Newborn Screening for Fabry Disease in Northeastern Italy: Results of Five Years of Experience

Genome-wide expression analysis in a Fabry disease human podocyte cell line

Fabry disease (FD) is an X-linked lysosomal disease caused by an enzyme deficiency of alpha-galactosidase A (α-gal A). This deficiency leads to the accumulation of glycosphingolipids in lysosomes, resulting in a range of clinical symptoms. The complex pathogenesis of FD involves lysosomal dysfunction, altered autophagy, and mitochondrial abnormalities. Omics sciences, particularly transcriptomic analysis, comprehensively understand molecular mechanisms underlying diseases. This study focuses on genome-wide expression analysis in an FD human podocyte model to gain insights into the underlying mechanisms of podocyte dysfunction. Human control and GLA-edited podocytes were used. Gene expression data was generated using RNA-seq analysis, and differentially expressed genes were identified using DESeq2. Principal component analysis and Spearman correlation have explored gene expression trends. Functional enrichment and Reporter metabolite analyses were conducted to identify significantly affected metabolites and metabolic pathways. Differential expression analysis revealed 247 genes with altered expression levels in GLA-edited podocytes compared to control podocytes. Among these genes, 136 were underexpressed, and 111 were overexpressed in GLA-edited cells. Functional analysis of differentially expressed genes showed their involvement in various pathways related to oxidative stress, inflammation, fatty acid metabolism, collagen and extracellular matrix homeostasis, kidney injury, apoptosis, autophagy, and cellular stress response. The study provides insights into molecular mechanisms underlying Fabry podocyte dysfunction. Integrating transcriptomics data with genome-scale metabolic modeling further unveiled metabolic alterations in GLA-edited podocytes. This comprehensive approach contributes to a better understanding of Fabry disease and may lead to identifying new biomarkers and therapeutic targets for this rare lysosomal disorder.

Detection of α-Galactosidase A Reaction in Samples Extracted from Dried Blood Spots Using Ion-Sensitive Field Effect Transistors

Fabry disease is a lysosomal storage disorder caused by a significant decrease in the activity or absence of the enzyme α-galactosidase A. The diagnostics of Fabry disease during newborn screening are reasonable, due to the availability of enzyme replacement therapy. This paper presents an electrochemical method using complementary metal-oxide semiconductor (CMOS)-compatible ion-sensitive field effect transistors (ISFETs) with hafnium oxide-sensitive surfaces for the detection of α-galactosidase A activity in dried blood spot extracts. The capability of ISFETs to detect the reaction catalyzed by α-galactosidase A was demonstrated. The buffer composition was optimized to provide suitable conditions for both enzyme and ISFET performance. The use of ISFET structures as sensor elements allowed for the label-free detection of enzymatic reactions with melibiose, a natural substrate of α-galactosidase A, instead of a synthetic fluorogenic one. ISFET chips were packaged with printed circuit boards and microfluidic reaction chambers to enable long-term signal measurement using a custom device. The packaged sensors were demonstrated to discriminate between normal and inhibited GLA activity in dried blood spots extracts. The described method offers a promising solution for increasing the widespread distribution of newborn screening of Fabry disease.

Current Status of Newborn Bloodspot Screening Worldwide 2024: A Comprehensive Review of Recent Activities (2020-2023)

Newborn bloodspot screening (NBS) began in the early 1960s based on the work of Dr. Robert "Bob" Guthrie in Buffalo, NY, USA. His development of a screening test for phenylketonuria on blood absorbed onto a special filter paper and transported to a remote testing laboratory began it all. Expansion of NBS to large numbers of asymptomatic congenital conditions flourishes in many settings while it has not yet been realized in others. The need for NBS as an efficient and effective public health prevention strategy that contributes to lowered morbidity and mortality wherever it is sustained is well known in the medical field but not necessarily by political policy makers. Acknowledging the value of national NBS reports published in 2007, the authors collaborated to create a worldwide NBS update in 2015. In a continuing attempt to review the progress of NBS globally, and to move towards a more harmonized and equitable screening system, we have updated our 2015 report with information available at the beginning of 2024. Reports on sub-Saharan Africa and the Caribbean, missing in 2015, have been included. Tables popular in the previous report have been updated with an eye towards harmonized comparisons. To emphasize areas needing attention globally, we have used regional tables containing similar listings of conditions screened, numbers of screening laboratories, and time at which specimen collection is recommended. Discussions are limited to bloodspot screening.

