Targeted screening for the detection of Pompe disease in patients with unclassified limb-girdle muscular dystrophy or asymptomatic hyperCKemia using dried blood: A Spanish cohort.

We aimed to screen for Pompe disease in patients with unclassified limb-girdle muscular dystrophy (LGMD) or asymptomatic hyperCKemia using dried blood spot (DBS) assays. Subsequently, we aimed to calculate the diagnostic delay between initial symptom presentation and the diagnosis. A prospective, multicenter, observational study was conducted in 348 patients: 146 with unclassified LGMD and 202 with asymptomatic or paucisymptomatic hyperCKemia. We quantified levels of acid alpha-glucosidase (GAA) from dried blood spots analyzed fluorometrically. The test was positive in 20 patients, and Pompe disease was confirmed by genetic testing in 16. Undiagnosed Pompe disease was detected in 7.5% of patients with LGMD and in 2.5% of patients with persistent, idiopathic elevation of serum creatine kinase. The c.-32-13 T > G mutation was found most commonly. The diagnostic delay was 15 years on average. In conclusion, DBS tests are useful and reliable screening tools for Pompe disease. We recommend the dried blood spot test to be included in the diagnostic work-up of patients with unclassified myopathies with proximal weakness and/or hyperCKemia of unknown cause and, when positive, to define the diagnosis, it will have to be confirmed by biochemical and/or molecular genetic analysis.

[Diagnosis and therapy of late onset Pompe disease]. / Diagnose und Therapie des Late-onset-Morbus-Pompe.

As Pompe disease glycogen storage disease type 2 with a severely reduced life expectancy is now a treatable disorder, accurate diagnostic procedures and evidence-based indications for therapy are mandatory. We screened the literature for consensus reports and published trial data of late-onset Pompe disease. These data were summarized in a Delphi consensus method approach. The clinical suspicion of late-onset Pompe disease should be substantiated by the validated dry blood spot test measurement for acid α-glucosidase activity. Alternatively, enzyme activity analysis in lymphocytes is also feasible. Glucosidase α gene sequencing for verifying the diagnosis is recommended. A muscle biopsy including measurements of acid α-glucosidase activity and glycogen concentration is warranted for differential diagnosis in selected cases. The confirmed diagnosis should lead to a multidisciplinary treatment approach, possibly including enzyme replacement therapy.

Expert recommendations for the laboratory diagnosis of MPS VI.

Mucopolysaccharidosis VI (MPS VI) is a lysosomal storage disease caused by a deficiency of N-acetylgalactosamine 4-sulfatase (arylsulfatase B, ASB). This enzyme is required for the degradation of dermatan sulfate. In its absence, dermatan sulfate accumulates in cells and is excreted in large quantities in urine. Specific therapeutic intervention is available; however, accurate and timely diagnosis is crucial for maximal benefit. To better understand the current practices for diagnosis and to establish diagnostic guidelines, an international MPS VI laboratory diagnostics scientific summit was held in February of 2011 in Miami, Florida. The various steps in the diagnosis of MPS VI were discussed including urinary glycosaminoglycan (uGAG) analysis, enzyme activity analysis, and molecular analysis. The following conclusions were reached. Dilute urine samples pose a significant problem for uGAG analysis and MPS VI patients can be missed by quantitative uGAG testing alone as dermatan sulfate may not always be excreted in large quantities. Enzyme activity analysis is universally acknowledged as a key component of diagnosis; however, several caveats must be considered and the appropriate use of reference enzymes is essential. Molecular analysis supports enzyme activity test results and is essential for carrier testing, subsequent genetic counseling, and prenatal testing. Overall the expert panel recommends caution in the use of uGAG screening alone to rule out or confirm the diagnosis of MPS VI and acknowledges enzyme activity analysis as a critical component of diagnosis. Measurement of another sulfatase enzyme to exclude multiple sulfatase deficiency was recommended prior to the initiation of therapy. When feasible, the use of molecular testing as part of the diagnosis is encouraged. A diagnostic algorithm for MPS VI is provided.

International cooperation in the expansion of a newborn screening programme in Lebanon: a possible model for other programmes.

