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

Aseptic meningitis and Fabry disease

OBJECTIVE

Fabry disease is caused by enzymatic defects in alpha-galactosidase A that leads to the accumulation of glycosphingolipids throughout the body, resulting in a multisystemic disorder. The most common neurological manifestations are neuropathic pain, autonomic nervous system dysfunction and strokes, but some rarer neurological manifestations exist. Among these, aseptic meningitis is a possible complication. Our objectives were to measure the prevalence of this complication in a cohort of patients with Fabry disease, and to describe its clinical features.

METHODS

We conducted a retrospective review of Fabry disease patients followed at our tertiary referral center between 1995 and September 2023 with at least one episode of meningitis, and performed a systematic review to identify similar published cases.

RESULTS

Four patients out of 107 (3.7%) had at least one episode of aseptic meningitis. Our systematic review identified 25 other observations. The median age of these 29 patients was 29.0 years, the median cerebrospinal fluid leukocyte count was 24 cells/mm3 with a predominance of lymphocytes in 64.7% of cases. In 82.8% of the patients, the diagnosis of Fabry disease was unknown before the meningitis. Large artery stenosis was present in 17.2% of patients and 57.1% of patients had a recent stroke concomitant with the meningitis. Several differential diagnoses were evoked, such as multiple sclerosis or central nervous system vasculitis.

INTERPRETATION

Our study suggests that Fabry disease should be considered as a cause of aseptic meningitis. The pathophysiological mechanisms underlying meningeal inflammation remain largely unknown but may reflect the dysregulation of pro-inflammatory signaling pathways.

No evidence of Fabry disease in a patient with the new p.Met70Val GLA gene variant

BACKGROUND

Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by variants in GLA gene leading to deficient α-galactosidase A enzyme activity. This deficiency leads to the accumulation of glycosphingolipids, particularly globotriaosylceramide (Gb3), in various tissues and organs, which can result in life-threatening complications. The clinical presentation of the disease can vary from the "classic" phenotype with pediatric onset and multi-organ involvement to the "later-onset" phenotype, which presents with predominantly cardiac symptoms. In recent years, advances in screening studies have led to the identification of an increasing number of variants of unknown significance that have not yet been described, and whose pathogenic role remains undetermined.

METHODS

In this clinical report, we describe the case of an asymptomatic adult female who was found to have a new variant of unknown significance, p.Met70Val. Given the unknown pathogenic role of this variant, a thorough analysis of the potential organ involvement was conducted. The clinical data were analyzed retrospectively.

RESULTS

The analysis revealed that there were no signs of significant organ involvement, and the benignity of the variant was confirmed.

CONCLUSION

This case underscores the importance of a comprehensive evaluation of new variants of unknown significance to establish their pathogenicity accurately.

Pregnancy outcomes of Fabry disease in Austria (PROFABIA)-a retrospective cohort-study

BACKGROUND

Pregnancy and delivery outcomes in women with Fabry disease are not well described.

METHODS

Retrospective cohort-study of women with Fabry disease in Austria using a specific questionnaire and the Austrian Mother-Child Health Passport.

RESULTS

Out of a total of 44 enrolled women (median age at study entry 44 years, p25: 30, p75: 51), 86.4% showed signs and symptoms of Fabry disease with an increase in pain burden during pregnancy, primarily in women with moderate pain before pregnancy. Thirty-two of 44 women with Fabry disease reported a total of 70 pregnancies (median age at first pregnancy 24 years, p25: 21, p75: 31), 61 (87.1%) of which resulted in 64 live births including 3 sets of twins, six miscarriages (8.6%) in five women, and three induced abortions (4.3%) in two women. Risk factors for poor maternal and foetal outcomes during pregnancy, overrepresented in our cohort as compared to the general population, were hypertension (n = 10, 16.4%), proteinuria (n = 17, 27.9%) and smoking (n = 24, 39.3%). Preeclampsia was reported in 7 pregnancies (11.5%). Fifty-one (79.7%) children were born at term and 13 (20.3%) were preterm (including one neonatal death), with a median gestational age of 39 weeks (p25: 38, p75: 40) and delivery by C-section in 15 pregnancies (24.6%). Thirteen (20.3%) children presented with low birth weight and 18 (28.1%) were small for their gestational age. In comparison to global and national data-sets, preeclampsia, prematurity, low birth weight, being small for their gestational age as well as inpatient stay were significantly more common in patients with Fabry disease.

