Fabry Nephropathy: An Evidence-Based Narrative Review

Case report: enzyme replacement therapy for Fabry disease presenting with proteinuria and ventricular septal thickening

Fabry disease (FD) is an uncommon, X-linked, lysosomal storage disease that causes defects in the glycosphingolipid metabolic pathway due to deficient or absent lysosomal α-galactosidase (α-Gal A) activity. This leads to the accumulation of globotriaosylceramide (GL-3) within lysosomes in a wide range of cells, including endothelial, cardiac, renal, and corneal cells, and consequently, the progressive appearance of clinical symptoms in target organs. Enzyme replacement therapy (ERT), which involves the exogenous supplementation of α-Gal A enzyme and has been successfully administered for treating FD.Here, we report a case of a 37-year-old male with complaints of recurrent proteinuria and ventricular septal thickening. A renal biopsy revealed vacuolization and foamy changes in podocytes, and the presence of myelin-like bodies and zebra bodies. The white blood cell α-Gal A activity was very low, while the Lyso-GL-3 level was high. Additionally, genetic analysis revealed a gene variant c.902G > A p. Arg301Gln. The patient was diagnosed with FD, and subsequently received intravenous ERT with a dose of Agalsidase α (0.2 mg/kg, 17.5 mg every 2 weeks). Currently, the values of proteinuria and ventricular septum thickness remain stable during the 6-month follow-up. Initiating ERT at an early age can effectively decrease the deposition of GL-3, attenuate the progressive clinical manifestations of FD, and provide greater long-term benefits.

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.

Fatigue as hallmark of Fabry disease: role of bioenergetic alterations

Fabry disease (FD) is a lysosomal storage disorder due to the impaired activity of the α-galactosidase A (GLA) enzyme which induces Gb3 deposition and multiorgan dysfunction. Exercise intolerance and fatigue are frequent and early findings in FD patients, representing a self-standing clinical phenotype with a significant impact on the patient's quality of life. Several determinants can trigger fatigability in Fabry patients, including psychological factors, cardiopulmonary dysfunctions, and primary alterations of skeletal muscle. The "metabolic hypothesis" to explain skeletal muscle symptoms and fatigability in Fabry patients is growing acknowledged. In this report, we will focus on the primary alterations of the motor system emphasizing the role of skeletal muscle metabolic disarrangement in determining the altered exercise tolerance in Fabry patients. We will discuss the most recent findings about the metabolic profile associated with Fabry disease offering new insights for diagnosis, management, and therapy.

Outcomes and management of kidney transplant recipients with Fabry disease: a review

Fabry disease is an X-linked inheritable lysosomal storage disease caused by various mutations of the galactosidase α gene resulting in α-galactosidase deficiency. Chronic kidney disease (CKD) is one of the most significant consequences of Fabry disease, with risk of end-stage kidney disease (ESKD) in this population. Like for other patients with ESKD, kidney transplant is the optimal treatment for Fabry disease patients with ESKD. However, enzyme replacement therapy and newer Fabry disease treatments remain important to mitigate other end organ damage such as cardiomyopathy post transplantation. This review is a primer on Fabry disease, which examines the outcomes of disease in the context of kidney transplant prior to, and during, the enzyme replacement treatment era, medical treatment of kidney transplant recipients with Fabry disease, and progress in screening studies.

Monitoring of anti-drug antibodies and disease-specific biomarkers in three patients from a Japanese Fabry family treated with enzyme replacement therapy

