Enzyme Activity In Leukocytes Research Articles

THE GLA D313Y MUTATION IN FABRY DISEASE: DIAGNOSTIC DILEMMAS AND THERAPEUTIC CONSIDERATIONS

Abstract Fabry disease is a genetic disorder caused by mutations in the GLA gene, which encodes alpha–galactosidase A, leading to enzyme dysfunction and subsequent accumulation of glycosphingolipids. In the classical form, it occurs in childhood or early adolescence with renal, cardiac, and neurological involvement, resulting in a poor prognosis. The GLA D313Y is a missense mutation resulting in a significant reduction of enzyme activity in plasma, while leukocyte enzyme activity remains within normal limits, leading to a "pseudo–deficiency" of enzyme activity with uncertain pathogenicity. In literature, it has been observed that individuals with this mutation may present predominantly with central neurologic manifestations, characterized by multifocal white matter lesions. Historically they do not receive indications for initiating enzyme replacement or molecular chaperone therapies. We present the case of a man affected by arterial hypertension and history of chronic lower limb pain who experienced a lacunar stroke at the age of 35. The GLA D313Y mutation was identified and enzyme activity assay in plasma was within normal limits, precluding the initiation of enzyme replacement therapy. Over the following years, he suffered two additional ischemic strokes, a progressive decline in renal function to stage 3, and acute coronary syndrome. Transthoracic echocardiography revealed hypertrophic non–obstructive cardiomyopathy (SIVd 20 mm) with normal biventricular ejection fraction. Cardiac magnetic resonance showed late gadolinium enhancement of inferior junctional and inferior wall in middle segment (Fig.1). Considering the patient‘s clinical conditions involving multi–organ impairment, an enzymatic activity test was performed on leukocytes, revealing a reduced activity. This prompted the decision to initiate enzyme replacement therapy. This case report supports the hypothesis that the D313Y mutation may be associated with a later presentation and not only neurological involvement. In our experience, it’s mandatory to proceed with the determination of leukocyte enzyme activity in presence of normal enzyme activity in plasma. As an alternative, the detection of glycosphingolipids’ accumulation could be useful, but myocardial and renal biopsy poses a high bleeding risk, especially in anticoagulated or antiaggregated patients. The authors propose considering the initiation of therapy in patients with the D313Y mutation who exhibit significant organ involvement.

Pompe disease - What do we currently know about the disease?


 Introduction: Pompe disease (PD) is a rare metabolic disorder caused by a partial or complete deficiency of acid α-glucosidase (GAA) which leads to lysosomal accumulation of glycogen. Excessive amounts of glycogen accumulate mainly in the cells of the heart and skeletal muscles and cause dysfunction of these tissues. It is inherited in an autosomal recessive manner. The most common diagnostic methods include genetic tests and the measurement of enzyme activity in leukocytes or fibroblasts. A screening test is also available that tests the enzyme activity in dried blood spot (DBS). The treatment of PD is mostly based on synthetic GAA enzyme supply to the patients. The therapy reduces glycogen storage and improves muscle function, decreases heart size and prolongs the lives of those with infantile form of PD. In the adult onset of the disease treatment increases physical efficiency and reduces the progression of respiratory failure.
 
 
 Aim of the study: Systematization of current knowledge about Pompe disease with particular emphasis on possible clinical presentations, diagnostics and therapeutic options.
 Material and methods: Literature review based on PubMed data using the following keywords: Pompe disease, Glycogenosis type ii, glucosidase alpha
 Summary : Pompe disease is a rare disease with many problems related to diagnosis and possible therapies. Its symptoms can be very misleading and cause a delay in diagnosis . It is critical to start the therapy as soon as possible to best manage the disease. The prognosis of PD is poor, especially in children under 12 months of age. Gene therapy research is currently underway and early results are very promising. There is still much to learn about dealing with this disease.