Diagnosis of Fabry Disease Using Alpha-Galactosidase A Activity or LysoGb3 in Blood Fails to Identify Up to Two Thirds of Female Patients

Anderson-Fabry disease is a lysosomal storage disorder caused by mutations in the GLA gene, which encodes the enzyme α-galactosidase A. The GLA gene is located on the X-chromosome, causing an X-linked pathology: due to lyonization, female patients usually manifest a variable symptomatology, ranging from asymptomatic to severe phenotypes. The confirmation of the clinical diagnosis of Fabry disease, achieved by measuring α-galactosidase A activity, which is usually the first test used, shows differences between male and female patients. This assay is reliable in male patients with causative mutations in the GLA gene, in whom the enzymatic activity is lower than normal values; on the other hand, in female Fabry patients, the enzymatic activity is extremely variable between normal and pathological values. These fluctuations are also found in female patients' blood levels of globotriaosylsphingosine (LysoGb3) for the same reason. In this paper, we present a retrospective study conducted in our laboratories on 827 Fabry patients with causative mutations in the GLA gene. Our results show that 100% of male patients had α-galactosidase A activity below the reference value, while more than 70% of female patients had normal values. It can also be observed that almost half of the female patients with pathogenic mutations in the GLA gene showed normal values of LysoGb3 in blood. Furthermore, in women, blood LysoGb3 values can vary over time, as we show in a clinical case presented in this paper. Both these tests could lead to missed diagnoses of Fabry disease in female patients, so the analysis of the GLA gene represents the main diagnostic test for Fabry disease in women to date.

Fabry disease: a rare disorder calling for personalized medicine

Fabry Disease (FD) is a genetic disease caused by a deficiency in the activity of lysosomal galactosidase A (α-GalA), an enzyme responsible for the catabolism of globotriaosylceramide (Gb3). Since lysosomes are present throughout the body and play a crucial role in catabolism and recycling of cytosolic compounds, FD can affect multiple organs and result in various symptoms, including renal, cardiovascular, neurological, cutaneous, and ophthalmic manifestations. Due to the nonspecific symptoms and the rarity of FD, it is often diagnosed late in life. However, introducing targeted therapies such as enzyme replacement therapy (ERT) and chaperone therapy has significantly improved FD's natural history and prognosis by restoring α-GalA enzyme activity. Despite the advancements, there are limitations to the currently available therapies, which has prompted research into new potential treatments for FD, including alternative forms of enzyme replacement therapy, substrate reduction therapy, mRNA therapy, and genetic therapy. In this review, we analyze the epidemiology, pathophysiology, and treatment of FD, with particular emphasis on promising therapeutic opportunities that could shift the treatment of this rare disease from a standardized to a personalized approach soon.

Experience with cascade screening: A comprehensive family pedigree analysis of two index patients with Fabry disease

The wide range of clinical symptoms observed in patients with Fabry disease (FD) often leads to delays in diagnosis and initiation of treatment. Delayed initiation of therapy may result in end-organ damage, such as chronic renal failure, hypertrophic cardiomyopathy, and stroke. Although some tools are available to identify undiagnosed patients, new comprehensive screening methods are needed. In this study, the outcomes of the cascade screening applied to three index cases with FD from 2 familes were investigated. In the pedigree analysis, 280 individuals were included; out of them, 131 individuals underwent genetic testing and cascade screening for FD. During the screening program, a total of 45 individuals were diagnosed, with a diagnostic ratio of 1:15. The average age at diagnosis for all individuals was 30.9 ± 17.7 years, and %25 were pediatric cases (mean age 9.5 ± 5.9 years). Thirty affected relatives were diagnosed from the two index cases in Family 1 and 15 individuals were diagnosed from one index case in Family 2. There were 13 consanguineous marriages observed among 2 pedigres, in two both spouses  were affected, leading to two homozygous affected daughters in one couple. In regions where there is a high prevalence of consanguineous marriages, implementing the cascade screening approach to identify all individuals at risk can be beneficial for patients with FD, specifically women and children.