We monitored anti-drug antibodies and disease-specific biomarkers in three patients with a nonsense mutation from a Japanese Fabry family treated with enzyme replacement therapy (ERT). In two male patients from the family, neutralizing anti-drug antibodies were induced at an early stage of ERT, the antibody titer peak being found at an earlier stage of ERT in the patient treated with 1.0 mg/kg agalsidase beta than in that treated with 0.2 mg/kg agalsidase alfa. Then, the antibody titers decreased with continuation of ERT. The formation of neutralizing anti-drug antibodies adversely affected the plasma globotriaosylsphingosine (Lyso-Gb3) level and urinary globotriaosylceramide (Gb3) excretion in both patients, the impact being greater in the patient treated with 0.2 mg/kg agalsidase alfa than in that treated with 1.0 mg/kg agalsidase beta. The difference might be explained by the different doses of the infused enzymes based on supersaturation of the antibodies. In a heterozygous Fabry female from the family, no sign of antibody formation was found, and both the plasma Lyso-Gb3 level and urinary Gb3 excretion, which were moderately increased at the baseline, decreased gradually. No deterioration of the manifestations or laboratory findings was observed during ERT in either of the patients. Thus, monitoring of anti-drug antibodies and biomarkers in these Fabry patients provided us with important information on their pathological condition during ERT.

Kidney and lipids: novel potential therapeutic targets for dyslipidemia in kidney disease?

INTRODUCTION

Altered lipid distribution and metabolism may lead to the development and/or progression of chronic kidney disease (CKD). Dyslipidemia is a major risk factor for CKD and increases the risk of cardiovascular events and mortality. Therefore, lipid-lowering treatments may decrease cardiovascular risk and prevent death.

AREAS COVERED

Key players involved in regulating lipid accumulation in the kidney; contribution of lipids to CKD progression, lipotoxicity, and mitochondrial dysfunction in kidney disease; recent therapeutic approaches for dyslipidemia.

EXPERT OPINION

The precise mechanisms for regulating lipid metabolism, particularly in kidney disease, are poorly understood. Guidelines for lipid-lowering therapy for CKD are controversial. Several hypolipemic therapies are available, but compared to others, statin therapy is the most common. No clinical trial has evaluated the efficacy of proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) in preventing cardiovascular events or improving kidney function among patients with CKD or kidney transplant recipients. Attractive alternatives, such as PCSK9-small interfering RNA (siRNA) molecules or evinacumab are available. Additionally, several promising agents, such as cyclodextrins and the FXR/TGR5 dual agonist, INT-767, can improve renal lipid metabolism disorders and delay CKD progression. Drugs targeting mitochondrial dysfunction could be an option for the treatment of dyslipidemia and lipotoxicity, particularly in renal diseases.

Brazilian consensus recommendations for the diagnosis, screening, and treatment of individuals with fabry disease: Committee for Rare Diseases - Brazilian Society of Nephrology/2021

Fabry disease (FD) is an X-linked inherited disorder caused by mutations in the GLA gene encoding enzyme alpha-galactosidase A (α-Gal A). The purpose of this study was to produce a consensus statement to standardize the recommendations concerning kidney involvement in FD and provide advice on the diagnosis, screening, and treatment of adult and pediatric patients. This consensus document was organized from an initiative led by the Committee for Rare Diseases (Comdora) of the Brazilian Society of Nephrology (SBN). The review considered randomized clinical trials, real-world data studies, and the expertise of its authors. The purpose of this consensus statement is to help manage patient and physician expectations concerning the outcomes of treatment. Our recommendations must be interpreted within the context of available evidence. The decisions pertaining to each individual case must be made with the involvement of patients and their families and take into account not only the potential cost of treatment, but also concurrent conditions and personal preferences. The Comdora intends to update these recommendations regularly so as to reflect recent literature evidence, real-world data, and appreciate the professional experience of those involved. This consensus document establishes clear criteria for the diagnosis of FD and for when to start or stop specific therapies or adjuvant measures, to thus advise the medical community and standardize clinical practice.

Comparative urinary globotriaosylceramide analysis by thin-layer chromatography-immunostaining and liquid chromatography-tandem mass spectrometry in patients with Fabry disease