Updated Confirmatory Diagnosis for Mucopolysaccharidoses in Taiwanese Infants and the Application of Gene Variants

Mucopolysaccharidosis (MPS) is a lysosomal storage disease caused by genetic defects that result in deficiency of one specific enzyme activity, consequently impairing the stepwise degradation of glycosaminoglycans (GAGs). Except for MPS II, the other types of MPS have autosomal recessive inheritance in which two copies of an abnormal allele must be present in order for the disease to develop. In this study, we present the status of variant alleles and biochemistry results found in infants suspected of having MPS I, II, IVA, and VI. A total of 324 suspected infants, including 12 for MPS I, 223 for MPS II, 72 for MPS IVA, and 17 for MPS VI, who were referred for MPS confirmation from newborn screening centers in Taiwan, were enrolled. In all of these infants, one specific enzyme activity in dried blood spot filter paper was lower than the cut-off value in the first blood sample, as well asin a second follow-up sample. The confirmatory methods used in this study included Sanger sequencing, next-generation sequencing, leukocyte enzyme fluorometric assay, and GAG-derived disaccharides in urine using tandem mass spectrometry assays. The results showed that five, nine, and six infants had MPS I, II, and IVA, respectively, and all of them were asymptomatic. Thus, a laboratory diagnosis is extremely important to confirm the diagnosis of MPS. The other infants with identified nucleotide variations and reductions in leukocyte enzyme activities were categorized as being highly suspected cases requiring long-term and intensive follow-up examinations. In summary, the final confirmation of MPS depends on the most powerful biomarkers found in urine, i.e., the quantification of GAG-derived disaccharides including dermatan sulfate, heparan sulfate, and keratan sulfate, and analysis of genetic variants can help predict outcomes and guide treatment.

Long-term effect of hematopoietic cell transplantation on systemic inflammation in patients with mucopolysaccharidoses

AbstractMucopolysaccharidoses (MPS) are devastating inherited diseases treated with hematopoietic cell transplantation (HCT). However, disease progression, especially skeletal, still occurs in all patients. Secondary inflammation has been hypothesized to be a cause. To investigate whether systemic inflammation is present in untreated patients and to evaluate the effect of HCT on systemic inflammation, dried blood spots (n = 66) of patients with MPS (n = 33) treated with HCT between 2003 and 2019 were included. Time points consisted of pre-HCT and, for patients with MPS type I (MPS I), also at 1, 3, and 10 years of follow-up. Ninety-two markers of the OLINK inflammation panel were measured and compared with those of age-matched control subjects (n = 31) by using principal component analysis and Wilcoxon rank sum tests with correction. Median age at transplantation was 1.3 years (range, 0.2-4.8 years), and median time of pre-HCT sample to transplantation was 0.1 year. Normal leukocyte enzyme activity levels were achieved in 93% of patients post-HCT. Pretransplant samples showed clear separation of patients and control subjects. Markers that differentiated pre-HCT between control subjects and patients were mainly pro-inflammatory (50%) or related to bone homeostasis and extracellular matrix degradation (33%). After 10 years' follow-up, only 5 markers (receptor activator of nuclear factor kappa-Β ligand, osteoprotegerin, axis inhibition protein 1 [AXIN1], stem cell factor, and Fms-related tyrosine kinase 3 ligand) remained significantly increased, with a large fold change difference between patients with MPS I and control subjects. In conclusion, systemic inflammation is present in untreated MPS patients and is reduced upon treatment with HCT. Markers related to bone homeostasis remain elevated up to 10 years after HCT and possibly reflect the ongoing skeletal disease, making them potential biomarkers for the evaluation of new therapies.

Leukocyte Phosphomannomutase and Phosphomannose Isomerase Activity in an Indian Cohort.

Advances in molecular sequencing technology has increased the diagnostic yield for Congenital disorder of glycosylation (CDG). However, novel variants or those of uncertain significance (vus) often pose a challenge and in such cases confirmed diagnosis can be warranted through enzyme analysis of these defects. We thus, aimed to optimize leukocyte-based enzyme assays for first two enzymes involved in N-glycosylation pathway i.e. Phosphomannomutase (PMM) and Phosphomannose isomerase (MPI). Study population comprised of 50 healthy non-alcoholic adults and 20 pediatric controls. Leukocyte enzyme activity was measured by monitoring the conversion of NADP to NADPH at 340nm. The conditions were optimized and precision was assessed for both low and normal activity leukocyte controls. Enzyme activities for PMM and MPI in healthy individuals were measured in the range 1.6-3.9 and 7-20nmol/min/mg protein respectively and did not vary with age and gender. The precision for both PMM and MPI showed %CV of 19.9 and 19.8 respectively. The enzyme activity in leukocyte pellet was found to be stable for up to 9months when stored at -80°C. The enzyme assays are optimized for PMM and MPI and can be used for evaluation of CDG patients in India.

