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Fabry disease (FD) is an X-linked lysosomal storage disorder with multi-system involvement including cerebrovascular disease. Patients with FD also have a high risk of ischaemic stroke and TIA. White matter hyperintensities are common, but their clinical impact on cognition remains uncertain. Previous studies have examined the neuropsychological profile of FD, but have been inconclusive in part due to methodological limitations including small sample sizes. We sought to address these limitations in a case-control study of 26 patients with Fabry disease with mild to moderate disease symptoms matched with 18 healthy controls for age and premorbid intellectual level. We obtained detailed neuropsychological data and MRI neuroimaging data on the severity of white matter changes. Mood was accounted for as a possible confounder. Our results showed significant compromise of executive functions and information processing speed for the FD group. Error analyses suggested that the compromise of executive functions could not be entirely accounted for by slowed information processing speed. We demonstrated significant correlations between cognitive decline and the overall volume of white matter hyperintensities in the FD group. Our results point to significant compromise of cognition in FD even without stroke or mood difficulties. This suggests that neuropsychological assessment and rehabilitation should be routinely offered to patients with FD.

Enzyme replacement therapy (ERT) with recombinant α‐galactosidase A (r‐αGAL A) for the treatment of Fabry disease has been available for over 15 years. Long‐term treatment may slow down disease progression, but cardiac, renal, and cerebral complications still develop in most patients. In addition, lifelong intravenous treatment is burdensome. Therefore, several new treatment approaches have been explored over the past decade. Chaperone therapy (Migalastat; 1‐deoxygalactonojirimycin) is the only other currently approved therapy for Fabry disease. This oral small molecule aims to improve enzyme activity of mutated α‐galactosidase A and can only be used in patients with specific mutations. Treatments currently under evaluation in (pre)clinical trials are second generation enzyme replacement therapies (Pegunigalsidase‐alfa, Moss‐aGal), substrate reduction therapies (Venglustat and Lucerastat), mRNA‐ and gene‐based therapy. This review summarises the knowledge on currently available and potential future options for the treatment of Fabry disease.

Fabry disease (FD) is a lysosomal storage disease, treatable by enzyme replacement therapy (ERT) that substitutes deficient α-galactosidase A (AGAL). The formation of neutralising anti-drug antibodies (ADA) inhibiting AGAL activity during infusion is associated with disease progression in affected male patients. In this study we analysed if ADAs also inhibit endothelial enzyme uptake as well as intracellular enzyme activity. Therefore, fluorescence-labelled AGAL in combination with ADA-positive sera from FD patients (n = 8) was used to analyse enzyme uptake in endothelial and FD-specific cells. Furthermore, immune adsorption and a comprehensive ADA epitope mapping were performed. Pre-incubation of AGAL with ADAs significantly inhibited intracellular enzyme activity, which was rescued by immune adsorption (both P < .01). ADAs from some patients also inhibited enzyme uptake. ADA epitope mapping identified an epitope at position 121 to 140 aa potentially responsible for uptake inhibition for these patients. Further analyses revealed the presence of stable AGAL/ADA-immune complexes at pH 4.5 and decreased intracellular enzyme activity in endothelial cells (P < .001). Finally, the pre-incubation of AGAL with ADAs resulted in a reduced depletion of intracellular globotriaosylceramide in patient-derived AGAL-deficient cells, demonstrating a direct negative impact of ADAs on intracellular clearance. Neutralising ADAs may not only inhibit infused AGAL activity, but according to their epitopes can also inhibit endothelial AGAL uptake. Indeed, internalised AGAL/ADA-complexes may not dissociate, underlining the importance of novel therapeutic approaches for ADA reduction and prevention to increase therapy efficiency in affected patients.

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

Patients with Fabry disease (FD) have a high prevalence of depressive symptoms and can suffer from cognitive impairment, negatively affecting their life. The course of cognitive functioning and depressive symptoms in FD is unknown. The aim of this prospective cohort study was to describe changes in cognitive functioning and depressive symptoms and to identify related variables in patients with FD over 1 year. Assessments were conducted twice, using a neuropsychological test battery and the Centre of Epidemiological Studies Depression scale (CESD). Eighty‐one patients were included of which 76 patients (94%) completed both assessments (age: 44 years, 34% men, 75% classical phenotype). A significant decrease in cognitive functioning was found in four patients (5%), with patients regressing from excellent to average/good. Changes were not related to sex, phenotype, stroke, IQ or CESD scores. CESD scores ≥16 were present in 29 patients (38%) at baseline. Using the reliable change index a decrease in CESD scores was found in six patients (8%). Decreased CESD scores were independently related to employing a positive and problem solving coping style and increased CESD scores to an avoiding and brooding coping style and worsening health perception. We found no major changes in cognitive functioning in patients with FD during 1 year follow‐up making it an unsuitable outcome in FD treatment trials. Considering the high prevalence of persistent depressive symptoms, assessment of depressive symptoms should be part of routine follow‐up. Altering coping styles and health perception may improve psychological well‐being in FD.

