Phenotypic characteristics of the p.Asn215Ser (p.N215S) GLA mutation in male and female patients with Fabry disease: A multicenter Fabry Registry study

Stratification of Fabry mutations in clinical practice: a closer look at α-galactosidase A-3D structure

BACKGROUND

Fabry disease (FD) is an X-linked lysosomal storage and multi-system disorder due to mutations in the α-galactosidase A (α-GalA) gene. We investigated the impact of individual amino acid exchanges in the α-GalA 3D-structure on the clinical phenotype of FD patients.

PATIENTS AND METHODS

We enrolled 80 adult FD patients with α-GalA missense mutations and stratified them into three groups based on the amino acid exchange location in the α-GalA 3D-structure: patients with active site mutations, buried mutations and other mutations. Patient subgroups were deep phenotyped for clinical and laboratory parameters and FD-specific treatment.

RESULTS

Patients with active site or buried mutations showed a severe phenotype with multi-organ involvement and early disease manifestation. Patients with other mutations had a milder phenotype with less organ impairment and later disease onset. α-GalA activity was lower in patients with active site or buried mutations than in those with other mutations (P < 0.01 in men; P < 0.05 in women) whilst lyso-Gb3 levels were higher (P < 0.01 in men; <0.05 in women).

CONCLUSIONS

The type of amino acid exchange location in the α-GalA 3D-structure determines disease severity and temporal course of symptom onset. Patient stratification using this parameter may become a useful tool in the management of FD patients.

Improvement of gastrointestinal symptoms in a significant proportion of male patients with classic Fabry disease treated with agalsidase beta: A Fabry Registry analysis stratified by phenotype

Background

Fabry disease is an inherited disorder of glycolipid metabolism with progressive involvement of multiple organs, including the gastrointestinal tract, in classically affected male patients. Clinical presentations in males with later-onset Fabry phenotypes are more heterogeneous and largely dependent on the level of residual α-galactosidase A activity.

Methods

We assessed agalsidase beta treatment outcomes of gastrointestinal symptoms in adult males with classic or later-onset Fabry disease. Self-reports of abdominal pain and diarrhea ('present'/'not present' since previous assessment) at last clinical visit (≥0.5 year of follow-up) were compared with treatment-baseline.

Results

Classic male patients were considerably younger at first treatment than the fewer males with later-onset phenotypes (36 vs. ~47 years) and reported gastrointestinal symptoms more frequently at baseline (abdominal pain: 56% vs. 13%; diarrhea: 57% vs. 23%). As compared with baseline, significantly fewer classic patients reported abdominal pain after a median of 4.7 years of treatment (N = 171, 56% vs. 41%, P < 0.001). Moreover, significantly fewer patients reported diarrhea after 5.5 years of follow-up (N = 169, 57% vs. 47%, P < 0.05). Among the males with later-onset phenotypes, albeit statistically non-significant, abdominal pain reports reduced after a median of 4.2 years (N = 48, 13% vs. 4%) and diarrhea reports reduced after a median of 4.4 years of treatment (N = 47, 23% vs. 13%).

Conclusions

Sustained treatment with agalsidase beta was associated with improvement in abdominal pain and diarrhea in a significant proportion of classic male Fabry patients. Males with later-onset phenotypes reported gastrointestinal symptoms much less frequently at baseline as compared with classic patients, and non-significant reductions were observed.

Is the alpha-galactosidase A variant p.Asp313Tyr (p.D313Y) pathogenic for Fabry disease? A systematic review

The identification of pathogenic GLA variants plays a central role in the establishment of a definite Fabry disease (FD) diagnosis. We aimed to review and interpret the published data on the p.Asp313Tyr (p.D313Y) variant pathogenicity and clinical relevance. We performed a systematic review of peer-reviewed publications and case-reports on individuals and populations harbouring the p.Asp313Tyr variant. Overall, 35 studies were included in this review. We collected data regarding the clinical manifestations, alpha-galactosidase A enzyme activity, levels of the biomarkers globotriaosylceramide (Gb₃ ) and sphingosine-globotriaosylceramide (lyso-Gb₃ ) and histological findings of p.Asp313Tyr carriers. The prevalence of p.Asp313Tyr in populations at risk for FD (kidney, heart, neurologic disorders, or symptomatic populations) was calculated. We found high residual enzyme activity, low frequency of clinical features specific for FD, non-elevated lysoGb₃ /Gb₃ concentrations and lack of intracellular Gb₃ accumulation in biopsies in the p.Asp313Tyr carriers. The prevalence of the variant in populations at risk for FD was comparable to the reported frequency in the general population. A possible higher frequency was only observed in neurologic disorders. p.Asp313Tyr can be classified as neutral or variant of unknown significance. Further investigations will be helpful to clarify a possible association between the variant and manifestations in the brain vessels.