Development and Validation of Leukocyte Enzyme Activity Assay by LC-MS/MS for Diagnosis of Krabbe Disease and Other Lysosomal Storage Diseases

Abstract Background Deficiency of the lysosomal enzyme galactosylcerebrosidase (GALC) causes Krabbe disease. The diagnosis for Krabbe disease includes measurement of GALC enzymatic activity by radioisotope assay or accumulation of metabolite psychosine. To improve current diagnostic workflow and assay performance, we developed and validated a leukocyte enzymatic assay by using liquid chromatography tandem mass spectrometry (LC-MS/MS) for lysosomal storage diseases. Methods Leukocytes were separated and extracted from whole blood samples, and total protein was quantitated by BCA method. Commercialized and multiplexed substrates, internal standards, and buffer were incubated with cell lysates. The lysosomal enzymes in leukocytes metabolized the artificial substrate into product which is structurally identical to the internal standard. Liquid-liquid extraction was performed and supernatant was dried down and reconstituted. Liquid chromatography separation was achieved by Waters CSH C18, 2.1 x 50 mm column and Acquity UPLC system. A Waters Xevo TQS tandem mass spectrometer was used for mass detection. Results Enzymatic reaction products for six lysosomal enzymes were chromatographically resolved from substrate breakdown products through 3.5 minutes gradient liquid chromatography. Intra-assay imprecision was determined by 11 replicates of samples containing low and high concentration (CV<15%). Carryover was determined by assaying triplicates of cell lysate-free cocktails directly after injection of high enzyme activity sample (less than 0.1%). No matrix effect was found. The GALC enzyme activity was calculated and standardized by corresponding product and internal standard ratios from 5-point standard curve. The range of enzyme activity from three, known affected patients is 0.01–0.07 (nmol/hr/mg protein); whereas, two identified carriers had enzyme activate in the range of 0.14–0.40 (nmol/hr/mg protein). The reference interval was established from 63 residual, unaffected samples and was 0.12–5.97 (1.44±1.44) nmol/hr/mg protein. Conclusions A simple and multiplexed LC-MS/MS assay was developed which can measure small amounts of residual GALC enzyme activity in leukocytes. This confirmatory assay will aid in the diagnosis and prognosis (i.e. differentiate disease severity) of Krabbe disease and other lysosomal storage disorders.

A genetic and clinical study of individuals with nonsyndromic retinopathy consequent upon sequence variants in HGSNAT, the gene associated with Sanfilippo C mucopolysaccharidosis.

Pathogenic variants in the gene HGSNAT (heparan‐α‐glucosaminide N‐acetyltransferase) have been reported to underlie two distinct recessive conditions, depending on the specific genotype, mucopolysaccharidosis type IIIC (MPSIIIC)—a severe childhood‐onset lysosomal storage disorder, and adult‐onset nonsyndromic retinitis pigmentosa (RP). Here we describe the largest cohort to‐date of HGSNAT‐associated nonsyndromic RP patients, and describe their retinal phenotype, leukocyte enzymatic activity, and likely pathogenic genotypes. We identified biallelic HGSNAT variants in 17 individuals (15 families) as the likely cause of their RP. None showed any other symptoms of MPSIIIC. All had a mild but significant reduction of HGSNAT enzyme activity in leukocytes. The retinal condition was generally of late‐onset, showing progressive degeneration of a concentric area of paramacular retina, with preservation but reduced electroretinogram responses. Symptoms, electrophysiology, and imaging suggest the rod photoreceptor to be the cell initially compromised. HGSNAT enzymatic testing was useful in resolving diagnostic dilemmas in compatible patients. We identified seven novel sequence variants [p.(Arg239Cys); p.(Ser296Leu); p.(Phe428Cys); p.(Gly248Ala); p.(Gly418Arg), c.1543‐2A>C; c.1708delA], three of which were considered to be retina‐disease‐specific alleles. The most prevalent retina‐disease‐specific allele p.(Ala615Thr) was observed heterozygously or homozygously in 8 and 5 individuals respectively (7 and 4 families). Two siblings in one family, while identical for the HGSNAT locus, but discordant for retinal disease, suggest the influence of trans‐acting genetic or environmental modifying factors.

