Gene Mutations Versus Clinically Relevant Phenotypes

The natural course of Fabry disease in a Finnish R227X cohort

BackgroundFabry Disease (FD) is characterized by globotriaosylceramide-3 (Gb3) accumulation in several tissues and a small fibre neuropathy (SFN), however the underlying mechanisms are poorly known. This study aimed to: 1) ascertain the presence of Gb3 deposits in skin samples, by an immunofluorescence method collected from FD patients with classical GLA mutations or late-onset FD variants or GLA polymorphisms; 2) correlate skin GB3 deposits with skin innervation.Methodswe studied 52 genetically-defined FD patients (32 with classical GLA mutations and 20 with late-onset variants or GLA polymorphisms), 15 patients with SFN associated with a specific cause and 22 healthy controls. Subjects underwent skin biopsy to evaluate Gb3 deposits and epi-dermal innervation.ResultsSkin Gb3 deposits were found in all FD patients with classical GLA mutations but never in FD patients with late-onset variants or GLA polymorphisms or in patients with SFN and healthy controls. Abnormal deposits were found inside different skin structures but never inside axons. FD patients with GB3 deposits showed lower skin innervation than FD patients with late-onset variants or polymorphisms.Conclusions1) Skin Gb3 deposits are specific to FD patients with classical GLA mutations; 2) Gb3 deposits were associated with lower skin innervation but they were not found inside axons, suggesting an indirect damage on peripheral small fibre innervation.

Elevation of urinary globotriaosylceramide (GL3) in infants with Fabry disease

When and How to Diagnose Fabry Disease in Clinical Pratice

Introduction Fabry disease (FD) is an X-linked sphingolipidosis characterized by pathogenic variants in the GLA gene, which affect alpha-galactosidase A activity. Studies on body composition in FD patients have shown conflicting results. There is significant variability in weight and body mass index (BMI) among FD patients, likely due to chronic inflammatory status, gastrointestinal and renal disturbances, inactivity, exercise intolerance, and medications. However, there is no study that evaluate body composition using dual-energy X-ray absorptiometry (DXA) in FD patients compared to healthy controls. Objectives To assess body composition by DXA in Brazilian male FD patients and to compare the findings with those of healthy controls (HC). Additionally, to correlate the DXA measurements with Lyso-Gb3 concentrations, the main substrate accumulated in the disease. Method Fifteen genotype-confirmed classic male FD patients and 20 sex/age-matched HC had body composition evaluated by DXA. Lyso-Gb3 levels were obtained for FD patients. Results Mean age was 44.2 ± 12.3 years and 44.9 ± 11.8 years in FD patients and HC, respectively (p = 0.87). BMI in FD patients (22.9 ± 3.7 kg/m2) was not statistically different from HC (24.8 ± 2.4 kg/m2, p = 0.07). Appendicular lean mass was lower in FD patients (20,324 ± 2808 g) than HC (25529 ± 2535 g, p < 0.0001), as well as the appendicular lean mass index (7.24 ± 0.89 vs. 8.72 ± 0.80 kg/m2, p < 0.0001). There were no differences between patients and controls regarding fat mass or fat percentage. Lyso-Gb3 levels were inversely correlated with lean mass (r = - 0.63, p = 0.01), fat mass (r = - 0,68, p = 0.005) and fat percentage (r = - 0.64, p = 0.01). Conclusion Adult FD patients in this cohort had lower lean mass than controls. Lyso-Gb3 accumulation is associated with lower values of lean mass, fat mass and fat percentage in FD patients.

Fabry disease is an X-linked glycosphingolipidosis caused by deficient synthesis of the enzyme α-galactosidase A, which results in accumulations of globotriaosylceramide (GL-3) in systemic tissues. Nephropathy is a dominant feature of Fabry disease. It still remains unclear how the nephropathy progresses. Recombinant agalsidase replacement therapy is currently the only approved, specific therapy for Fabry disease. The optimal dose of replacement enzyme also still remains unclear. The worldwide shortage of agalsidase-β in 2009 forced dose reduction of administration. It showed that the proteinuria emerged like surges, followed by temporary plasma GL-3 elevations in the early stages of classic Fabry disease. Additionally, it also showed that 1 mg/kg of agalsidase-β every other week could clear the GL-3 accumulations from podocytes and was required to maintain negative proteinuria and normal plasma GL-3 levels. This observation of a young patient with classic Fabry disease about 5 years reveals that the long-term, low-dose agalsidase-β caused proteinuria surges, but not persistent proteinuria, followed by temporary plasma GL-3 elevations, and agalsidase-β at 1 mg/kg every other week could clear accumulated GL-3 from podocytes and was required to maintain normal urinalysis and plasma GL-3 levels.

