Identification of patients with Pompé disease using routine pathology results: PATHFINDER (creatine kinase) study.

AIMS: Adult-onset inherited errors of metabolism can be difficult to diagnose. Some cases of potentially treatable myopathy are caused by autosomal recessive acid α-1,4 glucosidase (acid maltase) deficiency (Pompé disease). This study investigated whether screening of asymptomatic patients with elevated creatine kinase (CK) could improve detection of Pompé disease. METHODS: Pathology databases in six hospitals were used to identify patients with elevated CK results (>2× upper limit of normal). Patients were recalled for measurement of acid α-1,4 glucosidase activity in dried blood spot samples. RESULTS: Samples were obtained from 812 patients with elevated CK. Low α-glucosidase activity was found in 13 patients (1.6%). Patients with neutropaenia (n=4) or who declined further testing (n=1) were excluded. Confirmation plasma specimens were obtained from eight individuals (1%) for a white cell lysosomal enzyme panel, and three (0.4%) were confirmed to have low α-1,4-glucosidase activity. One patient was identified as a heterozygous carrier of an acid α-1,4 glucosidase c.-32-13 G>T mutation. Screening also identified one patient who was found to have undiagnosed Fabry disease and one patient with McArdle's disease. One patient later presented with Pompé's after an acute illness. Including the latent case, the frequency of cases at 0.12% was lower than the 2.5% found in studies of patients with raised CK from neurology clinics (p<0.001). CONCLUSIONS: Screening pathology databases for elevated CK may identify patients with inherited metabolic errors affecting muscle metabolism. However, the frequency of Pompé's disease identified from laboratory populations was less than that in patients referred for neurological investigation.

Methods for a prompt and reliable laboratory diagnosis of Pompe disease: report from an international consensus meeting.

Pompe disease is an autosomal recessive disorder of glycogen metabolism caused by a deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA). It presents at any age, with variable rates of progression ranging from a rapidly progressive course, often fatal by one-year of age, to a more slowly, but nevertheless relentlessly progressive course, resulting in significant morbidity and premature mortality. In infants, early initiation of enzyme replacement therapy is needed to gain the maximum therapeutic benefit, underscoring the need for early diagnosis. Several new methods for measuring GAA activity have been developed. The Pompe Disease Diagnostic Working Group met to review data generated using the new methods, and to establish a consensus regarding the application of the methods for the laboratory diagnosis of Pompe disease. Skin fibroblasts and muscle biopsy have traditionally been the samples of choice for measuring GAA activity. However, new methods using blood samples are rapidly becoming adopted because of their speed and convenience. Measuring GAA activity in blood samples should be performed under acidic conditions (pH 3.8-4.0), using up to 2 mM of the synthetic substrate 4-methylumbelliferyl-alpha-D-glucoside or glycogen (50 mg/mL), in the presence of acarbose (3-9 microM) to inhibit the isoenzyme maltase-glucoamylase. The activity of a reference enzyme should also be measured to confirm the quality of the sample. A second test should be done to support the diagnosis of Pompe disease until a program for external quality assurance and proficiency testing of the enzymatic diagnosis in blood is established.

A Senile Case of Late-onset Pompe's Disease.

A 72-year-old, seemingly healthy, Japanese man suddenly lost consciousness. At the emergency room, the patient's Glasgow coma scale score was 10 and a thoracic breathing pattern was observed. An arterial blood gas analysis indicated acute hypercarbic respiratory failure. He was placed on non-invasive positive pressure ventilation. The next day he was alert. Manual muscle testing revealed that his face, neck and limb muscle strength were normal. He could walk, and Gowers' sign was not observed. Computed tomography showed atrophy of the paravertebral, abdominal wall and diaphragm crura muscles, without apparent limb muscle involvement. Pompe's disease was diagnosed based on the results of biochemical and genetic tests for acid alpha-glucosidase.

Long-term efficacy after [E1-, polymerase-] adenovirus-mediated transfer of human acid-alpha-glucosidase gene into glycogen storage disease type II knockout mice.