Опыт внедрения неонатального скрининга болезни Гоше с использованием искусственного флуорогенного субстрата

Важность неонатального скрининга болезни Гоше во многом обусловлена созданием эффективной патогенетически обоснованной терапии. Постановка диагноза строится на обнаружении снижения активности фермента бета-глюкоцереброзидазы в лейкоцитах периферической крови. Newborn screening of Gaucher diseases is important because of the development of treatment options that improve clinical outcome. The diagnosis of Gaucher disease relies on demonstration of deficient glucocerebrosidase enzyme activity in peripheral blood leukocytes.

Clinical and Genetic Varieties of Gaucher Disease in Iraqi Children

AbstractGaucher disease (GD), which is due to a deficiency in the lysosomal enzyme β-glucocerebrosidase, is a rare genetic disorder. It is characterized by a wide variety of clinical manifestations and severity of symptoms, making it difficult to manage. A cross-sectional hospital-based genetic study was undertaken with 32 pediatric patients. We recruited 21 males and 11 females diagnosed with GD, with a male-to-female ratio of 1.91:1. The mean age of the study population was 8.79 ± 4.37 years with an age range from 8 months to 17 years. We included patients on clinical evaluation from 2011 to 2019. An enzyme assay test was used to measure β-glucosidase enzyme activity in leukocytes and the GBA gene study was performed by polymerase chain reaction technique. We found GD type 1 in 27 (84.37%) participants, GD type 3 in five (15.63%) participants, while none classified as GD type 2. The dominant mutation in GD 1 was N370S in 81.5%, of which two-thirds were homozygous. The second common mutation in this type of disease (L444P) was present in nine cases (40.9%), two of whom were homozygous (9.9%). Meanwhile, R463C was present in six cases (27.27%), of whom one was homozygous. In GD 3, the dominant mutation was L444P as seen in 80% of the patients followed by N370S and R463C in 20%. This study shows that the most common mutant allele in this study was N370S, followed by L444P. Further large-scale studies with more advanced designs are recommended to explore the sequences of GBA genes.

Tp-e interval and Tp-e/QT ratio and their association with left ventricular diastolic dysfunction in Fabry disease without left ventricular hypertrophy

IntroductionIn the early stage of the Fabry disease, diastolic dysfunction can occur before left ventricular hypertrophy (LVH). Cardiovascular complications, most of which are seen as malignant arrhythmias and heart failure, are the leading causes of death in these patients. The aim of the present study was to assess repolarization parameters of Fabry patients in early stage (without LVH) and to show the relationship between these parameters and left ventricular diastolic dysfunction. MethodsThis cross-sectional single center study was carried out with newly diagnosed 23 Fabry patients and 20 healthy individuals, between April 2016 and September 2019. Diagnosis of Fabry disease was based on a measurement of enzyme activity in leukocytes and was confirmed by genetic analysis. Basic, demographic and clinical features were reviewed. The risk of ventricular arrhythmia was evaluated by calculating the electrocardiographic, the Tp–e and QT interval, corrected QT (QTc), Tp–e/QT and Tp–e/QTc ratios. Left ventricular systolic and diastolic dysfunctions were evaluated using echocardiography. ResultsTp-e interval (86.9 ± 6.2 vs. 73.8 ± 6.3 ms; p < 0.001), Tp-e/QT ratio (0.23 ± 0.008 vs. 0.21 ± 0.01; p < 0.001) and Tp-e/QTc ratio (0.21 ± 0.007vs. 0.18 ± 0.017; p < 0.001) were significantly higher in Fabry patients than the control group. There was a significant positive correlation between Tp-e interval and E/e' ratio (r = 0.626, p = 0.003) and Tp-e/QTc ratio and E/e' ratio (r = 0.578, p = 0.008) in Fabry patients. ConclusionOur study showed that the Tp-e interval, Tp-e/QT ratio, and Tp-e/QTc ratio, which are evaluated electrocardiographically in patients with pre-hypertrophic Fabry patients, are prolonged compared to normal healthy individuals. The most significant finding was the positive correlation found between repolarization parameters and LV diastolic dysfunction. These results may be indicative of an early subclinical cardiac involvement in Fabry patients, considering the diastolic dysfunction severity.

An At-Risk Population Screening Program for Mucopolysaccharidoses by Measuring Urinary Glycosaminoglycans in Taiwan.

