Pompe Disease: Diagnosis and Management. Evidence-Based Guidelines from a Canadian Expert Panel

Biomarker testing for lysosomal diseases: A technical standard of the American College of Medical Genetics and Genomics (ACMG)

Measurement of lysosomal disease (LD) biomarkers can reveal valuable information about disease status. Lyso-globotriaosylceramide (lyso-Gb3), glucosylsphingosine (lyso-Gb1), galactosylsphingosine (psychosine), and glucose tetrasaccharide (Glca1-6Glca1-4Glca1-4Glc, Glc4) are biomarkers associated with Fabry, Gaucher, Krabbe, and Pompe disease, respectively. Clinical biomarker testing is performed to guide patient management, including monitoring disease progression and initiating treatment, and in diagnostic evaluations of either symptomatic patients or asymptomatic individuals with a positive family history or abnormal newborn screen. Biomarker analysis can be performed through independent analysis of a single analyte or as a multiplex assay measuring analytes for more than one disorder utilizing liquid chromatographic separation and tandem mass spectrometric detection. These guidelines were developed to provide technical standards for biomarker analysis, results interpretation, and results reporting, highlighting Fabry, Gaucher, Krabbe, and Pompe diseases as examples.

The lived experience of mothers caring for school-age children with Pompe disease: A qualitative study

PURPOSE

To explore the lived experiences of mothers caring for school-age children with Pompe disease.

DESIGN AND METHODS

A qualitative study using a descriptive phenomenology approach. Semi-structured interviews were conducted from October to December 2022 with 10 mothers of school-age children diagnosed with Pompe disease, which were identified through the Taiwan Pompe Disease Association. Colaizzi's phenomenological method was employed for data analysis.

RESULTS

The study identified five themes in the caregiving experiences of mothers: 1. unwavering parenting beliefs; 2. child-centric approach; 3. focus on peer relationships and coping strategies; 4. integration of learning, treatment, and rehabilitation; and 5. embracing and navigating life's challenges. Mothers balanced education, treatment, and rehabilitation for their children with Pompe disease, offering perspectives into the caregiving experience.

CONCLUSIONS

This study highlights the complex experiences of mothers caring for children with Pompe disease, emphasizing the importance of comprehensive support.

PRACTICE IMPLICATIONS

Insights into the perspectives of mothers can aid health-care professionals in understanding the challenges faced by families with children diagnosed with Pompe disease and can enable the development of strategies for providing comprehensive psychological support to improve mental health outcomes for these children and their families. Increased awareness among health-care professionals and in the society leads to an informed and empathetic approach to addressing the unique challenges faced by children with Pompe disease and their families.

Non-invasive optoacoustic imaging of glycogen-storage and muscle degeneration in late-onset Pompe disease

Pompe disease (PD) is a rare autosomal recessive glycogen storage disorder that causes proximal muscle weakness and loss of respiratory function. While enzyme replacement therapy (ERT) is the only effective treatment, biomarkers for disease monitoring are scarce. Following ex vivo biomarker validation in phantom studies, we apply multispectral optoacoustic tomography (MSOT), a laser- and ultrasound-based non-invasive imaging approach, in a clinical trial (NCT05083806) to image the biceps muscles of 10 late-onset PD (LOPD) patients and 10 matched healthy controls. MSOT is compared with muscle magnetic resonance imaging (MRI), ultrasound, spirometry, muscle testing and quality of life scores. Next, results are validated in an independent LOPD patient cohort from a second clinical site. Our study demonstrates that MSOT enables imaging of subcellular disease pathology with increases in glycogen/water, collagen and lipid signals, providing higher sensitivity in detecting muscle degeneration than current methods. This translational approach suggests implementation in the complex care of these rare disease patients.

104-week efficacy and safety of cipaglucosidase alfa plus miglustat in adults with late-onset Pompe disease: a phase III open-label extension study (ATB200-07)

The phase III double-blind PROPEL study compared the novel two-component therapy cipaglucosidase alfa + miglustat (cipa + mig) with alglucosidase alfa + placebo (alg + pbo) in adults with late-onset Pompe disease (LOPD). This ongoing open-label extension (OLE; NCT04138277) evaluates long-term safety and efficacy of cipa + mig. Outcomes include 6-min walk distance (6MWD), forced vital capacity (FVC), creatine kinase (CK) and hexose tetrasaccharide (Hex4) levels, patient-reported outcomes and safety. Data are reported as change from PROPEL baseline to OLE week 52 (104 weeks post-PROPEL baseline). Of 118 patients treated in the OLE, 81 continued cipa + mig treatment from PROPEL (cipa + mig group; 61 enzyme replacement therapy [ERT] experienced prior to PROPEL; 20 ERT naïve) and 37 switched from alg + pbo to cipa + mig (switch group; 29 ERT experienced; 8 ERT naive). Mean (standard deviation [SD]) change in % predicted 6MWD from baseline to week 104 was + 3.1 (8.1) for cipa + mig and - 0.5 (7.8) for the ERT-experienced switch group, and + 8.6 (8.6) for cipa + mig and + 8.9 (11.7) for the ERT-naïve switch group. Mean (SD) change in % predicted FVC was - 0.6 (7.5) for cipa + mig and - 3.8 (6.2) for the ERT-experienced switch group, and - 4.8 (6.5) and - 3.1 (6.7), respectively, in ERT-naïve patients. CK and Hex4 levels improved in both treatment groups by week 104 with cipa + mig treatment. Three patients discontinued the OLE due to infusion-associated reactions. No new safety signals were identified. Cipa + mig treatment up to 104 weeks was associated with overall maintained improvements (6MWD, biomarkers) or stabilization (FVC) from baseline with continued durability, and was well tolerated, supporting long-term benefits for patients with LOPD.Trial registration number: NCT04138277; trial start date: December 18, 2019.

The value of knowing: preferences for genetic testing to diagnose rare muscle diseases

BACKGROUND

Genetic testing can offer early diagnosis and subsequent treatment of rare neuromuscular diseases. Options for these tests could be improved by understanding the preferences of patients for the features of different genetic tests, especially features that increase information available to patients.

METHODS

We developed an online discrete-choice experiment using key attributes of currently available tests for Pompe disease with six test attributes: number of rare muscle diseases tested for with corresponding probability of diagnosis, treatment availability, time from testing to results, inclusion of secondary findings, necessity of a muscle biopsy, and average time until final diagnosis if the first test is negative. Respondents were presented a choice between two tests with different costs, with respondents randomly assigned to one of two costs. Data were analyzed using random-parameters logit.