An expert consensus document on the management of cardiovascular manifestations of Fabry disease

Fabry disease (FD) is an X-linked lysosomal storage disorder caused by pathogenic variants in the α-galactosidase A (GLA) gene that leads to reduced or undetectable α-galactosidase A enzyme activity and progressive accumulation of globotriaosylceramide and its deacylated form globotriaosylsphingosine in cells throughout the body. FD can be multisystemic with neurological, renal, cutaneous and cardiac involvement or be limited to the heart. Cardiac involvement is characterized by progressive cardiac hypertrophy, fibrosis, arrhythmias, heart failure and sudden cardiac death. The cardiac management of FD requires specific measures including enzyme replacement therapy or small pharmacological chaperones in patients carrying amenable pathogenic GLA gene variants and more general management of cardiac symptoms and complications. In this paper, we summarize current knowledge of FD-related heart disease and expert consensus recommendations for its management.

Two related Chinese Fabry disease patients with a p.N215S pathological variant who presented with nephropathy

Fabry disease is an X-linked lysosomal storage disease resulting from a mutation in the GLA gene that encodes α-galactosidase A. The p.N215S (c.644A > G [p.Asn215Ser]) genotype is the most common later-onset variant reported in individuals of European or North American descent. It is usually referred to as a cardiac variant, although manifestations in other organ systems have been observed. In this report, we describe a nephropathy presentation in two related Chinese Fabry disease patients with p.N215S.

Late-Onset Fabry Disease Presenting With Ventricular Tachycardia Originating From Typical Inferolateral Scar

Late-onset cardiac Fabry disease is not uncommon among patients with unexplained left ventricular hypertrophy. Despite a less severe phenotype, life-threatening complications are possible in late-onset cardiac Fabry and may be the first presentation of the disease. Classical imaging features support the diagnosis; however, the presence of less common findings, such as ischemic features, should not lead to overlooking the diagnosis. Indeed, the coexistence of Fabry and ischemic heart disease is possible, even in the absence of obstructive coronary artery disease. Therefore, a high level of suspicion should be maintained, even in the presence of atypical presentations.

Genetic Testing for Diagnosis of Hypertrophic Cardiomyopathy Mimics

Background

Genetic testing is helpful for diagnosis of hypertrophic cardiomyopathy (HCM) mimics. Little data are available regarding the yield of such testing and its clinical impact.

Methods

The HCM genetic database at our center was used for identification of patients who underwent HCM-directed genetic testing including at least 1 gene associated with an HCM mimic ( GLA , TTR , PRKAG2 , LAMP2 , PTPN11 , RAF1 , and DES ). Charts were retrospectively reviewed and genetic and clinical data extracted.

Results

There were 1731 unrelated HCM patients who underwent genetic testing for at least 1 gene related to an HCM mimic. In 1.45% of cases, a pathogenic or likely pathogenic variant in one of these genes was identified. This included a yield of 1% for Fabry disease, 0.3% for familial amyloidosis, 0.15% for PRKAG2 -related cardiomyopathy, and 1 patient with Noonan syndrome. In the majority of patients, diagnosis of the HCM mimic based on clinical findings alone would have been challenging. Accurate diagnosis of an HCM mimic led to change in management (eg, enzyme replacement therapy) or family screening in all cases.

Conclusions

Genetic testing is helpful in the diagnosis of HCM mimics in patients with no or few extracardiac manifestations. Adding these genes to all HCM genetic panels should be considered.