Fabry disease is a glycosphingolipidosis caused by deficient activity of α-galactosidase A; it is one of a few diseases that are associated with priapism, an abnormal prolonged erection of the penis. The goal of this study was to investigate the pathogenesis of Fabry disease-associated priapism in a mouse model of the disease. We found that Fabry mice develop late-onset priapism. Neuronal nitric oxide synthase (nNOS), which was predominantly present as the 120-kDa N-terminus-truncated form, was significantly upregulated in the penis of 18-month-old Fabry mice compared to wild type controls (~fivefold). Endothelial NOS (eNOS) was also upregulated (~twofold). NO level in penile tissues of Fabry mice was significantly higher than wild type controls at 18 months. Gene transfer-mediated enzyme replacement therapy reversed abnormal nNOS expression in the Fabry mouse penis. The penile nNOS level was restored by antiandrogen treatment, suggesting that hyperactive androgen receptor signaling in Fabry mice may contribute to nNOS upregulation. However, the phosphodiesterase-5A expression level and the adenosine content in the penis, which are known to play roles in the development of priapism in other etiologies, were unchanged in Fabry mice. In conclusion, these data suggested that increased nNOS (and probably eNOS) content and the consequential elevated NO production and high arterial blood flow in the penis may be the underlying mechanism of priapism in Fabry mice. Furthermore, in combination with previous findings, this study suggested that regulation of NOS expression is susceptible to α-galactosidase A deficiency, and this may represent a general pathogenic mechanism of Fabry vasculopathy.

Lysosomal storage disorders are strong candidates for the development of specific innovative therapies. The discovery of enzyme deficiencies is an important milestone in understanding the underlying cause of disease. Being able to replace the first missing enzyme in a lysosomal storage required three decades of dedicated research. Successful drug development for lysosomal storage disorders was fostered by the U.S. Orphan Drug Act. Various optimization strategies have the potential to overcome the current limitations of enzyme replacement therapies. In addition, substrate reduction therapies are an alternative approach to treat lysosomal storage disorders, chemical chaperones enhance residual enzyme activity, and small molecules can facilitate substrate transport through subcellular compartments. Bone-marrow derived multipotent stem cells and gene therapies have received FDA orphan drug designation status. The science of small clinical trials played an essential role: non-neurological endpoints, biomarker, and regulatory alignment are key factors in successful drug development for lysosomal storage disorders. Being able to treat brain disease is the next frontier. This review is dedicated to the memory of Roscoe O. Brady, an early pioneer in the research of lysosomal storage diseases.

Background Hearing loss (HL) is a well-known feature of Fabry disease (FD). Its presence and characteristics have mainly been studied in adult patients, while only limited data are available on the presence and degree of HL in children with FD. This prompted us to study hearing sensitivity in pediatric FD patients. Methods All available audiograms of the Dutch and Norwegian children with FD were retrospectively collected. First, hearing sensitivity was determined by studying hearing thresholds at low, high, and ultra-high frequencies in children with FD and comparing them to zero dB HL, i.e., healthy children. In addition, the presence and type of slight/mild HL (defined as hearing thresholds at low frequencies of 25–40 dB HL) and moderate to severe HL (hearing thresholds >40 dB HL) at first visit were analyzed. If available, follow-up data were used to estimate the natural course of hearing sensitivity and HL in children with FD. Results One-hundred-thirteen audiograms of 47 children with FD (20 boys, median age at first audiogram 12.0 (range 5.1–18.0) years) were analyzed. At baseline, slight/mild or moderate to severe HL was present in three children (6.4%, 2 boys). Follow-up measurements showed that three additional children developed HL before the age of 18. Of these six children, five had sensorineural HL, most likely caused by FD. Compared to healthy children (zero dB HL), FD children showed increased hearing thresholds at all frequencies (p 8 kHz). Hearing sensitivity at these ultra-high frequencies deteriorated in a period of 5 years of follow-up. Conclusion A minority of children with FD show slight/mild or moderate to severe HL, but their hearing thresholds are poorer than the reference values for normal-hearing children. Clinical trials in FD children should demonstrate whether HL can be prevented or reversed by early treatment and should specifically study ultra-high frequencies. Electronic supplementary material The online version of this article (doi:10.1007/s10545-017-0051-5) contains supplementary material, which is available to authorized users.