In Fabry disease, accumulation of glycolipids, predominantly globotriaosylceramide (Gb3), affects the kidneys, and nephropathy is one of the important disorders that influence the disease severity and prognosis of patients. Urinary Gb3 has been analyzed for diagnosis and monitoring of Fabry disease. In this study, we analyzed urinary Gb3 by thin-layer chromatography (TLC)-immunostaining and liquid chromatography (LC)-tandem mass spectrometry (MS/MS). An improved qualitative method, TLC-immunostaining, revealed excessive urinary Gb3 excretion in 100 (8/8), 88 (14/16), and 74% (45/61) of the classic Fabry males, later-onset Fabry males, and Fabry females examined, respectively. This authentic method is robust, easy, economic, and hardly affected by abundant urinary sediment, and this is useful for diagnosing individual Fabry patients. LC-MS/MS can determine the level of Gb3 in urine with high sensitivity, and it revealed that the Gb3 excretion level was higher in the order of classic Fabry males, later-onset Fabry males, Fabry females, and controls, respectively, and this is expected to be a useful quantitative method not only for diagnosis but also for predicting the progression of Fabry nephropathy. As to the relation of the urinary Gb3 level and renal events, our study revealed that the urinary Gb3 level in Fabry patients experiencing renal events tended to be higher than that in ones who did not have any renal events in each phenotypic group of the disease.

Pathogenesis and Molecular Mechanisms of Anderson-Fabry Disease and Possible New Molecular Addressed Therapeutic Strategies

Anderson-Fabry disease (AFD) is a rare disease with an incidenceof approximately 1:117,000 male births. Lysosomal accumulation of globotriaosylceramide (Gb3) is the element characterizing Fabry disease due to a hereditary deficiency α-galactosidase A (GLA) enzyme. The accumulation of Gb3 causes lysosomal dysfunction that compromises cell signaling pathways. Deposition of sphingolipids occurs in the autonomic nervous system, dorsal root ganglia, kidney epithelial cells, vascular system cells, and myocardial cells, resulting in organ failure. This manuscript will review the molecular pathogenetic pathways involved in Anderson-Fabry disease and in its organ damage. Some studies reported that inhibition of mitochondrial function and energy metabolism plays a significant role in AFD cardiomyopathy and in kidney disease of AFD patients. Furthermore, mitochondrial dysfunction has been reported as linked to the dysregulation of the autophagy-lysosomal pathway which inhibits the mechanistic target of rapamycin kinase (mTOR) mediated control of mitochondrial metabolism in AFD cells. Cerebrovascular complications due to AFD are caused by cerebral micro vessel stenosis. These are caused by wall thickening resulting from the intramural accumulation of glycolipids, luminal occlusion or thrombosis. Other pathogenetic mechanisms involved in organ damage linked to Gb3 accumulation are endocytosis and lysosomal degradation of endothelial calcium-activated intermediate-conductance potassium ion channel 3.1 (KCa3.1) via a clathrin-dependent process. This process represents a crucial event in endothelial dysfunction. Several studies have identified the deacylated form of Gb3, globotriaosylsphingosine (Lyso-Gb3), as the main catabolite that increases in plasma and urine in patients with AFD. The mean concentrations of Gb3 in all organs and plasma of Galactosidase A knockout mice were significantly higher than those of wild-type mice. The distributions of Gb3 isoforms vary from organ to organ. Various Gb3 isoforms were observed mainly in the kidneys, and kidney-specific Gb3 isoforms were hydroxylated. Furthermore, the action of Gb3 on the KCa3.1 channel suggests a possible contribution of this interaction to the Fabry disease process, as this channel is expressed in various cells, including endothelial cells, fibroblasts, smooth muscle cells in proliferation, microglia, and lymphocytes. These molecular pathways could be considered a potential therapeutic target to correct the enzyme in addition to the traditional enzyme replacement therapies (ERT) or drug chaperone therapy.