Ultra-rare ultra-care: Assessing the impact of caring for children with ultra rare diseases

BACKGROUND

We sought to assesses the impact of caring for children with ultra rare diseases (URDs) on family carers and to analyse the way these experiences differ among the caregivers of children diagnosed through prenatal or newborn screening, and those with symptom-based diagnosis.

METHODS

A total of 200 caregivers of 219 URDs children completed an on-line survey regarding the challenges and experiences of caregivers of URDs children.

RESULTS

The majority of URD caregivers felt burdened by their children's health problems, emotional and behavioural changes. 46.5% reported feelings of care overload, 43% coped poorly with the stress, and many experienced a variety of feelings of distress towards the role of caregiver. While most caregivers struggled with the diagnostic odyssey and were dissatisfied with the healthcare services for URD children, caregivers of children diagnosed through prenatal or newborn screening were significantly less burdened than the parents of children with symptom-based diagnoses.

CONCLUSION

Although caregivers of URDs children experience physical and emotional strain, they are often neglected by the healthcare system. A bio-psychosocial approach to URDs should therefore also include family caregivers' physical and psychosocial needs. Apart from financial and emotional support, enhancing access to genetic testing and newborn screening should be prioritised.

Light and Shadows in Newborn Screening for Lysosomal Storage Disorders: Eight Years of Experience in Northeast Italy

In the last two decades, the development of high-throughput diagnostic methods and the availability of effective treatments have increased the interest in newborn screening for lysosomal storage disorders. However, long-term follow-up experience is needed to clearly identify risks, benefits and challenges. We report our 8-year experience of screening and follow-up on about 250,000 neonates screened for four lysosomal storage diseases (Pompe disease, mucopolysaccharidosis type I, Fabry disease, Gaucher disease), using the enzyme activity assay by tandem mass spectrometry, and biomarker quantification as a second-tier test. Among the 126 positive newborns (0.051%), 51 infants were confirmed as affected (positive predictive value 40%), with an overall incidence of 1:4874. Of these, three patients with infantile-onset Pompe disease, two with neonatal-onset Gaucher disease and four with mucopolysaccharidosis type I were immediately treated. Furthermore, another four Gaucher disease patients needed treatment in the first years of life. Our study demonstrates the feasibility and effectiveness of newborn screening for lysosomal storage diseases. Early diagnosis and treatment allow the achievement of better patient outcomes. Challenges such as false-positive rates, the diagnosis of variants of uncertain significance or late-onset forms and the lack of treatment for neuronopathic forms, should be addressed.

A new multiplex analysis of glucosylsphingosine and globotriaosylsphingosine in dried blood spots by tandem mass spectrometry

Background

Gaucher's and Fabry's disease are two of the most common treatable lysosomal storage diseases, and have a wide spectrum of clinical symptoms. Early detection is important, because timely initiation of treatments can improve the disease status and prevent complications. However disease manifestations develop in childhood, diagnosis is delayed until adulthood partly due to the limitations of the currently used diagnostic pathway. The aim of this research is to develop and validate a multiplex assay and defining reference ranges, which do not exist at this moment, to improve and facilitate the entire diagnostic work up and enable treatment in an earlier stage of disease.

Methods and findings

Biomarkers glucosylsphingosine (GlcSph) and globotriaosylsphingosine (Lyso-Gb3) were detected and quantified using LC-MS/MS on dried blood spots. We developed an improved and new extraction method that allowed to measure GlcSph and Lyso-Gb3 in a multiplex analytical platform. After validation of the method, samples of 1480 individuals with normal enzymatic activity were collected to determine age and gender-related reference ranges.Our combination method showed a good linearity, precision, accuracy and limit of quantification with lack of carry-over following the specific international CLSI guidelines. The suggested protocol is robust, efficient, sensitive, specific, comprehensive and relatively cheap in order to accelerate the diagnostic process for both lysosomal storage diseases. The samples, with normal enzymatic activity, defined statistical relevant and clinical correct reference ranges for each specific age group by gender.