Natural history of the late-onset phenotype of Fabry disease due to the p.F113L mutation

BACKGROUND

The common GLA gene mutation p.F113L causes late-onset phenotype of Fabry disease (FD) with predominant cardiac manifestations. A founder effect of FD due to this mutation was found in the Portuguese region of Guimarães. Our study aims to deepen the knowledge on the natural history of this late-onset variant.

METHODS

203 consecutive adult Fabry patients with p.F113L mutation (79 males; mean age 46 ± 18 years), from this region, were submitted at baseline to a predefined diagnostic protocol. The occurrence of FD manifestations was analyzed in each decade of age in both genders.

RESULTS

In males, left ventricular hypertrophy (40.2%) and late gadolinium enhancement (21.4%) arose over 30 years; heart failure (HF) (21.9%), ventricular tachycardia (8.9%) and conduction disorders over 40 years; and bifascicular (13.1%) and complete atrioventricular blocks (5.9%) beyond 50 years of age. Cardiac manifestations occurred more commonly and 1-2 decades earlier in males; their frequency increased with age. Septum and posterior wall thickness, LV mass, QRS interval duration and pro-BNP levels increased with age in both genders. Mean survival free from HF (64 ± 1 vs. 76 ± 2 years) and pacemaker (71 ± 2 vs. 86 ± 1 years) was higher in females (p < .001). Albuminuria A2/A3 (33.7%), brain white matter lesions (50.3%) and sensorineural deafness (44.7%) arose before 30 years of age in both genders, increasing with age. Renal failure and stroke were rare. Lysosomal inclusions were demonstrated in podocytes of patients with proteinuria.

CONCLUSION

This study improves the knowledge on natural history of late-onset variants of FD, carrying major impact on clinical decisions and guidelines.

Cardiomyopathy and kidney function in agalsidase beta-treated female Fabry patients: a pre-treatment vs. post-treatment analysis

AIMS

Long-term treatment effect studies in large female Fabry patient groups are challenging to design because of phenotype heterogeneity and lack of appropriate comparison groups, and have not been reported. We compared long-term cardiomyopathy and kidney function outcomes after agalsidase beta treatment with preceding treatment-naive outcomes.

METHODS AND RESULTS

Self-controlled pretreatment and post-treatment comparison (piecewise mixed linear modelling) included Fabry female patients ≥18 years at treatment initiation who received agalsidase beta (0.9-1.1 mg/kg every other week) for ≥2 years, with ≥2 pretreatment and ≥2 post-treatment outcome measurements during 10-year follow-up. Left ventricular posterior wall thickness (LVPWT)/interventricular septal thickness (IVST) and estimated glomerular filtration rate (eGFR, Chronic Kidney Disease Epidemiology Collaboration creatinine equation) analyses included 42 and 86 patients, respectively, aged 50.0 and 46.3 years at treatment initiation, respectively. LVPWT and IVST increased pretreatment (follow-up 3.5 years) but stabilized during 3.6 years of treatment (LVPWT: n = 38, slope difference [95% confidence interval (CI)] = -0.41 [-0.68, -0.15] mm/year, P_{pre-post difference}  <0.01; IVST: n = 38, slope difference = -0.32 [-0.67, 0.02] mm/year, P_{pre-post difference}  = 0.07). These findings were not modified by renal involvement or antiproteinuric agent use. Compared with the treatment-naive period (follow-up 3.6 years), eGFR decline remained modest and stabilized within normal ranges during 4.1 years of treatment (slope difference, 95% CI: -0.13 [-1.15, 0.89] mL/min/1.73m² /year, P_{pre-post difference}  = 0.80).

CONCLUSIONS

Cardiac hypertrophy, progressing during pretreatment follow-up, appeared to stabilize during sustained agalsidase beta treatment. eGFR decline remained within normal ranges. This suggests that treatment may prevent further Fabry-related progression of cardiomyopathy in female patients and maintain normal kidney function.

Retinal hyperreflective foci in Fabry disease

Background

Fabry disease (FD) is an X-linked inherited storage disorder caused by deficiency of lysosomal alpha-Galactosidase A. Here we describe new retinal findings in patients with FD assessed by Spectral domain optical coherence tomography (SD-OCT) and their possible clinical relevance.

