Fabry disease and vascular risk factors: future strategies for patient-based studies and the knockout murine model

Fabry disease is secondary to deficiency of the lysosomal enzyme alpha-galactosidase A, leading to altered glycosphingolipid metabolism and accumulation that is often associated with endothelial dysfunction. Current evidence suggests that there is impairment of the vascular nitric oxide pathway, with abnormalities evident in the cerebral circulation and in the dermal vasculature of patients with Fabry disease. Some of these findings have been confirmed in a mouse model of Fabry disease. The murine model, however, allows investigation of Fabry disease at a non-clinical level and a near complete investigation of biological processes within an affected tissue. This is of particular utility in allowing gene expression analysis of clinically inaccessible tissues such as the aorta.Conclusion: Future developments in array technology for proteins and DNA single nucleotide polymorphism analysis, together with gene expression microarray analysis, may open a new chapter in our understanding of the biology of lysosomal storage disorders.     

Structure-function relationships in alpha-galactosidase A

With recent interest in the molecular mechanisms responsible for Fabry disease, the number of known mutations in the GLA gene which encodes alpha-galactosidase A has expanded considerably. Combining a large database of Fabry disease-causing mutations with the recently determined crystal structure of human alpha-galactosidase A allows for a new understanding of the atomic defects in the protein responsible for Fabry disease. We have conducted a systematic survey of the known Fabry disease-causing mutations and analyzed the mutations in the context of the alpha-galactosidase A structure. We have applied quantitative methods for identifying the plausible effect of each mutation on the alpha-galactosidase A protein. We present the analysis of 331 different defects in the GLA gene leading to non-native proteins in patients with Fabry disease. These mutations include 278 missense mutations, 49 nonsense mutations, and four single amino acid deletions. CONCLUSION: Over half of the residues in the protein have been found to have changes in patients with Fabry disease. Most of these genetic mutations lead to disruption of the hydrophobic core of the protein, thus Fabry disease is primarily a disease of protein-folding. Further understanding of alpha-galactosidase A, one of the best studied members of the lysosomal storage disease family, will lead to increased understanding of other lysosomal storage diseases and other protein-folding diseases.     

Disease manifestations and X inactivation in heterozygous females with Fabry disease

AIM: Fabry disease is an X-linked lysosomal storage disorder characterized by an accumulation of neutral glycosphingolipids in multiple organ systems caused by alpha-galactosidase A deficiency due to mutations in the GLA gene. The majority of heterozygous females show the characteristic signs and symptoms of the disease, and some of them are severely affected. The current hypothesis for the occurrence of disease manifestations in females is skewed X inactivation favouring the mutant GLA allele. METHOD: We analyzed the patterns of X inactivation in the leukocytes of 28 biochemically and genetically characterized symptomatic Fabry disease heterozygotes and their correlation with clinical and biochemical disease expression. RESULTS: X inactivation patterns in symptomatic females who are heterozygous for Fabry disease did not differ from those of female controls of the same age (p = 0.669). Thirteen (46%) of the 28 females with Fabry disease showed random X inactivation, ten (36%) moderate skewing, and five (18%) highly skewed X inactivation. Segregation analysis was performed in the families of six females who had highly or moderately skewed X inactivation. In four of these females, skewing favoured the wild-type GLA allele and in the other two skewing favoured the mutant allele. Patterns of X inactivation or the extent of skewing were not related to the severity of clinical manifestations or to residual enzyme activity. CONCLUSION: In this study we provide evidence that heterozygous females with Fabry disease show random X inactivation. Our data do not support the hypothesis that the occurrence and severity of disease manifestations in the majority of Fabry heterozygotes are related to skewed X inactivation.     

Disease manifestations and X inactivation in heterozygous females with Fabry disease

