At-Risk Testing for Pompe Disease Using Dried Blood Spots: Lessons Learned for Newborn Screening.

Pompe disease (GSD II) is an autosomal recessive disorder caused by deficiency of the lysosomal enzyme acid-α-glucosidase (GAA, EC 3.2.1.20), leading to generalized accumulation of lysosomal glycogen especially in the heart, skeletal, and smooth muscle, and the nervous system. It is generally classified based on the age of onset as infantile (IOPD) presenting during the first year of life, and late onset (LOPD) when it presents afterwards. In our study, a cohort of 13,627 samples were tested between January 2017 and December 2018 for acid-α-glucosidase (GAA, EC 3.2.1.20) deficiency either by fluorometry or tandem mass spectrometry (MS). Testing was performed for patients who displayed conditions of unknown etiology, e.g., CK elevations or cardiomyopathy, in the case of infantile patients. On average 8% of samples showed activity below the reference range and were further assessed by another enzyme activity measurement or molecular genetic analysis. Pre-analytical conditions, like proper drying, greatly affect enzyme activity, and should be assessed with measurement of reference enzyme(s). In conclusion, at-risk testing can provide a good first step for the future introduction of newborn screening for Pompe disease. It yields immediate benefits for the patients regarding the availability and timeliness of the diagnosis. In addition, the laboratory can introduce the required methodology and gain insights in the evaluation of results in a lower throughput environment. Finally, awareness of such a rare condition is increased tremendously among local physicians which can aid in the introduction newborn screening.

Investigating the suitability of high-resolution mass spectrometry for newborn screening: identification of hemoglobinopathies and ß-thalassemias in dried blood spots.

A fast and reliable method for the determination of hemoglobinopathies and thalassemias by high-resolution accurate mass spectrometry (HRAM/MS) is presented. The established method was verified in a prospective clinical study (HRAM/MS vs. high-pressure liquid chromatography [HPLC]) of 5335 de-identified newborn samples from the Hamburg area. The analytical method is based on a dual strategy using intact protein ratios for thalassemias and tryptic digest fragments for the diagnosis of hemoglobinopathies. Due to the minimal sample preparation and the use of flow injection, the assay can be considered as a high-throughput screening approach for newborn screening programs (2 min/sample). Using a simple dried blood spot (DBS) extraction (tryptic digest buffer), the following results were obtained: (1) a carrier incidence of 1:100 newborns (35 FAS, nine FAC, eight FAD and two FAE), and (2) no homozygous affected patient was detected. Using the HRAM/MS protocol, an unknown Hb mutation was identified and confirmed by genetic testing. In addition to greater specificity toward rare mutations and ß-thalassemia, the low price/sample (1-2€) as well as an automated data processing represent the major benefits of the described HRAM/MS method.

Diagnostic strategy for females suspected of Fabry disease.

A total of 11 948 females suspicious of Fabry disease were tested by a combined biochemical and genetic approach. The enzyme activity, together with the concentration of lyso-GL-3 (lyso-Gb3) biomarker in dried blood spots (DBS), substantially improved the diagnostic detection of Fabry disease in females compared to the enzyme activity alone. Abnormal values for both were highly suspicious of Fabry disease (97% positive predictive value [PPV], similar to PPV in males). In cases with one abnormal biochemical value, elevated lyso-GL-3 is a far more important indicator than low enzyme activity (39% PPV vs 6% PPV). Cases with clearly negative results for both biochemical parameters are unlikely to have Fabry disease, even in clinically highly suspicious cases.

Obstructive sleep apnea and craniofacial appearance in MPS type I-Hurler children after hematopoietic stem cell transplantation.