Fabry disease is an X-linked genetic disorder caused by defects in the α-galactosidase A (GLA) gene, and heterogeneous mutations lead to quantitative and/or qualitative defects in GLA protein in male patients with Fabry disease. Random X-chromosomal inactivation modifies the clinical and biochemical features of female patients with Fabry disease. Functional polymorphisms have been frequently reported in recent times, and these increase the difficulty of understanding the pathogenetic basis of the disease. To date, GLA protein level has been measured using an enzyme-linked immunosorbent assay (ELISA). However, ELISA is not highly sensitive due to the high background noise. In this paper, we introduce a novel application of the immuno-polymerase chain reaction (PCR) method (termed Multiple Simultaneous Tag [MUSTag]) for measurement of the GLA protein level in blood samples. We compared the sensitivities of the MUSTag method with plates or magnetic beads with those of ELISA for recombinant human GLA and found that the apparent maximal sensitivity was higher for the former than for the latter. We then measured the GLA concentrations in serum and plasma from male patients with classic Fabry disease (Male Fabry), females with Fabry disease (Female Fabry), male subjects harboring the functional polymorphism p.E66Q (E66Q), and control (Control) subjects. Our results revealed that compared to the MUSTag plate and ELISA, the MUSTag beads assay afforded a clearer estimation of the GLA protein levels in the serum and plasma with minimal or no background noise, although all the methods could differentiate between the Male Fabry, E66Q, and Control groups. The Female Fabry group showed characteristic heterogeneity, which was consistent with the X-linked inheritance. This novel method is expected to be useful for the sensitive determination of GLA level in blood and elucidation of the pathogenetic basis of Fabry disease.

Fabry disease is a rare lysosomal storage disorder caused by mutations in the GLA gene, which, without treatment, can cause significant renal dysfunction. We evaluated the effects of enzyme replacement therapy with agalsidase alfa on renal decline in patients with Fabry disease using data from the Fabry Outcome Survey (FOS) registry. Male patients with Fabry disease aged >16 years at agalsidase alfa start were stratified by low (≤0.5 g/24 h) or high (>0.5 g/24 h) baseline proteinuria and by ‘classic’ or ‘non-classic’ phenotype. Overall, 193 male patients with low (n = 135) or high (n = 58) baseline proteinuria were evaluated. Compared with patients with low baseline proteinuria, those with high baseline proteinuria had a lower mean ± standard deviation baseline eGFR (89.1 ± 26.2 vs. 106.6 ± 21.8 mL/min/1.73 m2) and faster mean ± standard error eGFR decline (−3.62 ± 0.42 vs. −1.61 ± 0.28 mL/min/1.73 m2 per year; p < 0.0001). Patients with classic Fabry disease had similar rates of eGFR decline irrespective of baseline proteinuria; only one patient with non-classic Fabry disease had high baseline proteinuria, preventing meaningful comparisons between groups. In this analysis, baseline proteinuria significantly impacted the rate of eGFR decline in the overall population, suggesting that early treatment with good proteinuria control may be associated with renoprotective effects.