RESULTS

A total of 600 online respondents, aged 18 to 50 years, were recruited from the U.S. general population and included in the final analysis. Tests that targeted more diseases, required less time from testing to results, included information about unrelated health risks, and were linked to shorter time to the final diagnosis were preferred and associated with diseases with available treatment. Men placed relatively more importance than women on tests for diseases with available treatments. Most of the respondents would be more willing to get a genetic test that might return unrelated health information, with women exhibiting a statistically significant preference. While respondents were sensitive to cost, 30% of the sample assigned to the highest cost was willing to pay $500 for a test that could offer a diagnosis almost 2 years earlier.

CONCLUSION

The results highlight the value people place on the information genetic tests can provide about their health, including faster diagnosis of rare, unexplained muscle weakness, but also the value of tests for multiple diseases, diseases without treatments, and incidental findings. An earlier time to diagnosis can provide faster access to treatment and an end to the diagnostic journey, which patients highly prefer.

Long-term safety and efficacy of cipaglucosidase alfa plus miglustat in individuals living with Pompe disease: an open-label phase I/II study (ATB200-02)

Cipaglucosidase alfa plus miglustat (cipa + mig) is a novel, two-component therapy for Pompe disease. We report data from the Phase I/II ATB200-02 study for up to 48 months of treatment. Four adult cohorts, including one non-ambulatory ERT-experienced (n = 6) and three ambulatory cohorts, (two enzyme replacement therapy [ERT]-experienced cohorts [2-6 years (n = 11) and ≥ 7 years (n = 6)]), one ERT-naïve cohort (n = 6), received 20 mg/kg intravenous-infused cipa plus 260 mg oral mig biweekly. Change from baseline (CFBL) for multiple efficacy endpoints at 12, 24, 36, and 48 months, pharmacodynamics, pharmacokinetics, safety, and immunogenicity data were assessed. Six-minute walking distance (% predicted) improved at 12, 24, 36, and 48 months: pooled ambulatory ERT-experienced cohorts, mean(± standard deviation [SD]) CFBL: 6.1(± 7.84), n = 16; 5.4(± 10.56), n = 13; 3.4(± 14.66), n = 12; 5.9(± 17.36), n = 9, respectively; ERT-naïve cohort: 10.7(± 3.93), n = 6; 11.0(± 5.06), n = 6; 9.0(± 7.98), n = 5; 11.7(± 7.69), n = 4, respectively. Percent predicted forced vital capacity was generally stable in ERT-experienced cohorts, mean(± SD) CFBL - 1.2(± 5.95), n = 16; 1.0(± 7.96), n = 13; - 0.3(± 6.68), n = 10; 1.0(± 6.42), n = 6, respectively, and improved in the ERT-naïve cohort: 3.2(± 8.42), n = 6; 4.7(± 5.09), n = 6; 6.2(± 3.35), n = 5; 8.3(± 4.50), n = 4, respectively. Over 48 months, CK and Hex4 biomarkers improved in ambulatory cohorts. Overall, cipa + mig was well tolerated with a safety profile like alglucosidase alfa. ATB200-02 results show the potential benefits of cipa + mig as a long-term treatment option for Pompe disease. Trial registration number: NCT02675465 January 26, 2016.

Interplay between mitochondrial dysfunction and lysosomal storage: challenges in genetic metabolic muscle diseases with a focus on infantile onset Pompe disease

Background

Pompe disease (PD) is a rare, progressive autosomal recessive lysosomal storage disorder that directly impacts mitochondrial function, leading to structural abnormalities and potentially culminating in heart failure or cardiogenic shock. The clinical course and molecular mechanisms of the disease remain incompletely understood.

Methods

We performed a retrospective analysis to examine the clinical manifestations, genetic traits, and the relationship between PD and mitochondrial function in a pediatric patient. This comprehensive evaluation included the use of ultrasound echocardiograms, computed tomography (CT) scans, electrocardiograms, mutagenesis analysis, and structural analysis to gain insights into the patient's condition and the underlying mechanisms of PD. For structural analysis and visualization, the structure of protein data bank ID 5KZX of human GAA was used, and VMD software was used for visualization and analysis.

Results

The study revealed that a 5-month-old male infant was admitted due to fever, with physical examination finding abnormal cardiopulmonary function and hepatomegaly. Laboratory tests and echocardiography confirmed heart failure and hypertrophic cardiomyopathy. Despite a week of treatment, which normalized body temperature and reduced pulmonary inflammation, cardiac abnormalities did not show significant improvement. Further genetic testing identified a homozygous mutation c.2662G>T (p.E888) in the GAA gene, leading to a diagnosis of Infantile-Onset Pompe Disease (IOPD).

Conclusions

Although enzyme replacement therapy can significantly improve the quality of life for patients with PD, enhancing mitochondrial function may represent a new therapeutic strategy for treating PD.

[Diagnosis and Management of Late-Onset Pompe Disease]

Pompe disease is a lysosomal storage disorder, with onset between the first weeks after birth and adulthood, depending on its phenotype. It can affect multiple organ systems and presents itself with a wide variety of symptoms. Thus, recognizing Pompe disease is difficult. Especially since enzyme replacement therapy for Pompe disease was introduced (in Germany in 2006), early diagnosis by means of enzyme activity determination from dried blood spot analysis and genetic verification has become important for outcome and quality of life. When facing an obscure muscular disorder, it is crucial to consider Pompe disease. This article provides an overview about Pompe disease and focuses on the diagnosis of the late onset type. The most important aspects of interdiciplinary care for patients with Pompe disease are presented. Additionally, it contains a section focusing on psychosocial challenges for children with Pompe disease and their families, which may include mental disorders and social retreat, and gives advice on how to support parents of affected children.