Methods

54 eyes of 27 FD patients and 54 eyes of 27 control subjects were included. The ophthalmic examination included visual acuity testing, tonometry, slit lamp and fundus examination. SD-OCT imaging of the macula was performed in all subjects. Central retinal thickness and retinal nerve fiber layer analysis were quantified. Vessel tortuosity was obtained by a subjective scoring and mathematically calculated. Inner retinal hyperreflective foci (HRF) were quantified, clinically graded and correlated with a biomarker of Fabry disease (lyso-Gb3).

Results

In comparison to an age-matched control group, a significant amount of HRF was identified in macular SD-OCT images in FD patients. These HRF were localized within the inner retinal layers. Furthermore, lyso-Gb3 levels correlated significantly with the quantitative evaluation of HRF (p < 0,001). In addition, the vessel tortuosity was remarkably increased in FD patients compared to control persons and correlated significantly with lyso-G3 levels (p = 0.005). A further subanalysis revealed significantly higher HRF and vessel tortuosity scores in male patients with the classic FD phenotype.

Conclusions

The observational, cross sectional, comparative study describes novel intraretinal findings in patients with FD. We were able to identify suspicious HRF within the inner retinal layers. These findings were not accompanied by functional limitations, as visual acuity remained unchanged. However, HRF correlated well with lyso-Gb3, a degradation product of the accumulating protein Gb3 and might potentially indicate Gb3 accumulation within the highly metabolic and densely vascularized macula.

Migalastat: A Review in Fabry Disease

Fabry disease is a rare lysosomal disorder characterized by deficient or absent α-galactosidase A activity resulting from mutations in the GLA gene. Migalastat (Galafold™), a pharmacological chaperone, stabilizes and facilitates trafficking of amenable mutant forms of α-galactosidase A enzyme from the endoplasmic reticulum to lysosomes and increases its lysosomal activity. Oral migalastat is the first pharmacological chaperone approved for treating patients [aged ≥ 18 years (USA and Canada) or ≥ 16 years in other countries] with Fabry disease who have a migalastat-amenable GLA mutation. In the FACETS trial in enzyme replacement therapy (ERT)-naive patients with GLA mutations amenable or non-amenable to migalastat, there was no significant difference between the migalastat and placebo groups for the proportion of patients achieving a ≥ 50% reduction in the number of globotriaosylceramide (GL-3) inclusions/kidney interstitial capillary (KIC) at 6 months [primary endpoint; intent-to-treat (ITT) population]. In the modified ITT population (i.e. patients with migalastat-amenable GLA mutations), relative to placebo, migalastat treatment significantly reduced the mean number of GL-3 inclusions/KIC and plasma lyso-globotriaosylsphingosine levels at 6 months. Among evaluable patients, migalastat maintained renal function and reduced cardiac mass after ≤ 24 months’ therapy. In the ATTRACT trial in ERT-experienced patients, renal function was maintained during 18 months of migalastat or ERT; however, migalastat significantly reduced cardiac mass compared with ERT. Migalastat was generally well tolerated in both of these trials. Given its convenient oral regimen and the limited therapeutic options available, migalastat is an important treatment option for Fabry disease in patients with migalastat-amenable GLA mutations.

Prominent longitudinal strain reduction of left ventricular basal segments in treatment-naïve Anderson-Fabry disease patients

AIMS

Little is known about regional longitudinal strain (LS) distribution in early stages of Anderson-Fabry disease (AFD) cardiomyopathy. We investigated regional left ventricular (LV) patterns of LS strain and base-to-apex behaviour of LS in treatment-naïve AFD patients.

METHODS AND RESULTS

Twenty-three consecutive AFD patients at diagnosis and 23 healthy controls without cardiovascular risk factors and matched for age and sex to the patients, underwent a comprehensive evaluation of target organs. An echo-Doppler exam, including determination of regional and global LS strain (GLS) was obtained. The average LS of 6 basal (BLS), 6 middle (MLS), and 5 apical (ALS) segments and relative regional strain ratio [ALS/(BLS + MLS)] were also calculated. Ejection fraction and diastolic indices did not differ between the two groups. LV mass index was greater in AFD (P < 0.01). GLS (P = 0.006), BLS (P < 0.0001), and MLS (P = 0.003), but not ALS, were lower in AFD patients and relative regional strain ratio was higher in AFD (P < 0.01) than in controls. These analyses were confirmed separately in the two genders and even after excluding patients with wall hypertrophy. By subdividing AFD patients according to lysoGB3 levels, 9 patients with lysoGB3 ≥ 1.8 ng/L had lower ALS compared to 11 patients with lysoGB3 < 1.8 ng/L (P < 0.01).