BackgroundFabry disease (FD) is an X-linked lysosomal disorder due to mutations in the GLA gene resulting in defective enzyme alpha-galactosidase A. FD patients are frequently misdiagnosed, commonly for rheumatic diseases. Determining pathogenicity of a mutation depends of in silico predictions but mostly on available clinical information and interpretation may change in light of evolving knowledge. Similar signs and symptoms in carriers of GLA gene genetic variants of unknown significance or of benign variants may hamper diagnosis. This study reviews rheumatic and immune-mediated manifestations in a cohort of Brazilian FD patients with classic mutations and also in subjects with GLA gene A143T and R118C mutations. Misdiagnoses, time to correct diagnosis or determination of GLA gene status, time to treatment initiation and reasons for treatment prescription in A143T and R118C subjects are reviewed.MethodsGenotype confirmed classic FD patients (n = 37) and subjects with GLA gene mutations A143T and R118C (n = 19) were referred for assessment. Subjects with R118C and A143T mutations had been previously identified during screening procedures at hemodialysis units. All patients were interviewed and examined by a rheumatologist with previous knowledge of disease and/or mutation status. A structured tool developed by the authors was used to cover all aspects of FD and of common rheumatic conditions. All available laboratory and imaging data were reviewed.ResultsThirty-seven consecutive FD patients were interviewed – 16 male / 21 female (mean age: 43.1 years) and 19 consecutive subjects with GLA gene mutations R118C and A143T were evaluated – 8 male / 11 female (mean age: 39.6 years); 15 [R118C] / 4 [A143T]. Misdiagnosis in FD patients occurred in 11 males (68.8%) and 13 females (61.9%) of which 10 males and 9 females were previously diagnosed with one or more rheumatic conditions, most frequently rheumatic fever or “rheumatism” (unspecified rheumatic disorder). Median time for diagnosis after symptom onset was 16 years (range, 0–52 years). Twenty-two patients were treated with enzyme replacement therapy (ERT) – 13 male and 9 female. Median time to ERT initiation after FD diagnosis was 0.5 years (range, 0–15 years). Rheumatic manifestations occurred in 68.4% of R118C and A143T subjects. Two subjects had been prescribed ERT because of renal disease [R118C] and neuropsychiatric symptoms [A143T].ConclusionMisdiagnoses occurred in 64.8% of FD patients, most frequently for rheumatic conditions. Median time for correct diagnosis was 16 years. Rheumatic manifestations are also frequent in subjects with GLA gene R118C and A143T mutations. These results reinforce the need to raise awareness and increase knowledge about Fabry disease among physicians, notably rheumatologists, who definitely have a role in identifying patients and determining disease burden. Decision to start treatment should consider expert opinion and follow local guidelines.

Fabry disease (FD, OMIM 301500) is an X-linked disorder of glycosphingolipid metabolism resulting from the deficient activity of alpha-galactosidase A, a lysosomal acid hydrolase, leading to progressive lysosomal accumulation of incompletely metabolized neutral glycosphingolipids. Cardiac involvement is frequent. The objective of this study was to characterize the cardiac abnormalities in male patients affected with classic Fabry disease and define the context in which the clinicians were able to make the diagnosis. Clinical evaluation, laboratory tests, electrocardiography (ECG) and echocardiography were performed in 20 hemizygous men (mean age 39 years, range 12-65 years). The context of diagnosis was obtained by review of patients' charts. Left ventricular hypertrophy (LVH) and/or concentric remodeling were found in 12 patients (60%). Structural changes in mitral and aortic valves were found in 25% and 10% of cases, respectively. The sensitivity of the ECG Romhilt-Estes score for LVH was high (80%). Short PR interval (40%), ST segment abnormalities and conduction delay were frequent on ECG. Left ventricular mass index, ECG scores for LVH and systolic pulmonary pressure correlated positively with age. There was no relation between classic vascular risk factors and coronary artery disease, transient ischemic attack (TIA) or stroke. Diagnosis of Fabry disease was frequently suggested by nephrologists, dermatologists or geneticists. Echocardiograph and ECG abnormalities are frequently observed in patients with Fabry disease. Cardiologists should be aware of the diagnosis of Fabry disease in patients presenting with LVH, concentric remodeling, mitral and aortic valve thickening on echocardiography, short PR interval and conduction defects on ECG.