Conclusion

We report a multiplex LC-MS/MS method and relevant reference ranges that are appropriate for the targeted screening, diagnosis and follow-up of Fabry and Gaucher disease.

c.376A>G, (p.Ser126Gly) Alpha-Galactosidase A mutation induces ER stress, unfolded protein response and reduced enzyme trafficking to lysosome: Possible relevance in the pathogenesis of late-onset forms of Fabry Disease

Fabry Disease (FD) (OMIM 301500) is a metabolic X-linked inherited lysosomal storage disorder that results from the deficient activity of Alpha-Galactosidase A (Alpha-Gal), a lysosomal hydrolase that cleaves neutral glycosphingolipids with terminal N-linked galactosyl moieties, mainly globotriaosylceramides (Gb3). The enzyme, encoded by a 12-kb gene mapping on the long arm (Xq22.1 region) of the X chromosome, is constituted by a glycosylated subunit of approximately 55 kD, synthesized as an inactive precursor that undergoes maturation in endoplasmic reticulum (ER) and Golgi apparatus before being delivered to the lysosome to form a functional dimer. The gene is comprised of seven exons and, so far, >1000 different mutations have been described as associated to FD (www.dbfgp.org/dbFgp/fabry/FabryGP.htm). Clinical phenotypes are divided in two main classes, classic or non-classic, based on clinical and biochemical findings. Non-classic FD, usually recognized as late-onset forms with oligosymptomatic phenotype, presents with symptoms restricted solely to cardiocytes, kidneys or brain associated to missense misfolding mutations. In the group of the non-classic FD, special attention should be given to patients carrying the c.376A > G (p.Ser126Gly) mutation. The lack of clear experimental evidences on its pathogenetic role, despite the clinical pictures of the patients with severe ischaemic lesions, renal involvement and acroparesthesias, led many authors to classify this mutation as inconsistent, non-pathogenetic, and consequently not eligible to the current pharmacological treatments for FD. To shed light on the cellular processes affected by this mutation and to assess if the biochemical pathways involved with, could really have a significant pathogenetic impact, we studied the mutation in silico and in COS-7 and HEK 293 cell models. We found p.Ser126Gly, even retaining both high degree of synthesis and residual activity, is mostly stacked into the ER inducing unfolded protein response (UPR) with reduced trafficking to the lysosome. These data strongly suggest that p.Ser126Gly could trigger a pathogenetic mechanism different from the classic and well assessed increased turnover with loss of biological activity described for other missense mutations. This mechanism seems mainly related to a negative gain of function, with ER retention and UPR activation and could lead, via inflammation and/or apoptosis, to irreversible cell damage.

Clinical utility of urinary mulberry bodies/cells testing in the diagnosis of Fabry disease

Introduction

Variants in the galactosidase alpha (GLA) gene cause Fabry disease (FD), an X-linked lysosomal storage disorder caused by α-galactosidase A (α-GAL) deficiency. Recently, disease-modifying therapies have been developed, and simple diagnostic biomarkers for FD are required to initiate these therapies in the early stages of the disease. Detection of urinary mulberry bodies and cells (MBs/MCs) is beneficial for diagnosing FD. However, few studies have evaluated the diagnostic accuracy of urinary MBs/MCs in FD. Herein, we retrospectively evaluated the diagnostic ability of urinary MBs/MCs for FD.

Methods

We analyzed the medical records of 189 consecutive patients (125 males and 64 females) who underwent MBs/MCs testing. Out of these, two female patients had already been diagnosed with FD at the time of testing, and the remaining 187 patients were suspected of having FD and underwent both GLA gene sequencing and/or α-GalA enzymatic testing.