Platelet and myeloid cell phenotypes in a rat model of Fabry disease

Fabry disease results from a deficiency of the lysosomal enzyme ⍺-Galactosidase-A (⍺-Gal A) and is estimated to occur in approximately 1:4100 live births. Characteristic of the disease is the accumulation of α-Gal-A substrates, primarily the glycosphingolipids (GSLs) globotriaosylceramide and globotriaosylsphingosine. Thrombotic events are a significant concern for Fabry patients, with strokes contributing to a significant decrease in overall lifespan. Currently, the mechanisms underlying the increased risk of thrombotic events experienced by Fabry patients are incompletely defined. Using a rat model of Fabry disease, we provide an improved understanding of the mechanisms linking GSL accumulation to thrombotic risk. We found that ⍺-Gal A-deficient rats accumulate myeloid-derived leukocytes at sites of GSL accumulation, including in the bone marrow and circulation, and that myeloid-derived leukocyte and megakaryocyte populations were prominent among cell types that accumulated GSLs. In the circulation, ⍺-Gal A-deficient rats had increases in cytokine-producing cell types and a corresponding elevation of pro-inflammatory cytokines. Lastly, circulating platelets from ⍺-Gal A-deficient rats accumulated a similar set of ⍺-Galactosidase-A substrates as was observed in megakaryocytes in the bone marrow, and exhibited increased platelet binding to fibrinogen in microfluidic and flow cytometric assays.

Precision medicine in Fabry disease

Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by mutations in the α-galactosidase A (GLA) gene, leading to a deficiency in α-galactosidase A. The lysosomal accumulation of glycosphingolipids, primarily globotriaosylceramide (Gb3) and its deacylated form, globotriaosylsphingosine (lyso-Gb3), results in progressive renal failure, cardiomyopathy associated with cardiac arrhythmia and recurrent cerebrovascular events, significantly limiting life expectancy in affected patients. In male patients, a definitive diagnosis of FD involves demonstrating a GLA deficiency in leucocytes. In females, because of the potential high residual enzymatic activity, the diagnostic gold standard requires molecular genetic analyses. The current treatment options for FD include recombinant enzyme replacement therapies (ERTs) with intravenous agalsidase-α (0.2 mg/kg body weight) or agalsidase-β (1 mg/kg body weight) every 2 weeks as well as an oral pharmacological chaperone (migalastat 123 mg every other day) that selectively and reversibly binds to the active sites of amenable mutant forms of the GLA enzyme. These therapies facilitate cellular Gb3 clearance and an overall improvement of disease burden. However, ERT can lead to infusion-associated reactions, as well as the formation of neutralizing anti-drug antibodies in ∼40% of all ERT-treated males, leading to an attenuation of therapy efficacy. This article reviews the clinical presentation, diagnosis and interdisciplinary clinical management of FD and discusses the therapeutic options, with a special focus on precision medicine, accounting for individual variability in genetic mutations, Gb3 and lyso-Gb3 levels, allowing physicians to predict more accurately which prevention and treatment strategy is best for which patient.

Circulating miRNAs as Biomarkers for Mitochondrial Neuro-Gastrointestinal Encephalomyopathy

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an ultra-rare disease for which there are currently no validated outcome measures for assessing therapeutic intervention efficacy. The aim of this study was to identify a plasma and/or serum microRNA (miRNA) biomarker panel for MNGIE. Sixty-five patients and 65 age and sex matched healthy controls were recruited and assigned to one of four study phases: (i) discovery for sample size determination; (ii) candidate screening; (iii) candidate validation; and (iv) verifying the performance of the validated miRNA panel in four patients treated with erythrocyte-encapsulated thymidine phosphorylase (EE-TP), an enzyme replacement under development for MNGIE. Quantitative PCR (qPCR) was used to profile miRNAs in serum and/or plasma samples collected for the discovery, validation and performance phases, and next generation sequencing (NGS) analysis was applied to serum samples assigned to the candidate screening phase. Forty-one differentially expressed candidate miRNAs were identified in the sera of patients (p < 0.05, log₂ fold change > 1). The validation cohort revealed that of those, 27 miRNAs were upregulated in plasma and three miRNAs were upregulated in sera (p < 0.05). Through binary logistic regression analyses, five plasma miRNAs (miR-192-5p, miR-193a-5p, miR-194-5p, miR-215-5p and miR-34a-5p) and three serum miRNAs (miR-192-5p, miR-194-5p and miR-34a-5p) were shown to robustly distinguish MNGIE from healthy controls. Reduced longitudinal miRNA expression of miR-34a-5p was observed in all four patients treated with EE-TP and coincided with biochemical and clinical improvements. We recommend the inclusion of the plasma exploratory miRNA biomarker panel in future clinical trials of investigational therapies for MNGIE; it may have prognostic value for assessing clinical status.

