Urine analysis of glucose tetrasaccharide by HPLC; a useful marker for the investigation of patients with Pompe and other glycogen storage diseases

A high performance liquid chromatography method, adapted from an established urinary sugars method, has been developed for the analysis of a tetraglucose oligomer (Glc₄) in urine. Pompe disease results from defects in the activity of lysosomal acid α-glucosidase (GAA) with patients typically excreting increased amounts of Glc₄. Rapid determination of GAA in dried blood spots is now possible. However, enzymatic analysis is unable to discriminate between patients with Pompe disease and those individuals harbouring pseudo deficiency mutations. This method was able to quantify Glc₄ levels in all patients analysed with an established diagnosis of Pompe disease, and all controls analysed had Glc₄ levels below the limit of detection for this method. Importantly the method was able to discriminate between an individual known to harbour a pseudo Pompe mutation and patients with Pompe disease, providing a useful supporting test to enzymatic analysis. Sequential measurement of urinary Glc₄ has been proposed to monitor the effects of enzyme replacement therapy (ERT). We observed a clear decrease in Glc₄ levels following commencement of treatment in three patients studied. Additionally, raised levels of Glc₄ were observed in patients with glycogen storage disease (GSD) type Ia and type III suggesting that this method may have applications in other GSDs.     

Genetics of type II glycogenosis: Assignment of the human gene for acid α-glucosidase to chromosome 17

We have studied somatic cell hybrids between thymidine kinase (EC 2.7.1.75) deficient mouse cells and human diploid fibroblasts for the expression of human acid alpha-glucosidase (EC 3.2.1.20). A deficiency in this enzyme is associated with the type II glycogenosis or Pompe disease. All 30 somatic cell hybrids selected in hypoxanthine/aminopterin/thymidine medium expressed human acid alpha-glucosidase and galactokinase (EC 2.7.1.6) and retained human chromosome 17; counterselection of the same hybrids in medium containing 5-bromodeoxyuridine resulted in the growth of hybrids that concordantly lost the expression of human acid alpha-glucosidase and galactokinase as well as human chromosome 17. Hybrids between thymidine kinase-deficient mouse cells and fibroblasts from a patient with Pompe disease that contained human chromosome 17 were found not to express human acid alpha-glucosidase. Because we have already shown that hybrids between mouse peritoneal macrophages and GM54VA simian virus 40-transformed human cells selectively retain human chromosome 17 and lose all other human chromosomes, we tested 13 independent mouse macrophage x GM54VA hybrid clones, including two that retained human chromosome 17 and no other human chromosomes, for the expression of human acid alpha-glucosidase and galactokinase. All 13 hybrid clones were found to express these human enzymes. Thus, we conclude that the gene coding for human acid alpha-glucosidase is located on human chromosome 17.     

Familial adult-onset Pompe disease associated with unusual clinical and histological features

The adult-onset form of Pompe disease had a wide clinical spectrum, ranging from asymptomatic patients with increased CK to muscle cramps and pain syndrome or rigid-spine syndrome. In addition clinical severity and disease progression are greatly variable. We report on a family with 3 siblings characterized by an unusual adult-onset Pompe disease including dysphagia and weakness of tongue, axial and limb-girdle muscles, in association with atypical globular inclusions in muscle fibres. Our study confirms the great clinical and histological variability of adult-onset Pompe disease and further supports the need of careful evaluation of bulbar function in patients affected by this pathology.Key words: Pompe disease, globular inclusions, bulbar symptomsGlycogen storage disease type II (Pompe disease or acid maltase deficiency) is a rare autosomal recessive muscular disorder characterized by deficiency of acidalfa glucosidase (GAA), determining accumulation of glycogen in the lysosomes, mainly in cardiac and skeletal muscle cells. Typical phenotypes of glycogenosis type II include the severe classic infantile form, characterized by severe muscle weakness and hypertrophic cardiomyopathy, almost invariably fatal by 12 months, a "non-classic" form presenting between 1 and 2 years of age and the lateonset form, presenting at any time after the age of 1 year, including juvenile and adult-onset subtypes, which are considered as part of a continuous clinical spectrum (1). In particular the adult-onset form presents with slowly progressive proximal lower limb and/or paraspinal muscle weakness, often followed by restrictive respiratory failure, which could be life-threatening, as it is in infants and children (2). However the clinical spectrum of adultonset form is wide, ranging from asymptomatic patients with increased CK to muscle cramps and pain syndrome or rigid-spine syndrome (2, 3). Furthermore clinical severity and disease progression is greatly variable.We report on a family with 3 siblings with an unusual adult-onset Pompe disease clinically characterized by weakness of bulbar, axial and limb-girdle muscles in association with atypical histopathological changes.     