Aim: Fabry disease is an X-linked lysosomal storage disorder characterized by an accumulation of neutral glycosphingolipids in multiple organ systems caused by α-galactosidase A deficiency due to mutations in the GLA gene. The majority of heterozygous females show the characteristic signs and symptoms of the disease, and some of them are severely affected. The current hypothesis for the occurrence of disease manifestations in females is skewed X inactivation favouring the mutant GLA allele.
Method: We analyzed the patterns of X inactivation in the leukocytes of 28 biochemically and genetically characterized symptomatic Fabry disease heterozygotes and their correlation with clinical and biochemical disease expression.
Results: X inactivation patterns in symptomatic females who are heterozygous for Fabry disease did not differ from those of female controls of the same age ( p = 0.669). Thirteen (46%) of the 28 females with Fabry disease showed random X inactivation, ten (36%) moderate skewing, and five (18%) highly skewed X inactivation. Segregation analysis was performed in the families of six females who had highly or moderately skewed X inactivation. In four of these females, skewing favoured the wild-type GLA allele and in the other two skewing favoured the mutant allele. Patterns of X inactivation or the extent of skewing were not related to the severity of clinical manifestations or to residual enzyme activity.
Conclusion: In this study we provide evidence that heterozygous females with Fabry disease show random X inactivation. Our data do not support the hypothesis that the occurrence and severity of disease manifestations in the majority of Fabry heterozygotes are related to skewed X inactivation.     

Long-term expressed human α-Galactosidase A in tissues of HαG transgenic mice

BACKGROUND: Human alpha-galactosidase A (halphaG) is an essential lysosomal enzyme in catalyzing the hydrolysis of ceramide trihexoside in humans. Effects have been directed to develop effective gene and replacement therapies for the deficiency of halphaG, Fabry disease. In recent years, halphaG transgenic mice (TGM) have been established, and the expression of halphaG in their general organs has been reported. However, detailed distribution of the cells expressing halphaG have not yet been defined. METHODS: The distribution of halphaG in organs of the halphaG-TGM was studied by means of immunohistochemistry and enzyme assay. RESULTS: Immunohistochemical analysis revealed a systematic halphaG expression in the TGM, including endothelial cells of the bone marrow, liver, spleen, pancreas, lungs, uriniferous tubules in the kidneys, and choroids plexus in the brain. Enzyme assay demonstrated a persistent expression of halphaG in the TGM during 14-20 months after birth. CONCLUSION: A long-term expression of halphaG in organs may indicate halphaG-TGM as a useful tool in the research of gene and replacement therapies for Fabry disease.     

Gaucher and Fabry diseases: from understanding pathophysiology to rational therapies

Over the past 40 years there has been remarkable development in our understanding of the pathophysiology of lysosomal storage disorders. This review describes the research carried out on the sphingolipid storage disorders from the first demonstration of the underlying metabolic abnormality in Gaucher disease to the development of enzyme replacement therapy for Gaucher and Fabry diseases. Initial developments in gene therapy are also described.
Conclusion : The introduction of enzyme replacement therapy has provided a lifeline for patients with Gaucher or Fabry disease. It is anticipated that future developments, including gene therapy, will provide additional therapeutic options.     

Gaucher and Fabry diseases: from understanding pathophysiology to rational therapies

Over the past 40 years there has been remarkable development in our understanding of the pathophysiology of lysosomal storage disorders. This review describes the research carried out on the sphingolipid storage disorders from the first demonstration of the underlying metabolic abnormality in Gaucher disease to the development of enzyme replacement therapy for Gaucher and Fabry diseases. Initial developments in gene therapy are also described. CONCLUSION: The introduction of enzyme replacement therapy has provided a lifeline for patients with Gaucher or Fabry disease. It is anticipated that future developments, including gene therapy, will provide additional therapeutic options.     

The Mainz Severity Score Index (MSSI): development and validation of a system for scoring the signs and symptoms of Fabry disease

Fabry disease is a rare lysosomal storage disorder caused by the deficient activity of the lysosomal enzyme alpha-galactosidase A. The resultant storage of undegraded glycolipids leads to the progressive development of potentially life-threatening manifestations affecting multiple organ systems in the body. This paper describes the development of the Mainz Severity Score Index (MSSI), a scoring system for patients with Fabry disease.Conclusion: The MSSI score has been proven to be representative in patients with 'classic' Fabry disease and may be useful for monitoring clinical improvement in patients receiving enzyme replacement therapy.     

The Mainz Severity Score Index (MSSI): development and validation of a system for scoring the signs and symptoms of Fabry disease

Fabry disease is a rare lysosomal storage disorder caused by the deficient activity of the lysosomal enzyme α-galactosidase A. The resultant storage of undegraded glycolipids leads to the progressive development of potentially life-threatening manifestations affecting multiple organ systems in the body. This paper describes the development of the Mainz Severity Score Index (MSSI), a scoring system for patients with Fabry disease.
Conclusion: The MSSI score has been proven to be representative in patients with 'classic' Fabry disease and may be useful for monitoring clinical improvement in patients receiving enzyme replacement therapy.     