Vesicular protein sorting-associated proteins (VPS, including VPS11) are indispensable in the endocytic network, in particular the endosome-lysosome biogenesis. Exome sequencing revealed the homozygous variant p.Leu387_ Gly395del in the VPS11 gene in two siblings. On immunoblotting, the mutant VPS11 protein showed a distinctly reduced immunostaining intensity. The children presented with primary and severe developmental delay associated with myoclonic seizures, spastic tetraplegia, trunk and neck hypotonia, blindness, hearing loss, and microcephaly. Neuro-imaging showed severe hypomyelination affecting cerebral and cerebellar white matter and corpus callosum, in the absence of a peripheral neuropathy. Electron microscopy of a skin biopsy revealed clusters of membranous cytoplasmic bodies in dermal unmyelinated nerve axons, and numbers of vacuoles in eccrine sweat glands, similar to what is seen in a classic lysosomal storage disease (LSD). Bone marrow cytology showed a high number of storage macrophages with a micro-vacuolated cytoplasm. Biochemically, changes in urinary glycosphingolipids were reminiscent of those in prosaposin deficiency (another LSD). The clinical and neuro-imaged features in our patients were almost identical to those in some recently reported patients with another variant in the VPS11 gene, p.Cys846Gly; underlining the presumed pathogenic potential of VPS11 defects. A new feature was the morphological evidence for lysosomal storage in VPS11 deficiency: This newly characterised disease can be viewed as belonging to the complex field of LSD. Electronic supplementary material The online version of this article (doi:10.1007/s10545-016-9961-x) contains supplementary material, which is available to authorized users.

In the light of clinical experience in infantile onset Pompe patients, the immunological impact on the tolerability and long-term efficacy of enzyme replacement therapy (ERT) for lysosomal storage disorders has come under renewed scrutiny. This article details the currently proposed immunological mechanisms involved in the development of anti-drug antibodies and the current therapies used in their treatment. Given the current understanding of the adaptive immune response, it focuses particularly on T cell dependent mechanisms and the paradigm of using lymphocytic negative selection as a predictor of antibody formation. This concept originally postulated in the 1970s, stipulated that the genotypically determined lack of production or production of a variant protein determines an individual's lymphocytic repertoire. This in turn is the key factor in determining the potential severity of an individual's immunological response to ERT. It also highlights the need for immunological assay standardization particularly those looking at describing the degree of functional impact, robust biochemical or clinical endpoints and detailed patient subgroup identification if the true evaluations of impact are to be realised.

Moss-aGalactosidase A (moss-aGal) is a moss-derived version of human α-galactosidase developed for enzyme replacement therapy in patients with Fabry disease. It exhibits a homogenous N-glycosylation profile with >90% mannose-terminated glycans. In contrast to mammalian cell produced α-galactosidase, moss-aGal does not rely on mannose-6-phosphate receptor mediated endocytosis but targets the mannose receptor for tissue uptake. We conducted a phase 1 clinical trial with moss-aGal in six patients with confirmed diagnosis of Fabry disease during a 28-day schedule. All patients received a single dose of 0.2 mg/kg moss-aGal by i.v.-infusion. Primary endpoints of the trial were safety and pharmacokinetics; secondary endpoints were pharmacodynamics by analyzing urine and plasma Gb3 and lyso-Gb3 concentrations. In all patients, the administered single dose was well tolerated. No safety issues were observed. Pharmacokinetic data revealed a stable nonlinear profile with a short plasma half-life of moss-aGal of 14 minutes. After one single dose of moss-aGal, urinary Gb3 concentrations decreased up to 23% 7 days and up to 60% 28 days post-dose. Plasma concentrations of lyso-Gb3 decreased by 3.8% and of Gb3 by 11% 28 days post-dose. These data reveal that a single dose of moss-aGal was safe, well tolerated, and led to a prolonged reduction of Gb3 excretion. As previously shown, moss-aGal is taken up via the mannose receptor, which is expressed on macrophages but also on endothelial and kidney cells. Thus, these data indicate that moss-aGal may target kidney cells. After these promising results, phase 2/3 clinical trials are in preparation.

Journal of Inherited Metabolic Disease published by John Wiley & Sons Ltd on behalf of SSIEM Pegunigalsidase alfa, a novel PEGylated, covalently crosslinked form of α-galactosidase A developed as enzyme replacement therapy (ERT) for Fabry disease (FD), was designed to increase plasma half-life and reduce immunogenicity, thereby enhancing efficacy compared with available products. Symptomatic adults with FD participated in this open-label, 3-month dose-ranging study, followed by a 9-month extension. Three cohorts were enrolled in a stepwise manner, each receiving increased doses of pegunigalsidase alfa: 0.2, 1.0, 2.0 mg/kg, via intravenous infusion every other week. Pharmacokinetic analysis occurred on Day 1 and Months 3, 6, and 12. Kidney biopsies at baseline and Month 6 assessed peritubular capillary globotriaosylceramide (Gb3) content. Renal function, cardiac parameters, and other clinical endpoints were assessed throughout. Treatment-emergent adverse events (AEs) and presence of immunoglobulin G (IgG) antidrug antibodies (ADAs) were assessed. Sixteen patients completed 1 year's treatment. Mean terminal plasma half-life (each cohort) ranged from 53 to 121 hours. All 11 male and 1 of 7 female patients presented with classic FD phenotype, in whom renal peritubular capillary Gb3 inclusions were reduced by 84%. Mean estimated glomerular filtration rate was 111 mL/min/1.73 m 2 at baseline, remaining stable throughout treatment. Three patients developed treatment-induced IgG ADAs; following 1 year's treatment, all became ADA-negative. Nearly all treatment-emergent AEs were mild or moderate. One patient withdrew from the study following a serious related AE. Pegunigalsidase alfa may represent an advance in ERT for FD, based on its unique pharmacokinetics and apparent low immunogenicity.