Glycogen storage disease type II (GSD-II) is a lethal, autosomal recessive metabolic myopathy caused by a lack of acid-alpha-glucosidase (GAA) activity in the cardiac and skeletal muscles. Absence of adequate intralysosomal GAA activity results in massive amounts of glycogen accumulation in multiple muscle groups, resulting in morbidity and mortality secondary to respiratory embarrassment and/or cardiomyopathy. In a mouse model of GSD-II, we demonstrate that infection of the murine liver with a modified adenovirus (Ad) vector encoding human GAA (hGAA) resulted in long-term persistence of the vector in liver tissues for at least 6 months. Despite both a rapid shutdown of hGAA mRNA expression from the vector, as well as the elicitation of anti-hGAA antibody responses (hGAA is a foreign antigen in this model), the hGAA secreted by the liver was taken up by all muscle groups analyzed and, remarkably, persisted in them for at least 6 months. The persistence of the protein also correlated with long-term correction of pathologic intramuscular glycogen accumulations in all muscle groups tested, but most notably the cardiac tissues, which demonstrated a significantly decreased glycogen content for at least 190 days after a single vector injection. The results suggest that gene therapy strategies may have the potential to significantly improve the clinical course for GSD-II patients.

Helios gene gun particle delivery for therapy of acid maltase deficiency.

Autosomal recessive deficiency of lysosomal acid maltase (GAA) or glycogen storage disease type II (GSDII) results in a spectrum of phenotypes including a rapidly fatal infantile disorder (Pompe's), juvenile, and a late-onset adult myopathy. The infantile onset form presents as hypotonia with massive accumulation of glycogen in skeletal and heart muscle, with death due to cardiorespiratory failure. Adult patients with the slowly progressive form develop severe skeletal muscle weakness and respiratory failure. Particle bombardment is a safe, efficient physical method in which high-density, subcellular-sized particles are accelerated to high velocity to carry DNA into cells. Because it does not depend on a specific ligand, receptor, or biochemical features on cell surfaces, particle-mediated gene transfer can be readily applied to a variety of systems. We evaluated particle bombardment as a delivery system for therapy of GSDII. We utilized a vector carrying the CMV promoter linked to the human GAA cDNA. Human GSDII cell lines (fibroblasts and lymphoid) as well as ex vivo with adult-onset peripheral blood cells (lymphocytes and monocytes) were transiently transfected by bombardment with a Helios gene gun delivering gold particles coated with the GAA expression plasmid. All cell types showed an increase in human GAA activity greater than 50% of normal activity. Subsequently, GAA -/- mice were treated every 2 weeks for 4 months by particle bombardment to the epidermis of the lower back and hind limbs. Muscle weakness in the hind and forelimbs was reversed. These data suggest that particle delivery of the GAA cDNA by the Helios gene gun may be a safe, effective treatment for GSDII.

Case report: lysosomal glycogen storage disease with normal acid maltase: an unusual form of hypertrophic cardiomyopathy with rapidly progressive heart failure.

A 14-year-old boy with mild mental retardation, myopathy, and nonobstructive hypertrophic cardiomyopathy (HCM) with clinical and histopathologic features consistent with lysosomal glycogen storage disease with normal acid maltase is described. The case illustrates the aggressive nature of the cardiomyopathy of this syndrome. This condition is associated with malignant ventricular arrhythmias, relentlessly progressive ventricular dilatation, dysfunction, and sudden death. It is important to recognize this unusual and malignant form of HCM to precipitate low early diagnosis by muscle biopsy. Patients with this condition would be excellent candidates for life-saving heart transplant as the myopathy and mental retardation are mild and nonprogressive. The underlying biochemical defect and mode of inheritance of this syndrome are unclear. However, a significant proportion are genetically related and thus, relatives may benefit from family screening.

Heterozygote detection in a family of Lapland dogs with a recessively inherited metabolic disease: canine glycogen storage disease type II.

The control of recessively inherited inborn errors of metabolism may benefit from quantitative biochemical screening assays enabling the identification of heterozygous individuals. Based on the principle of partial enzyme deficiency in heterozygotes, an attempt was made to identify heterozygous animals in a Lapland dog family with canine glycogen storage disease type II (acid alpha-glucosidase deficiency). Acid alpha-glucosidase activity was determined in peripheral blood leucocyte extracts of 12 related Lapland dogs, two of which were obligate heterozygotes. The use of an antiserum against acid alpha-glucosidase was necessary to increase the specificity of the assay. Twice the obligate heterozygous enzyme level was assumed to indicate the homozygous normal level. Five dogs were designated as presumptive heterozygotes, and five as presumptive normal homozygotes. The results in two dogs were inconclusive. The information obtained in this preliminary investigation may be helpful in the control of the disease in the Lapland dog breed.

