alpha-Galactosidase A deficiency in Dutch patients on dialysis: a critical appraisal of screening for Fabry disease.

INTRODUCTION: Fabry disease or alpha-galactosidase A (alpha-Gal A) deficiency is an X-linked lysosomal storage disorder that often leads to renal insufficiency in males and occasionally in females. The disease is rare, but its prevalence may be underestimated due to its variable clinical picture. Enzyme supplementation therapy with rHu-alphaGal A is currently available. Limited experience has so far shown that therapy may at best stabilize renal function. Despite these preliminary findings, much effort is being put into screening high-risk groups for undiagnosed alpha-Gal A deficiency. We studied the prevalence of alpha-Gal A deficiency in a Dutch dialysis cohort to establish possible underdiagnosis. We discuss the benefits of screening for Fabry disease. METHODS: Activity of alpha-Gal A in whole blood was measured in a group of 508 male Dutch dialysis patients. RESULTS: Of the 508 patients studied only one patient, already known with Fabry disease, had a alpha-Gal A deficiency, a prevalence of 0.22% (95 CI 0-1.1%). CONCLUSIONS: No undiagnosed Fabry patients were found, indicating that in our studied cohort there is no large-scale underestimation of its prevalence. Even though screening of dialysis patients for Fabry disease might identify patients who remain otherwise unrecognized, screening of high-risk populations for alpha-Gal A deficiency should be carried out with caution since long-term efficacy of treatment is currently unknown.     

Fabry Disease in Hemodialysis Patients in Southern Brazil: Prevalence Study and Clinical Report

Background. Fabry disease (FD) is a lysosomal storage disorder caused by a deficiency of α-Galactosidase A (α-Gal A). Fabry nephropathy typically progresses throughout the fifth decade to end-stage renal disease (ESRD), requiring hemodialysis and/or kidney transplantation. Objective. To estimate the prevalence of FD among ESRD males on hemodialysis treatment in Rio Grande do Sul, the southernmost state of Brazil. Methods. Screening for α-Gal A activity was performed by a dried blood spot (normal reference value: >1.5 nmoles/hour/mL). Positive screening results were confirmed by plasma α-Gal A activity assay (reference value: >3.3 nmoles/hour/mL). Results. Five hundred fifty-eight male patients on hemodialysis were evaluated. Of these, only two had low α-Gal A activity and were diagnosed with Fabry disease (0.36%). One of these, age 42, had left ventricular hypertrophy and renal manifestations of Fabry disease without the classic symptoms. The other, age 46, had the classical manifestations of angiokeratomas, acroparesthesias, hypohidrosis, and ocular opacities. Conclusions. Although the prevalence of Fabry disease was very low in our study (0.36%), routine screening of male hemodialysis patients would enable earlier identification of many other affected relatives in their families who might benefit from specific clinical treatment.     

Identification of Fabry's disease by the screening of alpha-galactosidase A activity in male and female hemodialysis patients

BACKGROUND: Although previous studies reported that the prevalence of Fabry's disease was 0.16 - 1.2% in hemodialysis (HD) patients based on measurement of a-galactosidase A (alpha-Gal A) activity, few reports detected female patients by the screening for alpha-Gal A. Here we determined the prevalence of Fabry's disease not only in male but also in female HD patients by measuring alpha-Gal A. METHODS: Plasma alpha-Gal A was measured in 696 consecutive males (n = 401) and females (n = 295) on HD. Patients with low plasma alpha-Gal A were examined for leukocyte alpha-Gal A, and patients with low leukocyte alpha-Gal A underwent alpha-Gal A gene sequence analysis for possible mutations, and family survey. RESULTS: Among 15 patients with low plasma alpha-Gal A activity, 4 male patients with low leukocyte alpha-Gal A and 1 female patient revealing low plasma alpha-Gal A were detected in 696 HD patients (0.7% of total patients). 3 of these 5 patients were already diagnosed to have the classical type of Fabry's disease. The other 2 patients were newly diagnosed as Fabry's disease, and did not have typical manifestations of Fabry's disease other than renal failure and left ventricular hypertrophy. DNA analysis of these 2 newly diagnosed patients revealed that each had an alpha-Gal missense mutation, previously identified (E66Q, M2961). CONCLUSION: Fabry's disease should be considered in the etiology of unexplained end-stage renal disease. Not only affected males but also affected females undergoing HD patients can be readily diagnosed by alpha-Gal A activities and gene analysis. These patients and their family members may benefit from enzyme replacement therapy for Fabry's disease.     