Case report: Chronic pain in a pediatric patient with late-onset pompe disease

Pompe disease (PD) is a rare inherited metabolic disorder of deficient or absent acid alpha-glucosidase (GAA), resulting in defective lysosomal glycogen catabolism. Muscle weakness, respiratory deficiency and gastrointestinal symptoms are commonly monitored in PD. However, pain and associated psychological symptoms are less focused upon. A pediatric patient with late-onset Pompe disease (LOPD) comorbid with chronic pain is presented. Symptoms of pain in the feet were first reported between 6 and 7 years of age and were attributed to growing pains. Following progression of lower body pain, weakness, fatigue, and difficulties with ambulation, a thorough clinical assessment including genetic testing was performed, which led to a diagnosis of LOPD at 9 years of age. ERT with recombinant human alglucosidase alfa was subsequently started. The patient's clinical status is compounded by depressed mood, anxiety, and attention deficit hyperactivity disorder, which may further exacerbate pain. A multidisciplinary pain treatment approach consisting of orthopedics, physical therapy, and psychosocial therapy aimed at enhancing pain coping skills is described for this LOPD patient. This case highlights the need for a greater understanding of pain generation and identification of optimized pain treatment approaches in children with LOPD that can be implemented alongside ERT.

Novel Mutation in the Feline GAA Gene in a Cat with Glycogen Storage Disease Type II (Pompe Disease)

Glycogen storage disease type II (Pompe disease: PD) is an autosomal recessively inherited fatal genetic disorder that results from the deficiency of a glycogen hydrolyzing enzyme, acid α-glucosidase encoded by the GAA gene. Here, we describe the molecular basis of genetic defects in an 8-month-old domestic short-haired cat with PD. The cat was previously diagnosed with PD based on the clinical and pathological findings of hypertrophic cardiomyopathy and excessive accumulation of glycogen in the cardiac muscles. Sanger sequencing was performed on 20 exons of the feline GAA gene using genomic DNA extracted from paraffin-embedded liver tissues. The affected cat was found to be homozygous for the GAA:c.1799G>A mutation resulting in an amino acid substitution (p.R600H) of acid α-glucosidase, a codon position of which is identical with three missense mutations (p.R600C, p.R600L, and p.R600H) causing human infantile-onset PD (IOPD). Several stability and pathogenicity predictors have also shown that the feline mutation is deleterious and severely decreases the stability of the GAA protein. The clinical, pathological, and molecular findings in the cat were similar to those of IOPD in humans. To our knowledge, this is the first report of a pathogenic mutation in a cat. Feline PD is an excellent model for human PD, especially IOPD.

Unusual Evolution of Hypertrophic Cardiomyopathy in Non-Compaction Myocardium in a Pompe Disease Patient

Classic infantile Pompe disease is characterized by a severe phenotype with cardiomyopathy and hypotonia. Cardiomyopathy is generally hypertrophic and rapidly regresses after enzyme replacement therapy. In this report, for the first time, we describe a patient with infantile Pompe disease and hypertrophic cardiomyopathy that evolved into non-compaction myocardium after treatment. The male newborn had suffered since birth with hypertrophic cardiomyopathy and heart failure. He was treated with standard enzyme replacement therapy (ERT) (alglucosidase alfa) and several immunomodulation cycles due to the development of anti-ERT antibodies, without resolution of the hypertrophic cardiomyopathy. At the age of 2.5 years, he was treated with a new combination of ERT therapy (cipaglucosidase alfa) and a chaperone (miglustat) for compassionate use. After 1 year, the cardiac hypertrophy was resolved, but it evolved into non-compaction myocardium. Non-compaction cardiomyopathy is often considered to be a congenital, primitive cardiomyopathy, due to an arrest of compaction of the myocardium wall during the embryonal development. Several genetic causes have been identified. We first describe cardiac remodeling from hypertrophic cardiomyopathy to a non-compaction form in a patient with infantile Pompe disease treated with a new ERT. This has important implications both for the monitoring of Pompe disease patients and for the understanding of the pathophysiological basis of non-compaction myocardium.

Expert Group Consensus on early diagnosis and management of infantile-onset pompe disease in the Gulf Region

BACKGROUND

Infantile-onset Pompe disease (IOPD) is a rare and devastating, autosomal recessive lysosomal storage disorder that manifests immediately after birth. In severe IOPD cases, complete/almost-complete acid alpha-glucosidase enzyme deficiency is observed. Considering the rapid progression of the disease, timely diagnosis and treatment are important; even slight delays can remarkably alter the course of the disease. Enzyme replacement therapy (ERT) with recombinant human acid alpha-glucosidase is safe and beneficial for IOPD patients. However, there is heterogeneity in the patient response to ERT. The factors influencing treatment effectiveness include the patient's age at the time of treatment initiation, pre-existing muscle damage, and cross-reactive immunologic material (CRIM) status at baseline. Immunomodulation along with ERT is the recently developed therapeutic approach that has been included in the therapeutic armamentarium of IOPD for optimizing clinical benefits, particularly in CRIM-negative IOPD patients. However, there is a dearth of published data on the early diagnosis and clinical position of the immunomodulation protocol along with ERT in the treatment of IOPD in the Gulf region.

METHODS AND RESULTS

Expert panel meetings, involving six experts from the Kingdom of Saudi Arabia, Kuwait, Oman, Qatar, and the United Arab Emirates, were convened to develop consensus-based recommendations addressing current diagnostic and management challenges for patients with IOPD in the Gulf region. Furthermore, this consensus guideline may be implemented in clinical practice for the timely diagnosis and management of patients with IOPD.

CONCLUSION

The expert consensus will help clinicians to make appropriate and timely decisions regarding immunomodulation initiation and ERT treatment in IOPD patients in the Gulf region.

The Clinical Management of Pompe Disease: A Pediatric Perspective

Pompe disease (PD) is an inherited metabolic disorder caused by a deficiency of acid α-glucosidase (GAA), leading to lysosomal accumulation of glycogen, mainly in skeletal and cardiac muscles as well as the nervous system. Patients with PD develop cellular dysfunction and muscle damage. PD can be classified into two classic forms, namely infantile-onset PD (IOPD) and late-onset PD (LOPD). Delayed treatment, particularly in IOPD, would result in significant organ damage and early death. Nonetheless, early diagnosis and timely treatment are often hampered by the rarity of PD and its wide variety of, but overlapping, symptoms. This article reviews the common clinical presentations of PD and outlines the essentials of PD management. In particular, the implications of newborn screening (NBS) and clinical performance of enzyme replacement therapy (ERT) are highlighted.

Benefit of 5 years of enzyme replacement therapy in advanced late onset Pompe. A case report of misdiagnosis for three decades with acute respiratory failure at presentation

We report on a 57 year old female patient who presented in acute respiratory failure with severe generalized weakness. She was previously misdiagnosed for over three decades as polymyositis. She was treated with enzyme replacement therapy (ERT) for over five years, after being diagnosed with late onset Pompe Disease (LOPD). She returned to independent living with the use of non invasive ventilation at nights. ERT should be considered in the management of patients with advanced LOPD and the effects of ERT closely monitored.