Background: The mucopolysaccharidoses (MPSs) are a group of rare lysosomal storage disorders characterized by the accumulation of glycosaminoglycans (GAGs) and which eventually cause progressive damage to various tissues and organs. We developed a feasible MPS screening algorithm and established a cross-specialty collaboration platform between medical geneticists and other medical specialists based on at-risk criteria to allow for an earlier confirmative diagnosis of MPS. Methods: Children (<19 years of age) with clinical signs and symptoms compatible with MPS were prospectively enrolled from pediatric clinics between July 2013 and June 2018. Urine samples were collected for a non-specific total GAG analysis using the dimethylmethylene blue (DMB) spectrophotometric method, and the quantitation of three urinary GAGs (dermatan sulfate (DS), heparan sulfate (HS), and keratan sulfate (KS)) was performed by liquid chromatography/tandem mass spectrometry (LC-MS/MS). The subjects with elevated urinary GAG levels were recalled for leukocyte enzyme activity assay and genetic testing for confirmation. Results: Among 153 subjects enrolled in this study, 13 had a confirmative diagnosis of MPS (age range, 0.6 to 10.9 years—three with MPS I, four with MPS II, five with MPS IIIB, and one with MPS IVA). The major signs and symptoms with regards to different systems recorded by pediatricians at the time of the decision to test for MPS were the musculoskeletal system (55%), followed by the neurological system (45%) and coarse facial features (39%). For these 13 patients, the median age at the diagnosis of MPS was 2.9 years. The false negative rate of urinary DMB ratio using the dye-based method for these 13 patients was 31%, including one MPS I, two MPS IIIB, and one MPS IVA. However, there were no false negative results with urinary DS, HS and KS using the MS/MS-based method. Conclusions: We established an at-risk population screening program for MPS by measuring urinary GAG fractionation biomarkers using the LC-MS/MS method. The program included medical geneticists and other medical specialists to increase awareness and enable an early diagnosis by detecting MPS at the initial onset of clinical symptoms.

4092Magnetic resonance imaging of Fabry disease cardiomyopathy in patients receiving oral chaperone therapy

Abstract Background Fabry disease is a lysosomal storage disorder with multiple organ involvement. Renal and cardiac symptoms can lead to dialysis and myocardial hypertrophy with fibrosis, responsible for heart failure with preserved ejection fraction (HFpEF). Enzyme replacement therapy (ERT) is available for all patients with Fabry disease since 2001, requiring infusions every other week. Since May 2016, the chaperone migalastat represents a novel form of specific therapy as the first oral therapy available for certain Fabry patients. Through this molecule the function of the mutated enzyme α-galactosidase A can be restored. Recent trials have shown positive cardiac effects of chaperone therapy using echocardiography; however, MRI investigations further evaluating these findings are not available yet. Objective To evaluate cardiac effects of migalastat therapy in patients with amenable α-galactosidase A mutations in the prospective monocentric HEAL-FABRY registry (NCT03362164). Methods and results Comprehensive clinical investigations including serial MRI were conducted at baseline before initiation of migalastat therapy and at least one year thereafter in all patients without contraindications such as pacemakers or ICDs. Out of 29 patients included in the study (mean age at start of therapy 52.8±14 years, total range 20–74 years), until then 12 patients with MRI data completed the 1-year follow-up. At 1 year, enzyme activity in leucocytes increased from 0.06 to 0.21 nmol/min/mg protein (p=0.001). Distinctive changes over time were observed not only in diastolic but also systolic parameters. The systolic myocardial mass index was reduced by 2.39% (p=0.10). In the AHA segment number 5, most important for classification of severe myocardial damage in Fabry patients, late gadolinium enhancement was reduced by 8.58% in all 5 patients with verified progressive fibrosis (p=0.14). One patient stopped migalastat therapy due to personal reasons. No significant side effects were observed. Analysis of LGE (systolic phase) Conclusion These preliminary MRI data show positive effects of migalastat therapy in patients with Fabry disease and cardiac involvement. Compared to echocardiography, MRI has the potential to allow for comprehensive additional analyses regarding both cardiac morphology and function.