CONCLUSION

In naïve AFD patients, we observed an early reduction of LV LS, involving mainly LV basal myocardial segments. Nevertheless, the association found between the higher lysoGB3 levels and the lower apical cap LS demonstrates that apical segments LS, despite still normal, is not spared at diagnosis.

Lyso-Gb3 modulates the gut microbiota and decreases butyrate production

Fabry disease is a rare X-linked lysosomal storage disorder resulting from deficient activity of α-galactosidase A, leading to the accumulation of glycosphingolipids such as globotriaosylsphingosine (lyso-Gb3). The gastrointestinal symptoms of this disease may be disabling, and the life expectancy of affected patients is shortened by kidney and heart disease. Our hypothesis was that lyso-Gb3 may modify the gut microbiota. The impact of a clinically relevant concentration of lyso-Gb3 on mono- or multispecies bacterial biofilms were evaluated. A complex bacterial community from the simulated transverse colon microbiota was studied using quantitative PCR to estimate different bacterial group concentrations and a HPLC was used to estimate short-chain fatty acids concentrations. We found that lyso-Gb3 increased the biofilm-forming capacity of several individual bacteria, including Bacteroides fragilis and significantly increased the growth of B. fragilis in a multispecies biofilm. Lyso-Gb3 also modified the bacterial composition of the human colon microbiota suspension, increasing bacterial counts of B. fragilis, among others. Finally, lyso-Gb3 modified the formation of short-chain fatty acids, leading to a striking decrease in butyrate concentration. Lyso-Gb3 modifies the biology of gut bacteria, favoring the production of biofilms and altering the composition and short-chain fatty-acid profile of the gut microbiota.

Strong increase of leukocyte apha-galactosidase A activity in two male patients with Fabry disease following oral chaperone therapy

Background

Fabry disease (OMIM 301500) is an X‐linked disorder caused by alpha‐galactosidase A (α‐Gal A) deficiency. The administration of a pharmacologic chaperone (migalastat) in Fabry patients with amenable mutations has been reported to improve or stabilize organ damages and reduce lyso‐Gb3 plasma level. An increase of α‐Gal A activity has been observed in vitro in cells expressing amenable GLA mutations when incubated with migalastat. The impact of the drug on α‐Gal A in vivo activity has been poorly studied.

Methods

We conducted a retrospective analysis of two unrelated male Fabry patients with p.Asn215Ser (p.N215S) variant.

Results

We report the important increase of α‐Gal A activity in blood leukocytes reaching normal ranges of activity after about 1 year of treatment with migalastat. Cardiac parameters improved or stabilized with the treatment.

Conclusion

We confirm in vivo the effects of migalastat that have been observed in N215S carriers in vitro. The increase of α‐Gal A activity may be the strongest marker for biochemical efficacy. The normalization of enzyme activity could become the new therapeutic target to achieve.

Why systematic literature reviews in Fabry disease should include all published evidence

Fabry disease is an X-linked inherited, progressive disorder of lipid metabolism resulting from the deficient activity of the enzyme α-galactosidase. Enzyme replacement therapy (ERT) with recombinant agalsidase, with intravenous infusions of either agalsidase beta or agalsidase alfa, is available and clinical experience now exceeds 15 years. There are very few randomised, placebo-controlled clinical trials evaluating the outcomes of ERT. Data are often derived from observational, registry-based studies and case reports. Pooled analysis of data from different sources may be limited by the heterogeneity of the patient populations, outcomes and treatment. Therefore, comprehensive systematic literature reviews of unpooled data are needed to determine the effects of ERT on disease outcomes. A systematic literature search was conducted in the Embase and PubMed (MEDLINE) databases to retrieve original articles that evaluated outcomes of ERT in patients with Fabry disease; the outcome data were analysed unpooled. The literature analysis included the full range of published literature including observational studies and case series/case reports. Considerable heterogeneity was found among the studies, with differences in sample size, statistical methods, ERT regimens and patient demographic and clinical characteristics. We have demonstrated the value of performing an unpooled systematic literature review of all published evidence of ERT outcomes in Fabry disease, highlighting that in a rare genetic disorder like Fabry disease, which is phenotypically diverse, different patient populations can require different disease management and therapeutic goals depending on age, genotype, and disease severity/level of organ involvement. In addition, these findings are valuable to guide the design and reporting of new clinical studies.