Fabry disease: detection of undiagnosed hemodialysis patients and identification of a "renal variant" phenotype

BACKGROUND: Fabry disease is an X-linked recessive lysosomal storage disease resulting from deficient alpha-galactosidase A (alpha-Gal A) activity. Renal failure is a major debilitating complication in classically affected males. To determine if this disorder is underdiagnosed in patients with end-stage renal disease (ESRD), the frequency of unrecognized males with Fabry disease on chronic hemodialysis was determined. METHODS: Plasma alpha-Gal A activity was measured in 514 consecutive males with ESRD on hemodialysis. Patients with low alpha-Gal A activity were evaluated clinically and their alpha-Gal A mutations were determined. RESULTS: Six (1.2%) of 514 hemodialysis patients had low plasma alpha-Gal A activities and a previously identified (E66Q, A97V, M296I) or novel (G373D) missense mutation. At ages 30 to 68 years, five patients lacked the classic manifestations of angiokeratoma, acroparesthesias, hypohidrosis, and ocular opacities, while the sixth lacked angiokeratoma and ocular changes. Five had left ventricular hypertrophy (LVH). CONCLUSION: The clinical spectrum of Fabry disease includes a "renal variant" phenotype in patients without classic symptoms who develop ESRD. Affected males undergoing hemodialysis or renal transplantation can be readily diagnosed by plasma alpha-Gal A assays. These patients and their family members may benefit from enzyme replacement therapy for the later, life-threatening cardiovascular and cerebrovascular complications of Fabry disease.     

Identification of a novel mutation and prevalence study for fabry disease in Japanese dialysis patients

Fabry disease--a genetic disorder characterized by the accumulation of globotriaosylceramide in cell lysosomes resulting from an X-linked deficiency of α-galactosidase A activity--presents with multiorgan manifestations, including progressive renal disease. Recently, its prevalence has been reported to be higher in hemodialysis (HD) patients than in the general population. We, therefore, examined patients on maintenance dialysis living in the Nagasaki Prefecture, Japan, to clarify the prevalence of Fabry disease. We screened 933 patients on maintenance dialysis, who were residents of Nagasaki Prefecture in Japan, for α-galactosidase A activity using a dried blood spot on filter paper. Patients with low α-galactosidase A activity were clinically assessed; subsequently, genetic analysis of the α-Galactosidase A gene (MIM:30064) was performed in these patients. Of the 933 patients, 55 had low α-galactosidase A activity; of these, one male and two females had α-Galactosidase A mutations. The prevalence of Fabry disease was thus 0.32%, which was similar to that reported previously. However, one mutation was newly identified, while the E66Q mutation observed in two patients was as previously identified. These two patients with the E66Q mutation were excluded because of the possibility of polymorphism; the prevalence of Fabry disease in the HD population was finally calculated to be 0.11%. The prevalence of Fabry disease in patients on maintenance dialysis living in Nagasaki Prefecture was 0.32%. Dried blood spot screening was considered as a simple and effective method for screening patients on maintenance dialysis for Fabry disease.     

Combined Heart and Kidney Transplantation in a Patient with Fabry Disease in the Enzyme Replacement Therapy Era

Fabry disease (FD) is an X-linked genetic disease, resulting from the deficiency of alpha-galactosidase A, a lysosomal enzyme responsible for the cleavage of glycosphingolipids. In absence of enzyme replacement therapy (ERT), globotriaosylceramide (Gb3) accumulates in tissue, leading to progressive organ damage with severe renal, cardiac and central nervous system complications.
We herein describe the first case of successful combined and simultaneous heart and kidney transplantation in a young male patient with FD complicated by end-stage renal disease and severe heart failure not responding to late-onset ERT.
Combined heart and kidney transplantation can be recommended for Fabry patients with end-stage renal disease and overt hypertrophic cardiomyopathy, severe ischemic or valvular heart disease.     