Nutritional co-therapy with 1,3-butanediol and multi-ingredient antioxidants enhances autophagic clearance in Pompe disease

Alglucosidase alpha is an orphan drug approved for enzyme replacement therapy (ERT) in Pompe disease (PD); however, its efficacy is limited in skeletal muscle because of a partial blockage of autophagic flux that hinders intracellular trafficking and enzyme delivery. Adjunctive therapies that enhance autophagic flux and protect mitochondrial integrity may alleviate autophagic blockage and oxidative stress and thereby improve ERT efficacy in PD. In this study, we compared the benefits of ERT combined with a ketogenic diet (ERT-KETO), daily administration of an oral ketone precursor (1,3-butanediol; ERT-BD), a multi-ingredient antioxidant diet (ERT-MITO; CoQ10, α-lipoic acid, vitamin E, beetroot extract, HMB, creatine, and citrulline), or co-therapy with the ketone precursor and multi-ingredient antioxidants (ERT-BD-MITO) on skeletal muscle pathology in GAA-KO mice. We found that two months of 1,3-BD administration raised circulatory ketone levels to ≥1.2 mM, attenuated autophagic buildup in type 2 muscle fibers, and preserved muscle strength and function in ERT-treated GAA-KO mice. Collectively, ERT-BD was more effective vs. standard ERT and ERT-KETO in terms of autophagic clearance, dampening of oxidative stress, and muscle maintenance. However, the addition of multi-ingredient antioxidants (ERT-BD-MITO) provided the most consistent benefits across all outcome measures and normalized mitochondrial protein expression in GAA-KO mice. We therefore conclude that nutritional co-therapy with 1,3-butanediol and multi-ingredient antioxidants may provide an alternative to ketogenic diets for inducing ketosis and enhancing autophagic flux in PD patients.

Unexplained Left Ventricular Hypertrophy with Symptomatic High-Grade Atrioventricular Block in Elderly Patients: A Case Report

Left ventricular hypertrophy (LVH) is common among older adults. Amidst all causes, Fabry disease (FD) should be considered when LVH occurs with family history, specific clinical manifestations, or cardiac alert signs. Here, we report a case of a 76-year-old male who presented late onset concentric LVH with symptomatic high-grade atrioventricular (AV) block. After dual-chamber pacemaker implantation, interrogation revealed frequent right ventricular (RV) pacing with a wide QRS duration. The patient developed heart failure symptoms with rapid deterioration of LV systolic function. Pacing-induced cardiomyopathy (PICM) was suspected, and the pacemaker was upgraded to biventricular pacing. Further FD surveys were performed, including biochemical examinations, cardiac biopsies, and genetic sequencing, and the patient was ultimately diagnosed with a cardiac variant of FD. Particularly, we strongly suggest that physiologic pacing should be initially considered for patients with FD who have symptomatic high-grade AV block, rather than traditional RV pacing to prevent PICM.

Experienced fatigue in people with rare disorders: a scoping review on characteristics of existing research

BACKGROUND

Experienced fatigue is an under-recognized and under-researched feature in persons with many different rare diseases. A better overview of the characteristics of existing research on experienced fatigue in children and adults with rare diseases is needed. The purpose of this review was to map and describe characteristics of existing research on experienced fatigue in a selection of rare diseases in rare developmental defects or anomalies during embryogenesis and rare genetic diseases. Furthermore, to identify research gaps and point to research agendas.

METHODS

We applied a scoping review methodology, and performed a systematic search in March 2020 in bibliographic databases. References were sorted and evaluated for inclusion using EndNote and Rayyan. Data were extracted on the main research questions concerning characteristics of research on experienced fatigue (definition and focus on fatigue, study populations, research questions investigated and methods used).

RESULTS

This review included 215 articles on ten different rare developmental defects/anomalies during embryogenesis and 35 rare genetic diseases. Of the 215 articles, 82 had investigation of experienced fatigue as primary aim or outcome. Included were 9 secondary research articles (reviews) and 206 primary research articles. A minority of articles included children. There were large differences in the number of studies in different diseases. Only 29 of 215 articles gave a description of how they defined the concept of experienced fatigue. The most common research-question reported on was prevalence and/ -or associations to fatigue. The least common was diagnostics (development or validation of fatigue assessment methods for a specific patient group). A large variety of methods were used to investigate experienced fatigue, impeding comparisons both within and across diagnoses.

CONCLUSION

This scoping review on the characteristics of fatigue research in rare diseases found a large variety of research on experienced fatigue. However, the minority of studies had investigation of experienced fatigue as a primary aim. There was large variation in how experienced fatigue was defined and also in how it was measured, both within and across diagnoses. More research on experienced fatigue is needed, both in children and adults with rare diseases. This review offers a basis for further research.

Glycogen storage disease in a young cat with heart failure

An 8‐month‐old domestic short‐haired female cat presented with acute tachypnea, poor growth, hypothermia, and lethargy. Thoracic radiography showed cardiomegaly with mild pleural effusion, and transthoracic echocardiography identified dilatation of both atria and left ventricular systolic dysfunction. Although clinical signs improved temporarily with treatment, the cat died of pulmonary edema 135 days after the first visit. At necropsy, the heart was grossly enlarged. Microscopic examination of the heart identified severe vacuolization of cardiac muscle cells in histologic sections stained with hematoxylin and eosin. Examination of periodic acid‐Schiff stained preparations of formalin‐fixed heart tissue disclosed coarse granules within vacuoles that disappeared on predigestion with diastase, indicating that they were glycogen. On the basis of these findings, a necropsy diagnosis of glycogen storage disease type II (Pompe disease) was made. This report is the first case of a young cat with clinical signs closely resembling infantile Pompe disease of humans.

Importance of Timely Treatment Initiation in Infantile-Onset Pompe Disease, a Single-Centre Experience

Classic infantile Pompe disease (IPD) is a rare lysosomal storage disorder characterized by severe hypertrophic cardiomyopathy and profound muscle weakness. Without treatment, death occurs within the first 2 years of life. Although enzyme replacement therapy (ERT) with alglucosidase alfa has improved survival, treatment outcome is not good in many cases and is largely dependent on age at initiation. The objective of the study was (a) to analyse the different stages in the diagnosis and specific treatment initiation procedure in IPD patients, and (b) to compare clinical and biochemical outcomes depending on age at ERT initiation (<1 month of age vs. <3 months of age). Here, we show satisfactory clinical and biochemical outcomes in two IPD patients after early treatment initiation before 3 months of life with immunomodulatory therapy in the ERT-naïve setting, with a high ERT dose from the beginning. Despite the overall good evolution, the patient who initiated treatment <1 month of life presented even better outcomes than the patient who started treatment <3 months of life, with an earlier normalization of hypertrophic cardiomyopathy, along with CK normalization, highlighting the importance of early treatment initiation in this progressive disease before irreversible muscle damage has occurred.