CONCLUSIONS

Our cohort-study in women with Fabry disease shows an increase of pain burden during pregnancies and clearly points to an increased risk for preeclampsia, prematurity, and neonates small for gestational age. With a substantial number of high-risk pregnancies, neonatal outcomes are somewhat worse in Fabry disease than in the general public. Thus, we provide valuable data enabling informed decision-making in pregnancy counselling for Fabry disease.

Phenotypic Expression and Outcomes in Patients with the p.Arg301Gln GLA Variant in Anderson-Fabry Disease

The p.Arg301Gln variant in the α -galactosidase A gene (GLA) has been poorly described in the literature. The few reports show controversial information, with both classical and nonclassical Anderson-Fabry Disease (AFD) presentation patterns. The aim of this study was to analyze the penetrance, clinical phenotype, and biochemical profile of an international cohort of patients carrying the p.Arg301Gln genetic variant in the GLA gene. This was an observational, international, and retrospective cohort case series study of patients carrying the p.Arg301Gln variant in the GLA gene associated with AFD disease. Forty-nine p.Arg301Gln GLA carriers, 41% male, were analyzed. The penetrance was 63% in the entire cohort and 1.5 times higher in men. The mean age of symptoms onset was 41 years; compared to women, men presented symptoms earlier and with a shorter delay to diagnosis. The typical clinical triad-cornea verticillate, neuropathic pain, and angiokeratomas-affected only 20% of the cohort, with no differences between genders. During follow-up, almost 20% of the patients presented some type of nonfatal cardiovascular and renal event (stroke, need for dialysis, heart failure, and arrhythmias requiring intracardiac devices), predominantly affecting men. Residual levels were the most common finding of α-GAL A enzyme activity, only a few women had a normal level; a small proportion of men had undetectable levels. The incidence of combined outcomes including all causes of death was 33%, and the cumulative incidence of all-cause mortality was 9% at the follow-up. Patients carrying the p.Arg301Gln GLA variant have a high penetrance, with predominantly cardiorenal involvement and clinical onset of the disease in middle age. Only a small proportion showed the classic clinical presentation of AFD. As in other X-linked diseases, males were more affected by severe cardiovascular and renal events. This genotype-phenotype correlation could be useful from a practical clinical point of view and for future decision making.

In vitro characterization of cells derived from a patient with the GLA variant c.376A>G (p.S126G) highlights a non-pathogenic role in Fabry disease

Fabry disease (FD) is a life-limiting disorder characterized by intracellular globotriaosylceramide (Gb3) accumulations. The underlying α-galactosidase A (α-GAL A) deficiency is caused by variants in the gene GLA. Variants of unknown significance (VUS) are frequently found in GLA and challenge clinical management. Here, we investigated a 49-year old man with cryptogenic lacunar cerebral stroke and the chance finding of the VUS S126G, who was sent to our center for diagnosis and initiation of a costly and life-long FD-specific treatment. We combined clinical examination with in vitro investigations of dermal fibroblasts (HDF), induced pluripotent stem cells (iPSC), and iPSC-derived sensory neurons. We analyzed α-GAL A activity in iPSC, Gb3 accumulation in all three cell types, and action potential firing in sensory neurons. Neurological examination and small nerve fiber assessment was normal except for reduced distal skin innervation. S126G iPSC showed normal α-GAL A activity compared to controls and no Gb3 deposits were found in all three cell types. Baseline electrophysiological characteristics of S126G neurons showed no difference compared to healthy controls as investigated by patch-clamp recordings. We pioneer multi-level cellular characterization of the VUS S126G using three cell types derived from a patient and provide further evidence for the benign nature of S126G in GLA, which is of great importance in the management of such cases in clinical practice.