Tandem mass spectrometry (MS/MS) is rapidly gaining support, even in less-developed nations, as the method of choice for the newborn screening of metabolic disorders, although difficulties in acquiring this technology may at times be major obstacles in several Middle East and North Africa (MENA) countries. In Lebanon, international cooperation allowed this acquisition at the Newborn Screening Laboratory (NSL) of the Saint Joseph University (USJ) in the capital city of Beirut. NSL is currently screening up to 20% of all newborns in Lebanon. The expansion was made possible through initial collaboration with the Metabolic Laboratory at the Hamburg University Medical Center (HUMC) and subsequently with other centres. During phase I of the expansion (2006-2007), blood spots were shipped to HUMC with rapid couriers twice a week and electronic reports were sent back generally within 4 days after shipment. Positive cases were recalled to NSL and new specimens were sent back for confirmation at HUMC. During that first phase, the Beirut staff received training at the HUMC and in other centres. Phase II was a transitory period of 4 months during which machines were installed in Beirut and working procedures were adopted and documented. The activity has now entered a consolidation phase (Phase III) in which all measurements are exclusively performed in Beirut while HUMC acts as a backup centre. International cooperation remains crucial for periodic quality assurance procedures, and for supporting the transformation of the USJ-NSL into a training centre able to transfer MS/MS technology to the MENA region.

Membrane translocation of glutaric acid and its derivatives.

The neurodegenerative disorder glutaric aciduria type I (GA I) is characterized by increased levels of cytotoxic metabolites such as glutaric acid (GA) and 3-hydroxyglutaric (3OHGA). The present report summarizes recent investigations providing insights into mechanisms of intra- and intercellular translocation of these metabolites. Initiated by microarray analyses in a mouse model of GA I, the sodium-dependent dicarboxylate cotransporter 3 (NaC3) was the first molecule identified to mediate the translocation of GA and 3OHGA with high and low affinity, respectively. More recently, organic anion transporters (OAT) 1 and 4 have been reported to be high-affinity transporters for GA and 3OHGA as well as D-2- and L-2-hydroxyglutaric acid (D2OHGA, L2OHGA). The concerted action of NaC3 and OATs may be important for the directed uptake and excretion of GA, 3OHGA, D2OHGA and L2OHGA in kidney proximal tubule cells. In addition, experimental data on cultured neuronal and glial cells isolated from mouse brain demonstrated that GA rather than 3OHGA may competitively inhibit the anaplerotic supply of tricarboxylic acid cycle intermediates from astrocytes to neurons. The identification of GA and GA derivative transporters may represent targets for new approaches to treat patients with GA I and related disorders.

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.

Direct comparison of enzyme measurements from dried blood and leukocytes from male and female Fabry disease patients.

Anderson-Fabry disease is an X-linked disorder that is caused by deficiency of the lysosomal enzyme alpha-galactosidase A. Symptoms include chronic progressive painful small-fibre neuropathy, cornea verticillata, renal failure and heart disease. Interestingly, female heterozygous patients may also show severe symptoms. After clinical suspicion, usually the determination of alpha-galactosidase activity in leukocytes is requested first. Alternatively, an enzymatic assay using dried blood specimens has been described. Dried blood samples require less material and are substantially more stable (several months at room temperature) than whole-blood specimens. To validate the new method and to asses its usefulness for diagnosis of female patients, enzyme activities of alpha-galactosidase, beta-galactosidase and beta-glucuronidase from 78 known Fabry patients were compared (29 males, 47 females) between both materials. In summary, the determination of alpha-galactosidase activity using dried blood and leukocytes as well as the ratio of alpha-galactosidase to beta-glucuronidase in dried blood can improve the diagnostic specificity in cases of female patients who are difficult to identify when only leukocyte enzyme activities are considered.

The ratio of alpha-galactosidase to beta-glucuronidase activities in dried blood for the identification of female Fabry disease patients.

Female heterozygous patients with Fabry disease are difficult to identify because of the relatively high residual activity of alpha-galactosidase. We systematically evaluated the activities of various lysosomal enzymes in dried blood samples from Fabry patients and found that the beta-glucuronidase activity was frequently elevated. The ratio of alpha-galactosidase to beta-glucuronidase proved to be a helpful tool for the diagnosis of female Fabry disease patients.

Hyperchylomicronaemia due to lipoprotein lipase deficiency as a cause of false-positive newborn screening for biotinidase deficiency.

Two cases of molecular genetically proven lipoprotein lipase deficiency are reported. Both patients were detected owing to a false-positive neonatal screening test for biotinidase deficiency. We conclude that both the fluorimetric and the colorimetric screening tests for biotinidase deficiency used with dried blood samples are affected by severe hyperchylomicronaemia and that, most probably, severe plasma turbidity interferes with the assay.