BackgroundFabry disease (FD) results from X-linked inheritance of a mutation in the GLA gene, encoding for alpha galactosidase A, and is characterized by heterogeneous clinical manifestations. Two phenotypes have been described “Classic” and “late onset” which cannot be predicted exclusively by genotype. The latter has been considered an attenuated form of the disease often affecting a single organ system commonly the heart. Recent studies have demonstrated that cardiac outcomes are similar in patients with classic and late onset mutations. In this study we investigate the relationship between clinical heterogeneity and plasma lyso-Gb3 in a large single centre cohort of N215S patients and compare this to patients with other mutations.MethodsIn this single-centre, retrospective, cross-sectional study we analysed a cohort of 251 FD patients: 84 N215S mutation (37 males) and 167 non-N215S mutations (58 males). The Mainz severity score index (MSSI) was used as an index of overall disease severity. Cardiac function and morphology were assessed by electrocardiogram and echocardiogram. Left ventricular mass was calculated using the Devereux formula and the left ventricular mass index (LVMI) calculated to adjust for height (g/m2.7). The presence of white matter lesions was assessed by cerebral MRI or computed tomography (CT). GFR was measured by radio-isotope (chromium-EDTA) method and adjusted for patient height (ml/min/m2.7), and urinary protein quantification was undertaken by 24 hour urine collection. Plasma globotriaosylsphingosine (lyso-Gb3) was analysed prior to ERT in 84 patients.ResultsN215S patients showed later symptom onset (males: p< 0.0001, females: p<0.03), later development of left ventricular hypertrophy (LVH) (median survival without LVH: 41 (non-N215S) vs. 64 (N215S) years, p< 0.0001), later development of proteinuria (median survival without proteinuria 43 (non-N215S) vs 71 years (N215S), p< 0.0001), later occurrence of cerebrovascular events (stroke/ Transient Ischaemic Attacks (TIA); median survival without stroke: 74 years (non-N215S) vs. not reached (N215S), p< 0.02), later decline in renal function to GFR <60 ml/min/1.73m2 (median survival: 56 (non-N215S) vs. 72 (N215S) years, p< 0.01), and greater overall survival (median survival 81 (N215S) vs. 66 (non-N215S) years, p< 0.0006). Lyso-Gb3 was found to be less elevated in N215S compared to non-N215S male and female patients. However, the N215S population eventually reached an overall severity measured by MSSI comparable to the non-N215S without equivalent elevation of lyso-Gb3 (means: 6.7 vs. 74.3 nmol/L, p < 0.001). In addition, N215S patients showed strong correlations between lyso-Gb3 levels and LVMI, GFR, and MSSI. These associations became stronger when we investigated individuals’ life time exposure to lyso-Gb3 (calculated as [lyso-Gb3]*age): MSSI (r2 = 0.88, p< 0.0001), LVMI (r2 = 0.59, p< 0.005), and GFR (r2 = 0.75, p = 0.0001).ConclusionThese results demonstrate that the N215S mutation results in a late onset phenotype involving the heart and other organs. Correlations between clinical manifestations and plasma lyso-Gb3 variations in this group suggest a Fabry-relevant disease mechanism for the heterogeneity observed in this group.

Fabry disease is a rare, progressive, X-linked inherited storage disorder due to absent or deficient of lysosomal alfa galactosidase A activity. Deficient activity of alfa-galactosidase A results in progressive accumulation of globotriaosylceramide in a variety of tissues and organs including myocardium, kidney and nerve system. This disorder predominantly affects males; however, female heterozygotes may also be affected with a less severe clinical picture. Classic Fabry disease is usually diagnosed in early age of childhood because of multiorgan involvement whereas cardiac and renal variants of Fabry are manifested in 30-50 years of age because of late onset of clinical picture in which other organs involvement are uncommon. Although Fabry is known as a very rare disease, its prevalence is reported to be higher in patients with ventricular hypertrophy, chronic kidney disease and cryptogenic stroke. From the cardiology point of view, the most important key finding of the disease is unexplained ventricular hypertrophy. However, in clinical practice, ventricular hypertrophy is usually thought to be due to hypertrophic cardiomyopathy in the absence of hypertension or aortic stenosis and Fabry disease is often undiagnosed or overlooked. Early diagnosis and enzyme replacement therapy have been shown to significantly improve prognosis. The aim of this paper is to provide a comprehensive review including epidemiology, prognosis, clinical presentation, diagnosis and therapeutic approaches of cardiac variant of Fabry based on the available data in the literature.