Prevalence of Fabry disease and GLA variants in young patients with acute stroke: The challenge to widen the screening. The Fabry-Stroke Italian Registry

BACKGROUND

Fabry disease (FD) is a treatable X-linked lysosomal storage disorder caused by GLA gene variants leading to alpha-galactosidase A deficiency. FD is a rare cause of stroke, and it is still controversial whether in stroke patients FD should be searched from the beginning or at the end of the diagnostic workup (in cryptogenic strokes).

METHODS

Fabry-Stroke Italian Registry is a prospective, multicentric screening involving 33 stroke units. FD was sought by measuring α-galactosidase A activity (males) and by genetic tests (males with reduced enzyme activity and females) in patients aged 18-60 years hospitalized for TIA, ischemic stroke, or intracerebral hemorrhage. We diagnosed FD in patients with 1) already known pathogenic GLA variants; 2) novel GLA variants if additional clinical, laboratory, or family-derived criteria were present.

RESULTS

Out of 1906 patients, we found a GLA variant in 15 (0.79%; 95%CI 0.44-1.29) with a certain FD diagnosis in 3 (0.16%; 95%CI 0.03-0.46) patients, none of whom had hemorrhage. We identified 1 novel pathogenic GLA variant. Ischemic stroke etiologies in carriers of GLA variants were: cardioaortic embolism (33%), small artery occlusion (27%), other causes (20%), and undetermined (20%). Mild severity, recurrence, previous TIA, acroparesthesias, hearing loss, and small artery occlusion were predictors of GLA variant.

CONCLUSION

In this large multicenter cohort the frequency of FD and GLA variants was consistent with previous reports. Limiting the screening for GLA variants to patients with cryptogenic stroke may miss up to 80% of diagnoses. Some easily recognizable clinical features could help select patients for FD screening.

Diagnosing Fabry nephropathy: the challenge of multiple kidney disease

Fabry disease (FD) is an X-linked inherited lysosomal disorder due to a deficiency of the enzyme alpha-galactosidase A (α-gla) due to mutations in the GLA gene. These mutations result in plasma and lysosome accumulation of glycosphingolipids, leading to progressive organ damage and reduced life expectancy. Due to the availability of specific disease-modifying treatments, proper and timely diagnosis and therapy are essential to prevent irreversible complications. However, diagnosis of FD is often delayed because of the wide clinical heterogeneity of the disease and multiple organ involvement developing in variable temporal sequences. This observation is also valid for renal involvement, which may manifest with non-specific signs, such as proteinuria and chronic kidney disease, which are also common in many other nephropathies. Moreover, an additional confounding factor is the possibility of the coexistence of FD with other kidney disorders. Thus, suspecting and diagnosing FD nephropathy in patients with signs of kidney disease may be challenging for the clinical nephrologist. Herein, also through the presentation of a unique case of co-occurrence of autosomal dominant polycystic kidney disease and FD, we review the available literature on cases of coexistence of FD and other renal diseases and discuss the implications of these conditions. Moreover, we highlight the clinical, laboratory, and histological elements that may suggest clinical suspicion and address a proper diagnosis of Fabry nephropathy.

