementary information as biomarkers for disease characterisation and progression. Our study aimed to further investigate the correlation of MRS with clinical parameters for motor and cognitive function by using a model free MRS analysis approach that would be precise and straightforward to implement. Materials and methods53 MRS datasets derived from 29 patients (10 late-infantile, 19 juvenile) and 12 controls were acquired using a semi-LASER CSI sequence covering a slice through the centrum semiovale above the corpus callosum. We defined four regions of interest in the white matter (frontal white matter [FWM] and the cortico-spinal tract [CST] area, each left and right) and one in cortical grey matter. Spectra were analysed using a model and fitting free approach by calculating the definite integral of 10 intervals which were distributed along the whole spectrum. These 10 intervals were orientated towards the main peaks of the metabolites N-acetylaspartate (NAA), creatine, myo-inositol, choline, glutamine/glutamate and aspartate to approximately attribute changes in the intervals to corresponding metabolites. Their ratios to the main creatine peak integral were correlated with clinical parameters assessing motor and cognitive abilities. Furthermore, in a post-hoc analysis, NAA levels of a subset of 21 MR datasets were correlated to NAA levels in urine measured by 1H (proton) nuclear magnetic resonance (NMR) spectroscopy.The applied interval integration method was validated in the control cohort against the standard approach, using spectral profile templates of known metabolites (LCModel). Both methods showed good agreement, with coefficients of variance being slightly lower for our approach compared to the related LCModel results. Moreover, the new approach was able to extract information out of the frequency range around the main peaks of aspartate and glutamine where LCModel showed only few usable values for the respective metabolites. ResultsMLD spectra clearly differed from controls. The most pronounced differences were found in white matter (much less in grey matter), with larger values corresponding to main peaks of myo-inositol, choline and aspartate, and smaller values associated with NAA and glutamine. Late-infantile patients had more severe changes compared to later-onset patients, especially in intervals corresponding to NAA, aspartate, myo-inositol, choline and glutamine.There was a high correlation of several intervals in the corticospinal tract region with motor function (with the most relevant interval corresponding to NAA peak with a correlation coefficient of −0.75; p < 0.001), while cognitive function, by means of IQ, was found to be most correlating in frontal white matter corresponding to the NAA peak (r = 0.84, p < 0.001).The post-hoc analysis showed that the main NAA peak interval correlated negatively with the NAA in urine (r = −0.584, p < 0.001). ConclusionThe applied model and fitting free interval integration approach to analyse MRS data of a semi-LASER sequence at 3T suits well to detect and quantify pathological changes in MLD patients through the different courses of the disease and correlates well with clinical symptoms while showing smaller dimensions of variation compared to the more sophisticated single metabolite analysis using LCModel. NAA seems the most clinically meaningful biomarker to use in this context. Its correlation with urine measurements further underlines its potential as a clinically and biologically useful parameter of disease progression in MLD.

Preliminary Study of Structural Changes of Glucose-6-Phosphate Dehydrogenase Deficiency Variants.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzyme deficiency disorder affecting over 400 million individuals worldwide. G6PD protects red blood cells (RBC) from the harmful effects of oxidative substances. There are more than 400 G6PD mutations, of which 186 variants have shown to be linked to G6PD deficiency by decreasing the activity or stability of the enzyme. Different variants manifest different clinical phenotypes which complicate comprehending the mechanism of the disease. In order to carry out computational approaches to elucidate the structural changes of different G6PD variants that are common to the Asian population, a complete G6PD monomer-ligand complex was constructed using AutoDock 4.2, and the molecular dynamics simulation package GROMACS 4.6.7 was used to study the protein dynamics. The G410D and V291M variants were chosen to represent classes I and II respectively and were created by in silico site-directed mutagenesis. Results from the Root mean square deviation (RMSD), Root mean square fluctuation (RMSF) and Radius of gyration (Rg) analyses provided insights on the structure - function relationship for the variants. G410D indicated impaired dimerization and structural NADP binding while the impaired catalytic activity for V291M was indicated by a conformational change at its mutation site.

