Neurology of Fabry disease

Neurological complications in Fabry disease

The human lysosomal enzymes alpha-galactosidase (alpha-GAL, EC 3.2.1.22) and alpha-N-acetylgalactosaminidase (alpha-NAGAL, EC 3.2.1.49) share 46% amino acid sequence identity and have similar folds. The active sites of the two enzymes share 11 of 13 amino acids, differing only where they interact with the 2-position of the substrates. Using a rational protein engineering approach, we interconverted the enzymatic specificity of alpha- GAL and alpha-NAGAL. The engineered alpha-GAL (which we call alpha-GAL(SA)) retains the antigenicity of alpha-GAL but has acquired the enzymatic specificity of alpha-NAGAL. Conversely, the engineered alpha-NAGAL (which we call alpha-NAGAL(EL)) retains the antigenicity of alpha-NAGAL but has acquired the enzymatic specificity of the alpha-GAL enzyme. Comparison of the crystal structures of the designed enzyme alpha-GAL(SA) to the wild-type enzymes shows that active sites of alpha-GAL(SA) and alpha-NAGAL superimpose well, indicating success of the rational design. The designed enzymes might be useful as non-immunogenic alternatives in enzyme replacement therapy for treatment of lysosomal storage disorders such as Fabry disease.

In this issue, Banikazemi and colleagues' landmark trial on Fabry disease provides a crucial path toward lowering the morbidity of this disease. Among other findings, they determined that hemizygou...

Fabry disease is an X-linked disorder caused by a deficiency of lysosomal alpha-galactosidase A resulting in accumulation of alpha-D-galatosyl conjugated glycosphingolipids. Clinical manifestations include a small-fiber neuropathy associated with debilitating pain and hypohidrosis. We report the effect of a 3-year open-label extension of a previously reported 6-month placebo-controlled enzyme replacement therapy (ERT) trial in which 26 hemizygous patients with Fabry disease received 0.2 mg/kg of alpha-galactosidase A every 2 weeks. The effect of ERT on neuropathic pain scores while off pain medications, quantitative sensory testing, quantitative sudomotor axon reflex test (QSART), and thermoregulatory sweat test (TST) is reported. In the patients who crossed-over from placebo to ERT (n = 10), mean pain-at-its-worst scores on a 0-10 scale decreased (from 6.9 to 4.5). There was a significant reduction in the threshold for cold and warm sensation in the foot. At the 3-year time-point, pre-ERT sweat excretion in 17 Fabry patients was 0.24 +/- 0.33 microl/mm(2) vs. 1.05 +/- 0.81 in concurrent controls (n = 38). Sweat function improved 24-72 h post-enzyme infusion (0.57 +/- 0.71 microl/mm(2)) and normalized in four anhidrotic patients. TST confirmed the QSART results. We conclude that prolonged ERT in Fabry disease leads to a modest but significant improvement in the clinical manifestations of the small-fiber neuropathy associated with this disorder. QSART may be useful to further optimize the dose and frequency of ERT.

Utilidad del tratamiento de sustitución enzimática en la enfermedad de Fabry

BackgroundFabry disease is caused by a deficiency of the lysosomal enzyme α-galactosidase, resulting in progressive accumulation of globotriaosylceramide (GL-3). The disease can manifest early during childhood and adolescence. Enzyme replacement therapy (ERT) with recombinant human α-galactosidase is the first specific treatment for Fabry disease and has been available in Europe since 2001. This paper presents the findings of a systematic literature review of clinical outcomes with ERT in paediatric patients with Fabry disease. MethodsA comprehensive systematic review of published literature on ERT in Fabry disease was conducted in January 2017. The literature analysis included all original articles reporting outcomes of ERT in paediatric patients. ResultsTreatment-related outcomes in the paediatric population were reported in six publications derived from open-label clinical trials and in 10 publications derived from observational or registry-based studies. ERT was shown to significantly reduce plasma and urine GL-3 levels in paediatric patients with Fabry disease. The effect of ERT on GL-3 clearance from renal podocytes appeared to be agalsidase dose-dependent. ERT relieved pain and improved gastrointestinal symptoms and quality of life. ConclusionsBased on the published literature, the use of ERT in paediatric patients can significantly clear GL-3 accumulation, ameliorate the early symptoms of Fabry disease, and improve quality of life. Treatment with ERT in paediatric patients with Fabry disease may be important to prevent further disease progression and overt organ damage.