Low-dose agalsidase beta treatment in male pediatric patients with Fabry disease: A 5-year randomized controlled trial

BACKGROUND

Fabry disease is a rare, X-linked, lifelong progressive lysosomal storage disorder. Severely deficient α-galactosidase A activity in males is associated with the classic phenotype with early-onset, multisystem manifestations evolving to vital organ complications during adulthood. We assessed the ability of 2 low-dose agalsidase beta regimens to lower skin, plasma, and urine globotriaosylceramide (GL-3) levels, and influence clinical manifestations in male pediatric Fabry patients.

METHODS

In this multicenter, open-label, parallel-group, phase 3b study, male patients aged 5-18 years were randomized to receive agalsidase beta at 0.5 mg/kg 2-weekly (n = 16) or 1.0 mg/kg 4-weekly (n = 15) for 5 years. All had plasma/urine GL-3 accumulation but no clinically evident organ involvement. The primary outcome was GL-3 accumulation in superficial skin capillary endothelium (SSCE).

RESULTS

The mean age was 11.6 (range: 5-18) years and all but one of the 31 patients had classic GLA mutations. In the overall cohort, shifts from non-0 to 0-scores for SSCE GL-3 were significant at years 1, 3, and 5, but results were variable. Plasma GL-3 normalized and urine GL-3 reduced substantially. Higher anti-agalsidase beta antibody titers were associated with less robust SSCE GL-3 clearance and higher urine GL-3 levels. Renal function remained stable and normal. Most Fabry signs and symptoms tended to stabilize; abdominal pain was significantly reduced (-26.3%; P = .0215). No new clinical major organ complications were observed. GL-3 accumulation and cellular and vascular injury were present in baseline kidney biopsies (n = 7). Treatment effects on podocyte GL-3 content and foot process width were highly variable. Fabry arteriopathy overall increased in severity. Two patients withdrew and 2 had their agalsidase beta dose increased.

CONCLUSIONS

Our findings increase the limited amount of available data on long-term effects of enzyme replacement therapy in pediatric, classic Fabry patients. The low-dose regimens studied here over a period of 5 years did not demonstrate a consistent benefit among the patients in terms of controlling symptomatology, urine GL-3 levels, and pathological histology. The current available evidence supports treatment of pediatric, classic male Fabry patients at the approved agalsidase beta dose of 1.0 mg/kg 2-weekly if these patients are considered for enzyme replacement therapy with agalsidase beta.

Fabry disease in cardiology practice: Literature review and expert point of view

Fabry disease is an X-linked progressive multisystemic genetic sphingolipidosis caused by deficient activity of lysosomal α-galactosidase A. Men aged>30 years and women aged>40 years most often present with unexplained left ventricular hypertrophy, usually concentric and non-obstructive, but sometimes mimicking sarcomeric hypertrophic cardiomyopathy, particularly when isolated, as in the cardiac or late-onset variant of the disease. In hypertrophic cardiomyopathy cohorts, up to 1% of patients have been diagnosed with Fabry disease. Frequent cardiac symptoms include chronotropic incompetence, severe conduction disturbances and arrhythmias, heart failure and sudden death, and cardiovascular complications are currently the leading cause of death at a mean age of 55 years in men and 66 years in women. Complementary to screening for extracardiac manifestations, the initial cardiac evaluation should include long-duration electrocardiogram recordings, echocardiography and late gadolinium and T1 mapping magnetic resonance imaging. Abnormalities of a non-hypertrophied inferolateral wall at the base of the left ventricle (thinning, decreased strain, midwall fibrosis) and low native T1 signal on magnetic resonance imaging are evocative. Aggressive cardiac management may include the control of cardiovascular risk factors, anticoagulation, permanent cardiac pacing and/or an implantable cardioverter defibrillator device, while antiarrhythmics and beta-blockers should be used with caution. Specific therapy should be initiated at the earliest stage, when the first structural or functional cardiac abnormalities are detected, and should include enzyme replacement therapy (available since 2001) or chaperone therapy (available since 2016) (the use of which is limited to patients with Fabry disease and an amenable α-galactosidase A [GLA] gene mutation).