Enzyme replacement therapy (ERT) is an effective treatment for several lysosomal storage disorders (LSDs). Intravenously infused enzymes are taken up by tissues through either the mannose 6-phosphate receptor (M6PR) or the mannose receptor (MR). It is generally believed that M6PR-mediated endocytosis is a key mechanism for ERT in treating LSDs that affect the non-macrophage cells of visceral organs. However, the therapeutic efficacy of MR-mediated delivery of mannose-terminated enzymes in these diseases has not been fully evaluated. We tested the effectiveness of a non-phosphorylated α-galactosidase A produced from moss (referred to as moss-aGal) in vitro and in a mouse model of Fabry disease. Endocytosis of moss-aGal was MR-dependent. Compared to agalsidase alfa, a phosphorylated form of α-galactosidase A, moss-aGal was more preferentially targeted to the kidney. Cellular localization of moss-aGal and agalsidase alfa in the heart and kidney was essentially identical. A single injection of moss-aGal led to clearance of accumulated substrate in the heart and kidney to an extent comparable to that achieved by agalsidase alfa. This study suggested that mannose-terminated enzymes may be sufficiently effective for some LSDs in which non-macrophage cells are affected, and that M6P residues may not always be a prerequisite for ERT as previously considered. Electronic supplementary material The online version of this article (doi:10.1007/s10545-015-9886-9) contains supplementary material, which is available to authorized users.

Fabry disease (FD) is a multi-systemic X-linked lysosomal disorder caused by the deficient activity of α-galactosidase-A enzyme, which leads to accumulation of glycosphingolipids in various body tissues. The N215S mutation is a known variant of FD, with a late onset cardiac phenotype. Consensus guidelines acknowledged the use of globotriaosylsphingosine (Lyso-Gb

Fabry disease, a rare X-linked α-galactosidase A deficiency, causes progressive lysosomal accumulation of globotriaosylceramide (GL-3) in a variety of cell types. As the disease progresses, renal failure, left ventricular hypertrophy, and strokes may occur. Enzyme replacement therapy (ERT), with recombinant α-galactosidase A, is currently available for use to reduce GL-3 deposits. However, although it improves cardiac function and decreases left ventricular mass, GL-3 clearance upon ERT has been demonstrated in cardiac capillary endothelium but not in cardiomyocytes of patients. Relevant models are needed to understand the pathogenesis of cardiac disease and explore new therapeutic approaches. We generated induced pluripotent stem cells (iPSC) from Fabry patients and differentiated them into cardiomyocytes. In these cells, GL-3 accumulates in the lysosomes over time, resulting in phenotypic changes similar to those found in cardiac tissue from Fabry patients. Using this human in vitro model, we demonstrated that substrate reduction therapy via glucosylceramide synthase inhibition was able to prevent accumulation and to clear lysosomal GL-3 in cardiomyocytes. This new in vitro model recapitulates essential features of cardiomyocytes from patients with Fabry disease and therefore provides a useful and relevant tool for further investigations of new therapy.

To determine the effectiveness of enzyme replacement therapy (ERT) for adults and children with Fabry disease. Cohort study including prospective and retrospective clinical data. Age- and gender-adjusted treatment effects were estimated using generalised linear mixed models. Treated patients contributed data before and during treatment and untreated patients contributed natural history data. Consenting adults (N = 289) and children (N = 22) with a confirmed diagnosis of Fabry disease attending a specialist Lysosomal Storage Disorder treatment centre in England. At recruitment 211 adults and seven children were on ERT (range of treatment duration, 0 to 9.7 and 0 to 4.2 years respectively). Clinical outcomes chosen to reflect disease progression included left ventricular mass index (LVMI); proteinuria; estimated glomerular filtration rate (eGFR); pain; hearing and transient ischaemic attacks (TIA)/stroke. We found evidence of a statistically significant association between time on ERT and a small linear decrease in LVMI (p = 0.01); a reduction in the risk of proteinuria after adjusting for angiotensin-converting enzyme inhibitors and angiotensin receptor blockers (p

Current available evidence on long-term effectiveness of enzyme replacement therapy (ERT) for Fabry disease is limited. More insight is needed whether ERT effectiveness differs in patients with and without baseline end-organ damage. Through a systematic review, untreated and ERT treated males and females with Fabry disease were compared for main clinical outcomes: renal function, left ventricular mass (LVmass), cerebral white matter lesions (WMLs) and end-organ complications. Through a meta-analysis ERT effectiveness was estimated in different disease stages. Two reviewers assessed quality of the included studies according to guidelines for prognosis research. Data were synthesized using a random effects meta-analysis. Thirty-one studies were systematically reviewed while six studies were included in the meta-analysis. In patients with a GFR > 60 ml/min/1.73 m(2), decline of renal function was similar for treated and untreated patients. Only ERT treated males with a GFR