Molecular targets and approaches to restore autophagy and lysosomal capacity in neurodegenerative disorders

Autophagy is a catabolic process that promotes cellular fitness by clearing aggregated protein species, pathogens and damaged organelles through lysosomal degradation. The autophagic process is particularly important in the nervous system where post-mitotic neurons rely heavily on protein and organelle quality control in order to maintain cellular health throughout the lifetime of the organism. Alterations of autophagy and lysosomal function are hallmarks of various neurodegenerative disorders. In this review, we conceptualize some of the mechanistic and genetic evidence pointing towards autophagy and lysosomal dysfunction as a causal driver of neurodegeneration. Furthermore, we discuss rate-limiting pathway nodes and potential approaches to restore pathway activity, from autophagy initiation, cargo sequestration to lysosomal capacity.

Correlation of GAA Genotype and Acid-α-Glucosidase Enzyme Activity in Hungarian Patients with Pompe Disease

Pompe disease is caused by the accumulation of glycogen in the lysosomes due to a deficiency of the lysosomal acid-α-glucosidase (GAA) enzyme. Depending on residual enzyme activity, the disease manifests two distinct phenotypes. In this study, we assess an enzymatic and genetic analysis of Hungarian patients with Pompe disease. Twenty-four patients diagnosed with Pompe disease were included. Enzyme activity of acid-α-glucosidase was measured by mass spectrometry. Sanger sequencing and an MLPA of the GAA gene were performed in all patients. Twenty (83.33%) patients were classified as having late-onset Pompe disease and four (16.66%) had infantile-onset Pompe disease. Fifteen different pathogenic GAA variants were detected. The most common finding was the c.-32-13 T > G splice site alteration. Comparing the α-glucosidase enzyme activity of homozygous cases to the compound heterozygous cases of the c.-32-13 T > G disease-causing variant, the mean GAA activity in homozygous cases was significantly higher. The lowest enzyme activity was found in cases where the c.-32-13 T > G variant was not present. The localization of the identified sequence variations in regions encoding the crucial protein domains of GAA correlates with severe effects on enzyme activity. A better understanding of the impact of pathogenic gene variations may help earlier initiation of enzyme replacement therapy (ERT) if subtle symptoms occur. Further information on the effect of GAA gene variation on the efficacy of treatment and the extent of immune response to ERT would be of importance for optimal disease management and designing effective treatment plans.

Pain Phenotypes in Rare Musculoskeletal and Neuromuscular Diseases

For patients diagnosed with a rare musculoskeletal or neuromuscular disease, pain may transition from acute to chronic; the latter yielding additional challenges for both patients and care providers. We assessed the present understanding of pain across a set of ten rare, noninfectious, noncancerous disorders; Osteogenesis Imperfecta, Ehlers-Danlos Syndrome, Achondroplasia, Fibrodysplasia Ossificans Progressiva, Fibrous Dysplasia/McCune-Albright Syndrome, Complex Regional Pain Syndrome, Duchenne Muscular Dystrophy, Infantile- and Late-Onset Pompe disease, Charcot-Marie-Tooth Disease, and Amyotrophic Lateral Sclerosis. Through the integration of natural history, cross-sectional, retrospective, clinical trials, & case studies we described pathologic and genetic factors, pain sources, phenotypes, and lastly, existing therapeutic approaches. We highlight that while rare diseases possess distinct core pathologic features, there are a number of shared pain phenotypes and mechanisms that may be prospectively examined and therapeutically targeted in a parallel manner. Finally, we describe clinical and research approaches that may facilitate more accurate diagnosis, monitoring, and treatment of pain as well as elucidation of the evolving nature of pain phenotypes in rare musculoskeletal or neuromuscular illnesses.

Health and economic outcomes of newborn screening for infantile-onset Pompe disease

PURPOSE

To estimate health and economic outcomes associated with newborn screening (NBS) for infantile-onset Pompe disease in the United States.

METHODS

A decision analytic microsimulation model simulated health and economic outcomes of a birth cohort of 4 million children in the United States. Universal NBS and treatment was compared with clinical identification and treatment of infantile-onset Pompe disease. Main outcomes were projected cases identified, costs, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios (ICERs) over the life course.

RESULTS

Universal NBS for Pompe disease and confirmatory testing was estimated to cost an additional $26 million annually. Additional medication costs associated with earlier treatment initiation were $181 million; however, $8 million in medical care costs for other services were averted due to delayed disease progression. Infants with screened and treated infantile-onset Pompe disease experienced an average lifetime increase of 11.66 QALYs compared with clinical detection. The ICER was $379,000/QALY from a societal perspective and $408,000/QALY from the health-care perspective. Results were sensitive to the cost of enzyme replacement therapy.

CONCLUSION

Newborn screening for Pompe disease results in substantial health gains for individuals with infantile-onset Pompe disease, but with additional costs.

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

ABSTRACT

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.

Orofacial features and pediatric dentistry in the long-term management of Infantile Pompe Disease children

Background

Glycogen storage disease type II (GSDII) or Pompe disease is a rare autosomal recessive metabolic disorder that leads to intracellular glycogen storage in many tissues, mainly in skeletal muscle, heart and liver. Facial muscle weakness and altered craniofacial growth are very common in Pompe disease children. In this paper we describe the orofacial features in two children affected by GSDII and illustrate a multidisciplinary approach that involved enzyme replace therapy, non-invasive ventilation (NIV) and pediatric dentistry with 5-year follow-up.

Results

Two Infantile Pompe Disease children were examined by a pediatric dentist at the age of 4 and 5 years old respectively. The orofacial examination showed typical facies with similar features: hypotonia of facial and tongue muscles, lip incompetence, narrow palate with reduction in transversal dimension of the upper dental arch, macroglossia, low position of the tip of the tongue, concave profile, Class III malocclusion with hypoplasia of maxillary-malar area and mandibular prognathism. Myofunctional therapy and orthodontic treatment consisted in oral muscle exercises associated to intraoral and extraoral orthodontic devices. NIV facial mask was substituted with a nasal pillow mask in order to avoid external pressure on the mid-face which negatively influences craniofacial growth.