Rare Diseases in Glycosphingolipid Metabolism.

Sphingolipidoses is a cluster of genetic rare disorders regarding glycosphingolipid metabolism, classified as lysosomal storage disorders (LSD). Here, we focus on eight inheritable diseases, including GM1 gangliosidosis, GM2 gangliosidosis, Fabry disease, Gaucher's disease, metachromatic leukodystrophy, Krabbe disease, Niemann-Pick disease A and B, and Farber disease. Mostly, pathogenic mutations in the key enzyme are loss-function, resulting in accumulation of substrates and deficiency of products. Thus, cellular overload of substrates causes lipotoxicity, which is deleterious to cellular and organ function. In the terms of clinical manifestations in sphingolipidoses, multiple systems and organs, especially central nervous system (CNS) are usually affected. As for diagnosis strategy, enzymatic activity assay and genetic sequencing are helpful. Up till now, limited treatment approaches have approved for treating sphingolipidoses, with some potential strategies for further evaluation. In general, enzyme replacement therapy (ERT), substrate reduction therapy (SRT), and molecular chaperones are feasible choices for enzyme deficiency disorders, but these therapies are limited to relieve CNS lesions and symptoms due to prevention from blood-brain barrier. Other possible treatments such as gene therapy, bone marrow transplantation (BMT), and hematopoietic stem cell transplantation (HSCT) need further evaluation.

Direct convective delivery of adeno-associated virus gene therapy for treatment of neurological disorders.

Molecular biological insights have led to a fundamental understanding of the underlying genomic mechanisms of nervous system disease. These findings have resulted in the identification of therapeutic genes that can be packaged in viral capsids for the treatment of a variety of neurological conditions, including neurodegenerative, metabolic, and enzyme deficiency disorders. Recent data have demonstrated that gene-carrying viral vectors (most often adeno-associated viruses) can be effectively distributed by convection-enhanced delivery (CED) in a safe, reliable, targeted, and homogeneous manner across the blood-brain barrier. Critically, these vectors can be monitored using real-time MRI of a co-infused surrogate tracer to accurately predict vector distribution and transgene expression at the perfused site. The unique properties of CED of adeno-associated virus vectors allow for cell-specific transgene manipulation of the infused anatomical site and/or widespread interconnected sites via antero- and/or retrograde transport. The authors review the convective properties of viral vectors, associated technology, and clinical applications.

Mucopolysaccharidosis type II: Enzyme Replacement Therapy Efficiency

Mucopolysaccharidosis type II (MPS II), or Hunter syndrome, is the hereditary lysosomal storage disease caused by pathological variants in IDS gene. Such variants lead to iduronate-2-sulfatase enzyme deficiency and glycosaminoglycan catabolism disorder. Major clinical signs are central nervous system lesion, disorders of musculoskeletal system, cardiovascular and respiratory systems pathologies, hepatosplenomegaly, hearing impairment. Enzyme replacement therapy (ERT) makes it possible to adjust metabolic processes in lysosomes of many organs and tissues, to improve clinical signs due to partial restoring of the damaged enzyme function. Cardiovascular pathology is the main cause of death in patients with MPS. In this regard we have studied efficiency of ERT with idursulfase and its effects on the cardiovascular system in 55 patients with MPS II. It has been shown that ERT started from an early age can significantly improve children's condition, reduce or event prevent cardiac involvement. Treatment gaps from 1 to 7 months due to economic or organizational factors in 12 patients caused worsening course of the disease.

Single enzyme nanoparticle, an effective tool for enzyme replacement therapy.