A novel homozygous mutation at the GAA gene in Mexicans with early-onset Pompe disease

Glycogen-storage disease type II, also named Pompe disease, is caused by the deficiency of the enzyme acid alpha-glucosidase, which originates lysosomal glycogen accumulation leading to progressive neuromuscular damage. Early-onset Pompe disease shows a debilitating and frequently fulminating course. To date, more than 300 mutations have been described; the majority of them are unique to each affected individual. Most early-onset phenotypes are associated with frameshift mutations leading to a truncated alpha-glucosidase protein with loss of function. Founder effects are responsible from many cases from few highprevalence world regions. Herein we described two apparently unrelated cases affected with classical early-onset Pompe disease, both pertaining to a small region from Central Mexico (the State of San Luis Potosí), the same novel homozygous frameshift mutation at gene GAA (c.1987delC) was demonstrated in both cases. This GAA gene deletion implies a change of glutamine to serine at codon 663, and a new reading frame that ends after 33 base pairs, which leads to the translation of a truncated protein. This report contributes to widen the knowledge on the effect of pathogenic mutations in Pompe disease. Here we postulate the existence of a founder effect.Key words: Early-onset Pompe disease, Acid maltase deficiency, Founder effectGlycogen storage disease type II (Online Mendelian Inheritance in Man, OMIM, accession number 232300), also called Pompe disease, was described by Johannes C. Pompe in 1932. The disorder is caused by a deficiency of the enzyme acid alpha-glucosidase (acid maltase, EC 3.2.1.20, Swiss) which originates lysosomal glycogen accumulation leading to lysosomal swelling, cellular damage and dysfunction (1-3). Affected individuals develop progressive neuromuscular damage, showing a debilitating and frequently fulminating course on the classical, early-onset type of the disease. Other main findings are hypertrophic cardiomyopathy, hypotonia, hepatomegaly, macroglossia, feeding problems and breath difficulty. Currently it is recognized that the late form of Pompe disease has a very variable phenotype that can be confused with a wide range of neuromuscular, pulmonary and cardiovascular diseases with mild, moderate or severe symptoms that present either alone or combined (4-6).Pompe disease has an autosomal recessive inheritance and it is caused by more than 300 mutations that occur all over the gene coding for acid alpha-glucosidase (GAA) located at locus 17q25.2q25.3. The molecular phenomenon responsible of the different types of clinical expression occur by the presence of two either homozygous or compound heterozygous pathogenic mutations in early-onset Pompe cases, whereas late-onset Pompe have one variant and one pathogenic mutation (7). The majority of disease-causing mutations are unique; nonetheless, relatively frequent mutations have been described in certain populations with a possible founder effect traced from the original mutated carrier to the newly occurring cases. Affected cases have been described worldwide with a few high-prevalence regions like South-Africa, Taiwan and Holland (1, 8-10).Herein, we described two unrelated cases affected with classical early-onset Pompe disease, both pertaining to the same small Mexican region, with the same novel homozygous frameshift mutation at gene GAA (c.1987delC), identified by complete gene sequencing.     