Apoptotic abnormalities in differential gene expression in peripheral blood mononuclear cells from children with Fabry disease

AIM: This study was designed to examine the effect of enzyme replacement therapy (ERT) on differential gene expression in peripheral blood mononuclear cells (PBMCs) of children with Fabry disease who had not previously been exposed to ERT. METHODS: Thirteen children with Fabry disease (age range, 6.5-17.0 years) were studied as part of a 6-month, open-label study of ERT with agalsidase alfa. Paired blood samples were taken at the start of the study and after 6 months of ERT. Further blood samples were also taken from 16 age-matched control subjects. PBMCs were isolated and, following RNA extraction, differential gene expression analysis was performed using the Human Genome U133 Plus 2.0 microarray. RESULTS: Twenty-one genes were determined to be differentially expressed in PBMCs of ERT-na?ve children with Fabry disease compared with healthy controls; neuronal apoptosis inhibitory protein ranked as the most significantly differentially expressed gene. Comparison of gene expression in children with Fabry disease prior to and after ERT showed that two genes were significantly differentially expressed (p < or = 0.05) following treatment; the expressed sequence tag (probe set ID, 243259_at) was downregulated, while expression of apoptosis-inducing factor was increased, possibly as an antioxidant counter-regulatory response. CONCLUSION: This study identifies a number of genes that are differentially expressed in a small cohort of children with Fabry disease relative to healthy controls. These genes may relate to the underlying biological abnormalities in Fabry disease.     

Fabry disease and the heart: an overview of the natural history and the effect of enzyme replacement therapy

Fabry disease is a genetic disorder caused by the deficiency of α-galactosidase A, resulting in the lysosomal accumulation of glycosphingolipids. Fabry disease may result in cardiac, cerebral and renal complications. Cardiac abnormalities in patients with Fabry disease were first described in the 1960s. In the 1990s a form of Fabry disease confined to the heart was reported; however, this variant is extremely rare and a more appropriate concept is of cardiac predominance of the disease in some patients. Up to 60% of males with classic Fabry disease have cardiac abnormalities, including left ventricular hypertrophy, valvular dysfunction and conduction abnormalities. Recent data suggest that left ventricular mass and systolic function in patients with Fabry disease improve after 12 months of enzyme replacement therapy (ERT); however, many of the patients studied are relatively young and have mild cardiac abnormalities, suggesting that more research into the efficacy of ERT in older patients is necessary.
Conclusion: Cardiac manifestations are common in patients with Fabry disease and are not confined to a 'cardiac variant' of the disease.     

Fabry disease and the heart: an overview of the natural history and the effect of enzyme replacement therapy

Fabry disease is a genetic disorder caused by the deficiency of alpha-galactosidase A, resulting in the lysosomal accumulation of glycosphingolipids. Fabry disease may result in cardiac, cerebral and renal complications. Cardiac abnormalities in patients with Fabry disease were first described in the 1960s. In the 1990s a form of Fabry disease confined to the heart was reported; however, this variant is extremely rare and a more appropriate concept is of cardiac predominance of the disease in some patients. Up to 60% of males with classic Fabry disease have cardiac abnormalities, including left ventricular hypertrophy, valvular dysfunction and conduction abnormalities. Recent data suggest that left ventricular mass and systolic function in patients with Fabry disease improve after 12 months of enzyme replacement therapy (ERT); however, many of the patients studied are relatively young and have mild cardiac abnormalities, suggesting that more research into the efficacy of ERT in older patients is necessary. Conclusion: Cardiac manifestations are common in patients with Fabry disease and are not confined to a 'cardiac variant' of the disease.     

Natural history of the cerebrovascular complications of Fabry disease

Fabry disease is a rare, X-linked lysosomal storage disease caused by an inborn deficiency of alpha-galactosidase A, which results in progressive accumulation of globotriaosylceramide in a range of cells and tissues. Neurological symptoms of Fabry disease, including peripheral neuropathy and cerebrovascular events, are among the most significant clinical aspects. In this paper we present the natural history and mechanisms involved in the cerebrovascular complications of Fabry disease using data reported in FOS-- the Fabry Outcome Survey--and other registries and clinical studies. We discuss ways in which these manifestations can be modified by intervention, including both general measures for cerebrovascular disease and enzyme replacement therapy. Conclusion: Data from FOS have provided important insights into the natural history of the cerebrovascular complications of Fabry disease. Furthermore, the database has demonstrated that significant renal or cardiac disease often co-exists with cerebrovascular disease, and may predispose patients with Fabry disease to neurological disability and stroke.     