Conclusions

This paper evidences that the pediatric dentist plays an important role in craniofacial growth control, oral function rehabilitation and, therefore, in the improvement of the quality of life of Pompe children and their families. Therefore an early pediatric dental evalutation should be included in the multidisciplinary management of children suffering from Infantile Pompe Disease.

Pompe disease: pathogenesis, molecular genetics and diagnosis

Pompe disease (PD) is a rare autosomal recessive disorder caused by mutations in the GAA gene, localized on chromosome 17 and encoding for acid alpha-1,4-glucosidase (GAA). Currently, more than 560 mutations spread throughout GAA gene have been reported. GAA catalyzes the hydrolysis of α-1,4 and α-1,6-glucosidic bonds of glycogen and its deficiency leads to lysosomal storage of glycogen in several tissues, particularly in muscle. PD is a chronic and progressive pathology usually characterized by limb-girdle muscle weakness and respiratory failure. PD is classified as infantile and childhood/adult forms. PD patients exhibit a multisystemic manifestation that depends on age of onset.

Early diagnosis is essential to prevent or reduce the irreversible organ damage associated with PD progression. Here, we make an overview of PD focusing on pathogenesis, clinical phenotypes, molecular genetics, diagnosis, therapies, autophagy and the role of miRNAs as potential biomarkers for PD.

A Newborn with Infantile-Onset Pompe Disease Improving after Administration of Enzyme Replacement Therapy: Case Report

Pompe disease (PD) is an autosomal recessive lysosomal storage disorder caused by a deficiency of acid α-1,4-glucosidase enzyme (GAA). PD has two forms, namely the infantile-onset and the late-onset form. In untreated cases, infantile-onset form usually leads to cardio-respiratory failure and death in the first year of life. Herein, we report a newborn with infantile-onset PD characterized by muscular hypotonia, respiratory distress, hypertrophic cardiomyopathy, hepatomegaly, elevated serum enzyme levels of aspartate aminotransferase of 117 IU/L (three times the normal value), alanine aminotransferase of 66 IU/L (1.8 times the normal value), lactate dehydrogenase of 558 IU/L (1.2 times the normal value), and creatine kinase >5,000 IU/L (16 times the normal value). Dried blood spot testing was performed and revealed decreased GAA enzymatic activity (0.07 nmol/mL/h, normal 0.93–7.33 nmol/mL/h). GAA gene analysis performed for confirming the diagnosis showed homozygous mutation c.896T >C (p.Leu299Pro). Initiation of enzyme replacement therapy (ERT) (ERT; 20 mg/kg, once every week) at 28 days of age resulted in weaning off from respiratory support within 1 week after treatment, normalization of cardiac abnormalities, and normal neuromotor development in the 16th month of age. Early diagnosis and early treatment with ERT, especially in the neonatal period, is of great importance to improve cardiac function and motor development in infantile-onset PD.

A non-invasive diagnostic assay for rapid detection and characterization of aberrant mRNA-splicing by nonsense mediated decay inhibition

BACKGROUND

Interpretation of genetic variants detected by sequencing of genomic DNA, which may cause splicing defects, regularly requires mRNA analysis. Usually, only bioinformatic testing is provided, because simple and non-invasive assay protocols are lacking. Furthermore, the detection of mis-splicing is often hampered by nonsense mediated mRNA decay (NMD).

METHODS

Starting from a case of Pompe disease with two potential splicing variants an assay for the analysis of splice defects in general was developed. We analyzed the transcripts from the gene of interest by standard methods after short-term culture of the patient's lymphocytes in the presence and absence of a NMD inhibitor. Variant and wild type transcript expression were quantified by allele specific PCR in the patient and both parents and the expression ratio with/without NMD inhibition was calculated for each transcript.

RESULTS

NMD detection in lymphocytes was optimized and evaluated by analyzing a naturally occurring NMD transcript. Several compounds inhibited NMD successfully, including potential therapeutic agents. Sample storage for up to 4 days at room temperature prior to lymphocyte isolation did not affect results. In a proof of concept we identified two candidate variants as severe splicing variants in a patient with Pompe disease, but the strategy can also be used to screen for any mis-spliced transcripts prone to NMD.

CONCLUSIONS

We developed a simple, non-invasive assay for the detection and characterization of potential splicing variants. This is essential, because early and near-term diagnosis and disease classification is required to facilitate therapy in many genetic diseases.

Is it Pompe Disease? Australian diagnostic considerations

Pompe Disease is a spectrum disorder with an evolving phenotype in which diagnostic delay is common. Contributing factors include the rarity of the disorder, its wide clinical spectrum, signs and symptoms that overlap with those of other neuromuscular disorders, variable diagnostic approaches, lack of awareness of the clinical manifestations and difficulties in completing the diagnostic inventory. International updates and recommendations have been published providing diagnostic guidelines and management criteria. However, questions remain in the Australian setting. A panel (two neurologists, one clinical geneticist) reviewed the literature, examined clinical questions of relevance to the Australian setting, and developed a framework for the guidance. A wider panel, comprising the initial panel plus eight additional members, critiqued the framework and contributed clinical guidance within the scope of their respective areas of clinical expertise. The resultant expert consensus recommendations build on currently available data to propose an appropriate management framework incorporating the diagnosis, classification, therapeutic approach, multidisciplinary care, and on-going monitoring of patients with Pompe Disease in the Australian setting. It is hoped that diagnostic delay can be reduced with appropriate recourse to evidence-based insights and practical advice on diagnosis and management tailored to the Australian setting.

The First Year Experience of Newborn Screening for Pompe Disease in California

The California Department of Public Health started universal newborn screening for Pompe disease in August 2018 with a two-tier process including: (1) acid alpha-glucosidase (GAA) enzyme activity assay followed by, (2) GAA gene sequencing analysis. This study examines results from the first year of screening in a large and diverse screening population. With 453,152 screened newborns, the birth prevalence and GAA enzyme activity associated with various types of Pompe disease classifications are described. The frequency of GAA gene mutations and allele variants are reported. Of 88 screen positives, 18 newborns were resolved as Pompe disease, including 2 classic infantile-onset and 16 suspected late-onset form. The c.-32-13T>G variant was the most common pathogenic mutation reported. African American and Asian/Pacific Islander newborns had higher allele frequencies for both pathogenic and pseudodeficiency variants. After the first year of Pompe disease screening in California, the disease distribution in the population is now better understood. With the ongoing long-term follow-up system currently in place, our understanding of the complex genotype-phenotype relationships will become more evident in the future, and this should help us better understand the clinical significance of identified cases.