Standardized nursing management of enzyme replacement therapy for late-onset Pompe disease

Pompe disease or glycogen storage disease type II is a rare autosomal recessive disorder caused by a deficiency of the lysosomal enzyme a-glucosidase. Although enzyme replacement therapy (ERT) with 2 weekly intervals following was considered an effective treatment for Pompe disease in 2006, few patients can afford to receive treatment in China because of the high cost. This study aimed to examine the standard management of enzyme replacement therapy for late-onset Pompe disease among patients over the age of 14 years from a nursing perspective in order to assess operating procedures. ERT injection fluid dispensing and infusion procedures using different methods were analyzed and compared in 3 patients with advanced Pompe disease for forming standard operation procedures. In addition, the impact of different methods on time consumption was analyzed by 1-way analysis of variance. There were significant differences in time consumption between different dispensing and infusion methods. The time of dispensing and infusing the injection fluids using the cooperative method was 15.97 minutes shorter than that using the conventional method (95% CI: 4.51–27.43, P = .012); the time using the modified method was 20.93 minutes shorter than that using the conventional method (95% CI: 9.47–32.39, P = .012); and there was no significant difference between the cooperative and modified methods (P = .431). Enzyme replacement therapy entails frequent treatment and strict nursing requirements related to the intravenous infusion process. In this context, a standard operating procedure can be used to control nursing times and labor costs effectively while ensuring a safe and effective infusion process.     

Glycogen storage disease types I and II: Treatment updates

Prior to 2006 therapy for glycogen storage diseases consisted primarily of dietary interventions, which in the case of glycogen storage disease (GSD) type II (GSD II; Pompe disease) remained essentially palliative. Despite improved survival and growth, long-term complications of GSD type I (GSD I) have not responded to dietary therapy with uncooked cornstarch or continuous gastric feeding. The recognized significant risk of renal disease and liver malignancy in GSD I has prompted efforts towards curative therapy, including organ transplantation, in those deemed at risk. Results of clinical trials in infantile Pompe disease with alglucosidase alfa (Myozyme) showed prolonged survival reversal of cardiomyopathy, and motor gains. This resulted in broad label approval of Myozyme for Pompe disease in 2006. Furthermore, the development of experimental therapies, such as adeno-associated virus (AAV) vector-mediated gene therapy, holds promise for the availability of curative therapy in GSD I and GSD II/Pompe disease in the future. Communicating editor: Verena Peters Competing interests: D. D. Koeberl, P. Kishnani and Y. T. Chen have received research/grant support from Genzyme Corporation. P. Kishnani is a member of the Pompe Disease Advisory Board for Genzyme Corporation. Y.T. Chen has served as a consultant for Genzyme. The clinical trials with rhGAA were supported by a grant from Genzyme Corporation at the various sites where patients were treated. rhGAA, in the form of Genzyme’s product, Myozyme, has now been approved by the US FDA and the European Union as therapy for Pompe disease. Duke University and the developers of the method of treatment and predecessors of the cell lines used to generate the enzyme (rhGAA) used in this clinical trial may benefit financially pursuant to the University’s Policy on Inventions, Patents and Technology Transfer, even if those cell lines are not used in the commercialized therapy.     

Clinical features of Pompe disease

Glycogen storage disease type II - also called Pompe disease or acid maltase deficiency - is an autosomal recessive metabolic disorder, caused by an accumulation of glycogen in the lysosome due to deficiency of the lysosomal acid alpha-glucosidase enzyme. Pompe disease is transmitted as an autosomal recessive trait and is caused by mutations in the gene encoding the acid α-glucosidase (GAA), located on chromosome 17q25.2-q25.3. The different disease phenotypes are related to the levels of residual GAA activity in muscles. The clinical spectrum ranging from the classical form with early onset and severe phenotype to not-classical form with later onset and milder phenotype is described.Key words: Glycogen storage disease type II, Pompe disease, GAA activity     

Pulmonary involvement in selected lysosomal storage diseases and the impact of enzyme replacement therapy: A state‐of‐the art review

Lysosomal storage disorders (LSDs) are multisystemic, progressive and clinically very heterogeneous. Respiratory complications are not regarded as the principal problems of LSDs, but significantly impact morbidity. In this review, we focus on pulmonary complications observed in late‐onset LSDs, their milder forms that are recognised in adulthood. We also discuss the effects of enzyme replacement therapy (ERT) on the respiratory system in patients with particular LSDs. We searched the PubMed database, retrieving research papers on pulmonary complications of LSDs currently treated with ERT (the conditions are abbreviated GD3; NPDB; LOPD; MPS I, II, IVA, VI; and FD) and the effects of such treatment. Although some studies indicated that ERT was helpful in terms of reducing chest computed tomography abnormalities, infection frequency and organomegaly, the data are not conclusive, and the mechanism of action of ERT in the respiratory system remains unclear for some LSDs including late‐onset Pompe disease and Gaucher disease type III. The optimal timing of treatment for pre‐symptomatic or symptomatic patients, treatment duration and whether such treatment modulates inflammation (as has been suggested in patients with Fabry disease), remain to be explored.     