BackgroundFabry disease, an X-linked lysosomal storage disorder, is associated with significant multisystem involvement, including small fiber neuropathy. While neuropathic pain is well-documented in females with Fabry disease, the objective confirmation of small fiber dysfunction in pediatric heterozygotes remains underreported. This study highlights the role of quantitative sensory testing (QST) in diagnosing small fiber neuropathy in young female patients.Case reportWe present twin sisters, heterozygous for a pathogenic GLA variant (c.298 A > T), who exhibited symptoms of small fiber neuropathy, including acroparesthesia and gastrointestinal dysfunction. QST revealed altered thermoalgesic and vibratory thresholds in one twin and isolated vibratory hyposensitivity in the other, supporting the diagnosis of small fiber neuropathy.DiscussionThese cases highlight the diagnostic challenge of Fabry disease, as neuropathic symptoms may be overlooked or attributed to other conditions in pediatric patients. The findings emphasize the need for early identification of small fiber dysfunction in heterozygous females, who are increasingly recognized as being clinically affected. The complex alterations in sensory processing reinforce the importance of integrating QST as an objective assessment tool for small fiber function in Fabry disease.ConclusionsSmall fiber neuropathy is an early and clinically relevant manifestation of Fabry disease in pediatric heterozygotes. Early recognition and intervention, including enzyme replacement therapy (ERT), are essential to mitigating disease progression and improving clinical outcomes. These cases underscore the utility of QST in confirming small fiber neuropathy and highlight its potential role in the early diagnosis and monitoring of Fabry-related neuropathy in pediatric patients.

Optimizing treatment to reach therapeutic goals in fabry disease

Severe neuropathic pain and hypohidrosis are important symptoms of Fabry disease, particularly in the first three decades of life. The pain is associated with a length-dependent small-fibre neuropathy that also causes a selective deficiency of cold perception. Cold exposure often accentuates the pain and worsens thermal perception. The hypohidrosis leads to poor exercise and heat tolerance. The mechanisms by which α-galactosidase A deficiency causes these physiological abnormalities are poorly understood. The stored glycolipid (globotriaosylceramide) may interfere with the function of cellular membrane proteins, such as ion channels, or may lead to cytotoxicity. The characteristic neuropathic pain can be symptomatically treated with various types of anticonvulsant drugs, such as carbamazepine. Improvement in neuropathic pain as a primary outcome measure has been useful in demonstrating that enzyme replacement therapy is effective in improving pain-related quality of life in Fabry disease. Conclusions: The dysfunction of the peripheral nervous system is easily assessable and more readily reversible with specific therapy than the destructive processes that occur in organs such as the kidney. In future, therefore, it is likely that neuropathic pain, quantitative sensory testing and hypohidrosis will serve as clinical outcome measures for studies of specific and effective therapies for Fabry disease.

Fabry disease (FD) is a rare X-linked recessive glycosphingolipid-storage disorder caused by deficient activity of the lysosomal enzyme alpha-galactosidase A. Intravenous enzyme replacement therapy (ERT) has been used to supplement deficient enzyme activity in patients with FD. Despite its clinical effect and manifestations, clear criteria for the clinical effectiveness and cost-effectiveness of ERT have not been well established. In this study, we investigated the pharmacodynamic actions and short-term effects of ERT in patients with FD through direct molecular profiling from blood samples of patients before and after ERT. Based on this comparison, we observed that immune/inflammation-related pathways and growth factor-related pathways such as innate/adaptive immune pathway, lymphocyte proliferation and leukocyte proliferation were actively regulated under ERT. We also found that TINAGL1, DAAM2, CDK5R1 and MYO5B known to be related with clinical symptoms of FD showed increased levels after ERT, leading to the amelioration of clinical manifestations. Especially the catabolic process-related genes, including USP15 and ERUN1, showed direct increasing after ERT in vivo in male patients. These results suggest that male patients with FD respond more actively to ERT than do female patients with FD. Pathway analysis revealed that oxidative phosphorylation pathway-related genes are downregulated under ERT. ERT has a role to protect the proteins from oxidative damage and such deactivation of oxidative phosphorylation is one of direct pharmacodynamic actions of ERT. These results extended our understanding of the pathophysiology of ERT. To our knowledge, this is the first study to observe the molecular basis for the mechanism of ERT in vivo through the comprehensive comparison of transcriptome study with next-generation sequencing data.