Results

Genetic testing did not confirm the diagnosis in 50 females (26.5%); hence, they were excluded from the evaluation. Two patients were previously diagnosed with FD, and sixteen were newly diagnosed. Among these 18 patients, 15, including two who had already developed HCM at diagnosis, remained undiagnosed until targeted genetic screening of at-risk family members of patients with FD was performed. The accuracy of urinary MBs/MCs testing exhibited a sensitivity of 0.944, specificity of 1, positive predictive value of 1, and negative predictive value of 0.992.

Conclusions

MBs/MCs testing is highly accurate in diagnosing FD and should be considered during the initial evaluation prior to genetic testing, particularly in female patients.

Consensus recommendations for the treatment and management of patients with Fabry disease on migalastat: a modified Delphi study

Objective

Fabry disease is a progressive disorder caused by deficiency of the α-galactosidase A enzyme (α-Gal A), leading to multisystemic organ damage with heterogenous clinical presentation. The addition of the oral chaperone therapy migalastat to the available treatment options for Fabry disease is not yet universally reflected in all treatment guidelines. These consensus recommendations are intended to provide guidance for the treatment and monitoring of patients with Fabry disease receiving migalastat.

Methods

A modified Delphi process was conducted to determine consensus on treatment decisions and monitoring of patients with Fabry disease receiving migalastat. The multidisciplinary panel comprised 14 expert physicians across nine specialties and two patients with Fabry disease. Two rounds of Delphi surveys were completed and recommendations on the use of biomarkers, multidisciplinary monitoring, and treatment decisions were generated based on statements that reached consensus.

Results

The expert panel reached consensus agreement on 49 of 54 statements, including 16 that reached consensus in round 1. Statements that reached consensus agreement are summarized in recommendations for migalastat treatment and monitoring, including baseline and follow-up assessments and frequency. All patients with Fabry disease and an amenable mutation may initiate migalastat treatment if they have evidence of Fabry-related symptoms and/or organ involvement. Treatment decisions should include holistic assessment of the patient, considering clinical symptoms and organ involvement as well as patient-reported outcomes and patient preference. The reliability of α-Gal A and globotriaosylsphingosine as pharmacodynamic response biomarkers remains unclear.

Conclusion

These recommendations build on previously published guidelines to highlight the importance of holistic, multidisciplinary monitoring for patients with Fabry disease receiving migalastat, in addition to shared decision-making regarding treatments and monitoring throughout the patient journey. GRAPHICAL ABSTRACT.

Population Frequency of Undiagnosed Fabry Disease in the General Population

Introduction

Fabry disease is an X-linked disorder that results from pathogenic GLA variants and can now be treated. Most studies of its population frequency have examined only males or attendees at kidney failure or cardiac clinics. This study determined the prevalence of undiagnosed Fabry disease from predicted pathogenic GLA variants in the general population.

Methods

The Genome Aggregation Database (gnomAD) was examined for predicted pathogenic GLA variants based on variant rarity (≤5), and transcript effect in 4 computational tools (CADD >20, PP2 >0.95, SIFT <0.05, Mutation Taster - Disease-causing) and amino acid conservation in vertebrates in a Clustal.

Results

Predicted pathogenic variants in GLA occurred in 1 in 3225 of the gnomAD population and 1 in 3478 of its control subset. Predicted pathogenic variants were more common in women than expected (3.1:1), which is consistent with men being excluded from gnomAD because of Fabry complications. Predicted pathogenic variants were not found in members of this cohort with South Asian, Ashkenazim, or Finnish ancestries. Variants identified as pathogenic in the Fabry database were found in 1 in 2651 individuals of the gnomAD database and pathogenic variants from ClinVar in 1 in 4420.

Discussion

The population frequency of 1 in 3225 for undiagnosed men and women with Fabry disease still represents an underestimate because our pathogenicity criteria were rigorous, the cohort did not include already-diagnosed individuals, and whole exome sequencing does not detect intronic variants and large deletions. This study confirms that Fabry disease is more common than previously recognized and still underdiagnosed especially in women.