OBJECTIVES: Mucopolysaccharidosis type I (MPS I) is an inherited lysosomal storage disorder characterized by severe multi-systemic organ manifestations including obstructive sleep apnea syndrome (OSAS). Hematopoietic stem cell transplantation (HSCT) is the treatment of choice in severe MPS I (MPS IH, Hurler syndrome). However, the effect of HSCT on OSAS in MPS IH still remains unclear. The purpose of this study was to analyze respiratory patterns during sleep following HSCT in MPS IH children and to relate these findings to craniofacial abnormalities. METHODS: Overnight polysomnographies of nine MPS IH children (mean age: 8.2 years) previously treated with HSCT were retrospectively analyzed. Magnetic resonance images of the head were assessed with regard to soft and hard tissue abnormalities of the upper respiratory tract. RESULTS: The mean apnea hypopnea index (AHI) was 5.3 events/h (range, 0.3-12.2), and the majority of apnea/hypopneas were obstructive. Whereas two patients had severe OSAS (AHI > 10) and two moderate OSAS (5 > AHI < 10), five patients had no evidence of OSAS (AHI < 2.0). Donor cell chimerism was significantly lower in MPS IH patients with OSAS as compared to patients without OSAS (p < 0.001). The upper airway space and the maxilla were significantly smaller and the adenoids larger in MPS IH patients with OSAS as compared to those of non-OSAS patients. CONCLUSION: OSAS was only observed in MPS IH patients with graft failure or low donor cell chimerism. Conversely, successful HSCT seems to ameliorate adenoid hyperplasia and maxillary constriction in MPS IH patients and thereby minimizes the risk of OSAS at least at younger ages.

Newborn Screening for Lysosomal Storage Disorders: Methodologies for Measurement of Enzymatic Activities in Dried Blood Spots.

All worldwide newborn screening (NBS) for lysosomal storage diseases (LSDs) is performed as a first-tier test by measurement of lysosomal enzymatic activities in dried blood spots (DBS). The currently two available methodologies used for measurement of enzymatic activities are tandem mass spectrometry (MS/MS) and digital microfluidics fluorimetry (DMF-F). In this chapter we summarize the workflows for the two platforms. Neither platform is fully automated, but the relative ease of workflow will be dependent upon the specific operation of each newborn screening laboratory on a case-by-case basis. We provide the screen positive rate (the number of below cutoff newborns per 100,000 newborns) from all NBS laboratories worldwide carrying out MS/MS-based NBS of one or more LSDs. The analytical precision of the MS/MS method is higher than that for DMF-F as shown by analysis of a common set of quality control DBS by the Centers for Disease Control and Prevention (CDC). Both the MS/MS and DMF-F platforms enable multiplexing of the LSD enzymes. An advantage of MS/MS over DMF-F is the ability to include assays of enzymatic activities and biomarkers for which no fluorimetric methods exist. Advantages of DMF-F over MS/MS are: 1) Simple to use technology with same-day turn-around time for the lysosomal enzymes with the fastest rates compared to MS/MS requiring overnight analytical runs.; 2) The DMF-F instrumentation, because of its simplicity, requires less maintenance than the MS/MS platform.

Megaphylogeny resolves global patterns of mushroom evolution.

Mushroom-forming fungi (Agaricomycetes) have the greatest morphological diversity and complexity of any group of fungi. They have radiated into most niches and fulfil diverse roles in the ecosystem, including wood decomposers, pathogens or mycorrhizal mutualists. Despite the importance of mushroom-forming fungi, large-scale patterns of their evolutionary history are poorly known, in part due to the lack of a comprehensive and dated molecular phylogeny. Here, using multigene and genome-based data, we assemble a 5,284-species phylogenetic tree and infer ages and broad patterns of speciation/extinction and morphological innovation in mushroom-forming fungi. Agaricomycetes started a rapid class-wide radiation in the Jurassic, coinciding with the spread of (sub)tropical coniferous forests and a warming climate. A possible mass extinction, several clade-specific adaptive radiations and morphological diversification of fruiting bodies followed during the Cretaceous and the Paleogene, convergently giving rise to the classic toadstool morphology, with a cap, stalk and gills (pileate-stipitate morphology). This morphology is associated with increased rates of lineage diversification, suggesting it represents a key innovation in the evolution of mushroom-forming fungi. The increase in mushroom diversity started during the Mesozoic-Cenozoic radiation event, an era of humid climate when terrestrial communities dominated by gymnosperms and reptiles were also expanding.