Proteomics for the study of new biomarkers in Fabry disease: State of the art

Nephropathy represents a major complication of Fabry Disease and its accurate characterization is of paramount importance in predicting the disease progression and assessing the therapeutic responses. The diagnostic process still relies on performing renal biopsy, nevertheless many efforts have been made to discover early reliable biomarkers allowing us to avoid invasive procedures. In this field, proteomics offers a sensitive and fast method leading to an accurate detection of specific pathological proteins and the discovery of diagnostic and prognostic biomarkers that reflect disease progression and facilitate the evaluation of therapeutic responses. Here, we report a review of selected literature focusing on the investigation of several proteomic techniques highlighting their advantages, limitations and future perspectives in their application in the routine study of Fabry Nephropathy.

Renal Manifestations of Fabry Disease: A Narrative Review

Purpose of review

In this narrative review, we describe general aspects, histological alterations, treatment, and implications of Fabry disease (FD) nephropathy. This information should be used to guide physicians and patients in a shared decision-making process.

Source of information

Original peer-reviewed articles, review articles, and opinion pieces were identified from PubMed and Google Scholar databases. Only sources in English were accessed.

Methods

We performed a focused narrative review assessing the main aspects of FD nephropathy. The literature was critically analyzed from a theoretical and contextual perspective, and thematic analysis was performed.

Key findings

FD nephropathy is related to the progressive accumulation of GL3, which occurs in all types of renal cells. It is more prominent in podocytes, which seem to play an important role in the pathogenesis of this nephropathy. A precise detection of renal disorders is of fundamental importance because the specific treatment of FD is usually delayed, making reversibility unlikely and leading to a worse prognosis.

Limitations

As no formal tool was applied to assess the quality of the included studies, selection bias may have occurred. Nonetheless, we have attempted to provide a comprehensive review on the topic using current studies from experts in FD and extensive review of the literature.

Unexplored regulatory sequences of divergently paired GLA and HNRNPH2 loci pertinent to Fabry disease in human kidney and skin cells: Presence of an active bidirectional promoter

Fabry disease (FD) is a rare hereditary disorder characterized by a wide range of symptoms caused by a variety of mutations in the galactosidase α (GLA) gene. The heterogeneous nuclear ribonucleoprotein (HNRNPH2) gene is divergently paired with GLA on chromosome X and is thought to be implicated in FD. However, insufficient information is available on the regulatory mechanisms associated with the expression of HNRNPH2 and the GLA loci. Therefore, the current study performed bioinformatics analyses to assess the GLA and HNRNPH2 loci and investigate the regulatory mechanisms involved in the expression of each gene. The regulatory mechanisms underlying GLA and HNRNPH2 were revealed. The expression of each gene was associated with a bidirectional promoter (BDP) characterized by the absence of TATA box motifs and the presence of specific transcription factor binding sites (TFBSs) and a CpG Island (CGI). The nuclear run-on transcription assay confirmed the activity of BDP GLA and HNRNPH2 transcription in 293T. Methylation-specific PCR analysis demonstrated a statistically significant variation in the DNA methylation pattern of BDP in several cell lines, including human adult epidermal keratinocytes (AEKs), human renal glomerular endothelial cells, human renal epithelial cells and 293T cells. The highest observed significance was demonstrated in AEKs (P<0.05). The results of the chromatin-immunoprecipitation assay using 293T cells identified specific TFBS motifs for Yin Yang 1 and nuclear respiratory factor 1 transcription factors in BDPs. The National Center for Biotechnology Information-single nucleotide polymorphism database revealed pathogenic variants in the BDP sequence. Additionally, a previously reported variant associated with a severe heterozygous female case of GLA FD was mapped in BDP. The results of the present study suggested that the expression of the divergent paired loci, GLA and HNRNPH2, were controlled by BDP. Mutations in BDP may also serve a role in FD and may explain clinical disease diversity.