Endothelial Cell Dysfunction and Hypoxia as Potential Mediators of Pain in Fabry Disease: A Human-Murine Translational Approach

Fabry disease (FD) is caused by α-galactosidase A (AGAL) enzyme deficiency, leading to globotriaosylceramide accumulation (Gb3) in several cell types. Pain is one of the pathophysiologically incompletely understood symptoms in FD patients. Previous data suggest an involvement of hypoxia and mitochondriopathy in FD pain development at dorsal root ganglion (DRG) level. Using immunofluorescence and quantitative real-time polymerase chain reaction (qRT PCR), we investigated patient-derived endothelial cells (EC) and DRG tissue of the GLA knockout (KO) mouse model of FD. We address the question of whether hypoxia and mitochondriopathy contribute to FD pain pathophysiology. In EC of FD patients (P1 with pain and, P2 without pain), we found dysregulated protein expression of hypoxia-inducible factors (HIF) 1a and HIF2 compared to the control EC (p < 0.01). The protein expression of the HIF downstream target vascular endothelial growth factor A (VEGFA, p < 0.01) was reduced and tube formation was hampered in the P1 EC compared to the healthy EC (p < 0.05). Tube formation ability was rescued by applying transforming growth factor beta (TGFβ) inhibitor SB-431542. Additionally, we found dysregulated mitochondrial fusion/fission characteristics in the P1 and P2 EC (p < 0.01) and depolarized mitochondrial membrane potential in P2 compared to control EC (p < 0.05). Complementary to human data, we found upregulated hypoxia-associated genes in the DRG of old GLA KO mice compared to WT DRG (p < 0.01). At protein level, nuclear HIF1a was higher in the DRG neurons of old GLA KO mice compared to WT mice (p < 0.01). Further, the HIF1a downstream target CA9 was upregulated in the DRG of old GLA KO mice compared to WT DRG (p < 0.01). Similar to human EC, we found a reduction in the vascular characteristics in GLA KO DRG compared to WT (p < 0.05). We demonstrate increased hypoxia, impaired vascular properties, and mitochondrial dysfunction in human FD EC and complementarily at the GLA KO mouse DRG level. Our data support the hypothesis that hypoxia and mitochondriopathy in FD EC and GLA KO DRG may contribute to FD pain development.

Sex Differences in Anderson-Fabry Cardiomyopathy: Clinical, Genetic, and Imaging Analysis in Women

Anderson-Fabry Disease (AFD) is a rare, systemic lysosomal storage disease triggered by mutations in the GLA gene, leading to α-galactosidase A (α-Gal A) deficiency. The disease's X-linked inheritance leads to more severe, early-onset presentations in males, while females exhibit variable, often insidious, manifestations, notably impacting cardiac health. This study aims to examine gender-based AFD cardiac manifestations in correlation with the variant type: classical (CL), late-onset (LO), or variants of uncertain significance (VUS). We analyzed data from 72 AFD patients (53 females, 19 males) referred to the "G. Rodolico" University Hospital, employing enzyme activity measurements, genetic analysis, periodic lyso-Gb3 monitoring, comprehensive medical histories, and advanced cardiac imaging techniques. Statistical analysis was performed using SPSS version 26. Our AFD cohort, with an average age of 45 ± 16.1 years, comprised 12 individuals with hypertrophy (AFD-LVH) and 60 without (AFD-N). Women, representing about 75% of the subjects, were generally older than men (47.2 ± 16.2 vs. 38.8 ± 14.6, p = 0.046). In the female group, 17% had CL variants, 43.3% LO, and 39.6% had VUS, compared to 21.1%, 36.8%, and 31.6% in the male group, respectively. Females exhibited significantly higher α-Gal A values (median 7.9 vs. 1.8 nmol/mL/h, p < 0.001) and lower lyso-Gb3 levels (1.5 [IQR 1.1-1.7] vs. 1.9 [1.5-17.3] nmol/L, p = 0.02). Regarding the NYHA class distribution, 70% of women were in class I and 28% in class II, compared to 84% and 16% of men, respectively. Among women, 7.5% exhibited ventricular arrhythmias (10.5% in men), and 9.4% had atrial fibrillation (10.5% in men). Cardiac MRIs revealed fibrosis in 57% of examined women, compared to 87% of men. Even among patients without LVH, significant differences persisted in α-Gal A and lyso-Gb3 levels (p = 0.003 and 0.04), as well as LVMi (61.5 vs. 77.5 g/sqm, p = 0.008) and GLS values (-20% vs. -17%, p = 0.01). The analysis underscored older age, decreased lyso-Gb3 deposition, reduced hypertrophy, and lesser GLS compromise in females, suggesting later disease onset. Severe cardiac patterns were associated with classic variants, while more nuanced manifestations were noted in those with VUS. Early GLS impairment in males, irrespective of hypertrophy, emphasized the role of subclinical damage in AFD.