The term "single enzyme nanoparticle" (SEN) refers to a chemically or biologically engineered single enzyme molecule. SENs are distinguished from conventional protein nanoparticles in that they can maintain their individual structure and enzymatic activity following modification. Furthermore, SENs exhibit enhanced properties as biopharmaceuticals, such as reduced antigenicity, and increased stability and targetability, which are attributed to the introduction of specific moieties, such as poly(ethylene glycol), carbohydrates, and antibodies. Enzyme replacement therapy (ERT) is a crucial therapeutic option for controlling enzyme-deficiency-related disorders. However, the unfavorable properties of enzymes, including immunogenicity, lack of targetability, and instability, can undermine the clinical significance of ERT. As shown in the cases of Adagen®, Revcovi®, Palynziq®, and Strensiq®, SEN can be an effective technology for overcoming these obstacles. Based on these four licensed products, we expect that additional SENs will be introduced for ERT in the near future. In this article, we review the concepts and features of SENs, as well as their preparation methods. Additionally, we summarize different types of enzyme deficiency disorders and the corresponding therapeutic enzymes. Finally, we focus on the current status of SENs in ERT by reviewing FDA-approved products.

HLA- and genotype-based risk assessment model to identify infantile onset pompe disease patients at high-risk of developing significant anti-drug antibodies (ADA)

In Pompe disease, anti-drug antibodies (ADA) to acid alpha-glucosidase (GAA) enzyme replacement therapy contribute to early mortality. Assessing individual risk for ADA development is notoriously difficult in (CRIM-positive) patients expressing endogenous GAA. The individualized T cell epitope measure (iTEM) scoring method predicts patient-specific risk of developing ADA against therapeutic recombinant human GAA (rhGAA) using individualized HLA-binding predictions and GAA genotype. CRIM-negative patients were six times more likely to develop high ADA titers than CRIM-positive patients in this retrospective study, whereas patients with high GAA-iTEM scores were 50 times more likely to develop high ADA titers than patients with low GAA-iTEM scores. This approach identifies high-risk IOPD patients requiring immune tolerance induction therapy to prevent significant ADA response to rhGAA leading to a poor clinical outcome and can assess ADA risk in patients receiving replacement therapy for other enzyme or blood factor deficiency disorders.

Will the FAbry STabilization indEX make its way to everyday clinical practice?

Despite several attempts at setting up a standardized disease severity score for Fabry disease in the past, none have been established in routine clinical practice due to the multisystem nature and complexity of this inherited enzyme deficiency disorder. In this issue, Mignani et al. report a large multicentre application of the FASTEX, an online tool to assess disease progress over time that offers simple data inputting and graphic illustration of disease progression or stabilization. Mignani et al. succeeded in validating the tool in a large cohort of Fabry patients, including females and non-classical phenotypes, building on the first FASTEX introduction in 2016. We report on our own practical experience with the tool and comment on some limiting factors in its use as well as possible future prospects.

Imaging of Nonmalignant Adrenal Lesions in Children.

The adrenal glands in children can be affected by a variety of benign lesions. The diagnosis of adrenal lesions can be challenging, but assessment of morphologic changes in correlation with the clinical presentation can lead to an accurate diagnosis. These lesions can be classified by their cause: congenital (eg, discoid adrenal gland, horseshoe adrenal gland, and epithelial cysts), vascular and/or traumatic (eg, adrenal hemorrhage), infectious (eg, granulomatous diseases), enzyme deficiency disorders (eg, congenital adrenal hyperplasia [CAH] and Wolman disease), benign neoplasms (eg, pheochromocytomas, ganglioneuromas, adrenal adenomas, and myelolipomas), and adrenal mass mimics (eg, extralobar sequestration and extramedullary hematopoiesis). Multimodality cross-sectional imaging helps to define the origin, extent, and relationship of these lesions to adjacent structures, as well as to guide treatment management. The anatomic and functional imaging modalities used to evaluate pediatric adrenal lesions include ultrasonography, computed tomography (CT), magnetic resonance imaging, and iodine 123 metaiodobenzylguanidine scintigraphy. Identifying the imaging features of nonmalignant adrenal lesions is helpful to distinguish these lesions from malignant adrenal neoplasms. Identifying characteristic imaging findings (eg, enlarged adrenal glands, with cerebriform surface, and stippled echogenicity in CAH; a T2-hyperintense mass with avid contrast enhancement in pheochromocytoma; low CT attenuation [<10 HU] and signal intensity drop on opposed-phase chemical shift images in adenoma; and enhancing suprarenal mass supplied by a systemic feeding artery in extralobar sequestration) can aid in making the correct diagnosis. In addition, clinical features (eg, ambiguous genitalia in CAH and hypertension in pheochromocytoma) can also guide the radiologist toward the correct diagnosis. ©RSNA, 2017.