Validity of a rapid and simple fluorometric tripeptidyl peptidase 1 (TPP1) assay using dried blood specimens to diagnose CLN2 disease.

PURPOSE: CLN2 disease is a genetic disorder caused by dysfunction of the lysosomal enzyme tripeptidyl peptidase 1 (TPP1) that belongs to the neuronal ceroid lipofuscinoses (NCL) and leads to epilepsy, dementia, and death in young persons. CLN2 disease has recently become treatable by enzyme replacement, which can only be effective when the disease is diagnosed early. We have investigated the reliability of a test for TPP1 deficiency in dried blood specimens (DBS) to detect CLN2 disease. RESULTS: During a 12-year period we have received 3882 samples for testing TPP1. Quality of samples was checked by measuring two additional lysosomal enzyme activities. For 50 samples with subnormal TPP1 activity and good sample quality, we obtained adequate clinical and molecular genetic data. All 50 patients had doubtless evidence of CLN2 disease (including seven atypical patients) as shown by clinical findings and the presence of known pathogenic CLN2 variants. Our institution is a major reference center for NCL, and we have never received information that a patient with a normal DBS test was later diagnosed with CLN2 disease. CONCLUSIONS: We consider our TPP1 test on DBS to be a reliable, convenient and inexpensive tool for a first diagnostic step in suspected CLN2 disease.

Recommendations for clinical monitoring of patients with acid sphingomyelinase deficiency (ASMD).

BACKGROUND: Acid sphingomyelinase deficiency (ASMD), a rare lysosomal storage disease, results from mutations in SMPD1, the gene encoding acid sphingomyelinase (ASM). As a result, sphingomyelin accumulates in multiple organs including spleen, liver, lung, bone marrow, lymph nodes, and in the most severe form, in the CNS and peripheral nerves. Clinical manifestations range from rapidly progressive and fatal infantile neurovisceral disease, to less rapidly progressing chronic neurovisceral and visceral forms that are associated with significant morbidity and shorter life span due to respiratory or liver disease. OBJECTIVES: To provide a contemporary guide of clinical assessments for disease monitoring and symptom management across the spectrum of ASMD phenotypes. METHODS: An international group of ASMD experts in various research and clinical fields used an evidence-informed consensus process to identify optimal assessments, interventions, and lifestyle modifications. RESULTS: Clinical assessment strategies for major organ system involvement, including liver, spleen, cardiovascular, pulmonary, and neurological/developmental are described, as well as symptomatic treatments, interventions, and/or life style modifications that may lessen disease impact. CONCLUSIONS: There is currently no disease-specific treatment for ASMD, although enzyme replacement therapy with a recombinant human ASM (olipudase alfa) is in clinical development. Current monitoring addresses symptoms and multisystem involvement. Recommended interventions and lifestyle modifications are designed to address morbidity and disease complications and improve patient quality of life. While infantile neurovisceral ASMD is uniformly fatal in early childhood, patients with chronic visceral and chronic neurovisceral ASMD require appropriate management throughout childhood and adulthood by an interdisciplinary clinical team.

Low Prevalence Estimates of Late-Onset Glycogen Storage Disease Type II in French-Speaking Belgium are not Due to Missed Diagnoses.