Enzyme analysis for Pompe disease in leukocytes; superior results with natural substrate compared with artificial substrates

Summary  Enzyme analysis for Pompe disease in leukocytes has been greatly improved by the introduction of acarbose, a powerful inhibitor of interfering α-glucosidases, which are present in granulocytes but not in lymphocytes. Here we show that the application of acarbose in the enzymatic assay employing the artificial substrate 4-methylumbelliferyl-α-d-glucoside (MU-αGlc) is insufficient to clearly distinguish patients from healthy individuals in all cases. Also, the ratios of the activities without/with acarbose only marginally discriminated Pompe patients and healthy individuals. By contrast, when the natural substrate glycogen is used, the activity in leukocytes from patients (n = 82) with Pompe disease is at most 17% of the lowest control value. The use of artificial substrate in an assay with isolated lymphocytes instead of total leukocytes is a poor alternative as blood samples older than one day invariably yield lymphocyte preparations that are contaminated with granulocytes. To diagnose Pompe disease in leukocytes we recommend the use of glycogen as substrate in the presence of acarbose. This assay unequivocally excludes Pompe disease. To also exclude pseudo-deficiency of acid α-glucosidase caused by the sequence change c.271G>A (p.D91N or GAA2; homozygosity in approximately 1:1000 caucasians), a second assay employing MU-αGlc substrate plus acarbose or DNA analysis is required. Competing interests: None declared References to electronic databases: Glycogen storage disease II (Pompe disease): #232300. Acid α-glucosidase: EC 3.2.1.3/20.     

Enzyme replacement and enhancement therapies for lysosomal diseases

Although first suggested by de Duve in 1964, enzyme replacement therapy (ERT) for lysosomal storage diseases did not become a reality until the early 1990s when its safety and effectiveness were demonstrated in type 1 Gaucher disease. Today, ERT is a reality for Gaucher disease, Fabry disease and mucopolysaccharidosis type I (MPS I), and clinical trials with recombinant human enzymes are ongoing in Pompe disease, MPS II and MPS VI, and are about to begin in Neimann-Pick B disease. In addition to ERT, enzyme enhancement therapy (EET) offers a novel therapeutic strategy to increase the residual function of mutant proteins. EET employs small molecules as 'pharmacological chaperones' to rescue misfolded and/or unstable mutant enzymes or proteins that have residual function. EET also offers the possibility of treating neurodegenerative lysosomal disorders since these small therapeutic molecules may cross the blood-brain barrier. The current status of ERT and the prospects for EET for lysosomal storage diseases are reviewed.     

Burden of illness of Pompe disease in patients only receiving supportive care

Background  

Pompe disease is an orphan disease for which enzyme replacement therapy (ERT) recently became available. This study aims to estimate all relevant aspects of burden of illness—societal costs, use of home care and informal care, productivity losses, and losses in health-related quality of life (HRQoL)—for adult Pompe patients only receiving supportive care.     

Effects of enzyme replacement therapy on five patients with advanced late-onset glycogen storage disease type II: a 2-year follow-up study

We examined the efficacy of 2-year enzyme replacement therapy (ERT) using recombinant human α-glucosidase (GAA; Myozyme?) in five long-term ventilator-dependent adults and aged patients with advanced, late-onset glycogen storage disease type II (GSDII, also known as Pompe disease). Although all patients had advanced respiratory failure and were ventilator-dependent for more than 6 years, four showed obvious improvements in muscle strength, pulmonary function, and activities of daily living after ERT. Improvement in each parameter was more prominent in the first year than in the second year. Values in the second year were still significantly better than those at study entry and indicate stabilization in the clinical status of all patients. These results suggest that ERT continues to be effective in the second year of treatment even in patients suffering from advanced late-onset GSDII disease with severe respiratory failure.     