Fabry disease: diagnosis and treatment

Fabry disease is an X-linked lysosomal storage disorder that results from a deficiency of the enzyme alpha-galactosidase A (alpha-Gal A). The lack of alpha-Gal A causes an intracellular accumulation of glycosphingolipids, mainly globotriaosyceramide (GL3). Affected organs include, among others, the vascular endothelium, heart, brain, and kidneys, leading to end-stage renal disease (ESRD). Since Fabry disease cannot be cured at present, clinical management is symptomatic. Enzyme replacement therapy (ERT) with recombinant alpha-Gal A has been introduced as a new therapeutic option for the treatment of Fabry patients. Short-term (one year) clinical studies have positively correlated ERT with improvement of clinical symptoms and microvascular endothelial cell clearance. Treatment outcome concerning severe organ manifestations such as proteinuria and renal function impairment, left ventricular hypertrophy, and heart failure in the long run has yet to be shown. In our studies we used sensitive and noninvasive techniques such as ultrasound-based strain rate imaging and magnetic resonance imaging (MRI), combined with MR-spectroscopy (MR-S), for the quantification of functional abnormalities at an early stage of the disease and during long-term follow-up. Future issues should determine the appropriate timing to start therapy and how children and heterozygous females should be managed. Given the diagnostic and therapeutic potential today, it is of importance to identify patients at an early stage and to start therapeutic intervention before progression of organ damage is inevitable.     

Agalsidase therapy in patients with Fabry disease on renal replacement therapy: a nationwide study in Italy.

BACKGROUND: In Fabry disease, end-stage renal disease (ESRD) and severe neurologic and cardiac complications represent the leading causes of late morbidity and mortality. A comprehensive Italian nationwide survey study was conducted to explore changes in cardiac status and renal allograft function in Fabry patients on renal replacement therapy (RRT) and enzyme replacement therapy (ERT). METHODS: This study was designed as a cross-sectional survey study with prospective follow-up. Of the 34 patients identified via searches in registries, 31 males and 2 females who received RRT and ERT (agalsidase beta in 30 patients, agalsidase alpha in 3) were included. Left ventricular mass index (LVMI), interventricular septal thickness at end diastole (IVSD), left ventricular posterior wall thickness (LVPWT) and renal allograft function were assessed at ERT baseline and subsequently at yearly intervals. RESULTS: The patients in the dialysis and transplant groups had been started on dialysis at age 42.0 and 37.1 years (mean), respectively, and patients in the transplant group received their renal allograft at age 39.8 years (mean). The mean age at the start of ERT was similar, 44.1 and 44.6 years, respectively. The mean RRT follow-up was 61.1 and 110.6 months for dialysis and transplant patients, respectively, whereas the ERT duration was 45.1 and 48.4 months, respectively. Cardiac parameters increased in dialysis patients. In transplant patients, mean LVMI seemed to plateau during agalsidase therapy at a lower level as compared to baseline. Decline in renal allograft function was relatively mild (-1.92 ml/min/year). Agalsidase therapy was well tolerated. Serious ERT-unrelated events occurred more often in the dialysis group. CONCLUSIONS: Kidney transplantation should be the standard of care for Fabry patients progressing towards ESRD. Transplanted Fabry patients on ERT may do better than patients remaining on maintenance dialysis. Larger, controlled studies in Fabry patients with ESRD will have to demonstrate if ERT is able to change the trajectory of cardiac disease and can preserve graft renal function.     

Echocardiographic and clinical findings in patients with Fabry disease during long-term enzyme replacement therapy: a nationwide Danish cohort study

Objectives: In patients with Fabry disease (FD), left ventricular hypertrophy and arrhythmias are frequently observed and cardiac involvement is the leading cause of death. Long-term efficacy of enzyme replacement therapy (ERT) on cardiac involvement is unclear. We assessed and compared long-term progression of cardiac involvement according to ERT and non-ERT. Methods: We retrospectively assessed and compared long-term progression of cardiac involvement in adult patients with FD in the nationwide Danish cohort. We followed clinical signs, symptoms and findings by echocardiography, electrocardiography and Holter-monitoring. Results: We included 66 patients; 47 patients (27 women) received ERT (ERT group) and 19 patients (15 women) did not (non-ERT group). The groups were followed for a median of 8 [0–12] years and 6 [0–13] years, respectively. Comparison between ERT and non-ERT receiving patients by left ventricular mass (echocardiographic assessment) and Sokolow-Lyon voltage- and Cornell product criteria (electrocardiographic assessment) revealed no significant differences. In the ERT group, we observed no change in left ventricular mass but a decrease in Sokolow-Lyon voltage- and Cornell product criteria from baseline to follow-up; 30?mm [15–53] vs. 25?mm [3–44], p?p?Discussion: We raise concerns regarding the efficacy and benefit of ERT on cardiac involvement in Fabry disease and stress the need for further research.     