Glycogen storage in multiple muscles of old GSD-II mice can be rapidly cleared after a single intravenous injection with a modified adenoviral vector expressing hGAA.

BACKGROUND: Glycogen storage disease II (GSD-II) is an autosomal recessive lysosomal storage disease, due to acid-alpha-glucosidase (GAA) deficiency. The disease is characterized by massive glycogen accumulation in the cardiac and skeletal muscles. There is early onset (infantile, also known as Pompe disease) as well as late onset (juvenile and adult) forms of GSD-II. Few studies have been published to date that have explored the consequences of delivering a potential therapy to either late onset GSD-II subjects, and/or early onset patients with long-established muscle pathology. One recent report utilizing GAA-KO mice transgenically expressing human GAA (hGAA) suggested that long-established disease in both cardiac and skeletal muscle is likely to prove resistant to therapies. To investigate the potential for disease reversibility in old GSD-II mice, we studied their responsiveness to exogenous hGAA exposure via a gene therapy approach that we have previously shown to be efficacious in young GAA-KO mice. METHODS: An [E1-, polymerase-] adenoviral vector encoding hGAA was intravenously injected into two groups of aged GAA-KO mice; GAA expression and tissue glycogen reduction were evaluated. RESULTS: After vector injection, we found that extremely high amounts of hepatically secreted hGAA could be produced, and subsequently taken up by multiple muscle tissues in the old GAA-KO mice by 17 days post-injection (dpi). As a result, all muscle groups tested in the old GAA-KO mice showed significant glycogen reductions by 17 dpi, relative to that of age-matched, but mock-injected GAA-KO mice. For example, glycogen reduction in heart was 84%, in quadriceps 46%, and in diaphragm 73%. Our data also showed that the uptake and the subsequent intracellular processing of virally expressed hGAA were not impaired in older muscles. CONCLUSIONS: Overall, the previously reported 'resistance' of old GAA-KO muscles to exogenous hGAA replacement approaches can be rapidly overcome after a single intravenous injection with a modified adenoviral vector expressing hGAA.

Determination of acid alpha-glucosidase activity in blood spots as a diagnostic test for Pompe disease.

BACKGROUND: Pompe disease is an autosomal recessive disorder of glycogen metabolism that is characterized by a deficiency of the lysosomal acid alpha-glucosidase. Enzyme replacement therapy for the infantile and juvenile forms of Pompe disease currently is undergoing clinical trials. Early diagnosis before the onset of irreversible pathology is thought to be critical for maximum efficacy of current and proposed therapies. In the absence of a family history, the presymptomatic detection of these disorders ideally can be achieved through a newborn-screening program. Currently, the clinical diagnosis of Pompe disease is confirmed by the virtual absence, in infantile onset, or a marked reduction, in juvenile and adult onset, of acid alpha-glucosidase activity in muscle biopsies and cultured fibroblasts. These assays are invasive and not suited to large-scale screening. METHODS: A sensitive immune-capture enzyme activity assay for the measurement of acid alpha-glucosidase protein was developed and used to determine the activity of this enzyme in dried-blood spots from newborn and adult controls, Pompe-affected individuals, and obligate heterozygotes. RESULTS: Pompe-affected individuals showed an almost total absence of acid alpha-glucosidase activity in blood spots. The assay showed a sensitivity and specificity of 100% for the identification of Pompe-affected individuals. CONCLUSIONS: The determination of acid alpha-glucosidase activity in dried-blood spots is a useful, noninvasive diagnostic assay for the identification of Pompe disease. With further validation, this procedure could be adapted for use with blood spots collected in newborn-screening programs.

Determination of acid alpha-glucosidase protein: evaluation as a screening marker for Pompe disease and other lysosomal storage disorders.

BACKGROUND: In recent years, there have been significant advances in the development of enzyme replacement and other therapies for lysosomal storage disorders (LSDs). Early diagnosis, before the onset of irreversible pathology, has been demonstrated to be critical for maximum efficacy of current and proposed therapies. In the absence of a family history, the presymptomatic detection of these disorders ideally can be achieved through a newborn screening program. One approach to the development of such a program is the identification of suitable screening markers. In this study, the acid alpha-glucosidase protein was evaluated as a marker protein for Pompe disease and potentially for other LSDs. METHODS: Two sensitive immunoquantification assays for the measurement of total (precursor and mature) and mature forms of acid alpha-glucosidase protein were used to determine the concentrations in plasma and dried blood spots from control and LSD-affected individuals. RESULTS: In the majority of LSDs, no significant increases above control values were observed. However, individuals with Pompe disease showed a marked decrease in acid alpha-glucosidase protein in both plasma and whole blood compared with unaffected controls. For plasma samples, this assay gave a sensitivity of 95% with a specificity of 100%. For blood spot samples, the sensitivity was 82% with a specificity of 100%. CONCLUSIONS: This study demonstrates that it is possible to screen for Pompe disease by screening the concentration of total acid alpha-glucosidase in plasma or dried blood spots.