Sleep breathing disorders and nocturnal respiratory pattern in patients with Glycogenosis type II

Patients affected by glycogenosis type II frequently present sleepdisordered breathing. The presence of symptoms suggestive of sleep breathing disorders was investigated, by a questionnaire, in 10 patients, affected by adult or juvenile forms of glycogenosis type II. Diurnal respiratory function, diaphragm weakness and nocturnal respiratory pattern were evaluated at the enrolment. In patients presenting sleep disordered breathing, the same parameters were re-evaluated after treatment with assisted non invasive ventilation. Out of 10 patients, 5 presented symptoms suggestive of sleep-disordered breathing at the baseline, 2 a pattern of sleep apnea syndrome and 3 nocturnal hypoventilation. All patients presented diaphragmatic weakness. No correlation was found between forced vital capacity values (FVC) in sit position and nocturnal respiratory disorders. Five patients with respiratory disorders were treated with non invasive ventilation. All patients – after one month of treatment - showed an improvement in symptoms with reduced diurnal hypersomnia (ESS < 10), absence of morning headaches and nocturnal awakenings, and reduced nicturia regardless the modality of ventilation. We recommend that all patients with glycogenosis type II, once diagnosed, are carefully monitored for the development of respiratory involvement, even in the absence of reduced FVC values and in the early stages of the disease, to receive appropriate therapy.Key words: glycogenosis, apnoea, hypopnea, hypoventilation, non invasive ventilation     

Limitations of enzyme replacement therapy: Current and future

Summary Orphan drug legislation passed in the USA in 1983 and in Europe in 1999 has encouraged biotechnology companies to develop treatments for diseases that the industry previously ignored because they affect only small numbers of people and promised only limited profitability. Incentives, exclusivity and the freedom to charge sufficient to cover development costs has led to a niche market, and patients with lysosomal storage disorders have been one of the main beneficiaries of these developments. The recombinant production of highly purified enzymes that are modified to improve tissue targeting has been a direct result of this legislation. The spectacular clinical and financial success of Cerezyme (and previously Ceredase, Genzyme) for the treatment of Gaucher disease has led to the development of enzyme replacement treatment(s) for Fabry disease and mucopolysaccharidoses types I and VI. A number of other enzyme replacement therapies are at an earlier stage in development and the next 12 months could see the launch of therapies for mucopolysaccharidosis type II and Pompe disease. Like all medical treatments, this approach has some limitations. Not all patients are suitable for treatment, some organs and tissues are corrected more readily than others, and there are problems with gauging efficacy in these highly variable disorders. Finally, the therapies are expensive, limiting access to patients from those countries that are able to afford expensive health care. Presented at the 42nd Annual Meeting of the SSIEM, Paris, 6–9 September 2005 Competing interests: None declared     

Unusual angiographic appearances of the left ventricle in 2 cases of Pompe's disease (glycogenosis type II).

The angiographic and haemodynamic findings in 2 cases of Pompe's disease (glycogenosis type II) indicated an abnormal trabecular pattern, not previously reported, on the left ventricular angiogram of both patients. This feature may be helpful in distinguishing Pompe's disease from other forms of myocardial abnormality.     

Unusual angiographic appearances of the left ventricle in 2 cases of Pompe's disease (glycogenosis type II).

The angiographic and haemodynamic findings in 2 cases of Pompe's disease (glycogenosis type II) indicated an abnormal trabecular pattern, not previously reported, on the left ventricular angiogram of both patients. This feature may be helpful in distinguishing Pompe's disease from other forms of myocardial abnormality.     

Oropharyngeal Dysphagia in Infants and Children with Infantile Pompe Disease

Pompe disease is a rare genetic progressive neuromuscular disorder. The most severe form, infantile Pompe disease, has historically resulted in early mortality, most commonly due to cardiorespiratory failure. Treatment with enzyme replacement therapy (ERT) using alglucosidase alfa (Myozyme^®) has extended the lifespan of individuals with this disease. With the introduction of ERT and the resultant improved survival, dysphagia is being encountered clinically with increasing regularity though systematic data remain unavailable. We retrospectively studied the oropharyngeal swallowing of 13 infants and children with Pompe disease using videofluoroscopy before initiation of ERT, allowing for baseline swallow function to be established in an untreated cohort. Dysphagia was present in all 13 subjects, even in a participant only 15 days old. Oral stage signs were present in 77%, most frequently a weak suck in 69%. Pharyngeal stage signs were present in 100%, including a pharyngeal swallow delay in 92% and pharyngeal residue in 77%. Airway invasion was present in 76.9% of subjects, including penetration in five (38.46%) and silent aspiration in an additional five (38.46%). No relationship in the relative involvement of swallowing, gross motor function, and cardiac disease appeared to be present.     