Fabry disease: clinical spectrum and evidence-based enzyme replacement therapy

The clinical spectrum of Fabry disease, an X-linked lysosomal storage disorder due to alpha-galactosidase A (alpha-Gal A) deficiency, has been expanded beyond the classic phenotype to include the recently recognized later-onset "cardiac" and "renal" variants. The clinical manifestations in each of these disease subtypes are presented with particular emphasis on early recognition among pediatric patients as well as identification of unrecognized patients diagnosed as hypertrophic cardiomyopathy or in renal dialysis clinics. Previously, treatment of patients with Fabry disease was limited to palliative care of the excruciating pain, cardiac and cerebrovascular manifestations, and renal failure. Recently, Fabry-specific enzyme replacement therapy (ERT) with recombinant alpha-Gal A (Fabrazyme) has proven safe and effective. The preclinical, Phase 1/2 and multicenter, double-blind, randomized, placebo-controlled Phase 3 and 4 trials provided the evidence for the safety and efficacy of Fabrazyme treatment. The preclinical and Phase 1/2 studies demonstrated that enzyme delivery to various tissues and GL-3 clearance were dose-dependent. The Phase 3 clinical trial and 3-year extension study provided long-term data documenting the safety and effectiveness of 1 mg/kg of Fabrazyme for this disease. Finally, the "top-line" data from the Phase 4 trial indicates that in patients with mildly to moderately advanced renal disease, Fabrazyme can slow the progression of renal, cardiac, and cerebrovascular events taken together or individually. The Phase 4 trial results also emphasize the importance of early treatment. In sum, these clinical trials provide the evidence-based safety and efficacy of Fabrazyme replacement therapy for Fabry disease.     

The frequency of Fabry disease with the E66Q variant in the α-galactosidase A gene in Japanese dialysis patients: a case report and a literature review

Fabry disease (FD) is an Xlinked disorder resulting in a deficiency in α-galactosidase A (α-Gal) activity. FD is one of the causes of progressive renal dysfunction, but its diagnosis is often delayed or missed completely. We herein report the case of a 70-year-old male who had been receiving hemodialysis (HD) for 23 y who was diagnosed with FD after his participation in a screening program for plasma α-Gal activity for 892 HD patients. He had a low plasma α-Gal activity level and was demonstrated to have an E66Q mutation in exon 2 of the α-Gal gene. One of his daughters had the same mutation. The proband died due to aspiration pneumonia before receiving enzyme replacement therapy. We reviewed previous studies and found E66Q mutation in 36% of Japanese FD patients on HD including the present case. The clinical characteristics of E66Q variant are also discussed.     

A nonsense mutation (R220X) in the alpha-galactosidase A gene causes typical Fabry disease in both genders

BACKGROUND: Fabry disease is an X-linked recessive disorder resulting from a deficiency of lysosomal alpha-galactosidase A (alpha-Gal A). Chronic renal failure is an important cause of death in patients with Fabry disease. We report on patients with Fabry disease (a hemizygous male and his mother) due to a nonsense mutation (R220X) in the alpha-Gal A gene. METHODS: The proband, a 41-year-old man, and his 71-year-old mother presented with renal and cardiac manifestations of Fabry disease. Histological examination and molecular analysis of the alpha-Gal A gene were performed. RESULTS: Typical histological findings of Fabry disease were observed in a renal biopsy specimen from the proband and in renal and myocardial necropsy specimens from the mother. Sequencing of a full-length alpha-Gal A cDNA from the proband indicated a C-T transition at codon 220, resulting in substitution of the predictable termination for arginine (R220X). Examination of genomic alpha-Gal A DNA revealed that the proband was a hemizygote and the mother was a heterozygous carrier for the mutation. CONCLUSION: This is the first detailed report of family members with Fabry disease due to a nonsense mutation (R220X) in the alpha-Gal A gene. Our study indicates that this mutation causes the typical disease in both genders.     

Enzyme therapy for Fabry disease: neutralizing antibodies toward agalsidase alpha and beta