Diels-Alder "click" crosslinked matrices within calcium alginate templated beads

Event Abstract Back to Event Diels-Alder "click" crosslinked matrices within calcium alginate templated beads Alison Stewart1, Nicholas A. Burke1 and Harald D. Stöver1 1 McMaster University, Department of Chemistry & Chemical Biology, Canada Introduction: Covalently crosslinkable polymer hydrogels are a promising approach for the treatment of hormone and enzyme-deficiency disorders[1]. These scaffolds help provide protection from the immune system for encapsulated therapeutic cells. This presentation describes the use of the Diels-Alder reaction between furan and maleimide as a crosslinking reaction to form synthetic hydrogel scaffolds within a calcium alginate template. Materials and Methods: Poly(methyl vinyl ether-alt-maleic anhydride) was functionalized with furan and maleimide to give PMM-FFA/MAL. Beads were formed via gelation of droplets of sodium alginate and PMM-FFA/MAL in NaCl gelling bath. Distribution of PMM-FFA/MAL within the bead core was determined using fluorescence microscopy. In-diffusion of fluorescently-labeled dextrans was used to probe the pore-size of the beads. To determine crosslinking time and degree, the alginate scaffold was liquefied using sodium citrate, following various curing times. Results and Discussion: It was found that the presence of PMM-FFA/MAL does not interfere with alginate gelation, and low polymer loss (3-12%) during gelation indicates efficient trapping within the beads. To investigate crosslinking time, matrix beads were exposed to sodium citrate after set crosslinking times and observed via confocal microscopy. It was shown that as incubation time increased, the degree of swelling subsequently decreased, due to extended time for the Diels-Alder reaction to form covalent crosslinks. Figure 1 shows the swelling of Alg-PMM-FFA25/MAL24 beads in sodium citrate at A) 10 minutes, B) 2.5h and C) 6h post-bead formation. To characterize degree of crosslinking, beads were incubated for 24h, followed by exposure to excess citrate for 6h. All bead compositions remained intact post-citrate extraction, indicating sufficient Diels-Alder crosslinking. The beads composed of Alg-PMM-FFA12/MAL9 exhibited the highest degree of swelling, due to their low number of functional groups. Surprisingly, Alg-PMM-FFA18/MAL17 and Alg-PMM-FFA25/MAL23 beads had identical swell ratios. It is hypothesized that once a critical number of crosslink points are achieved, chain mobility is sufficiently decreased such that no more crosslinks form. In-diffusion studies of fluorescently-labeled dextran showed that 10 and 70kDa dextrans are able to readily diffuse into all beads. The 250 and 500kDa dextrans are partially excluded from the beads, demonstrating that Alg-PMM-FFA/MAL matrix beads show differential permeability for lower and higher-MW species. As expected, citrate treated beads exhibit higher permeability compared with untreated beads, due to swelling. Conclusions: Diels-Alder coupling between diene and dienophile-modified polyanions was used to form covalently crosslinked beads within an alginate-mediated template. The beads exhibited sufficient crosslinking to withstand alginate liquefaction, while pore-size and swell ratio could be successfully controlled via polymer and functional group loading. On-going work is focused on characterization of physical properties, and applications in cell encapsulation. We would like to thank the Natural Sciences and Engineering Research Council (NSERC) of Canada for supporting this work through discovery and CREATE grants