ObjectiveTo assess the effectiveness and safety of enzyme replacement therapy (ERT) for treating Fabry disease in clinical practice.MethodsThe clinical data of patients with Fabry disease were retrospectively collected and screened according to inclusion and exclusion criteria. The effectiveness of ERT was evaluated by analyzing the improvement in renal dysfunction (decreased estimated glomerular filtration rate (eGFR) and proteinuria), cardiac system injury (mainly increased left ventricular mass index (LVMI)), and neuropathic pain after ERT treatment. The safety of ERT was measured by summarizing the occurrence of adverse events (AE) and adverse drug reactions (ADR) before and after ERT.ResultsSixteen patients with Fabry disease who underwent ERT treatment 2–36 times over a period of 2–89 weeks were enrolled in the study. Among them, 13 received symptomatic treatment based on the involvement of various organs, 14 were treated with anti-inflammatory and anti-allergic drugs, and 16 had no AE or ADR. After ERT, there was no significant difference in (eGFR, microalbumin (mALB), 24 h urinary protein quantitation (24 h PRO), urinary albumin/creatinine ratio (ACR), uric acid (UA), and β2 microglobulin (β2MG) (P > 0.05), and the renal function remained stable or improved; ERT could significantly reduce left ventricular mass index (LVMI) (P = 0.043) and lactate dehydrogenase (LDH) (P = 0.031), and other cardiac function indexes had an improvement trend or remained stable, but the difference was not significant (P > 0.05). After ERT, the degree of limb pain in three of the four minor patients improved.ConclusionsERT could effectively stabilize or improve renal and cardiac function and relieve neuropathic pain in patients with Fabry disease, and no AE occurred during treatment, and the clinical effectiveness and safety were satisfactory.

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<0.0001) and CD41 expression (20.3vs19.4 p=0.006 - with ADP:26.1vs21.9, p<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.

BackgroundFabry disease is an X-linked lysosomal storage disorder caused by GLA mutations, resulting in α-galactosidase (α-Gal) deficiency and accumulation of lysosomal substrates. Migalastat, an oral pharmacological chaperone being developed as...

Maladie de Fabry : une maladie du métabolisme par déficit d’une enzyme lysosomale (alpha-galactosidase), de transmission héréditaire liée au chromosome X accessible au traitement enzymatique de substitution

Enzyme replacement therapy (ERT) has been shown to stabilize certain aspects of Fabry disease (FD). However, in some patients on ERT, high antibody titres have been documented, with limited clinical improvement in systemic manifestations and often with significant adverse drug reactions. We present two related adolescent males with a 4.5 kb GLA deletion, not amenable to chaperone therapy, leading to profound reduction in α-galactosidase A (α-gal A) enzyme activity. Over a 3-year period of ERT, increasing IgG antibody titres against α-gal A were noted. After starting ERT serial urine globotriaosylceramide (Gb3) measurements showed an upward trend from 333 to 2260 μg/mmol creatinine for patient 1 and 1165 to 2260 μg/mmol creatinine for patient 2. Markedly increased levels of urine and plasma globotriaosylsphingosine (Lyso-Gb3) analogues were also found. The patients experienced recurrent infusion-associated reactions necessitating premedication and prolonged infusion times. Over the 3-year period of ERT, the patients experienced continued malaise, gastrointestinal symptoms and neuropathic pain. In addition, they had increasing anxiety related to their disease and apparent lack of response to ERT which led to a decision to ultimately stop ERT. No other approved treatment options are currently available for these patients. It is possible that the rapid development of the high antidrug neutralizing antibody (ADA) titres is related to the large GLA deletion leading to virtually absent enzyme activity. It remains unclear if their symptomatology during the period of receiving ERT is related to lack of its efficacy, the rising ADA titres, or both. These two patients highlight the need for further research into the management of antidrug antibodies and additional therapeutic approaches for FD. SynopsisThe development of very high antidrug antibody titres in response to ERT in two related adolescent males with FD highlight the need for other therapeutic options for patients in whom ERT or other currently approved therapies does not meet their treatment needs.