BACKGROUND: Fabry disease is an X-linked inherited disorder that is caused by excessive lysosomal globotriaosylceramide (CTH) storage due to a deficiency in alpha-galactosidase A (alpha-Gal A). Two recombinant enzyme preparations have been approved as treatment modality. We studied emergence and properties of alpha-Gal A antibodies in treated patients. METHODS: During the first 6 to 12 months of intravenous administration of recombinant enzymes (rh-alpha-Gal A) formation of antibodies was studied in 18 adult Fabry patients (two females). RESULTS: The female patients did not develop detectable amounts of antibodies following enzyme therapy. After 6 months of treatment with either agalsidase alpha or beta, 11/16 male patients showed high titers of immunoglobulin G (IgG) antibodies that cross-react in vitro similarly with both recombinant enzymes. The anti-rh-alpha-Gal A IgG neutralizes rh-alpha-Gal A activity in vitro for 65% to 95%. During infusion with rh-alpha-Gal A, circulating enzyme-antibody complexes are formed and these complexes are taken up by leukocytes in the peripheral blood. After 6 months of treatment all IgG-negative patients showed a significant (P < 0.01) reduction of urinary CTH (1890 +/- 797 to 603 +/- 291 nmol CTH/24hr urine), compared to IgG-positive patients (mean increase from 2535 +/- 988 to 2723 +/- 1212), suggesting a negative effect of circulating antibodies on renal tubular CTH clearance. CONCLUSION: Emergence of antibodies with in vivo neutralizing capacities is frequently encountered in treated Fabry disease patients. Complete cross-reactivity of these antibodies suggests that it is unlikely that switching from one to the other recombinant protein prevents the immune response and related effects. Further studies on the clinical implications of alpha-Gal A antibodies are essential.     

Anderson–Fabry disease: a case-finding study among male kidney transplant recipients in Austria

The diagnosis of Anderson–Fabry disease is often delayed or even missed. As severe renal manifestations are a hallmark of alfa-galactosidase A (AGAL) deficiency, we tested the hypothesis that Anderson–Fabry disease is under-recognized among male kidney transplant recipients. This nation-wide study in Austria enrolled 1306 patients (ca 65% of all kidney transplanted males) from 30 kidney centers. AGAL activity was determined from filter paper dried blood spots by a fluorescence assay. A positive screening test was defined by an AGAL activity below 1.5 nmol/h/ml. In patients with a positive blood spot-screening test, AGAL activity was re-examined in peripheral blood leukocytes. Genetic testing for mutations in the GLA gene was performed by sequencing to confirm the diagnosis of Anderson–Fabry disease. Two previously not recognized cases with Anderson–Fabry disease were identified. Our study is the first showing that a diagnosis of Anderson–Fabry disease can be missed even in patients who undergo kidney transplantation. Case-finding strategies may be considered a useful tool for diagnosis of this rare disease that may be somewhat more prevalent among kidney transplant recipients compared with dialysis populations.     

Kidney transplantation in patients with Fabry disease

Little is known about the effects of enzyme replacement therapy (ERT) in kidney transplant recipients with Fabry disease. Clinical characteristics of transplant recipients in the Fabry Outcome Survey (FOS) were therefore examined in patients with Fabry disease with or without ERT. Of the 837 European patients in FOS (March 2006), 34 male patients and two female patients had received kidney transplants. Mean age at transplantation was 37.6 ± 10.9 years, mean time since transplantation was 7.7 ± 6.4 years, median estimated glomerular filtration rate (eGFR) was 44.4 ml/min/1.73 m², and median proteinuria was 296 mg/24 h. Of 27 patients with baseline data, 59% had hypertension, 74% had left ventricular hypertrophy, 22% had cardiac valve disease, 30% had arrhythmia, and 22% had transient ischaemic attacks and 15% stroke. Twenty patients (74%; two female patients, 18 male patients) were receiving ERT with agalsidase alfa. At enrolment or at the start of ERT, median eGFRs were 59 and 35 ml/min/1.73 m² ( P  = 0.05) and median proteinuria levels were 240 and 420 mg/24 h (not significant) in treated and untreated patients respectively. Renal function remained stable in patients receiving ERT. In conclusion, agalsidase alfa is well tolerated in patients with Fabry disease who have undergone renal transplantation.     

Enzyme replacement therapy in Fabry's disease: recent advances and clinical applications

Fabry's disease is a rare X-linked recessive disorder resulting from deficient lysosomal enzyme, alpha-galactosidase A (alpha-Gal A) activity. The deficiency leads to progressive glycosphingolipid globotriaosylceramide (Gb3) accumulation in fluids and tissues, including vascular endothelium, connective tissue, kidney, heart, brain and peripheral nerves. Classic Fabry's disease in hemizygous males has high morbidity and mortality due to end-stage renal disease (ESRD) requiring hemodialysis (HD) or kidney transplantation, myocardial involvement and central nervous system (CNS) complications. Most heterozygous females can also suffer from this severe disease deterioration. Until recently, Fabry's disease management consisted of symptomatic and palliative treatment, but this has changed with the availability of the recombinant human alpha-Gal A enzyme, agalsidase. Two different agalsidase formulations have been obtained: one from human fibroblast (agalsidase alpha), and one from Chinese hamster ovary (CHO) cells (agalsidase beta). Both preparations underwent clinical trials that documented the feasibility, efficacy and safety of the treatment. In addition, several clinical observations have proved that agalsidase reduces the storage of the substrate from several organs and tissues and, consequently, improves signs and symptoms of Fabry's disease. Additional clinical experiences have confirmed the initial clinical trial results, but further studies are needed to evaluate the long-term outcome of enzyme replacement therapy (ERT). We reviewed the clinical trial observations, as well as subsequent clinical experiences with ERT in patients with Fabry's disease.     