Treating lysosomal storage disorders: What have we learnt?

The first enzyme replacement therapy (ERT) for a lysosomal storage disorder (LSD) was approved in 1991 and we now have more than 25 years of experience of treating patients with type 1 Gaucher disease. Because of the remarkable success of this therapy, enormous effort and resource has gone into developing other ERTs, for Gaucher (where three different enzyme preparations have now been approved) and for other LSDs. We now have more than 10 years of clinical experience in using ERT to treat Gaucher, Fabry, Pompe and MPS I, II, and VI. This article aims to assess the real-life experience of a selection of these innovative and expensive treatments to see if they have met the high expectations which were set for them when they launched.

Screening for late-onset Pompe disease in Poland

OBJECTIVES

We aimed to screen for late-onset Pompe disease using the dried blood spot (DBS) test in a cohort of patients with limb-girdle muscle weakness or persistent hyperCKemia.

MATERIALS AND METHODS

Patients with limb-girdle muscle weakness, persistently elevated CK, rigid spine syndrome, dyspnoea, myalgia or sibling of the patient diagnosed with LOPD were included in the study. Acid α-glucosidase (GAA) activity was measured on DBS by tandem mass spectrometry and followed by genetic testing when required. Study was conducted between June 2014 and May 2017.

RESULTS

A total of 337 patients aged 32.2 years (range 2-80) were included in the study. Late-onset Pompe disease was diagnosed in 10 patients (3.0% of tested cohort). All were compound heterozygotes with common c.32-13T>G mutation on one allele and missense or frameshift mutation on the other. Two of the mutations (c.1951delG and c.397T>G) were not reported previously. Seven of the patients started enzyme replacement therapy.

CONCLUSIONS

DBS test is a reliable method for screening for late-onset Pompe disease.

Comparison of recent pivotal recommendations for the diagnosis and treatment of late-onset Pompe disease using diagnostic nodes-the Pompe disease burden scale

Pompe disease is a rare autosomal-recessive disorder characterised by limb-girdle myopathy and respiratory weakness in the late-onset form (LOPD). Various mutations in the acid alpha-glucosidase gene lead to toxic lysosomal and extra-lysosomal glycogen accumulation in all organs due to ineffective glycogen clearance by the encoded enzyme. Only one randomized trial demonstrated beneficial effects of respiratory function and meters walked in the 6-min walking test with enzyme replacement therapy (ERT). These results were confirmed in several retrospective and prospective observations and in meta-analyses. Due to a potential lifelong therapy, moderate efficacy and high treatment costs time of ERT initiation and cessation is an ongoing matter of debate. So far, several national and international recommendations have been published with different criteria concerning diagnosis, initiation and cessation of ERT in LOPD. We therefore formally analysed recent published recommendations and consensus statements of LOPD using diagnostic nodes (DODES) as a special software tool. With DODES, an objective analysis becomes possible if the content of the recommendations is represented as algorithms using cross-compatible elements. This analysis formally disclosed both, areas of great heterogeneity and concordance for the diagnosis and management of LOPD and paved the way for a Pompe disease burden scale focussing on ERT initiation. According to this investigation further clinical research should concentrate on ERT in pre-symptomatic and severely affected LOPD patients and on cessation criteria for ERT as these issues are areas of international uncertainty and discordance.

Lysosomal storage disease overview

The lysosomal storage diseases (LSDs) are a group of inherited metabolic disorders that are caused for the most part by enzyme deficiencies within the lysosome resulting in accumulation of undegraded substrate. This storage process leads to a broad spectrum of clinical manifestations depending on the specific substrate and site of accumulation. Examples of LSDs include the mucopolysaccharidoses, mucolipidoses, oligosaccharidoses, Pompe disease, Gaucher disease, Fabry disease, the Niemann-Pick disorders, and neuronal ceroid lipofuscinoses. This review summarizes the main clinical features, diagnosis, and management of LSDs with an emphasis on those for which treatment is available.

Lysosomal storage disease overview

The lysosomal storage diseases (LSDs) are a group of inherited metabolic disorders that are caused for the most part by enzyme deficiencies within the lysosome resulting in accumulation of undegraded substrate. This storage process leads to a broad spectrum of clinical manifestations depending on the specific substrate and site of accumulation. Examples of LSDs include the mucopolysaccharidoses, mucolipidoses, oligosaccharidoses, Pompe disease, Gaucher disease, Fabry disease, the Niemann-Pick disorders, and neuronal ceroid lipofuscinoses. This review summarizes the main clinical features, diagnosis, and management of LSDs with an emphasis on those for which treatment is available.

Acute respiratory failure as presentation of late-onset Pompe disease complicating the diagnostic process as a labyrinth: a case report

Background

Acute respiratory failure can be triggered by several causes, either of pulmonary or extra-pulmonary origin. Pompe disease, or type II glycogen storage disease, is a serious and often fatal disorder, due to a pathological accumulation of glycogen caused by a defective activiy of acid α-glucosidase (acid maltase), a lysosomal enzyme involved in glycogen degradation. The prevalence of the disease is estimated between 1 in 40,000 to 1 in 300,000 subjects.

Case presentation

This case report describes a difficult diagnosis of late-onset Pompe disease (LOPD) in a 52 year old Caucasian woman with acute respiratory failure requiring orotracheal intubation and subsequent tracheostomy for long-term mechanical ventilation 24 h/day. Despite a complex diagnostic process including several blood tests, bronchoscopy with BAL, chest CT, brain NMR, electromyographies, only a muscle biopsy allowed to reach the correct diagnosis.

Discussion

The most frequent presentation of myopathies, including LOPD, is proximal limb muscle weakness. Respiratory related symptoms (dyspnea on effort, reduced physical capacity, recurrent infections, etc.) and respiratory failure are often evident in the later stages of the diseases, but they have been rarely described as the onset symptoms in LOPD. In our case, a third stage LOPD, the cooperation between pulmonologists and neurologists was crucial in reaching a correct diagnosis despite a very complex clinical scenario due to different confounding co-morbidities as potential causes of respiratory failure and an atypical presentation. In this patient, enzyme replacement therapy with infusion of alglucosidase alfa was associated with progressive reduction of ventilatory support to night hours, and recovery of autonomous walking.