Anderson-Fabry disease in heart failure

Anderson-Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the GLA gene that result in deficiency of the enzyme alpha-galactosidase A. The worldwide incidence of Fabry's disease is reported to be in the range of 1 in 40,000-117,000, although this value may be a significant underestimate given under recognition of symptoms and delayed or missed diagnosis. Deficiency in alpha-galactosidase A causes an accumulation of neutral glycosphingolipids such as globotriaosylceramide (Gb3) in lysosomes within various tissues including the vascular endothelium, kidneys, heart, eyes, skin and nervous system. Gb3 accumulation induces pathology via the release of pro-inflammatory cytokines, growth-promoting factors and by oxidative stress, resulting in myocardial extracellular matrix remodelling, left ventricular hypertrophy (LVH), vascular dysfunction and interstitial fibrosis. Cardiac involvement manifesting as ventricular hypertrophy, systolic and diastolic dysfunction, valvular abnormalities and conduction tissue disease is common in AFD and is associated with considerable cardiovascular morbidity and mortality from heart failure, sudden cardiac death and stroke-related death.

Phenotypic characteristics of the p.Asn215Ser (p.N215S) GLA mutation in male and female patients with Fabry disease: A multicenter Fabry Registry study

BACKGROUND

The p.Asn215Ser or p.N215S GLA variant has been associated with late-onset cardiac variant of Fabry disease.

METHODS

To expand on the scarce phenotype data, we analyzed natural history data from 125 p.N215S patients (66 females, 59 males) enrolled in the Fabry Registry (NCT00196742) and compared it with data from 401 patients (237 females, 164 males) harboring mutations associated with classic Fabry disease. We evaluated interventricular septum thickness (IVST), left ventricular posterior wall thickness (LVPWT), estimated glomerular filtration rate and severe clinical events.

RESULTS

In p.N215S males, mildly abnormal mean IVST and LVPWT values were observed in patients aged 25-34 years, and values gradually increased with advancing age. Mean values were similar to those of classic males. In p.N215S females, these abnormalities occurred primarily in patients aged 55-64 years. Severe clinical events in p.N215S patients were mainly cardiac (males 31%, females 8%) while renal and cerebrovascular events were rare. Renal impairment occurred in 17% of p.N215S males (mostly in patients aged 65-74 years), and rarely in females (3%).

CONCLUSION

p.N215S is a disease-causing mutation with severe clinical manifestations found primarily in the heart. Cardiac involvement may become as severe as in classic Fabry patients, especially in males.

Fabry disease revisited: Management and treatment recommendations for adult patients

Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the GLA gene leading to deficient α-galactosidase A activity, glycosphingolipid accumulation, and life-threatening complications. Phenotypes vary from the "classic" phenotype, with pediatric onset and multi-organ involvement, to later-onset, a predominantly cardiac phenotype. Manifestations are diverse in female patients in part due to variations in residual enzyme activity and X chromosome inactivation patterns. Enzyme replacement therapy (ERT) and adjunctive treatments can provide significant clinical benefit. However, much of the current literature reports outcomes after late initiation of ERT, once substantial organ damage has already occurred. Updated monitoring and treatment guidelines for pediatric patients with Fabry disease have recently been published. Expert physician panels were convened to develop updated, specific guidelines for adult patients. Management of adult patients depends on 1) a personalized approach to care, reflecting the natural history of the specific disease phenotype; 2) comprehensive evaluation of disease involvement prior to ERT initiation; 3) early ERT initiation; 4) thorough routine monitoring for evidence of organ involvement in non-classic asymptomatic patients and response to therapy in treated patients; 5) use of adjuvant treatments for specific disease manifestations; and 6) management by an experienced multidisciplinary team.