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.

Anderson-Fabry disease cardiomyopathy: an update on epidemiology, diagnostic approach, management and monitoring strategies

Anderson-Fabry disease (AFD) is an X-linked lysosomal storage disorder caused by deficient activity of the enzyme alpha-galactosidase. While AFD is recognized as a progressive multi-system disorder, infiltrative cardiomyopathy causing a number of cardiovascular manifestations is recognized as an important complication of this disease. AFD affects both men and women, although the clinical presentation typically varies by sex, with men presenting at a younger age with more neurologic and renal phenotype and women developing a later onset variant with more cardiovascular manifestations. AFD is an important cause of increased myocardial wall thickness, and advances in imaging, in particular cardiac magnetic resonance imaging and T1 mapping techniques, have improved the ability to identify this disease non-invasively. Diagnosis is confirmed by the presence of low alpha-galactosidase activity and identification of a mutation in the GLA gene. Enzyme replacement therapy remains the mainstay of disease modifying therapy, with two formulations currently approved. In addition, newer treatments such as oral chaperone therapy are now available for select patients, with a number of other investigational therapies in development. The availability of these therapies has significantly improved outcomes for AFD patients. Improved survival and the availability of multiple agents has presented new clinical dilemmas regarding disease monitoring and surveillance using clinical, imaging and laboratory biomarkers, in addition to improved approaches to managing cardiovascular risk factors and AFD complications. This review will provide an update on clinical recognition and diagnostic approaches including differentiation from other causes of increased ventricular wall thickness, in addition to modern strategies for management and follow-up.

Zebra-Sphinx: Modeling Sphingolipidoses in Zebrafish

Sphingolipidoses are inborn errors of metabolism due to the pathogenic mutation of genes that encode for lysosomal enzymes, transporters, or enzyme cofactors that participate in the sphingolipid catabolism. They represent a subgroup of lysosomal storage diseases characterized by the gradual lysosomal accumulation of the substrate(s) of the defective proteins. The clinical presentation of patients affected by sphingolipid storage disorders ranges from a mild progression for some juvenile- or adult-onset forms to severe/fatal infantile forms. Despite significant therapeutic achievements, novel strategies are required at basic, clinical, and translational levels to improve patient outcomes. On these bases, the development of in vivo models is crucial for a better understanding of the pathogenesis of sphingolipidoses and for the development of efficacious therapeutic strategies. The teleost zebrafish (Danio rerio) has emerged as a useful platform to model several human genetic diseases owing to the high grade of genome conservation between human and zebrafish, combined with precise genome editing and the ease of manipulation. In addition, lipidomic studies have allowed the identification in zebrafish of all of the main classes of lipids present in mammals, supporting the possibility to model diseases of the lipidic metabolism in this animal species with the advantage of using mammalian lipid databases for data processing. This review highlights the use of zebrafish as an innovative model system to gain novel insights into the pathogenesis of sphingolipidoses, with possible implications for the identification of more efficacious therapeutic approaches.

Clinical outcomes among young patients with Fabry disease who initiated agalsidase beta treatment before 30 years of age: An analysis from the Fabry Registry

BACKGROUND

Clinical manifestations of classic Fabry disease (α-galactosidase A deficiency) usually occur in childhood, while complications involving major organs typically develop in adulthood. Outcomes of Fabry-specific treatment among young patients have not been extensively reported. Our aim was to analyze clinical outcomes among patients aged 5-30 years at initiation of treatment with agalsidase beta using data from the Fabry Registry (NCT00196742, sponsor: Sanofi).