A number of studies have already investigated the prevalence of Fabry disease (FD) in adult patients with unexplained left ventricular hypertrophy (LVH) with rates varying from 0 % up to 12 % reflecting referral and gender bias as well as differences in diagnostic methodology. We aimed to perform a prospective screening study evaluating the prevalence of FD in male patients older than 30 years with strictly defined unexplained LVH followed by general cardiologists. A predefined number of 100 men with unexplained LVH, defined as maximal wall thickness ≥ 13 mm, were identified during an echocardiographic examination in primary cardiology practice and screened by assessing α-galactosidase A activity in dried blood spots (DBS) or in plasma. Four men (52 ± 4 years, maximal LV wall thickness 18 ± 3 mm) were diagnosed with FD confirmed by enzyme analysis in leukocytes as well as by genetic analysis. Mild extracardiac manifestations of FD were present in two of them. The prevalence of FD in our cohort of male patients followed in primary cardiology practice with strictly defined otherwise unexplained LVH was 4 %. We recommend systematic screening for FD in all men older than 30 years with LVH of unknown etiology even in the absence of obvious extracardiac manifestations of FD.

The advent of effective therapy for Fabry disease (FD) creates two challenges: (1) how do we identify individuals with the condition early in its natural history, and (2) how many people have the condition and require expensive therapy? Between 1981 and 2011, 17 new FD families were referred to the Northern Genetics Service in the North of England, the majority between 2005 and 2001. Since 2009 we have employed biochemical screening in dried blood spots from individuals with high risk phenotypes, such as left ventricular hypertrophy and unexplained renal failure, to identify four of the new index cases; and we have offered comprehensive cascade genetic testing to identify pre-symptomatic and symptomatic cases of FD in their 233 ‘at risk’ relatives. Overall, this combined approach identified a further 23 symptomatic cases of FD and 38 asymptomatic cases. The uptake of cascade genetic testing in this cohort was 48 %, which is similar to other inherited disorders for which there is an effective intervention. The minimum prevalence of GLA mutation in the North of England population at the end of 2011 was 1 in 40,800 and the prevalence of symptomatic FD was 1 in 64,600. Improved uptake of cascade genetic testing would increase these estimates to a maximum of 1 in 21,800 and 1 in 49,000 respectively. We suggest that any protocol for case identification should consist of targeted biochemical screening and coordinated cascade genetic testing.

Niemann-Pick disease (NPD) due to acid sphingomyelinase deficiency is a lipid storage disease resulting from the accumulation of sphingomyelin, predominantly within cells of the monocyte-macrophage system. In contrast to other lysosomal storage disorders, skeletal involvement in NPD has not been systematically studied. Pediatric and adult NPD-B patients underwent medical histories and physical examinations, DEXA scans to measure bone mineral content (BMC), and bone mineral density (BMD) and computed tomography scan or MRI of the abdomen for spleen volume. Z and/or T scores were calculated for the DEXA results. For the pediatric patients adjusted mean BMC (g) and BMD (g/cm2) of the lumbar spine, hip, and femoral neck was compared to control subjects. For determination of the relationship between spleen volume and lumbar spine BMD Z score, linear correlation analyses were performed. Lumbar spine Z scores for pediatric patients ranged from 0.061 to -4.879. Statistically significant decreases were observed for the adjusted mean BMC and BMD at the lumbar spine, hip, and femoral neck between the pediatric NPD-B cohort and control subjects. Most NPD-B adults were osteopenic or osteoporotic at one or more sites according the WHO classification of BMD. In NPD-B patients, the degree of splenomegaly was inversely correlated with lumbar spine BMD Z scores. Skeletal involvement is a common and previously unrecognized manifestation of NPD-B. The association between splenomegaly and BMD lends further support to spleen size as an indicator of disease severity.

Fabry disease is caused by deficient activity of α-galactosidase A and subsequent intracellular accumulation of glycosphingolipids, mainly globotriaosylceramide (Gb3). Vascular endothelial cells may play important roles in disease pathogenesis, and are one of the main target cell types in therapeutic interventions. In this study, we generated immortalized aortic endothelial cell lines from a mouse model of Fabry disease. These cells retained endothelial cell-specific markers and functions. Gb3 expression level in one of these clones (referred to as FMEC2) was highly susceptible to culture media, and appeared to be regulated by glucosylceramide synthase. Results also showed that Gb3 could be upregulated by hydrocortisone. FMEC2 express the mannose 6-phosphate receptor and sortilin but not the mannose receptor. Uptake studies suggested that sortilin plays a role in the binding and internalization of mammalian cell-produced α-galactosidase A. Moss-aGal (a plant-made enzyme) was endocytosed by FMEC2 via a receptor other than the aforementioned receptors. In conclusion, this study suggests that glucosylceramide synthase and hydrocortisone may play important roles in modulating Gb3 levels in Fabry mouse aortic endothelial cells, and that endocytosis of recombinant α-galactosidase A involves a combination of multiple receptors depending on the properties of the enzyme.