Rapid intranasal delivery of chloramphenicol acetyltransferase in the active form to different brain regions as a model for enzyme therapy in the CNS

BackgroundThe blood brain barrier (BBB) is critical for maintaining central nervous system (CNS) homeostasis by restricting entry of potentially toxic substances. However, the BBB is a major obstacle in the treatment of neurotoxicity and neurological disorders due to the restrictive nature of the barrier to many medications. Intranasal delivery of active enzymes to the brain has therapeutic potential for the treatment of numerous CNS enzyme deficiency disorders and CNS toxicity caused by chemical threat agents. New methodThe aim of this work is to provide a sensitive model system for analyzing the rapid delivery of active enzymes into various regions of the brain with therapeutic bioavailability. ResultsWe tested intranasal delivery of chloramphenicol acetyltransferase (CAT), a relatively large (75kD) enzyme, in its active form into different regions of the brain. CAT was delivered intranasally to anaesthetized rats and enzyme activity was measured in different regions using a highly specific High Performance Thin Layer Chromatography (HP-TLC)-radiometry coupled assay. Active enzyme reached all examined areas of the brain within 15min (the earliest time point tested). In addition, the yield of enzyme activity in the brain was almost doubled in the brains of rats pre-treated with matrix metalloproteinase-9 (MMP-9). Comparison with existing method (s)Intranasal administration of active enzymes in conjunction with MMP-9 to the CNS is both rapid and effective. ConclusionThe present results suggest that intranasal enzyme therapy is a promising method for counteracting CNS chemical threat poisoning, as well as for treating CNS enzyme deficiency disorders.

Late Onset Ornithine Transcarbamylase Deficiency Accompanying Severe HyperammonemiaAfter Cesarean Section: Case Report

Hyperammonemia is one of the common complications of porto-systemic shunt or liver failure. In patients without liver failure or porto-systemic shunt, hyperammonemia can be caused by urea cycle disorders. Nitrogen excretion pathway or enzyme deficiency disorder can result in any hyperammonemia, coma, or death that may cause severe clinical encephalopathy presenting with neurological symptoms. The most common cause of genetic disorders in the urea cycle is ornithine carbamoyltransferase deficiency. In this article, 28-year-old female patient who had late-onset ornithine carbamoyltransferase deficiency with severe acute hyperammonemia resulting coma and death after cesarian section is described. In addition, treatment of hyperammonemia including sodium benzoate, arginine, and hemodialysis were discussed.

Transcriptional and epigenetic basis for restoration of G6PD enzymatic activity in human G6PD-deficient cells

AbstractHDAC inhibitors (HDACi) increase transcription of some genes through histone hyperacetylation. To test the hypothesis that HDACi-mediated enhanced transcription might be of therapeutic value for inherited enzyme deficiency disorders, we focused on the glycolytic and pentose phosphate pathways (GPPPs). We show that among the 16 genes of the GPPPs, HDACi selectively enhance transcription of glucose 6-phosphate dehydrogenase (G6PD). This requires enhanced recruitment of the generic transcription factor Sp1, with commensurate recruitment of histone acetyltransferases and deacetylases, increased histone acetylation, and polymerase II recruitment to G6PD. These G6PD-selective transcriptional and epigenetic events result in increased G6PD transcription and ultimately restored enzymatic activity in B cells and erythroid precursor cells from patients with G6PD deficiency, a disorder associated with acute or chronic hemolytic anemia. Therefore, restoration of enzymatic activity in G6PD-deficient nucleated cells is feasible through modulation of G6PD transcription. Our findings also suggest that clinical consequences of pathogenic missense mutations in proteins with enzymatic function can be overcome in some cases by enhancement of the transcriptional output of the affected gene.