METHODS

Reported GLA variants were predicted to be associated with the classic phenotype or not classified in fabry-database.org. Linear mixed models were conducted to assess changes over ≥2-year follow-up in the estimated glomerular filtration rate (eGFR) stratified by low (LRI) and high (HRI) renal involvement (defined by proteinuria/albuminuria levels), and changes in interventricular septal thickness (IVST) and left ventricular posterior wall thickness (LVPWT) Z-scores stratified by median age at first treatment. Self-reports ('yes'/'no') of abdominal pain, diarrhea, chronic peripheral pain (denoting neuropathic pain), and acute pain crises at baseline were compared with reports after ≥0.5-year and ≥2.5-year follow-up using McNemar's test.

RESULTS

Male (n = 117) and female patients (n = 59) with LRI initiated treatment at a median age of 19.9 and 23.6 years, respectively, and were followed for a median of 6.3 and 5.0 years, respectively. The eGFR slopes were -1.18 (P_{from 0} <0.001) and -0.92 mL/min/1.73 m²/year (P_{from 0} = 0.040), respectively. Males with HRI (n = 23, median UPCR 1.0 g/g), who started treatment at a median age of 26.7 years, had an eGFR slope of -2.39 mL/min/1.73 m²/year (P_{from 0} <0.001; P_difference = 0.055, as compared with the slope of -1.18 mL/min/1.73 m²/year for LRI males) during a median follow-up of 5.6 years. Echocardiographic variables were stable among males, regardless of age, and among young females (median follow-up >5.5 years and ≥4.5 years, respectively). Older females (treatment initiation at median age 27.5 years) had a slope of LVPWT Z-scores of 0.18/year (n = 12, P_{from 0} = 0.028), whereas IVST Z-scores remained stable (n = 13, 0.10/year, P_{from 0} = 0.304) during a median follow-up of ≥3.7 years. These slopes did not significantly differ from slopes of younger females. Reports of chronic peripheral pain and acute pain crises by males, and of diarrhea and acute pain crises by females, significantly reduced after a median follow-up of ≥4.0 years. After a median follow-up of ≥5.4 years, reports of all four symptoms significantly decreased among males, whereas among females only reports of abdominal pain significantly decreased.

CONCLUSIONS

During sustained treatment with agalsidase beta in young Fabry patients with a predicted classic phenotype or with unclassified GLA variants with similar characteristics, the decline in eGFR was modest among male and female patients with LRI. The greater decline in eGFR among older, proteinuric (i.e., HRI) males may suggest a benefit of earlier treatment. Overall, echocardiographic variables remained stable, particularly among males and younger females. Significant reductions in symptom reports occurred primarily among males after longer follow-up and were less noticeable among females. These observed trends are suggestive of an overall improvement after treatment in young patients, but warrant larger longitudinal studies.

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.

Imaging of metabolic and overload disorders in tissues and organs

Metabolic and overload disorders are a heterogeneous group of relatively uncommon but important diseases. While imaging plays a key role in the early detection and accurate diagnosis in specific organs with a pivotal role in several metabolic pathways, most of these diseases affect different tissues as part of a systemic syndromes. Moreover, since the symptoms are often vague and phenotypes similar, imaging alterations can present as incidental findings, which must be recognized and interpreted in the light of further biochemical and histological investigations. Among imaging modalities, MRI allows, thanks to its multiparametric properties, to obtain numerous information on tissue composition, but many metabolic and accumulation alterations require a multimodal evaluation, possibly using advanced imaging techniques and sequences, not only for the detection but also for accurate characterization and quantification. The purpose of this review is to describe the different alterations resulting from metabolic and overload pathologies in organs and tissues throughout the body, with particular reference to imaging findings.

Nationwide screening of Fabry disease in patients with hypertrophic cardiomyopathy in Czech Republic

AIMS

Fabry disease (FD) is a rare X-linked genetic disorder caused by α-galactosidase A (AGALA) deficiency. Whereas 'classic' variant has multisystemic manifestation, the more recently described 'later-onset' variant is characterized by predominant cardiac involvement that often mimics hypertrophic cardiomyopathy (HCM).