Biotherapeutic target or sink: analysis of the macrophage mannose receptor tissue distribution in murine models of lysosomal storage diseases

Lysosomal storage diseases (LSDs) are metabolic disorders caused by enzyme deficiencies that lead to lysosomal accumulation of undegraded substrates. Enzyme replacement therapies (ERT) have been developed as treatments for patients with Gaucher, Niemann-Pick, Fabry, and Pompe diseases. Depending on the disease, the corresponding therapeutic enzyme is designed to be internalized by diseased cells through receptor-mediated endocytosis via macrophage mannose receptors (MMR) or mannose-6-phosphate receptors (M6PR). Enzymes developed to treat Gaucher and Niemann-Pick diseases are meant to target MMR-expressing cells, and in the case of Cerezyme [recombinant human β-glucocerebrosidase (rhβGC)] for treating Gaucher disease, glycans on the enzyme are modified to increase specificity toward this receptor. Due to heterogeneity in glycosylation on enzymes intended to target the M6PR, however, there may also be some unintended targeting to MMR-expressing cells, which could act as unwanted sinks. Examples include Fabrazyme [recombinant human α-galactosidase A (rhαGal)] for treating Fabry disease and Myozyme [recombinant human acid α-glucosidase (rhGAA)] for treating Pompe disease. It is therefore of great interest to better understand the cell type and tissue distribution of MMR in murine LSD models used to evaluate ERT efficacy and mechanism of action. In this study, we generated affinity-purified polyclonal antibody against murine MMR and used it to carry out a systematic examination of MMR protein localization in murine models of Gaucher, Niemann-Pick, Fabry, and Pompe diseases. Using immunohistochemistry, immunofluorescence, and confocal microscopy, we examined MMR distribution in liver, spleen, lung, kidney, heart, diaphragm, quadriceps, and triceps in these animal models and compared them with MMR distribution in wild-type mice.     

Cardiomuscular lysosomal glycogenosis in adults without known enzyme deficiency. A cause of familial myocardiopathy and lysosomal glycogen overload with normal acid maltase

An unusual form of familial myocardiopathy is reported. The disease affected siblings entering adulthood and presented as subclinical skeletal muscle and patent cardiac muscle lesions. Quadriceps muscle biopsy performed in a young man who subsequently died of cardial failure revealed excessive lysosomal glycogen storage, as in type II glycogenosis, but biochemistry showed normal enzymatic activity. In a sister with hypertrophic myocardiopathy only leucocytes were examined; they also showed normal enzymatic activity. Other clinical manifestations of this form of familial myocardiopathy are hypoglycaemia and moderate skeletal muscle involvement. At histology, the image is that of Pompe's disease, but the acid maltase level is normal. The condition seems to be transmitted as an autosomal dominant trait.     

Muscle fiber-type distribution, fiber-type-specific damage, and the Pompe disease phenotype

Pompe disease is a lysosomal storage disorder caused by acid α-glucosidase deficiency and characterized by progressive muscle weakness. Enzyme replacement therapy (ERT) has ameliorated patients’ perspectives, but reversal of skeletal muscle pathology remains a challenge. We studied pretreatment biopsies of 22 patients with different phenotypes to investigate to what extent fiber-type distribution and fiber-type-specific damage contribute to clinical diversity. Pompe patients have the same fiber-type distribution as healthy persons, but among nonclassic patients with the same GAA mutation (c.-32-13T>G), those with early onset of symptoms tend to have more type 2 muscle fibers than those with late-onset disease. Further, it seemed that the older, more severely affected classic infantile patients and the wheelchair-bound and ventilated nonclassic patients had a greater proportion of type 2x muscle fibers. However, as in other diseases, this may be caused by physical inactivity of those patients.