Natural history of the cerebrovascular complications of Fabry disease

Fabry disease is a rare, X-linked lysosomal storage disease caused by an inborn deficiency of α-galactosidase A, which results in progressive accumulation of globotriaosylceramide in a range of cells and tissues. Neurological symptoms of Fabry disease, including peripheral neuropathy and cerebrovascular events, are among the most significant clinical aspects. In this paper we present the natural history and mechanisms involved in the cerebrovascular complications of Fabry disease using data reported in FOS – the Fabry Outcome Survey – and other registries and clinical studies. We discuss ways in which these manifestations can be modified by intervention, including both general measures for cerebrovascular disease and enzyme replacement therapy.
Conclusion: Data from FOS have provided important insights into the natural history of the cerebrovascular complications of Fabry disease. Furthermore, the database has demonstrated that significant renal or cardiac disease often co-exists with cerebrovascular disease, and may predispose patients with Fabry disease to neurological disability and stroke.     

Genotype and phenotype in Fabry disease: analysis of the Fabry Outcome Survey

Aim: Mutations of the gene ( GLA ) encoding α-galactosidase A are implicated in Fabry disease, a progressive, X-chromosomal inherited lysosomal storage disorder. FOS – the Fabry Outcome Survey – was established as a long-term surveillance study to describe the natural course of Fabry disease and its response to enzyme replacement therapy in a large cohort of European patients. Clinical phenotype, age of onset and course of Fabry disease are very variable, even within the same family, which makes it difficult to define a genotype–phenotype relationship by analysing individual patients. The FOS database contains detailed medical information on a large cohort of patients and thus has the potential to provide important information to address this question. Methods: At the time of analysis, information on 545 patients belonging to 157 families from nine European countries had been entered into the FOS database. A GLA mutation has been reported in 365 individuals (65% and 68% of all males and females, respectively) in FOS. These data were used to analyse the relationship between genotype and phenotype in Fabry disease. Results: A highly significant positive correlation was found between the age at entry into FOS and the FOS Severity Index in male patients with GLA missense mutations ( p <0.001) as well as in those carrying other types of mutations ( p <0.001). A positive correlation was also found between the age at entry into FOS and the number of affected organs in male patients with missense mutations, irrespective of whether the change in the amino acid side chain predicted in the α-galactosidase A protein was classified as a conservative or non-conservative change.
Conclusion: The data presented here suggest that there is a correlation between genotype and clinical severity.     

Genotype and phenotype in Fabry disease: analysis of the Fabry Outcome Survey

AIM: Mutations of the gene (GLA) encoding alpha-galactosidase A are implicated in Fabry disease, a progressive, X-chromosomal inherited lysosomal storage disorder. FOS--the Fabry Outcome Survey - was established as a long-term surveillance study to describe the natural course of Fabry disease and its response to enzyme replacement therapy in a large cohort of European patients. Clinical phenotype, age of onset and course of Fabry disease are very variable, even within the same family, which makes it difficult to define a genotype-phenotype relationship by analysing individual patients. The FOS database contains detailed medical information on a large cohort of patients and thus has the potential to provide important information to address this question. METHODS: At the time of analysis, information on 545 patients belonging to 157 families from nine European countries had been entered into the FOS database. A GLA mutation has been reported in 365 individuals (65% and 68% of all males and females, respectively) in FOS. These data were used to analyse the relationship between genotype and phenotype in Fabry disease. RESULTS: A highly significant positive correlation was found between the age at entry into FOS and the FOS Severity Index in male patients with GLA missense mutations (p < 0.001) as well as in those carrying other types of mutations (p < 0.001). A positive correlation was also found between the age at entry into FOS and the number of affected organs in male patients with missense mutations, irrespective of whether the change in the amino acid side chain predicted in the alpha-galactosidase A protein was classified as a conservative or non-conservative change. CONCLUSION: The data presented here suggest that there is a correlation between genotype and clinical severity.     