Differential diagnosis of mucopolysaccharidosis and oligosaccharidosis of a sample of Egyptian children

Mucopolysaccharidosis (MPS) and oligosaccharidosis are lysosomal storage disorders (LSDs) that share many clinical features. The present study aimed to establish a protocol for the biochemical diagnosis of these disorders and their subtypes in affected Egyptian children as well as in pregnant females, in order to prepare children or fetus for enzyme replacement therapy. Urine, plasma and leukocyte samples were collected from 280 children with symptoms suggestive of LSDs. Fourteen amniotic fluid samples were collected from pregnant females having positive family history or having one affected sibling. Assessment of urinary glycosaminoglycans (GAGs) followed by two dimensional electrophoresis (2-DEP), thin layer chromatographic (TLC) for separation of oligosaccharides and plasma or leukocyte enzyme activity were performed. Six of pregnancies were diagnosed to have affected fetuses. 84 children had abnormal 2-DEP and classified as 26 MPS I, 10 MPS II, 24 MPS III and 24 MPS VI. Two were diagnosed as α-mannosidosis and 2 as GM1 gangliosidosis. In conclusion; MPS should be excluded before suspecting oligosaccharidosis. 2-DEP and TLC alone cannot rule out the diagnosis of either MPS or oligosaccharidosis and confirmation must be done by specific lysosomal enzymatic assay. Analysis of GAGs by 2-DEP in amniotic fluid can be promising method for prenatal diagnosis of MPS.

Cytochemical characterization of peripheral blood cell populations of two Cyprinidae, Carassius auratus and Ctenopharyngodon idellus.

Fish are the most diverse species of all vertebrate groups, and their blood cells have shown variable characteristics in terms of morphology. Cytochemical staining for enzyme activity in blood leukocytes will help assess the immune function of fish. We characterize blood cells from crucian carp (Carassius auratus) and grass carp (Ctenopharyngodon idellus) by using a Diff-Quick stain as well as different cytochemical methods. Blood specimens obtained from crucian carp and grass carp were evaluated after cytochemical staining for acid phosphatase (ACP), alkaline phosphatase (ALP), naphthol AS chloroacetate esterase (AS-DNCE), naphthyl acetate esterase (NAE), α-naphthyl butyrate esterase (NBE), peroxidase (MPO) and periodic acid-Schiff's reaction (PAS) using commercial kits. Blood cell types were evaluated based on their morphological characteristics and the presence or absence of specific chromogen. The expression pattern of enzymes was similar between the two Cyprinidae and was also broadly consistent with other fish species. However, there were some interesting differences detected between crucian carp and grass carp, including naphthol AS chloroacetate esterase activity in monocytes, peroxidase activity and location in thrombocytes. The ACP, ALP and MPO expressions of different leukocytes of the two Cyprinidae were evaluated by Image Pro Plus and were analysed for statistical significant differences. This investigation provides basic haematology and enzyme activity analyses for crucian carp and grass carp and serves as an approach to evaluating the immune response of fish.

Protein modeling and clinical description of a novel in-frame GLB1 deletion causing GM1 gangliosidosis type II.

BackgroundBeta‐galactosidase‐1 ( GLB1) is a lysosomal hydrolase that is responsible for breaking down specific glycoconjugates, particularly GM1 (monosialotetrahexosylganglioside). Pathogenic variants in GLB1 cause two different lysosomal storage disorders: GM1 gangliosidosis and mucopolysaccharidosis type IVB. In GM1 gangliosidosis, decreased β‐galactosidase‐1 enzymatic activity leads to the accumulation of GM1 gangliosides, predominantly within the CNS. We present a 22‐month‐old proband with GM1 gangliosidosis type II (late‐infantile form) in whom a novel homozygous in‐frame deletion (c.1468_1470delAAC, p.Asn490del) in GLB1 was detected.MethodsWe used an experimental protein structure of β‐galactosidase‐1 to generate a model of the p.Asn490del mutant and performed molecular dynamic simulations to determine whether this mutation leads to altered ligand positioning compared to the wild‐type protein. In addition, residual mutant enzyme activity in patient leukocytes was evaluated using a fluorometric assay.ResultsMolecular dynamics simulations showed the deletion to alter the catalytic site leading to misalignment of the catalytic residues and loss of collective motion within the model. We predict this misalignment will lead to impaired catalysis of β‐galactosidase‐1 substrates. Enzyme assays confirmed diminished GLB1 enzymatic activity (~3% of normal activity) in the proband.ConclusionsWe have described a novel, pathogenic in‐frame deletion of GLB1 in a patient with GM1 gangliosidosis type II.