METHODS AND RESULTS

Consecutive unrelated patients with HCM were screened for FD in 16 (out of 17) cardiac centres in the Czech Republic covering specialized cardiology care from June 2017 to December 2018. AGALA activity and globotriaosylsphingosine (lyso-Gb₃ ) levels were measured in all subjects using the dry blood spot method. FD was suspected in male patients with AGALA activity <1.2 μmol/h/L and in females with either low AGALA activity or lyso-Gb₃  > 3.5 ng/mL. Positive screening results were confirmed by genetic testing. We evaluated 589 patients (390 males, 66%) with HCM (mean maximal myocardial thickness 19.1 ± 4.3 mm). The average age was 58.4 ± 14.7 years. In total, 17 patients (11 males, 6 females) had a positive screening result, and subsequently, six of them (four males and two females) had a genetically confirmed pathogenic GLA mutation (total prevalence of 1.02%). Five of these patients were carrying the p.N215S mutation known to cause a typical later-onset cardiac FD.

CONCLUSIONS

We confirmed the prevalence of FD repeatedly reported in previous screening programmes (approximately 1% irrespective of gender) in a non-selected HCM population in Central Europe. Our findings advocate a routine screening for FD in all adult patients with HCM phenotype including both genders. The dry blood spot method used led to identification of clearly pathogenic variants.

An expert consensus on practical clinical recommendations and guidance for patients with classic Fabry disease

Fabry disease is an X-linked inherited lysosomal disorder that causes accumulation of glycosphingolipids in body fluids and tissues, leading to progressive organ damage and reduced life expectancy. It can affect both males and females and can be classified into classic or later-onset phenotypes. In classic Fabry disease, α-galactosidase A (α-Gal A) activity is absent or severely reduced and disease manifestations have an early onset that can affect multiple organs. In contrast, in later-onset Fabry disease, patients have residual α-Gal A activity and clinical features are primarily confined to the heart. Individualized therapeutic goals in Fabry disease are required due to varying phenotypes and patient characteristics, and the wide spectrum of disease severity. An international group of expert physicians convened to discuss and develop practical clinical recommendations for disease- and organ-specific therapeutic goals in Fabry disease, based on expert consensus and evidence identified through a structured literature review. Biomarkers reflecting involvement of various organs in adult patients with classic Fabry disease are discussed and consensus recommendations for disease- and organ-specific therapeutic goals are provided. These consensus recommendations should support the establishment of individualized approaches to the management of patients with classic Fabry disease by considering identification, diagnosis, and initiation of disease-specific therapies before significant organ involvement, as well as routine monitoring, to reduce morbidity, optimize patient care, and improve patient health-related quality of life.

Twenty years of the Fabry Outcome Survey (FOS): insights, achievements, and lessons learned from a global patient registry

Background

Patient registries provide long-term, real-world evidence that aids the understanding of the natural history and progression of disease, and the effects of treatment on large patient populations with rare diseases. The year 2021 marks the 20th anniversary of the Fabry Outcome Survey (FOS), an international, multicenter, observational registry (NCT03289065). The primary aims of FOS are to broaden the understanding of Fabry disease (FD), an X-linked lysosomal storage disorder, and to improve the clinical management of affected patients. Here, we review the history of FOS and the analyses and publications disseminated from the registry, and we discuss the contributions FOS studies have made in understanding FD.