Although previous studies have suggested a certain prevalence of Fabry disease (FD) in left ventricular hypertrophy (LVH) patients, the screening of FD is difficult because of its wide-ranging clinical phenotypes. We aimed to clarify the utility of combined measurement of plasma globotriaosylsphingosine (lyso-Gb3) concentration and α-galactosidase A activity (α-GAL) as a primary screening of FD in unexplained LVH patients. Between 2014 and 2016, both lyso-Gb3 and α-GAL were measured in 277 consecutive patients (male 215, female 62, age 25-79 years) with left ventricular wall thickness >12 mm on echocardiogram: 5 patients (1.8%) screened positive (2 (0.7%) showed high lyso-Gb3 and 4 (1.4%) had low α-GAL levels). Finally, 2 patients (0.7%) were diagnosed with clinically significant FD. In 1 case, a female heterozygote with normal α-GAL levels had genetic variants of unknown significance and was diagnosed as FD by endomyocardial biopsy. The other case was a male chronic renal failure patient requiring hemodialysis, and he had a p.R112H mutation. In both cases there were high lyso-Gb3 levels. The serum lyso-Gb3 level can be relevant for clinically significant FD, and combined measurement of lyso-Gb3 and α-GAL can provide better screening of FD in unexplained LVH patients.

Background: Cerebrovascular events represent a major cause of disability in young patients with Fabry disease (FD). However the pathogenesis of cerebrovascular events in these patients is not fully understood and prevention, besides enzyme replacement therapy (ERT), is empirically based on antiplatelet drugs. We evaluated platelet function in patients with FD without evidence of coronary or carotid atherosclerosis. Methods: Fifteen patients with genetically confirmed FD (mean age 42, 6 F) underwent treadmill exercise stress test (EST). Platelet reactivity was assessed by flow cytometry at baseline and at peak EST, with and without ADP stimulation, by measuring monocyte-platelet aggregate (MPA) formation (expressed as percentage of monocyte binding platelets) and CD41 expression (assessed as mean fluorescence intensity). All patients underwent carotid ultrasound and coronary angiography to rule out carotid or coronary artery disease. Patients on ERT were submitted to EST the day before drug infusion. Thirty healthy sex- and age-matched subjects were studied as controls. Results: Coronary angiography and carotid ultrasound showed no evidence of atherosclerosis in all FD patients; EST showed signs of ischemia in 3 patients with FD cardiomyopathy. Thirteen patients were on ERT at the time of the study. Compared to resting values, MPA and CD41 expression,with and without ADP stimulation, significantly increased after exercise in the FD group but not in controls. Exercise-induced values of MPA (20.1vs18.7, p=0.001 - with ADP:25.2vs22.0, p&lt;0.0001) and CD41 expression (20.3vs19.4 p=0.006 - with ADP:26.1vs21.9, p&lt;0.0001) were higher in FD patients than in controls, while resting values didn't significantly differ. Conclusions: High exercise-induced platelet reactivity has been reported in patients at high risk for thrombotic events, like those with coronary or peripheral atherosclerosis. In this study we found high exercise-induced platelet reactivity in patients with FD, suggesting that enhanced platelet reactivity may contribute to the pathogenesis of cerebrovascular events in these patients. Our data support the inclusion of antiplatelet drugs in conventional therapy for FD. The effect of ERT on platelet function remains to be clarified.

Fabry disease is an X-linked disorder of α-galactosidase A (GLA) deficiency. Our previous interim analysis (1 July 2014 to 31 December 2015) revealed plasma globotriaosylsphingosine as a promising primary screening biomarker for Fabry disease probands. Herein, we report the final results, including patients enrolled from 1 January to 31 December 2016 for evaluating the potential of plasma globotriaosylsphingosine and GLA activity as a combined screening marker. We screened 5691 patients (3439 males) referred from 237 Japanese specialty clinics based on clinical findings suggestive of Fabry disease using plasma globotriaosylsphingosine and GLA activity as primary screening markers, and GLA variant status as a secondary screening marker. Of the 14 males who tested positive in the globotriaosylsphingosine screen (≥2.0 ng/mL), 11 with low GLA activity (<4.0 nmol/h/mL) displayed GLA variants (four classic, seven late-onset) and one with normal GLA activity and no pathogenic variant displayed lamellar bodies in affected organs, indicating late-onset biopsy-proven Fabry disease. Of the 19 females who tested positive in the globotriaosylsphingosine screen, eight with low GLA activity displayed GLA variants (six classic, two late-onset) and five with normal GLA activity displayed a GLA variant (one classic) and no pathogenic variant (four late-onset biopsy-proven). The combination of plasma globotriaosylsphingosine and GLA activity can be a primary screening biomarker for classic, late-onset, and late-onset biopsy-proven Fabry disease probands.