BACKGROUND: Late-onset glycogen storage disease type II is associated with variable muscle phenotypes. Epidemiological data suggest that its prevalence is lower in Belgium than in bordering countries like The Netherlands. OBJECTIVE: We investigated whether such low estimated prevalence is due to missed diagnoses. METHODS: We screened 100 patients with muscle phenotypes of undetermined origin using a dried blood spot test for alpha-acid glucosidase (GAA) activity. Patients with low activity at screening were re-tested by the same method and, if low activity was confirmed, GAA gene analysis was performed. RESULTS: The screening test revealed lower than normal GAA activity in 15 patients, but in only two of them it was low enough to be considered in the disease range. Retesting confirmed lower than normal GAA activity in five patients, but in all of them it was above the disease range. A single patient carried a heterozygous known pathogenic GAA mutation, whose significance in this case remains undetermined. CONCLUSIONS: We conclude that reported low prevalence estimates in Belgium are not likely to be due to an underdiagnosis bias. Lower prevalence compared to neighbouring The Netherlands may be due to different ethnic stratification of our patients. Diagnostic strategies should keep into account the expected prevalence of a disease in specific populations.

A Description of Reference Ranges for Organic Acids in Urine Samples from A Pediatric Population in Iran.

BACKGROUND: Organic acids refer to a family of compounds that are intermediates in a variety of metabolic pathways. Many organic acids are present in urine from clinically normal individuals. Elevated levels of urine organic acids cause to the organic acidurias, disorders in which some metabolic pathways in organic acid metabolism are blocked. The present work identified major and minor urinary acidic metabolites in normal subjects, and their quantitative ranges in a pediatric population of Iran. METHODS: Two hundred and fifty-one healthy subjects, including 132 males and 119 females, from 2 days to 15 years of age were enrolled. Urinary organic acids were extracted from urine with organic solvents and identified and quantified by gas chromatography-mass spectrometry. RESULTS: The results provide a foundation on which to check results for patients with potentially abnormal organic acidurias. By this method 98 organic acids were identified in a pediatric population of Iran. CONCLUSION: The present work identifies and quantifies major and minor urinary metabolites excreted by normal subjects. We also analyzed urine from 30 patients with organic acid metabolism abnormalities and compared the concentrations of specific organic acids with those from urines of normal individuals.

Best practice in the measurement and interpretation of lysosomal acid lipase in dried blood spots using the inhibitor Lalistat 2.

Lysosomal acid lipase deficiency (LAL-D) is an inherited, autosomal recessive lysosomal storage disorder characterized by progressive damage in multiple organ systems. Diagnosis is especially important in infants, in whom the course of disease is rapidly lethal without treatment. The recent regulatory approval of recombinant human lysosomal acid lipase (LAL), sebelipase alfa, merits rapid diagnosis in clinical routine, particularly in infants. A method for measuring LAL activity in dried blood spot (DBS) samples using the highly specific LAL inhibitor Lalistat 2 is available. This method is shown to effectively discriminate between individuals with LAL-D and unaffected controls. With the increase in DBS LAL testing since the original publication of this method, a need to optimise assay performance has been identified. Here, we describe refinements to the DBS assay, including technical modifications, quality control measures and best-practice guidance for interpreting and reporting results. Particular attention is paid to alternatives to the use of mercuric chloride as the stop reagent and the choice of excitation wavelength for 4-methylumbelliferone palmitate under assay conditions at pH4.0. In addition, a simpler method of reporting results is proposed using cutoffs based on percentage mean normal enzyme activity.

Consensus recommendation for a diagnostic guideline for acid sphingomyelinase deficiency.

Disclaimer:This diagnostic guideline is intended as an educational resource and represents the opinions of the authors, and is not representative of recommendations or policy of the American College of Medical Genetics and Genomics (ACMG). The information should be considered a consensus based on expert opinion, as more comprehensive levels of evidence were not available in the literature in all cases. BACKGROUND: Acid sphingomyelinase deficiency (ASMD) is a rare, progressive, and often fatal lysosomal storage disease. The underlying metabolic defect is deficiency of the enzyme acid sphingomyelinase that results in progressive accumulation of sphingomyelin in target tissues. ASMD manifests as a spectrum of severity ranging from rapidly progressive severe neurovisceral disease that is uniformly fatal to more slowly progressive chronic neurovisceral and chronic visceral forms. Disease management is aimed at symptom control and regular assessments for multisystem involvement. PURPOSE AND METHODS: An international panel of experts in the clinical and laboratory evaluation, diagnosis, treatment/management, and genetic aspects of ASMD convened to review the evidence base and share personal experience in order to develop a guideline for diagnosis of the various ASMD phenotypes. CONCLUSIONS: Although care of ASMD patients is typically provided by metabolic disease specialists, the guideline is directed at a wide range of providers because it is important for primary care providers (e.g., pediatricians and internists) and specialists (e.g., pulmonologists, hepatologists, and hematologists) to be able to identify ASMD.Genet Med advance online publication 13 April 2017.