Cardiovascular survival in a cohort of 33 male Fabry patients followed for a median of 7.3 years at a single centre was most strongly associated in a Cox proportional hazard regression model with age and elevated arterial stiffness at baseline. Seven patients died of cardiovascular causes. The presence of cardiomyopathy and renal involvement (either clinical nephropathy or CKD stage >1) were also negatively associated with survival when analysed as single factors. In this small study, presence of hypertension and hypercholesterolemia at baseline did not significantly predict cardiovascular death. The significant effect of elevated arterial stiffness, especially in a small cohort, argues for its clinical utility in individual patient risk assessment and for further intervention studies focusing on therapeutic reduction.

The functional significance of missense mutations in genes encoding acid glycosidases of lysosomal storage disorders (LSDs) is not always clear. Here we describe a method of investigating functional properties of variant enzymes in vitro using a human embryonic kidney epithelial cell line. Site-directed mutagenesis was performed on the parental plasmids containing cDNA encoding for alpha-galactosidase A (α-Gal A) and acid maltase (α-Glu) to prepare plasmids encoding relevant point mutations. Mutant plasmids were transfected into HEK 293 T cells, and transient over-expression of variant enzymes was measured after 3 days. We have illustrated the method by examining enzymatic activities of four unknown α-Gal A and one α-Glu variants identified in our patients with Anderson-Fabry disease and Pompe diseases respectively. Comparison with control variants known to be either pathogenic or non-pathogenic together with over-expression of wild-type enzyme allowed determination of the pathogenicity of the mutation. One leader sequence novel variant of α-Gal A (p.A15T) was shown not to significantly reduce enzyme activity, whereas three other novel α-Gal A variants (p.D93Y, p.L372P and p.T410I) were shown to be pathogenic as they resulted in significant reduction of enzyme activity. A novel α-Glu variant (p.L72R) was shown to be pathogenic as this significantly reduced enzyme activity. Certain acid glycosidase variants that have been described in association with late-onset LSDs and which are known to have variable residual plasma and leukocyte enzyme activity in patients appear to show intermediate to low enzyme activity (p.N215S and p.Q279E α-Gal A respectively) in the over-expression system.

Cerebral micro- and macro-vasculopathy have been described in Fabry disease (FD). Neuronal globotriaosylceramide accumulation in selective cortical and brain stem areas including the hippocampus has been reported by autopsy studies in FD, but clinical surrogates as well as the clinical relevance of these findings have not been investigated so far. We measured the hippocampus volumes in a group of clinically affected patients with FD and correlated the findings with the cognitive performance of the patients. Hippocampal volumes were determined manually on T1-weighted MR-images of 25 FD patients (age 36.5 ± 11.0 years) and 20 age-matched controls. Additionally, individual white matter (WM) and gray matter (GM) volumes were measured using brain segmentation analyses. After controlling for age, white matter lesion (WML) volume, and WM/GM-volumes hippocampal volumes were significantly decreased in FD. These findings were substantially more pronounced in a subgroup of men with FD. WM and WM/GM volumes, and memory function did not significantly differ between patients and controls. In patients with FD hippocampal volumes were neither significantly correlated to WML volume nor to WM or WM/GM volumes. Hippocampus atrophy was not driven by the WML or other brain tissue atrophy and seems to correlate with the neuronal involvement in FD. In this young to middle-aged Fabry cohort the hippocampus degeneration was functionally compensated without memory impairment. Longitudinal studies are needed to determine whether this degenerative component in FD will progress and, in concert with the individual WML-load, predict subsequent cognitive decline.

Lysosomal storage disorders are inherited metabolic diseases in which a mutation in a gene encoding a lysosomal enzyme or lysosome-related protein results in the intra-cellular accumulation of substrate and reduced cell/tissue function. Few patients with neurodegenerative lysosomal storage disorders have access to safe and effective treatments although many therapeutic strategies have been or are presently being studied in vivo thanks to the availability of a large number of animal models. This review will describe the comparative advancement of a variety of therapeutic strategies through the 'research pipeline'. Our goal is to provide information for clinicians, researchers and patients/families alike on the leading therapeutic candidates at this point in time, and also to provide information on emerging approaches that may provide a safe and effective treatment in the future. The length of the pipeline represents the significant and sustained effort required to move a novel concept from the laboratory into the clinic.