Transplantation of allogeneic CD34-selected stem cells after fludarabine-based conditioning regimen for children with mucopolysaccharidosis 1H (M. Hurler).

Hurler syndrome (MPS1H) is a progressive inborn error of mucopolysaccharide metabolism leading to premature death. Allogeneic hematopoietic cell transplantation (HCT) can achieve stabilization and improve long-term survival. However, large studies have shown that preparative regimen-related toxicity (RRT) and graft failure rates have been relatively high. We transplanted five Hurler children with a fludarabine-based conditioning regimen, consisting of fludarabine/busulphan/ATG for matched family donor (MFD), with the addition of melphalan for mismatched family donor and matched unrelated donor (MUD) transplantations. Median age at HCT was 27 months (range 10-36). The source of stem cells was bone marrow in one MFD and CD34-selected PBSC in four patients. Median CD34+ cell dose was 25 x 10(6)/kg (range 11.5-54). No RRT > grade II was observed. All patients are surviving at a median of 32 months (range 14-41) and show sustained donor engraftment with 3/5 having full donor chimerism, and 2/5 mixed chimerism (> 85%). We conclude that this regimen is feasible and has low toxicity in Hurler children. In combination with high doses of CD34+ selected cells (> 10 x 10(6)/kg) and donor lymphocyte infusions, stable engraftment could be achieved in unrelated and mismatched related transplantations.

Efficiency of long-term tetrahydrobiopterin monotherapy in phenylketonuria.

Phenylketonuria, an inborn error of phenylalanine metabolism, occurs with a frequency of about 1 in 10,000 births and is treated with a strict dietary regimen. Recently, some patients with PKU have been found to show increased tolerance towards phenylalanine intake while receiving tetrahydrobiopterin (BH(4)) supplementation. We have treated two infants with BH(4)-responsive PKU with BH(4) for more than 2 years. No additional dietary control was required to maintain blood phenylalanine concentrations in the desired range. Both children have shown normal development. Generally, our results suggest that BH(4) treatment might be an option for some patients with mild PKU, as it frees them from dietary restrictions and thus improves their quality of life.

3-Hydroxyglutaric acid fails to affect the viability of primary neuronal rat cells.

Glutaric aciduria type I (GA I) is an autosomal recessive inherited metabolic disorder caused by deficiency of glutaryl-CoA dehydrogenase (GCD) resulting in the accumulation of 3-hydroxyglutaric acid (3OHG), glutaric acid and glutaconic acid in body fluids. GA I is characterized by a specific age- and brain region-dependent neuropathology. Previous studies using organotypic slice cultures of rats and primary chick embryo telencephalon cell cultures indicated that death of neurons is a consequence of an excitotoxic mechanism induced by 3OHG. We used primary neuronal cells of neonatal rats as a model system to test cell viability after treatment with 3OHG. Western blot analysis was used to prove the expression of functional N-methyl-D-aspartate (NMDA) receptors revealing no alteration in the expression of NMDA-2a and -2b receptor subtypes in response to 3OHG. When neuronal cells cultured for 10 or 20 days were treated with 1 mM glutamate, the viability of cells was reduced by 40%. This effect could be prevented by coincubation with the NMDA receptor antagonist MK801. In contrast, incubation of cells with 3OHG for up to 24 h in concentrations of 4-8 mM did not cause increased cell death as compared with untreated control cultures. These results indicate that 3OHG is not excitotoxic in this model of neuronal rat cell cultures despite the presence of functional NMDA receptors. Therefore, alternative or additional pathomechanisms than excitotoxicity may be relevant for neurodegeneration in GA I.

Infantile cobalamin deficiency with cerebral lactate accumulation and sustained choline depletion.

A remarkable, intermittent sudden-onset vigilance and movement disorder in an exclusively breast-fed infant is reported, which was caused by cobalamin depletion due to maternal vitamin B12 malabsorption. The lack of cobalamin caused a severe encephalopathy in the infant, whose brain displayed a striking loss of volume and a delay of myelination. Proton magnetic resonance spectroscopy revealed an accumulation of lactate in the gray and white matter of the brain and a sustained depletion of choline-containing compounds in the white matter, reflecting a reversible disturbance of oxidative energy metabolism in brain cells and a long-lasting hypomyelination disorder. The clinical picture in conjunction with MRI and spectroscopic data of this case study yields more insight into the functions of cobalamin in the cerebral metabolism.