Klüver-Bucy syndrome associated with a recessive variant in HGSNAT in two siblings with Mucopolysaccharidosis type IIIC (Sanfilippo C).

Klüver-Bucy syndrome (KBS) comprises a set of neurobehavioral symptoms with psychic blindness, hypersexuality, disinhibition, hyperorality, and hypermetamorphosis that were originally observed after bilateral lobectomy in Rhesus monkeys. We investigated two siblings with KBS from a consanguineous family by whole-exome sequencing and autozygosity mapping. We detected a homozygous variant in the heparan-α-glucosaminidase-N-acetyltransferase gene (HGSNAT; c.518G>A, p.(G173D), NCBI ClinVar RCV000239404.1), which segregated with the phenotype. Disease-causing variants in this gene are known to be associated with autosomal recessive Mucopolysaccharidosis type IIIC (MPSIIIC, Sanfilippo C). This lysosomal storage disease is due to deficiency of the acetyl-CoA:α-glucosaminidase-N-acetyltransferase, which was shown to be reduced in patient fibroblasts. Our report extends the phenotype associated with MPSIIIC. Besides MPSIIIA and MPSIIIB, due to variants in SGSH and NAGLU, this is the third subtype of Sanfilippo disease to be associated with KBS. MPSIII should be included in the differential diagnosis of young patients with KBS.

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.

Prevalence of Pompe disease in 3,076 patients with hyperCKemia and limb-girdle muscular weakness.

OBJECTIVE: We prospectively screened a large European cohort of patients presenting with hyperCKemia and/or limb-girdle muscular weakness (LGMW) for acid α-glucosidase (GAA) deficiency by dried blood spot (DBS) investigation. METHODS: DBS were collected from 3,076 consecutive adult patients from 7 German and British neuromuscular centers. All specimens were investigated for GAA deficiency by fluorometry. Samples with reduced enzyme activity were subsequently investigated for GAA gene mutations. RESULTS: Of 3,076 patients with DBS samples, 232 patients (7.6%) showed low GAA enzyme activity. Of these 232 patients, 55 (24%) presented with isolated hyperCKemia and 176 (76%) with hyperCKemia and LGMW. With both features present, 94% of the patients showed a low enzymatic activity. Mutational analysis found GAA gene mutations in 74 patients (2.4%); herein 70 patients were heterozygote for the common GAA gene splice-site mutation c.-32-13T>G. The most common clinical presentation in the confirmed Pompe cohort was a limb-girdle phenotype (85.3%) combined with ventilatory insufficiency (61%). Isolated hyperCKemia was found in 12%, while 2.7 had hyperCKemia and ventilatory insufficiency only. CONCLUSIONS: In a large cohort of unselected adult patients with hyperCKemia and/or LGMW, we found a prevalence of late-onset Pompe disease of 2.4%. Therefore, targeted screening of such a population should be encouraged in clinical practice.

Tolerability, safety, and pharmacokinetics of the novel cathepsin A inhibitor SAR164653 in healthy subjects.