An innovative approach to the treatment of Gaucher disease and possibly other metabolic disorders of the brain

The extraordinary benefit of enzyme replacement therapy (ERT) on the systemic manifestations of Gaucher disease was demonstrated in 1991. Since that time, investigators have devoted substantial effort to improve the delivery of enzymes to the brain because many hereditary metabolic disorders are characterized by extensive central nervous system involvement. Because the required supplemental enzyme is too large to cross the blood-brain barrier (BBB), ERT for central nervous system involvement was out of the question at that time. Several innovative strategies that have been reported to overcome this impediment are discussed. Recent investigations have provided additional insight concerning the pathogenesis of enzyme deficiency disorders. For many years it was presumed that alterations of the amino acid sequence of enzymes such as glucocerebrosidase reduced the catalytic activity of the enzyme. It has recently been shown that the decrease of glucocerebrosidase activity was the result of a quantitative loss of the amount of this enzyme. Significant increases of its activity were obtained with small molecule inhibitors of histone deacetylase that cross the BBB. The effect of such materials on neuronopathic Gaucher disease and other CNS metabolic disorders is discussed.

Spinal cord infarction remote from maximal compression in a patient with Morquio syndrome

Morquio syndrome, or mucopolysaccharidosis type IV, is a rare enzyme deficiency disorder and results in skeletal dysplasia. Odontoid dysplasia is common among affected patients, resulting in atlantoaxial instability and spinal cord compression. Surgical treatments include decompression and prophylactic fusion, during which intraoperative neuromonitoring is important to alert the surgical team to changes in cord function so that they can prevent or mitigate spinal cord injury. This report describes a 16-year-old girl with Morquio syndrome who developed paraplegia due to thoracic spinal cord infarction during foramen magnum and atlantal decompression. This tragic event demonstrates the following: 1) that patients with Morquio syndrome are at risk for ischemic spinal cord injury at levels remote from areas of maximal anatomical compression while under anesthesia in the prone position, possibly due to impaired cardiac output; 2) the significance of absent motor evoked potential responses in the lower limbs with preserved upper-limb responses in an ambulatory patient; 3) the importance of establishing intraoperative neuromonitoring baseline assessments prior to turning patients to the prone position following induction of anesthesia; and 4) the importance of monitoring cardiac output during prone positioning in patients with chest wall deformity.

Differenzialdiagnostische Bedeutung von Gelenkkontrakturen – unter besonderer Berücksichtigung rheumatischer Erkrankungen und der Mucopolysaccharidose Typ I

Progressive loss of joint mobility is the most frequent finding in patients with musculoskeletal complaints and may eventually result in a joint contracture. Occurring at all ages, impaired joint mobility may be the consequence of a number of heterogeneous causes, and thus a detailed evaluation and differential diagnosis are required. The diagnosis should be based on medical history and physical examination as well as imaging techniques and laboratory parameters, as appropriate. In particular, rheumatic disorders such as juvenile idiopathic arthritis (JIA) may be causal in paediatric patients, but hereditary enzyme deficiency disorders (e. g., mucopolysaccharidoses, Scheie disease) should be considered as well. In adults, the most common causes are post-traumatic conditions, osteoarthritis and inflammatory rheumatic diseases. Especially for paediatric patients, an early diagnosis provides the opportunity for appropriate treatment that may prevent irreversible physical and mental damage. On the basis of 5 case reports, the relevance of joint contractures is presented and diagnostic and therapeutic options are discussed.

Prenatal diagnosis of Gaucher disease

Gaucher disease (GD) is a rare disease but is the commonest enzyme deficiency disorder among the group of inherited lysosomal storage diseases [1]. It is caused by a deficiency in glucocerebrosidase (a lysosomal enzyme also referred to as acid beta-glucosidase) or, in rare cases, by a deficiency in the activator protein saposin C. Following genetic counselling and informed consent, direct enzymatic assay of acid beta-glucosidase on chorionic villi samples (CVS) can be offered to families in which GD has been diagnosed. We report prenatal diagnosis of GD by CVS in a couple with one child suffering from GD Type 1.