Global reach of over 20 years of experience in the patient-centered Fabry Registry: Advancement of Fabry disease expertise and dissemination of real-world evidence to the Fabry community

Fabry disease (FD, α-galactosidase A deficiency) is a rare, progressive, complex lysosomal storage disorder affecting multiple organ systems with a diverse spectrum of clinical phenotypes, particularly among female patients. Knowledge of its clinical course was still limited in 2001 when FD-specific therapies first became available and the Fabry Registry (NCT00196742; sponsor: Sanofi) was initiated as a global observational study. The Fabry Registry has now been operational for over 20 years, overseen by expert Boards of Advisors, and has collected real-world demographic and longitudinal clinical data from more than 8000 individuals with FD. Leveraging the accumulating evidence base, multidisciplinary collaborations have resulted in the creation of 32 peer-reviewed scientific publications, which have contributed to the greatly expanded knowledge on the onset and progression of FD, its clinical management, the role of sex and genetics, the outcomes of enzyme replacement therapy with agalsidase beta, and prognostic factors. We review how the Fabry Registry has evolved from its inception to become the largest global source of real-world FD patient data, and how the generated scientific evidence has helped to better inform the medical community, individuals living with FD, patient organizations, and other stakeholders. The patient-centered Fabry Registry fosters collaborative research partnerships with the overarching goal of optimizing the clinical management of patients with FD and is well positioned to add to its past achievements.

Newborn Screening for Fabry Disease: Current Status of Knowledge

Fabry disease is an X-linked progressive lysosomal disorder, due to α-galactosidase A deficiency. Patients with a classic phenotype usually present in childhood as a multisystemic disease. Patients presenting with the later onset subtypes have cardiac, renal and neurological involvements in adulthood. Unfortunately, the diagnosis is often delayed until the organ damage is already irreversibly severe, making specific treatments less efficacious. For this reason, in the last two decades, newborn screening has been implemented to allow early diagnosis and treatment. This became possible with the application of the standard enzymology fluorometric method to dried blood spots. Then, high-throughput multiplexable assays, such as digital microfluidics and tandem mass spectrometry, were developed. Recently DNA-based methods have been applied to newborn screening in some countries. Using these methods, several newborn screening pilot studies and programs have been implemented worldwide. However, several concerns persist, and newborn screening for Fabry disease is still not universally accepted. In particular, enzyme-based methods miss a relevant number of affected females. Moreover, ethical issues are due to the large number of infants with later onset forms or variants of uncertain significance. Long term follow-up of individuals detected by newborn screening will improve our knowledge about the natural history of the disease, the phenotype prediction and the patients' management, allowing a better evaluation of risks and benefits of the newborn screening for Fabry disease.

An expert consensus on the recommendations for the use of biomarkers in Fabry disease

Fabry disease is an X-linked lysosomal storage disorder caused by the accumulation of glycosphingolipids in various tissues and body fluids, leading to progressive organ damage and life-threatening complications. Phenotypic classification is based on disease progression and severity and can be used to predict outcomes. Patients with a classic Fabry phenotype have little to no residual α-Gal A activity and have widespread organ involvement, whereas patients with a later-onset phenotype have residual α-Gal A activity and disease progression can be limited to a single organ, often the heart. Diagnosis and monitoring of patients with Fabry disease should therefore be individualized, and biomarkers are available to support with this. Disease-specific biomarkers are useful in the diagnosis of Fabry disease; non-disease-specific biomarkers may be useful to assess organ damage. For most biomarkers it can be challenging to prove they translate to differences in the risk of clinical events associated with Fabry disease. Therefore, careful monitoring of treatment outcomes and collection of prospective data in patients are needed. As we deepen our understanding of Fabry disease, it is important to regularly re-evaluate and appraise published evidence relating to biomarkers. In this article, we present the results of a literature review of evidence published between February 2017 and July 2020 on the impact of disease-specific treatment on biomarkers and provide an expert consensus on clinical recommendations for the use of those biomarkers.