Lysosomal storage diseases (LSDs) are metabolic disorders caused by enzyme deficiencies that lead to lysosomal accumulation of undegraded substrates. Enzyme replacement therapies (ERT) have been developed as treatments for patients with Gaucher, Niemann-Pick, Fabry, and Pompe diseases. Depending on the disease, the corresponding therapeutic enzyme is designed to be internalized by diseased cells through receptor-mediated endocytosis via macrophage mannose receptors (MMR) or mannose-6-phosphate receptors (M6PR). Enzymes developed to treat Gaucher and Niemann-Pick diseases are meant to target MMR-expressing cells, and in the case of Cerezyme [recombinant human β-glucocerebrosidase (rhβGC)] for treating Gaucher disease, glycans on the enzyme are modified to increase specificity toward this receptor. Due to heterogeneity in glycosylation on enzymes intended to target the M6PR, however, there may also be some unintended targeting to MMR-expressing cells, which could act as unwanted sinks. Examples include Fabrazyme [recombinant human α-galactosidase A (rhαGal)] for treating Fabry disease and Myozyme [recombinant human acid α-glucosidase (rhGAA)] for treating Pompe disease. It is therefore of great interest to better understand the cell type and tissue distribution of MMR in murine LSD models used to evaluate ERT efficacy and mechanism of action. In this study, we generated affinity-purified polyclonal antibody against murine MMR and used it to carry out a systematic examination of MMR protein localization in murine models of Gaucher, Niemann-Pick, Fabry, and Pompe diseases. Using immunohistochemistry, immunofluorescence, and confocal microscopy, we examined MMR distribution in liver, spleen, lung, kidney, heart, diaphragm, quadriceps, and triceps in these animal models and compared them with MMR distribution in wild-type mice.

A biomarker is an analyte indicating the presence of a biological process linked to the clinical manifestations and outcome of a particular disease. In the case of lysosomal storage disorders (LSDs), primary and secondary accumulating metabolites or proteins specifically secreted by storage cells are good candidates for biomarkers. Clinical applications of biomarkers are found in improved diagnosis, monitoring disease progression, and assessing therapeutic correction. These are illustrated by reviewing the discovery and use of biomarkers for Gaucher disease and Fabry disease. In addition, recently developed chemical tools allowing specific visualization of enzymatically active lysosomal glucocerebrosidase are described. Such probes, coined inhibodies, offer entirely new possibilities for more sophisticated molecular diagnosis, enzyme replacement therapy monitoring, and fundamental research.

Background Pompe disease is an orphan disease for which enzyme replacement therapy (ERT) recently became available. This study aims to estimate all relevant aspects of burden of illness—societal costs, use of home care and informal care, productivity losses, and losses in health-related quality of life (HRQoL)—for adult Pompe patients only receiving supportive care. Methods We collected data on all relevant aspects of burden of illness via a questionnaire. We applied a societal perspective in calculating costs. The EQ-5D was used to estimate HRQoL. Results Eighty adult patients (87% of the total Dutch adult Pompe population) completed a questionnaire. Disease severity ranged from mild to severe. Total annual costs were estimated at €22,475 (range €0–169,539) per adult Pompe patient. Patients on average received 8 h of home care and 19 h of informal care per week. Eighty-five percent of the patients received informal care from one or more caregivers; 40% had stopped working due to their disease; another 20% had reduced their working hours. HRQoL for Pompe patients who only received supportive care was estimated at 0.72, 17% lower than the Dutch population at large. Conclusions Adult Pompe disease is associated with a considerable burden of illness at both the societal and patient levels. The disease leads to substantial costs and dependency on medical devices, home care, and informal care, and has a high impact on the patient’s social network. In addition, patients are limited in their ability to work and have significantly reduced HRQoL.

Newborn screening for Fabry disease in Taiwan Chinese has revealed a high incidence of the late-onset GLA mutation IVS4 + 919G→A (∼1 in 1,500–1,600 males). We studied 94 adults with this mutation [22 men, 72 women; mean age: men 57.8 ± 6.0 (range 42–68), women 39.1 ± 14.1 years (range 19–82)]. Plasma α-galactosidase A activity assay was 10.4 ± 11.2% of normal in the men and 48.6 ± 19.5% of normal in the women. Echocardiography in 90 of the adults revealed left ventricular hypertrophy (LVH) in 19 (21%), including 14 of 21 men (67%) and 5 of 69 women (7%). Microalbuminuria, based on the urine albumin-to-creatinine ratio measured on at least two occasions, was present in 17 of 86 subjects (20%) (men: 5/20, 25%; women 12/66, 18%). At least one ocular manifestation consistent with Fabry disease was present in 41 of 52 subjects (79%) who underwent ophthalmologic examination, including 8 (15%) with conjunctival vessel tortuosity, 15 (29%) with cornea verticillata, 10 (19%) with Fabry cataract, and 34 (65%) with retinal vessel tortuosity. Among subjects over 40 years of age, men were more likely than women to have LVH [14/21 (67%) vs 5/25 (20%), p < 0.001]. Cardiovascular, renal and ocular abnormalities are highly prevalent in adult Taiwan Chinese subjects with the Fabry mutation IVS4 + 919G→A. Our findings contribute to the limited understanding of the course of this late-onset disease variant and underscore the need for close follow up in such patients.