Direct multiplex assay of lysosomal enzymes in dried blood spots for newborn screening.

BACKGROUND: Newborn screening for deficiency in the lysosomal enzymes that cause Fabry, Gaucher, Krabbe, Niemann-Pick A/B, and Pompe diseases is warranted because treatment for these syndromes is now available or anticipated in the near feature. We describe a multiplex screening method for all five lysosomal enzymes that uses newborn-screening cards containing dried blood spots as the enzyme source. METHODS: We used a cassette of substrates and internal standards to directly quantify the enzymatic activities, and tandem mass spectrometry for enzymatic product detection. Rehydrated dried blood spots were incubated with the enzyme substrates. We used liquid-liquid extraction followed by solid-phase extraction with silica gel to remove buffer components. Acarbose served as inhibitor of an interfering acid alpha-glucosidase present in neutrophils, which allowed the lysosomal enzyme implicated in Pompe disease to be selectively analyzed. RESULTS: We analyzed dried blood spots from 5 patients with Gaucher, 5 with Niemann-Pick A/B, 11 with Pompe, 5 with Fabry, and 12 with Krabbe disease, and in all cases the enzyme activities were below the minimum activities measured in a collection of heterozygous carriers and healthy noncarrier individuals. The enzyme activities measured in 5-9 heterozygous carriers were approximately one-half those measured with 15-32 healthy individuals, but there was partial overlap of each condition between the data sets for carriers and healthy individuals. CONCLUSION: For all five diseases, the affected individuals were detected. The assay can be readily automated, and the anticipated reagent and supply costs are well within the budget limits of newborn-screening centers.

The activity of alpha-amylase and gamma-amylase in serum and pancreatic homogenate of rats with experimental liver damage treated with colchicine.

In connection with extending the therapeutic application of colchicine to include its use in the treatment of liver fibrosis in cirrhosis and possible harmful effects of this drug on other organs, the pancreas in particular, the authors studied this problem experimentally. For this purpose a model of experimental cirrhosis in rats produced with chronic administration of carbon tetrachloride was used, and in the third and ninth months of the experiment the activity of alpha-amylase and gamma-amylase was determined in the serum and pancreatic homogenate. The results did not show any unfavourable effect of colchicine administered in their therapeutic doses for long time periods on the pancreas in experimental rats and in healthy controls.

Serum enzyme pattern and local enzyme gradients in chronic chagasic patients.

Histochemical studies of myocardial biopsies from chronic chagasic patients at different evolutive stages showed a pattern primarily characterized by a marked increment in tissue enzymes such as mono-amine oxidase and lysosomal acid phosphatase. This cellular damage can be reflected by changes in certain serum enzymes associated with myocardial metabolism, specially in the coronary sinus, where the blood metabolized by the heart is drained. However, little is known about the possible changes in blood enzyme activity during chronic Chagas disease. In this investigation, the activity of the following enzymes glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT), alkaline phosphatase (ALP), acid maltase (AM), lactate dehydrogenase (LDH), alpha-hydroxybutyric dehydrogenase (alpha-HBDH or LDH1) and creatine phosphokinase (CPK) was measured in blood serum of the superior cava vein (SCV), coronary sinus (CS) and pulmonary (PA) and femoral (FA) arteries of 45 chronic chagasic patients, ages between 20 and 55 yr, at different evolutive stages (groups IA, IB, II and III). The results demonstrate that the average activity of the enzymes studied in chagasic patients, except LDH and CPK, are significantly altered (p < 0.05) in the majority of the arterial and venous blood samples. The finding of released GOT, GPT, ALP, acid maltase and alpha-HBDH in groups IA and IB is an indication of early myocardial damage in chronic chagasic patients without clinical evidence of cardiac disease. In conclusion, it is suggested that the possible evolutive pattern for myocardial damage could be established by the increment in coronary sinus blood of the enzymes GOT, acid maltase and alpha-HBDH.