Proteinuria and its consequences in renal disease

Chronic renal diseases that involve proteinuria are typically characterized by an inexorable progression to end-stage renal failure. Many studies suggest that this progression may be the result of factors, such as intraglomerular hypertension and glomerular hypertrophy, that are unrelated to the initial disease. This paper reviews the mechanisms of progression of chronic renal diseases and discusses therapeutic strategies that should prevent or minimize further renal damage and the applicability of these strategies to patients with the rare X-linked lysosomal storage disorder Fabry disease. Renal involvement is a major feature of Fabry disease, which is characterized by vacuolated epithelial cells in the glomerulus and distal tubules, resulting from lipid inclusions within these cells. Although enzyme replacement therapy is the key strategy to halt the progression of Fabry disease, additional therapeutic options include blood pressure control, reduction of proteinuria, lipid control and inhibition of the renin-angiotensin system.
Conclusion : A range of therapeutic options, used in conjunction with enzyme replacement therapy, may have beneficial effects on the renal manifestations of Fabry disease.     

Proteinuria and its consequences in renal disease

Chronic renal diseases that involve proteinuria are typically characterized by an inexorable progression to end-stage renal failure. Many studies suggest that this progression may be the result of factors, such as intraglomerular hypertension and glomerular hypertrophy, that are unrelated to the initial disease. This paper reviews the mechanisms of progression of chronic renal diseases and discusses therapeutic strategies that should prevent or minimize further renal damage and the applicability of these strategies to patients with the rare X-linked lysosomal storage disorder Fabry disease. Renal involvement is a major feature of Fabry disease, which is characterized by vacuolated epithelial cells in the glomerulus and distal tubules, resulting from lipid inclusions within these cells. Although enzyme replacement therapy is the key strategy to halt the progression of Fabry disease, additional therapeutic options include blood pressure control, reduction of proteinuria, lipid control and inhibition of the renin-angiotensin system. CONCLUSION: A range of therapeutic options, used in conjunction with enzyme replacement therapy, may have beneficial effects on the renal manifestations of Fabry disease.     

Enzyme reconstitution/replacement therapy for lysosomal storage diseases

PURPOSE OF REVIEW: Over the past 15 years, the lysosomal storage diseases have become paradigms for the specific treatment of monogenic disorders, particularly those affecting children. This review summarizes the phenotypes and recent literature regarding enzyme reconstitution (replacement) therapy and outcomes for such treatable lysosomal storage diseases: Gaucher disease, Fabry disease, Pompe disease and the mucopolysaccharidoses. RECENT FINDINGS: Recent clinical trials have shown that enzyme reconstitution therapy effectively treats many of the manifestations of the lysosomal storage diseases. When initiated early in the disease course, enzyme reconstitution therapy can reverse some disease manifestations, but may not completely alleviate the disease progression. Enzyme reconstitution therapy is generally well tolerated. Many adverse events are antibody-related, but can be managed without requiring cessation of enzyme reconstitution therapy. Documented IgE reactions, i.e. anaphylactoid, are quite rare (fewer than 1%). SUMMARY: Enzyme reconstitution therapy is a safe and effective treatment modality available for several of the lysosomal storage diseases. Owing to the short history of enzyme reconstitution therapy, the long-term outcomes of enzyme reconstitution therapy-treated individuals are unknown and require further investigation. Medical professionals must learn to identify patients likely to benefit from these life-changing therapies so as to prevent many of the devastating, irreversible complications of the lysosomal storage diseases.     

Diagnostic problems in a 17-year-old patient with gastrointestinal manifestations of Fabry disease

Fabry disease is a rare X-linked recessive lysosomal storage disorder caused by deficiency of lysosomal enzyme alpha-galactosidase, which leads to accumulation of globotriasylceramides (GL-3) in visceral tissues and vascular endothelium, causing multi-organ failure. We presenta case of Fabry disease in a 17-year-old patient with mainly gastrointestinal manifestations, diagnosed 10 years after the manifestation of first symptoms. Significant and progressive weight loss with abdominal pain and vomiting, leading to cachexia, were observed in early childhood. The patient was investigated for non-inflammatory bowel diseases, Raynaud syndrome, polimyositis, mitochondrial cytopathies, intestinal lypodystrophies and others. The symptoms of intenstinal pseudo-obstruction syndrome were observed and surgical treatment was instituted because of necrosis of the colon. There was progressive cachexia and parenteral nutrition had to be instituted. Finally, plasma alpha-galactosidase was measured, and its deficit confirmed Fabry disease. In conclusion gastrointestinal symptoms in the course of Fabry disease can obscure other characteristic symptoms, may be prodromal and leading. Heart and renal failure may not occur in children. Unexplained abdominal pain and malnutrition may be gastrointestinal manifestations of metabolic disorders.