Clinical, biochemical, and genetic analysis of the mitochondrial respiratory chain complex I deficiency.

Mitochondrial respiratory chain complex I deficiency is one of common mitochondrial disorders. However, the information is relatively little about the features of Chinese patients. In this study, the clinical, biological, and genetic analyses were performed in the children with respiratory chain complex I deficiency, in order to further understand the characteristics of the disease.Over a 3-year period, 67 patients (37 boys, 30 girls), presenting with unexplained multisystemic symptoms and signs were recruited. Clinical and laboratory data of the patients were summarized. Spectrophotometric assay was used for the analysis of mitochondrial complex I-V enzyme activity in peripheral leukocytes. The entire mitochondrial DNA (mtDNA) sequence was analysed for patients and their mothers.The children with respiratory chain complex I deficiency presented with multisystem dysfunction. Onset occurred before the third year of life in 96.9% patients without mtDNA mutation. Onset occurred before the third year of life in 76.5% of patients with mtDNA mutation (P = .03). About 51.5% of patients without mtDNA mutation had weakness, which is higher than 24% patients with mtDNA mutation (P = .02). Isolated complex I deficiency and combined complex I deficiency were found in 45 and 22 patients, respectively. The prevalence of isolated complex I deficiency was higher in the patients with mtDNA mutations (79.4%) than in the patients without mtDNA mutations (54.5%).Patients with nuclear DNA mutations are more likely to develop early onset in mitochondrial respiratory chain complex I deficiency. The patients with complex I deficiency of peripheral leukocytes may be more likely to be caused by mtDNA mutation.

Diagnosis of neuronal ceroid lipofuscinosis type 2 (CLN2 disease): Expert recommendations for early detection and laboratory diagnosis.

Neuronal ceroid lipofuscinoses (NCLs) are a heterogeneous group of lysosomal storage disorders. NCLs include the rare autosomal recessive neurodegenerative disorder neuronal ceroid lipofuscinosis type 2 (CLN2) disease, caused by mutations in the tripeptidyl peptidase 1 (TPP1)/CLN2 gene and the resulting TPP1 enzyme deficiency. CLN2 disease most commonly presents with seizures and/or ataxia in the late-infantile period (ages 2-4), often in combination with a history of language delay, followed by progressive childhood dementia, motor and visual deterioration, and early death. Atypical phenotypes are characterized by later onset and, in some instances, longer life expectancies. Early diagnosis is important to optimize clinical care and improve outcomes; however, currently, delays in diagnosis are common due to low disease awareness, nonspecific clinical presentation, and limited access to diagnostic testing in some regions. In May 2015, international experts met to recommend best laboratory practices for early diagnosis of CLN2 disease. When clinical signs suggest an NCL, TPP1 enzyme activity should be among the first tests performed (together with the palmitoyl-protein thioesterase enzyme activity assay to rule out CLN1 disease). However, reaching an initial suspicion of an NCL or CLN2 disease can be challenging; thus, use of an epilepsy gene panel for investigation of unexplained seizures in the late-infantile/childhood ages is encouraged. To confirm clinical suspicion of CLN2 disease, the recommended gold standard for laboratory diagnosis is demonstration of deficient TPP1 enzyme activity (in leukocytes, fibroblasts, or dried blood spots) and the identification of causative mutations in each allele of the TPP1/CLN2 gene. When it is not possible to perform both analyses, either demonstration of a) deficient TPP1 enzyme activity in leukocytes or fibroblasts, or b) detection of two pathogenic mutations in trans is diagnostic for CLN2 disease.

Encéphalopathie mitochondriale neuro-gastro-intestinale (MNGIE) : quand et comment l’évoquer devant une anorexie mentale atypique ?