Storage diseases with hypertrophic cardiomyopathy phenotype

Never judge a book by its cover, nor assume hypertrophic cardiomyopathy (HCM) as sarcomeric, as appearances can deceive. HCM phenocopies account for a 5–10% of the cases, mainly represented by storage diseases, flagged by the increasing prevalence of senile cardiac amyloid in developing countries. Multisystemic and heterogeneous presentation of these entities is a challenge for clinicians, and time delay in diagnosis is a major concern. Promising drugs and gene-specific tailored therapies are under development, therefore, more than ever, appropriate understanding of these conditions is mandatory for adequate early treatment and counselling.

In this review, storage disorders will be classified as extracellular and intracellular deposit storage diseases, focusing our attention on the most prevalent conditions from the cardiologist’s perspective.

Contractile activity attenuates autophagy suppression and reverses mitochondrial defects in skeletal muscle cells

Macroautophagy/autophagy is a survival mechanism that facilitates protein turnover in post-mitotic cells in a lysosomal-dependent process. Mitophagy is a selective form of autophagy, which arbitrates the selective recognition and targeting of aberrant mitochondria for degradation. Mitochondrial content in cells is the net balance of mitochondrial catabolism via mitophagy, and organelle biogenesis. Although the latter process has been well described, mitophagy in skeletal muscle is less understood, and it is currently unknown how these two opposing mechanisms converge during contractile activity. Here we show that chronic contractile activity (CCA) in muscle cells induced mitochondrial biogenesis and coordinately enhanced the expression of TFEB (transcription factor EB) and PPARGC1A/PGC-1α, master regulators of lysosome and mitochondrial biogenesis, respectively. CCA also enhanced the expression of PINK1 and the lysosomal protease CTSD (cathepsin D). Autophagy blockade with bafilomycin A1 (BafA) reduced mitochondrial state 3 and 4 respiration, increased ROS production and enhanced the accumulation of MAP1LC3B-II/LC3-II and SQSTM1/p62. CCA ameliorated this mitochondrial dysfunction during defective autophagy, increased PPARGC1A, normalized LC3-II levels and reversed mitochondrially-localized SQSTM1 toward control levels. NAC emulated the LC3-II reductions induced by contractile activity, signifying that a decrease in oxidative stress could represent a mechanism of autophagy normalization brought about by CCA. CCA enhances mitochondrial biogenesis and lysosomal activity, and normalizes autophagy flux during autophagy suppression, partly via ROS-dependent mechanisms. Thus, contractile activity represents a potential therapeutic intervention for diseases in which autophagy is inhibited, such as vacuolar myopathies in skeletal muscle, by establishing a healthy equilibrium of anabolic and catabolic pathways.

ABBREVIATIONS

AMPK: AMP-activated protein kinase; BafA: bafilomycin A1; BNIP3L: BCL2/adenovirus E1B interacting protein 3-like; CCA: chronic contractile activity; COX4I1: cytochrome c oxidase subunit 4I1; DMEM: Dulbecco's modified Eagle's medium; GFP: green fluorescent protein; LSD: lysosomal storage diseases; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MTORC1: mechanistic target of rapamycin kinase complex 1; NAC: N-acetylcysteine; PPARGC1A: peroxisome proliferative activated receptor, gamma, coactivator 1 alpha; PINK1: PTEN induced putative kinase 1; ROS: reactive oxygen species; SOD2: superoxide dismutase 2, mitochondrial; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB.

[Research advances in the diagnosis and treatment of Pompe disease]

Pompe disease, also called type II glycogen storage disease, is a rare autosomal recessive inherited disease caused by the storage of glycogen in lysosome due to acid α-glucosidase (GAA) deficiency, with the most severe conditions in the skeletal muscle, the myocardium, and the smooth muscle. Patients may have the manifestations of dyspnea and dyskinesia, with or without hypertrophic cardiomyopathy. GAA gene mutation has ethnic and regional differences, and new mutation sites are found with the advances in research. Gene analysis is the gold standard for the diagnosis of Pompe disease. Conventional methods, such as skin and muscle biopsies and dried blood spot test, have certain limitations for the diagnosis of this disease. In recent years, prenatal diagnosis and newborn screening play an important role in early diagnosis of this disease. Enzyme replacement therapy (ERT) has a satisfactory effect in the treatment of this disease, but it may lead to immune intolerance. New targeted gene therapy and modified ERT will be put into practice in the future. This article reviews the research advances in the diagnosis and treatment of Pompe disease.

Dnases in health and disease

DNA degradation is critical to healthy organism development and survival. Two nuclease families that play key roles in development and in disease are the Dnase1 and Dnase2 families. While these two families were initially characterized by biochemical function, it is now clear that multiple enzymes in each family perform similar, non-redundant roles in many different tissues. Most Dnase1 and Dnase2 family members are poorly characterized, yet their elimination can lead to a wide range of diseases, including lethal anemia, parakeratosis, cataracts and systemic lupus erythematosus. Therefore, understanding these enzyme families represents a critical field of emerging research. This review explores what is currently known about Dnase1 and Dnase2 family members, highlighting important questions about the structure and function of family members, and how their absence translates to disease.

An Official American Thoracic Society Workshop Report: Translational Research in Rare Respiratory Diseases

Rare respiratory diseases (RRDs) are a heterogeneous group of disorders that collectively represent a significant health care burden. In recent years, strong advocacy and policy initiatives have led to advances in the implementation of research and clinical care for rare diseases. The development of specialized centers and research networks has facilitated support for affected individuals as well as emerging programs in basic, translational, and clinical research. In selected RRDs, subsequent gains in knowledge have informed the development of targeted therapies and effective diagnostic tests, but many gaps persist. There was therefore a desire to identify the elements contributing to an effective translational research program in RRDs. To this end, a workshop was convened in October 2015 with a focus on the implementation of effective transnational research networks and collaborations aimed at developing novel diagnostic and therapeutic tools. Key elements included an emphasis on molecular pathogenesis, the continuing engagement of patient advocacy groups and policy makers, the effective use of preclinical models in the translational research pipeline, and the detailed phenotyping of patient cohorts. During the course of the workshop, current logistical and knowledge gaps were identified, and new solutions or opportunities were highlighted.