Screening of Fabry disease in patients with an implanted permanent pacemaker

BACKGROUND

Anderson-Fabry disease (AFD) is an X-linked inherited lysosomal disease caused by a defect in the gene encoding lysosomal enzyme α-galactosidase A (GLA). Atrio-ventricular (AV) nodal conduction defects and sinus node dysfunction are common complications of the disease. It is not fully elucidated how frequently AFD is responsible for acquired AV block or sinus node dysfunction and if some AFD patients could manifest primarily with spontaneous bradycardia in general population. The purpose of study was to evaluate the prevalence of AFD in male patients with implanted permanent pacemaker (PM).

METHODS

The prospective multicentric screening in consecutive male patients between 35 and 65 years with implanted PM for acquired third- or second- degree type 2 AV block or symptomatic second- degree type 1 AV block or sinus node dysfunction was performed.

RESULTS

A total of 484 patients (mean age 54 ± 12 years at time of PM implantation) were enrolled to the screening in 12 local sites in Czech Republic. Out of all patients, negative result was found in 481 (99%) subjects. In 3 cases, a GLA variant was found, classified as benign: p.Asp313Tyr, p.D313Y). Pathogenic GLA variants (classical or non-classical form) or variants of unclear significance were not detected.

CONCLUSION

The prevalence of pathogenic variants causing AFD in a general population sample with implanted permanent PM for AV conduction defects or sinus node dysfunction seems to be low. Our findings do not advocate a routine screening for AFD in all adult males with clinically significant bradycardia.

Association of Fabry Disease with Hearing Loss, Tinnitus, and Sudden Hearing Loss: A Nationwide Population-Based Study

Hearing loss and the related otologic manifestations are receiving increased scrutiny as significant causes of morbidity in Fabry disease. However, the relative risks of auditory deficits among patients with Fabry disease relative to the general population without a diagnosis of Fabry disease have not been studied. This study aims to explore the associations between Fabry disease and hearing-related manifestations using a nationwide population-based dataset. We identified study patients for this cross-sectional study from the 2015−2017 claims databases of the Taiwan Longitudinal Health Insurance Database 2005. We first identified 2312 patients aged over 20 years with a diagnosis of Fabry disease. We used propensity score matching to select five comparison patients per patient with Fabry disease and 11,560 comparison patients without Fabry disease. We used multivariable logistic regressions to estimate the odds ratios (ORs) and corresponding 95% confidence intervals (CIs) for tinnitus, hearing loss, and sudden deafness among Fabry disease patients vs. comparison patients. Chi-square tests showed statistically significant differences between patients with and without Fabry disease in the prevalence rates of tinnitus (16.7% vs. 11.7%, p < 0.001), hearing loss (7.5% vs. 6.2%, p = 0.014) and sudden deafness (1.7% vs. 1.0%, p = 0.005). Multiple logistic regression revealed that patients with Fabry disease were more likely to suffer from tinnitus, hearing loss and sudden deafness, with adjusted odds ratios of 1.513 (95% CI = 1.336−1.713), 1.246 (95% CI = 1.047−1.483), and 1.681 (95% CI = 1.166−2.423), respectively. We found that Fabry disease is significantly associated with certain auditory manifestations, including hearing loss, sudden deafness, and tinnitus.

The Benefits of Family Screening in Rare Diseases: Genetic Testing Reveals 165 New Cases of Fabry Disease among At-Risk Family Members of 83 Index Patients

Background: Fabry disease (FD, OMIM #301500) is a rare, progressive, X-linked, inherited genetic disease caused by a functional deficiency of lysosomal α-galactosidase, leading to the accumulation of glycosphingolipids in virtually all of the body’s cell types and fluids. Patients with rare genetic diseases and non-specific symptoms often experience substantial diagnostic delays, which can negatively impact the prompt initiation of treatment. If FD is not treated specifically, end organ damage (such as chronic renal failure, hypertrophic cardiomyopathy with arrhythmia, and strokes) impairs quality of life and reduces life expectancy. Patients and Methods: For 83 consecutive patients with FD referred to the Russian reference center for lysosomal storage diseases, family trees were built and genetic testing (cascade genotyping) was offered to family members. Results: The pathogenic GLA variant associated with FD was identified for all 83 probands. Family testing using cascade genotyping enabled the identification of 165 additional cases of FD among the tested 331 at-risk family members. Discussion: This is the first study to have described family screening in a large Russian cohort of patients with FD and chronic kidney disease. Raising awareness of FD among clinicians is important for earlier diagnosis and specific treatment.