IntroductionThe Mitochondrial Neurogastrointestinal Encephalopathy (MNGIE) disease is an extremely underrated syndrome beginning around the age of eighteen years. Because of its severity, this diagnosis should be considered when a patient presents an atypical anorexia nervosa. MNGIE disease is inherited in an autosomal recessive manner and related to mutations of the TYMP gene (ch22q13.32-qter), encoding the thymidine phosphorylase. The MNGIE is often misdiagnosed and is associated with a time to diagnostic of about 12 years after first symptoms. Thus this critical review aims to help clinicians better identify symptoms and paraclinical markers of the MNGIE as a differential diagnosis of atypical anorexia nervosa. MethodsA literature search was performed using PubMed and Google Scholar databases. ResultsThe clinical diagnosis of the MNGIE disease should be based on the association of severe loss of weight and some additional symptoms: (1) severe gastrointestinal dysmotility (nausea, vomiting, intestinal pseudo-obstruction), (2) ptosis or external ophtalmoplegia and (3) peripheral sensorimotor neuropathy. When MNGIE disease is clinically suspected, paraclinical testing can help to validate the MNGIE diagnostic: (1) Arterial blood test reveals lactic acidemia (e.g. an increased serum concentration of lactate without pH modifications), and (2) Brain MRI indicates leukoencephalopathy, usually asymptomatic. Direct evidence of MNGIE disease is based on specific testing of: (1) the thymidine phopshorylase enzyme activity in leukocytes is less than 10% of the control, (2) the increase of plasmatic thymidine (>3μmol/L) and the increase of plamatic deoxyuridine (>5μmol/L), (3) the evidence of mutations of the TYMP gene by molecular genetic testing. ConclusionThe MNGIE disease is a severe trouble with multisystemic complications. The thymidine phopshorylase enzyme activity in leukocytes should be measured as soon as possible when a patient presents atypical anorexia nervosa.

Cellular Uptake of Glucocerebrosidase in Gaucher Patients Receiving Enzyme Replacement Treatment.

Enzyme replacement therapy (ERT) is currently the standard treatment for patients with Gaucher disease typeI (GD1), but the pharmacokinetics have hardly been studied. This study aimed to quantify invivo enzyme activity in peripheral leukocytes from patients receiving long-term treatment with imiglucerase or velaglucerase for GD1, and set out to assess the process of enzymatic uptake by peripheral leukocytes. A prospective semi-experimental study was conducted. Four time points for blood withdrawal were planned per patient to quantify the intra-leukocyte enzymatic activity. In order to assess the uptake process, the rate of enzyme uptake by leukocytes (Rupt) and the rate of enzyme disappearance from the plasma (Rdis) were estimated. Eight GD1 patients were included. Intra-leukocyte activity was 24.31mU/mL [standard deviation (SD) 6.32mU/mL; coefficient of variation (CV) 25.96%] at baseline and 27.14mU/mL (SD 6.96mU/mL; CV25.65%) at 15min post-perfusion. The relationships with the administered dose were linear. The Rupt value was 37.73mU/mL/min [95% confidence interval (CI) 25.63-49.84] and showed a linear correlation with the administered enzyme dose (p<0.05), and the Rdis value was 189.43mU/mL/min (95% CI 80.31-298.55) and also showed a linear correlation with the dose (p<0.05). This was the first in vivo study to quantify the accumulated enzymatic activity in patients receiving ERT for GD1. It showed that intra-leukocyte activity at baseline and at 15min post-perfusion could be used as a possible marker for therapeutic individualization in patients receiving ERT for GD1.

Cost-Effectiveness of the Quantification of Enzymatic Activity in Leukocytes in Comparison to Its Nonrealization for a Rare Disease in Latin America: The Case of Mucopolysaccharidosis Type II in Colombia

BackgroundMucopolysaccharidosis (MPS) type II is produced by a deficiency of iduronate-2-sulfatase (I2S). The quantification of the enzyme activity in leukocytes is used as diagnostic confirmation of MPS. ObjectiveTo determinate the cost-effectiveness of the measurement of I2S enzyme activity in leukocytes compared with not carrying out the enzyme activity measurement for diagnostic confirmation of MPS II from the perspective of the Colombian health system. MethodsA cost-effectiveness analysis was conducted on the basis of a decision tree model. The measure of effectiveness was the correct diagnosis of cases of MPS II. The costs of I2S enzymatic quantification in leukocytes, consultation with a geneticist and with other specialists, and costs of diagnostic procedures were included. The time horizon was less than 1 year. A probabilistic sensitivity analysis was performed using Monte-Carlo simulation with 10,000 iterations. ResultsThe incremental cost was –US $43,145 with an incremental effectiveness of 42 cases. The probabilistic sensitivity analysis confirms the results of basal data, in which the quantification of I2S enzyme activity was less costly and more effective than the alternative. ConclusionsThe quantification of I2S enzymatic activity is a dominant technology for the diagnostic confirmation of MPS II, compared with not making the quantification, from the perspective of the Colombian health system.