Results

FOS was initiated in April 2001 and, as of January 2021, 4484 patients with a confirmed diagnosis and patient informed consent have been enrolled from 144 centers across 26 countries. Data from FOS have been published in nearly 60 manuscripts on a wide variety of topics relevant to FD. Analyses of FOS data have investigated the long-term effectiveness and safety of enzyme replacement therapy (ERT) with agalsidase alfa and its effects on morbidity and mortality, as well as the benefits of prompt and early treatment with agalsidase alfa on the progression of cardiomyopathy and the decline in renal function associated with FD. Based on analyses of FOS data, ERT with agalsidase alfa has also been shown to improve additional signs and symptoms of FD experienced by patients. FOS data analyses have provided a better understanding of the natural history of FD and the specific populations of women, children, and the elderly, and have provided practical tools for the study of FD. FOS has also provided methodology and criteria for assessing disease severity which contributed to the continuous development of medical practice in FD and has largely improved our understanding of the challenges and needs of long-term data collection in rare diseases, aiding in future rare disease real-world evidence studies.

Conclusion

FOS over the last 20 years has substantially increased the scientific knowledge around improved patient management of FD and continues to expand our understanding of this rare disease.

Fabry's Disease: The Utility of a Multidisciplinary Screening Approach

(1) Background: As a lysosomal storage disorder, Fabry’s disease (FD) shows variable clinical manifestations. We applied our multidisciplinary approach to identify any organ damage in a sample of adult patients with different pathogenic variants. (2) Methods: 49 participants (mean age 44.3 ± 14.2 years; 37 females), underwent a multidimensional clinical and instrumental assessment. (3) Results: At diagnosis, mean enzymatic activity was 5.2 ± 4.6 nM/mL/h in females and 1.4 ± 0.5 nM/mL/h in males (normal values > 3.0), whereas globotriaosylsphingosine was 2.3 ± 2.1 nM/L in females and 28.7 ± 3.5 nM/L in males (normal values < 2.0). Overall, cardiovascular, neurological, and audiological systems were the most involved, regardless of the variant detected. Patients with classic variants (10) showed typical multiorgan involvement and, in some cases, prevalent organ damage (cardiovascular, neurological, renal, and ocular). Those with late-onset variants (39) exhibited lower occurrence of multiorgan impairment, although some of them affected the cardiovascular and neurological systems more. In patients with lower enzymatic activity, the most frequent involvement was neurological, followed by peripheral vascular disease. (4) Conclusions: FD patients exhibited wide phenotypic variability, even at single-organ level, likely due to the individual genetic mutation, although other factors may contribute. Compared to the conventional management, a multidisciplinary approach, as that prompted at our Center, allows one to achieve early clinical detection and management.

Sphingosine-1-Phosphate Levels Are Higher in Male Patients with Non-Classic Fabry Disease

Fabry disease is an X-linked lysosomal disease in which defects in the alpha-galactosidase A enzyme activity lead to the ubiquitous accumulation of glycosphingolipids. Whereas the classic disease is characterized by neuropathic pain, progressive renal failure, white matter lesions, cerebral stroke, and hypertrophic cardiomyopathy (HCM), the non-classic phenotype, also known as cardiac variant, is almost exclusively characterized by HCM. Circulating sphingosine-1-phosphate (S1P) has controversially been associated with the Fabry cardiomyopathy. We measured serum S1P levels in 41 patients of the FFABRY cohort. S1P levels were higher in patients with a non-classic phenotype compared to those with a classic phenotype (200.3 [189.6−227.9] vs. 169.4 ng/mL [121.1−203.3], p = 0.02). In a multivariate logistic regression model, elevated S1P concentration remained statistically associated with the non-classic phenotype (OR = 1.03; p < 0.02), and elevated lysoGb3 concentration with the classic phenotype (OR = 0.95; p < 0.03). S1P levels were correlated with interventricular septum thickness (r = 0.46; p = 0.02). In a logistic regression model including S1P serum levels, phenotype, and age, age remained the only variable significantly associated with the risk of HCM (OR = 1.25; p = 0.001). S1P alone was not associated with cardiac hypertrophy but with the cardiac variant. The significantly higher S1P levels in patients with the cardiac variant compared to those with classic Fabry suggest the involvement of distinct pathophysiological pathways in the two phenotypes. S1P dosage could allow the personalization of patient management.