Towards quality assurance in the determination of lysosomal enzymes: a two-centre study.

The definitive diagnosis of lysosomal storage disorders depends on the determination of enzymatic activities in cells, tissues or body fluids. At present, neither an evaluation of the different methods nor an interlaboratory quality assurance scheme is available. We have therefore determined the activities of total hexosaminidase, hexosaminidase A and beta-galactosidase in the same samples (n = 15) at two metabolic centres in Germany. Three different enzymatic methods were employed, two of which were based on leukocytes as enzyme source and one on dried blood spots. The results obtained by the two different methods using leukocytes proved comparable. In contrast, assays with dried blood spots showed poor correlation with results from leukocytes, possibly because enzymatic activity in dried blood is mainly derived from soluble plasma proteins. Nevertheless, accurate detection of a true enzyme deficiency was also possible in dried blood spots. All enzymes were highly stable when mailed frozen (recovery 98-120%). Enzymatic activities in dried blood samples were also stable at room temperature and were not affected even by exposure to elevated temperatures (50 degrees C for 3 h). Dried blood seems to be especially well suited for mailing from distant healthcare facilities, although more accurate results can be expected from leukocytes. In summary, comparability and pitfalls within a lysosomal quality assurance programme were evaluated.

A hypothesis on the biochemical mechanism of BH(4)-responsiveness in phenylalanine hydroxylase deficiency.

We describe six children with tetrahydrobiopterin (BH(4)) responsive phenylalanine hydroxylase (PAH) deficiency. All patients carry two mutant alleles in the PAH gene. Cofactor deficiency was excluded. The effect of BH(4) administration was studied by correlating different oral BH(4) doses with plasma phenylalanine levels under defined protein intake. Our results indicate that oral BH(4) supplementation may be used as long-term treatment for individuals with BH(4)-responsive PAH deficiency, either without or in combination with a less restrictive diet. Previous in vitro studies have demonstrated that BH(4) inhibits PAH tetramers but activates PAH dimers. This may indicate, that BH(4)-responsiveness results from BH(4) induced stabilization of mutant PAH dimers. In addition, interindividual differences in the cellular folding apparatus may determine the tertiary structure and the amount of mutant PAH dimers and hence may account for divergent BH(4)-responsiveness reported for the same PAH genotype.

Severe phenotype despite high residual glutaryl-CoA dehydrogenase activity: a novel mutation in a Turkish patient with glutaric aciduria type I.

We report the first patient with the homozygous GCDH mutation M263V, displaying a high residual activity in fibroblasts of 30%, but presenting with a severe clinical phenotype.

The surgical technique and the age of the horse both influence the outcome of mosaicplasty in a cadaver equine stifle model.

Six pieces of grafts, 6.5 mm in diameter, 20 mm in length, were taken from each of 170 cadaver hindlimbs, using the cranial surface of the medial femoral trochlea for harvesting. The age of the horses varied between 4 months and 23 years. 30 limbs under the age of 12 years were selected for transplantation. Three of six grafts were transplanted into the medial femoral condyle using different combinations of tunnel depth and dilation. With ageing, a significant decline in transplantability was detected. In general, mosaicplasty cannot be recommended in horses above 11 years. Based on a previous clinical case (Bodó et al., 2000), a good surface alignment was indeed achieved with a combination of graft length drilling and dilation in most cases. However, the occasional entrapment of cartilage debris under the graft prevented perfect alignment in the present cadaver study in 27% of the grafts transplanted in this manner. Since the protrusion of grafts never exceeded 1.5 mm, we conclude that drilling 3-5 mm deeper than graft length with graft length deep dilation can avoid disadvantageous protrusion of the transplanted hyaline cartilage caps, achieving bone decompression at the same time.

Microscale determination of the absolute configuration of alpha-aryl-substituted alcohols by the CD exciton chirality method

The absolute configurations of a broad spectrum of aryl alcohols 1 have been determined for the first time by the CD exciton chirality method. The configurational assignment is additionally verified by computer modeling and lipase-catalyzed acetylation of the racemic alcohols. The CD-spectroscopic data have revealed that the S enantiomers of the benzoate derivatives 2 display a positive first Cotton effect and the R enantiomers a negative one at around 228 nm. Thus, the sense of the first Cotton effect of the benzoate derivative 2 allows a reliable assignment of the absolute configuration of the corresponding alcohol 1.