Variables Associated with Glomerular Hyperfiltration in Fabry Disease Patients

Background: Fabry disease is a genetic disorder caused by the deficiency of the lysosomal α-galactosidase A enzyme. This failure generates the storage of globotriaosylceramide in different cells with a progressive multi-organ involvement. Objectives: To report the prevalence of glomerular hyperfiltration in Fabry disease patients and the association with clinical variables. Methods: Adult patients (≥ 18 years) at the moment of FD diagnosis were evaluated. The variables studied were: central and peripheral nervous system compromise, presence of arterial hypertension, cardiac arrhythmia, left ventricular hypertrophy, albuminuria/proteinuria, cornea verticillata, gastrointestinal involvement, treatment with inhibitors of the renin-angiotensin-aldosterone system, deafness, and presence of angiokeratomas. Results: Forty-eight adults with Fabry disease (35.9 ± 11.7 years), 28 women (58.3%), and 20 men (41.7%) were analyzed. Nine (18.8%) patients with glomerular hyperfiltration, including six females and three males (mean age: 28.8 years), were detected. A significant association between and central nervous system (P = 0.021) and peripheral nervous system (P = 0.001) compromise, cardiac arrhythmia (P = 0.001), cornea verticillata (P = 0.009), and gastrointestinal involvement (P = 0.009) was observed. However, no association was found between glomerular hyperfiltration and proteinuria or treatment with inhibitors of the renin-angiotensin-aldosterone system. Conclusions: This research showed a higher prevalence of glomerular hyperfiltration in the younger group and a significant association between glomerular hyperfiltration and some typical manifestations of classic Fabry patients. Although more studies are needed, it is concluded that other mechanisms than glomerular hyperfiltration, like injury by glycosphingolipids deposit into the filtration barrier, might influence the protein loss in Fabry nephropathy.

Movement Disorders and Renal Diseases

Movement disorders often emerge from the interplay of complex pathophysiological processes involving the kidneys and the nervous system. Tremor, myoclonus, ataxia, chorea, and parkinsonism can occur in the context of renal dysfunction (azotemia and electrolyte abnormalities) or they can be part of complications of its management (dialysis and renal transplantation). On the other hand, myoglobinuria from rhabdomyolysis in status dystonicus and certain drugs used in the management of movement disorders can cause nephrotoxicity. Distinct from these well-recognized associations, it is important to appreciate that there are several inherited and acquired disorders in which movement abnormalities do not occur as a consequence of renal dysfunction or vice versa but are manifestations of common pathophysiological processes affecting the nervous system and the kidneys. These disorders are the emphasis of this review. Increasing awareness of these conditions among neurologists may help them to identify renal involvement earlier, take timely intervention by anticipating complications and focus on therapies targeting common mechanisms in addition to symptomatic management of movement disorders. Recognition of renal impairment in a patient with complex neurological presentation may narrow down the differentials and aid in reaching a definite diagnosis.

Massive accumulation of globotriaosylceramide in various tissues from a Fabry patient with a high antibody titer against alpha-galactosidase A after 6 years of enzyme replacement therapy

Fabry disease is an X-linked metabolic disorder due to a pathogenic mutation of the GLA gene. The accumulation of globotriaosylceramide (Gb3) damages multiple organs, including the heart, kidney and nervous system, especially in classical type Fabry disease. Enzyme replacement therapy (ERT) using recombinant alpha-galactosidase A has been shown to remove Gb3 from organs and to improve the prognosis of Fabry disease. We herein report the case of a 67-year-old classical type Fabry patient who had been treated with ERT for 6 years and who continuously showed a high antibody titer against recombinant alpha-galactosidase A during therapy. A post-mortem examination was performed after sudden death. A histological examination revealed the massive accumulation of Gb3 in various organs, even after long term ERT. In addition to the typical pathological findings as reported in tissue biopsy samples, the serious accumulation of Gb3 in the cardiac conduction system and the endocrine system was detected. Since the start of ERT for this patient might be too late to improve organ damage and prognosis, ERT should be started before the appearance of major organ involvement for the effective elimination of Gb3 and changes in the therapeutic strategy might be considered if the patient shows a high antibody titer against recombinant alpha-galactosidase A.