Exosome- and extracellular vesicle-based approaches for the treatment of lysosomal storage disorders

Cell-generated extracellular vesicles (EVs) are being engineered as biologically-inspired vehicles for targeted delivery of therapeutic agents to treat difficult-to-manage human diseases, including lysosomal storage disorders (LSDs). Engineered EVs offer distinct advantages for targeted delivery of therapeutics compared to existing synthetic and semi-synthetic nanoscale systems, for example with regard to their biocompatibility, circulation lifetime, efficiencies in delivery of drugs and biologics to target cells, and clearance from the body. Here, we review literature related to the design and preparation of EVs as therapeutic carriers for targeted delivery and therapy of drugs and biologics with a focus on LSDs. First, we introduce the basic pathophysiology of LDSs and summarize current approaches to diagnose and treat LSDs. Second, we will provide specific details about EVs, including subtypes, biogenesis, biological properties and their potential to treat LSDs. Third, we review state-of-the-art approaches to engineer EVs for treatments of LSDs. Finally, we summarize explorative basic research and applied applications of engineered EVs for LSDs, and highlight current challenges, and new directions in developing EV-based therapies and their potential impact on clinical medicine.

Newborn screening for Fabry disease in Oregon: Approaching the iceberg of A143T and variants of uncertain significance

Fabry disease newborn screening (NBS) has been ongoing in Oregon for over 41 months by first-tier enzyme quantitation and second-tier DNA testing. During that period the majority of abnormal referrals received (34/60) were for the presence of the controversial c.427G > A (p.Ala143Thr) aka A143T and the majority of non-A143T referrals were for other variants of uncertain significance (17/60) resulting in at least 32 infants with an inconclusive case outcome even after clinical evaluation and/or diagnostic testing. To date there has been no significant family history or onset of symptoms in individuals with an inconclusive outcome. Based on our experience, we have developed a framework for approaching A143T and other variants of uncertain clinical significance in an attempt to balance sensitivity with the unnecessary medicalization of healthy infants.

Challenging the traditional approach for interpreting genetic variants: Lessons from Fabry disease

Fabry disease (FD) is an X-linked genetic disease due to pathogenic variants in GLA. The phenotype varies depending on the GLA variant, alpha-galactosidase residual activity, patient's age and gender and, for females, X chromosome inactivation. Over 1000 variants have been identified, many through screening protocols more susceptible to disclose non-pathogenic variants or variants of unknown significance (VUS). This, together with the non-specificity of some FD symptoms, challenges physicians attempting to interpret GLA variants. The traditional way to interpreting pathogenicity is based on a combined approach using allele frequencies, genomic databases, global and disease-specific clinical databases, and in silico tools proposed by the American College of Medical Genetics and Genomics. Here, a panel of FD specialists convened to study how expertise may compare with the traditional approach. Several GLA VUS, highly controversial in the literature (p.Ser126Gly, p.Ala143Thr, p.Asp313Tyr), were re-analyzed through reviews of patients' charts. The same was done for pathogenic GLA variants with some specificities. Our data suggest that input of geneticists and physicians with wide expertise in disease phenotypes, prevalence, inheritance, biomarkers, alleles frequencies, disease-specific databases, and literature greatly contribute to a more accurate interpretation of the pathogenicity of variants, bringing a significant additional value over the traditional approach.

Lysosomal Storage Disorders: Molecular Basis and Therapeutic Approaches

Lysosomal storage disorders (LSDs) are a group of 60 rare inherited diseases characterized by a heterogeneous spectrum of clinical symptoms, ranging from severe intellectual disabilities, cardiac abnormalities, visceromegaly, and bone deformities to slowly progressive muscle weakness, respiratory insufficiency, eye defects (corneal clouding and retinal degeneration), and skin alterations [...].