Cathepsin A (CathA) is a lysosomal protein where it forms a stable complex with neuraminidase and ß-galactosidase. CathA also has enzymatic activity and is involved in the degradation of many peptides. CathA was recently discovered as a target for heart failure, fostering the development of CathA inhibitors with SAR164653 as a frontrunner. The first-in-man study investigated single oral doses from 20 to 800 mg of SAR164653 followed by repeat dose studies at doses up to 800 mg in healthy young and elderly subjects. SAR164653 was safe and well tolerated at doses up to 800 mg in healthy subjects, and a maximum tolerated dose could not be determined from the study. Activity of ß-galactosidase measured in leukocytes did not show any abnormalities. The tmax was 1.0 to 2.5 hours, and the t1/2 was ∼5-11 after single dosing; exposure increased less than dose proportional. Following multiple dosing, accumulation was not observed, Cmax and AUC0-24 increased in a dose-proportional manner, and t1/2 was around 14-20 hours. The novel CathA inhibitor SAR164653 was found to have a favorable safety profile in these early phase 1 studies, but further studies are required to confirm if SAR164653 is equally safe in patients undergoing long-term treatment.

Congenital Adrenal Hyperplasia with Non-functional Mutations in Both Alleles in a Clinically Unaffected Infant.

BACKGROUND: Results in neonatal screening programs aiming at detection of congenital adrenal hyperplasia (CAH) can only report elevated levels of 17-hydroxy-progesterone (17-OHP), without being able to differentiate presence or absence of salt loss. AIM: To predict presence or absence of salt loss in newborn infants with CAH. METHODS: The first specimen of suspected CAH in samples sent from People's Democratic Republic of Laos (Lao PDR) was investigated for known mutations in CAH associated with salt loss. RESULTS: Molecular genetic diagnosis revealed mutations associated with loss of function in both alleles; however, the infant was clinically unaffected even without any corticosteroid substitution therapy. CONCLUSIONS: Although molecular genetic methods can theoretically predict loss of function in CAH, our infant was clinically unaffected even without therapy at 6 years of age. We speculate that in CAH, remaining enzyme activity can be sufficiently high, despite the presence of loss of function mutations, which do not affect infants clinically.

The Prevalence of Sickle Cell Disease and Its Implication for Newborn Screening in Germany (Hamburg Metropolitan Area).

Sickle cell disease is among hereditary diseases with evidence that early diagnoses and treatment improves the clinical outcome. So far sickle cell disease has not been included in the German newborn screening program despite immigration from countries with populations at risk. To determine the birth prevalence we tested 17,018 newborns. High pressure liquid chromatography and subsequent molecular-genetic testing were used for the detection and confirmation of hemoglobin variants. The frequency of sickle cell disease-consistent genotypes was one in 2,385 newborns. Duffy-blood group typing showed evidence that affected children were likely of Sub-Saharan ancestry. An inclusion of sickle cell disease into the German newborn screening seems reasonable.

Homozygosity for the common GAA gene splice site mutation c.-32-13T>G in Pompe disease is associated with the classical adult phenotypical spectrum.

Homozygosity for the common Caucasian splice site mutation c.-32-13T>G in intron 1 of the GAA gene is rather rare in Pompe patients. We report on the clinical, biochemical, morphological, muscle imaging, and genetic findings of six adult Pompe patients from five unrelated families with the c.-32-13T>G GAA gene mutation in homozygous state. All patients had decreased GAA activity and elevated creatine kinase levels. Five patients, aged between 43 and 61 years (median 53 years), initially presented with myalgia, hyperCKaemia, and/or exercise induced fatigue at an age of onset (12-55 years). All but one had proximal lower limb weakness combined with axial weakness and moderate respiratory insufficiency; the sixth patient presented with hyperCKaemia only. Muscle biopsies showed PAS-positive vacuolar myopathy with lysosomal changes and reduced GAA activity. Muscle MRI of lower limb muscles revealed a moderate adipose substitution of the gluteal muscles, biceps femoris and slight fatty infiltration of all thigh muscles. One MRI of the respiratory muscles revealed a diaphragmatic atrophy with unilateral diaphragm elevation. So, the common Caucasian, so called mild, splice site mutation c.-32-13T>G in intron 1 of the GAA gene in a homozygote status reflects the full adult Pompe disease phenotype severity spectrum.