Aspartylglycosaminuria (AGU) is a lysosomal storage disease caused by deficient activity of glycosylasparaginase (AGA), and characterized by motor and mental retardation. Enzyme replacement therapy (ERT) in adult AGU mice with AGA removes the accumulating substance aspartylglucosamine from and reverses pathology in many somatic tissues, but has only limited efficacy in the brain tissue of the animals. In the current work, ERT of AGU mice was initiated at the age of 1 week with three different dosage schedules of recombinant glycosylasparaginase. The animals received either 3.4 U of AGA/kg every second day for 2 weeks (Group 1), 1.7 U/kg every second day for 9 days followed by an enzyme injection once a week for 4 weeks (Group 2) or 17 U/kg at the age of 7 and 9 days (Group 3). In the Group 1 and Group 3 mice, ERT reduced the amount of aspartylglucosamine by 34 and 41% in the brain tissue, respectively. No therapeutic effect was observed in the brain tissue of Group 2 mice. As in the case of adult AGU mice, the AGA therapy was much more effective in the somatic tissues than in the brain tissue of the newborn AGU mice. The combined evidence demonstrates that a high dose ERT with AGA in newborn AGU mice is up to twofold more effective in reducing the amount of the accumulated storage material from the brain tissue than ERT in adult AGU animals, indicating the importance of early detection and treatment of the disease.

Anderson-Fabry disease (AFD) is an X-linked inherited lysosomal storage disorder disease caused by a deficiency in the activity of the alpha-galactosidase enzyme. We investigated neuropsychological and psychiatric function in AFD patients. We studied 16 AFD patients, aged 7 to 61 years. Intelligence, language, vision-spatial abilities, memory, sensorimotor abilities, and attention and executive functions were tested with a computerized test battery as well as standard paper and pencil tests. The results were compared to known age-based norms. In addition, all patients were screened for lifelong DSM-IV Axis-I and Axis-II psychiatric diagnoses, and 4 were interviewed by a psychiatrist. Performance on most cognitive measures was within average range. All measures of information processing speed were significantly reduced, as were some measures of executive functions. Ten out of 16 patients met DSM-IV criteria for Axis I or Axis II diagnoses at some point in their lives. This preliminary study delineates a psychiatric and cognitive phenotype in AFD patients and contributes to the growing field of characterizing behavioral phenotypes of patients with genetic diseases. We suggest that psychiatric and neuro-psychological evaluation be included in the patient's evaluation.

Interest in newborn screening (NBS) for lysosomal storage disorders (LSDs) has increased significantly due to newly developed enzyme replacement therapy (ERT), the need for early diagnosis, and advances in technical developments. Since the central nervous system cannot be treated by ERT, neuronopathic LSDs are generally not the primary target of NBS. An exception is Krabbe disease, in which hematopoietic stem cell transplantation before the onset of symptoms has benefits. However, NBS for LSD relies on measuring enzyme activities, so the most severely affected individuals (usually patients with neuronopathic subtypes) will be detected together with patients with less severe disease. In the near future, NBS is likely to be developed for diseases such as Gaucher, Niemann-Pick A/B, and certain mucopolysaccharidoses. The ability to predict phenotypes (neuronopathic or not) by enzyme activity and genotyping will therefore be critical for adequate patient management. This article reviews the status of LSD screening and issues concerning detection of neuronopathic LSDs by screening.

The aim of this retrospective study was to determine the prevalence of lysosomal storage disorders (LSDs) in the Czech Republic. The data on cases diagnosed between 1975 and 2008 were collected and analyzed. The overall prevalence of LSDs in the Czech population (12.25 per 100,000) is comparable to that reported for the countries with well-established and advanced diagnostics of LSDs such as the Netherlands (14 per 100,000), Australia (12.9 per 100,000) and Italy (12.1 per 100,000). Relatively higher prevalence of LSDs was reported in the north of Portugal (25 per 100,000). Thirty-four different LSDs were diagnosed in a total of 478 individuals. Gaucher disease was the most frequent LSD with a birth prevalence of 1.13 per 100,000 births. The most frequent LSD groups were lipidoses, mucopolysaccharidoses, and neuronal ceroid lipofuscinoses, with combined prevalences of 5.0, 3.72, and 2.29 per 100,000 live births, respectively. Glycoproteinoses (0.57 per 100,000 live births), glycogenosis type II (0.37), and mucolipidoses (0.31) rarely occur in the Czech population, and a range of other LSDs have not been detected at all over the past three decades. Knowledge of the birth prevalence and carrier frequency of particular disorders is important in genetic counselling for calculation of the risk for the disorder in the other members of affected families. Earlier diagnosis of these disorders will permit timely intervention and may also result in lowering of the number of newborns with LSDs.