Kidney Transplant in Fabry Disease: A Revision of the Literature

Fabry disease is classified as a rare X-linked disease caused by a complete or partial defect of enzyme alpha-galactosidase, due to GLA gene mutations. This disorder leads to intracellular globotriaosylceramide (Gb3) deposition associated with increased Gb3 plasma levels. Most of the symptoms of the disease, involving kidneys, heart and nervous system, result from this progressive Gb3 deposition. The incidence is estimated in 1/50,000 to 1/117,000 in males. Fabry nephropathy begins with microalbuminuria and/or proteinuria, which, in the classic form, appear from childhood. Thus, a progressive decline of renal function can start at a young age, and evolve to kidney failure, requiring dialysis or renal transplantation. Enzyme replacement therapy (ERT), available since 2001 for Fabry disease, has been increasingly introduced into the clinical practice, with overall positive short-term and long-term effects in terms of ventricular hypertrophy and renal function. Kidney transplantation represents a relevant therapeutic option for Fabry nephropathy management, for patients reaching end-stage renal disease, but little is known about long-term outcomes, overall patient survival or the possible role of ERT after transplant. The purpose of this review is to analyze the literature on every aspect related to kidney transplantation in patients with Fabry nephropathy: from the analysis of transplant outcomes, to the likelihood of disease recurrence, up to the effects of ERT and its possible interference with immunosuppression.

The GALA project: practical recommendations for the use of migalastat in clinical practice on the basis of a structured survey among Italian experts

Background

Oral migalastat has recently been approved for the treatment of Anderson-Fabry disease (FD) in patients aged ≥16 years with amenable mutations on the basis of two phase III trials, FACETS and ATTRACT. However, with the introduction of migalastat into clinical practice, it is important to correctly identify the patients who may gain the most benefits from this therapy. Due to the relatively recent availability of migalastat, its role in clinical practice still has to be included in guidelines or recommendations. On these bases, a multidisciplinary group of Italian Experts in the treatment of FD has run the GALA project, with the aim to collect the opinions of expert physicians and to propose some starting points for an experience-based use of migalastat.

Results

Overall, although studies and data from longer-term follow-up with migalastat are still emerging, available evidence is consistent in showing that this molecule does represent a suitable therapy for the treatment of FD, in patients aged ≥16 years and with amenable mutations. The use of migalastat as an oral option appears to be overall safe, and experience thus far indicates potential for improving quality of life, controlling GI symptoms, stabilizing renal function and reducing cardiac hypertrophy.

Conclusion

Migalastat can be considered either as a first-line therapy – given its efficacy, extensive tissue penetration, convenient oral regimen, and the current limited therapeutic options available – or in patients on enzyme-replacement therapy (ERT) who experience side effects, with poor compliance to chronic i.v. therapy, or with clinical evidence of progression of the disease.

Fabry Disease Screening in Patients With Kidney Transplant: A Single-Center Study in Turkey

OBJECTIVES

Fabry disease is a rare X-linked multisystemic lysosomal storage disorder of the glycosphingolipid metabolic pathway. Nephropathy is one of the most important complications of Fabry disease, and patients with classical phenotype are at risk of developing endstage kidney disease. In this study, we investigated the use of screening for Fabry disease in kidney transplant recipients at our center.

MATERIALS AND METHODS

We screened 301 kidney transplant recipients with functioning grafts. Analyses for α-galactosidase A gene mutation were performed in all female and male kidney transplant recipients. We also measured leukocyte α-galactosidase A enzyme activity in patients with identified GLA mutation.