Cystatin C as a marker of early changes of renal function in Fabry nephropathy

BACKGROUND: A sensitive, feasible and reproducible marker for renal function is necessary to evaluate the clinical efficacy of enzyme replacement therapy (ERT) in Fabry nephropathy. Serum creatinine has some limitations and cystatin C has been proposed, in other nephropathies, as a useful marker of renal function. The use of cystatin C as a marker of glomerular filtration rate (GFR) was investigated in Fabry patients receiving ERT. METHODS: Renal function was evaluated with serum creatinine, serum cystatin C and estimated GFR (through Modification of Diet in Renal Disease [MDRD], Cockcroft-Gault [C&G] and Hoek formulae) in 21 Fabry patients receiving ERT with agalsidase alfa for 3 years and in 13 Fabry patients receiving agalsidase alfa for 4 years. RESULTS: During years of ERT while serum creatinine remained stable, cystatin C values showed a significant, increasing trend right from the first year of ERT. CONCLUSIONS: In Fabry disease, cystatin C is a sensitive and reliable marker of renal function, and it should be taken into account when evaluating GFR trends during ERT.     

Two-tier approach for the detection of alpha-galactosidase A deficiency in a predominantly female haemodialysis population.

INTRODUCTION: Fabry's disease (AFD) is an X-linked lysosomal storage disease, resulting from a deficiency in alpha-galactosidase A (AGALA). Untreated, this leads to precocious failure of vital organ function and death. As enzyme replacement therapy is available, it is of vital importance that affected individuals can be traced. MATERIALS AND METHODS: We set up a screening in the Flemish haemodialysis population using a two-tier approach. The first tier was a determination of alpha-galactosidase A activity using a dried blood spot on filter paper, in the second tier, patients with the lowest alpha-galactosidase levels were further subjected to mutation analysis of the GLA gene. RESULTS: 1284 patients (1047 women, 237 men) were evaluated for inclusion, eliminating patients with definite renal diagnoses. Total 922 patients (71.8 %) were screened (742 women, 180 men). Fifty seven patients were subjected to further genetic analysis. Three GLA mutation carriers were identified: two apparently nonrelated female patients carry the missense mutation p.Ala143Thr (c.427G > A), a missense mutation p.Trp236Arg (c.706T > C) was identified in a man. While the male patient had been clinically diagnosed with AFD, the female patients had remained unrecognized. Additional family based screening resulted in the identification of nine mutation carriers (four males and five females). DISCUSSION: We demonstrated that the prevalence of GLA mutation carriers in our haemodialysis population is 0.3%. Our results show that the proposed approach accurately detects AFD patients. We conclude that screening for AFD in high risk populations is a cost-effective, technically feasible and clinically valuable objective.     

Non-invasive high-risk screening for Fabry disease hemizygotes and heterozygotes

The most appropriate time for screening for Fabry disease (FD) is school age. For this reason, we developed non-invasive methods for measuring urinary alpha-galactosidase A (alpha-gal A) protein, using enzyme-linked immunosorbent assay (ELISA), and for globotriaosylceramide (GL-3), using tandem mass spectrometry (MS/MS). We measured these two biomarkers in the urine of previously diagnosed FD hemizygotes and heterozygotes, and in controls. All the classic FD hemizygotes were clearly distinguished from controls by either method alone, and combining the two assays produced 96% sensitivity for detecting heterozygotes. To assess the utility of these methods for screening school children and adults at high risk of FD, a pilot study was conducted. To distinguish FD from 432 controls, cut-off values for alpha-gal A protein and GL-3 were set at the 5th and 95th centile values of the controls, respectively. Among the high-risk patients, the measurements exceeded the cut-off values for both biomarkers in male and female subjects and were strong indicators for Fabry hemizygotes and heterozygotes. However, we recommend that if the results of the first measurements exceed the cut-off values for only one of these biomarkers, another urine sample should be requested for re-assay to confirm the result.