RESULTS

In 301 kidney transplant recipients, mean age was 42.9 ± 12.5 years, and the number of male patients was 180 (60%). Mean time after transplant was 79 ± 56 months, and estimated glomerular filtration rate was 66.8 ± 21 mL/min/1.73 m². One male patient who was diagnosed with Fabry disease before kidney transplant was also evaluated (mutation in the α-galactosidase A gene, c.1093_1101dup [p.Tyr365_lle367dup]). In 2 female patients, p.A143T (c.427G>A) mutation of unknown significance and p.D313Y (c.937G>T) heterozygous mutation were identified; however, leukocyte ?-galactosidase A enzyme activity was normal in these patients (63.7 and 67.3 nmol/h/mg protein). In the patient diagnosed with Fabry disease, family screening revealed 4 additional affected family members.

DISCUSSIONS

Although prevalence was shown to be low in our center (1/301 patients; 0.33%), screening studies in kidney transplant recipients may help to detect new patients before they develop life-threatening complications such as renal involvement.

MALDI imaging in Fabry nephropathy: a multicenter study

BACKGROUND

The current study evaluates the application of histology and in situ proteomics (MALDI-MSI) in Fabry nephropathy (FN), showing investigative and classification role for this coupled approach.

METHODS

A retrospective series of 14 formalin fixed paraffin embedded (FFPE) renal biopsies with diagnosis of FN and 1 biopsy from a patient bearing a galactosidase-α (GLA) genetic variant of unknown significance (GVUS, c.376A>G) have been classified for clinical characteristics. Groups were compared for histological differences (following the ISGFN scoring system). Moreover, renal biopsies from these cases have been analyzed with MALDI-MSI as previously described to find proteomic signatures among different mutations and phenotypes.

RESULTS

Comparison of clinical features revealed lower mean 24 h proteinuria in females (225 mg/24 h) than in males (1477.5 mg/24 h, p = 0.006). As for clinical characteristics, females significantly differed from males only for lower arterial sclerosis, with a mean value of 0.82 vs. 1.05 (p = 0.001). Proteomic analysis demonstrated specific signatures in different subgroups of FN patients. Moreover, MALDI correctly classified cases with undetermined mutation or GVUS.

CONCLUSIONS

The present study demonstrated the feasible application of MALDI-MSI in the analysis of FN FFPE renal biopsies, allowing the detection of putative signatures for phenotypic distinction and demonstrating genetic classification capabilities.

Optical Coherence Tomography Angiography Findings in Fabry Disease

BACKGROUND

Fabry disease (FD) is a X-linked recessive lysosomal storage disorder characterized by altered biodegradation of glycosphingolipids. It is a multisystem pathology, also involving ophthalmological systems that show modifications of the vessel wall due to glycosphingolipid deposits. Optical coherence tomography angiography (OCT-A) allows for an objective analysis of retinal microvasculature alterations, evaluating retinal vessel density in macular region.

METHODS

A total of 54 FD patients (34 females, 20 males, mean age 44.1 ± 15.6 years) and 70 controls (36 females, 34 males, mean age 42.3 ± 15.6 years) were included in this study. We evaluated vessel density in different macular areas (whole image, fovea, and parafovea) of both the superficial capillary plexus (SCP) and of the deep capillary plexus (DCP).

RESULTS

In the SCP there was a significantly lower vascular density in patients compared with controls in whole image (49.95 ± 5.17% vs. 51.99 ± 2.52%; p < 0.001), parafovea (52.01 ± 6.69% vs. 54.30 ± 2.61%; p = 0.002), and fovea (22.38 ± 9.01% vs. 29.31 ± 5.84%; p < 0.0001). In the DCP the vessel density was statistically increased in each macular area in patients compared with controls (54.82 ± 8.07% vs. 50.93 ± 5.46%; p = 0.005, 57.76 ± 7.26% vs. 53.59 ± 5.46%; p = 0.0001, and 39.75 ± 8.59% vs. 34.43 ± 8.68%; p < 0.0001 for whole image, parafovea, and fovea, respectively).

CONCLUSION

OCT-A analysis showed that the macular vessel density was significantly reduced in the SCP and increased in the DCP in FD patients compared with controls. These findings, which might be a consequence of the alteration of vascular wall occurring in FD, support the hypothesis that the evaluation of early retinal microvascular network changes could be a useful tool in the clinical evaluation of the disease.

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.