Fabry disease: a review of current management strategies

Female Fabry disease patients and X-chromosome inactivation

Fabry disease is an X-linked inherited lysosomal storage disorder caused by mutations in the gene encoding α-galactosidase A (GLA). Once it was thought to affect only hemizygous males. Over the last fifteen years, research has shown that most females carrying mutated allele also develop symptoms, demonstrating a wide range of disease severity, from a virtually asymptomatic to more classical profile, with cardiac, renal, and cerebrovascular manifestations. This variable expression in females is thought to be influenced by the process of X-chromosome inactivation (XCI). The aim of this study was to assess severity of the clinical phenotype, to analyze XCI patterns, and to estimate their effect on disease manifestation in twelve female Fabry disease patients from five unrelated Polish families. Our analyses revealed that patients presented with the broad range of disease expression - from mild to severe, and their clinical involvement did not correlate with XCI profiles. Female carriers of the mutation in the GLA gene with the random XCI may present with the wide range of disease signs and symptoms. Thus, XCI is not a main factor in the phenotype variability of Fabry disease manifestation in heterozygous females.

Home infusion program with enzyme replacement therapy for Fabry disease: The experience of a large Italian collaborative group

Fabry disease (FD) [OMIM 301500] is an X-linked lysosomal storage disorder caused by a deficiency of the lysosomal enzyme alpha-galactosidase A, resulting in progressive multisystem accumulation of globotriaosylceramide (Gb3). Although the introduction of Enzyme Replacement Therapy (ERT) resulted in a variety of clinical benefits, life-long intravenous (IV) treatment with ERT with an every other week schedule, may interfere with daily life activities and impact on QoL. We report here a multicentric, observational, longitudinal data analysis on a large cohort of 85 Italian FD patients (45 males, 40 females) from 11 out of 20 Italian regions, who received a cumulative number of 4269 home infusions of agalsidase alfa. For the whole cohort, the average duration of home therapy was 1 year and 11 months (range 3 months–4 years and 6 months), and during this period, compliance to treatment (number of infusions performed vs scheduled) reached 100%. The EQ-5 VAS scale was administered to patients to evaluate the self-reported QoL, 58% of patients showing an increase of EQ-5 VAS score at follow up compared to baseline (home treatment start) or remaining stable. A mild increase of average disease severity, measured through Mainz Severity Score Index (MSSI), was found during hospital treatment (p < 0,007), while it remained stable between the first home therapy infusion and last follow up. Interestingly, 4 out of 7 (57%) patients, showing an improvement in FD-related clinical status after starting home therapy, had previously a sub-optimal compliance to treatment during the period of hospital treatment management. Only 4 adverse non serious reactions (0,093%) were reported totally in 2 patients during home treatment.

We conclude that home infusions in eligible patients with FD are safe, contribute to improve treatment compliance and therapeutic clinical outcomes, and may have a positive impact on self-perceived QoL.

Efficacy and safety of enzyme-replacement-therapy with agalsidase alfa in 36 treatment-naïve Fabry disease patients

Background

Fabry disease (FD) is an X-linked lysosomal storage disorder resulting from the α-galactosidase A gene mutations. Enzyme-replacement-therapy (ERT) products for FD currently used include agalsidase alfa and agalsidase beta. There are many reports on efficacy and safety of ERT. However, most of the previous studies are done as a retrospective medical records analysis.

Methods

The Japan Fabry Research - 002 (JFR-002) was a prospective observational clinical study of 36 ERT-naïve FD patients (14 men and 22 women) at baseline (BL) and after initiation of ERT with agalsidase alfa 0.2 mg/kg every two weeks, a median period 62.5 months. The parameters measured included globotriaosylceramide (Gb3), globotriaosylsphingosine (Lyso-Gb3), left ventricular mass index (LVMI), brain natriuretic peptide (BNP), high-sensitivity troponin I (hs-Trop I), estimated glomerular filtration rate (eGFR), and anti-agalsidase alfa IgG antibody formation.

Results

All parameters remained steady during ERT treatment period. BNP levels in 14 patients whose BL levels were within the normal range (<19.5 pg/mL) remained within the same range, while 22 patients whose BL levels were abnormally high (≥19.5 pg/mL) gradually showed decreased levels after start of ERT. Gb3 and Lyso-Gb3 levels remarkably decreased after the initiation of ERT and remained low.

Conclusion

The JFR-002 suggests that agalsidase alfa is effective in maintaining organ function in FD patients, and that the incidence of infusion reactions related to the treatment with agalsidase alfa is low, indicating the good tolerability to this ERT.

Trial registration

The JFR-002 was retrospectively registered at Japan Medical Association Center for Clinical Trials (Registration number: JMA-IIA00291) on May 19th, 2017.

A new mutation found in newborn screening for Fabry disease evaluated by plasma globotriaosylsphingosine levels

A pilot study of newborn screening for Fabry disease was performed in Okinawa, Japan. A total of 2,443 neonates were screened using dried blood spot samples over 7 years starting in 2007. Of 13 neonates determined to have low α-galactosidase A (GLA) activity, one boy had a new missense mutation, p.G144D of the GLA gene. This mutation was considered to be a late-onset type, as evaluated based on plasma globotriaosylsphingosine levels and family history.

[Juvenile stroke - what is important?]

Stroke in young adults is a diagnostic and therapeutic challenge for all persons involved. Approximately 15% of ischemic strokes occur in young adults. Lack of awareness of the symptoms in emergency departments often results in delayed diagnosis and access to specific therapeutic options, such as revascularization. The causes are often heterogeneous and necessitate specific investigations. The etiology of juvenile stroke includes drug abuse, vasculitis and arteriopathies, such as reversible vasoconstriction syndrome and posterior reversible encephalopathy syndrome, although the prevalence of classical vascular risk factors is high. The most frequent causes of ischemic stroke in young adults are cardioembolism and microangiopathy; furthermore, dissection of vessels of the neck are more frequent compared to older patients. According to the results of currently available studies reperfusion strategies, such as intravenous fibrinolysis and mechanical thrombectomy are efficacious and safe in young patients.

Screening, diagnosis, and management of patients with Fabry disease: conclusions from a "Kidney Disease: Improving Global Outcomes" (KDIGO) Controversies Conference

Patients with Fabry disease (FD) are at a high risk for developing chronic kidney disease and cardiovascular disease. The availability of specific but costly therapy has elevated the profile of this rare condition. This KDIGO conference addressed controversial areas in the diagnosis, screening, and management of FD, and included enzyme replacement therapy and nonspecific standard-of-care therapy for the various manifestations of FD. Despite marked advances in patient care and improved overall outlook, there is a need to better understand the pathogenesis of this glycosphingolipidosis and to determine the appropriate age to initiate therapy in all types of patients. The need to develop more effective specific therapies was also emphasized.

Gender Differences in the Application of Spanish Criteria for Initiation of Enzyme Replacement Therapy for Fabry Disease in the Fabry Outcome Survey

Both male/female patients with Fabry disease (FD) may receive enzyme replacement therapy (ERT). Previously published analyses of the Fabry Outcome Survey (FOS; Shire-sponsored) database suggested gender differences in timing of ERT initiation. We assessed alignment of criteria for ERT initiation in the Spanish adult population included in FOS with recommendations of a Spanish national consensus. This retrospective analysis examined baseline clinical data of 88 adults (49 females) enrolled in the FOS database up to August 2014. Thirty-five (39.8%) patients were not receiving ERT: five (12.8%) males and 30 (61.2%) females. Baseline disease severity on the FOS-derived Mainz Severity Score Index was lower in untreated males (median (interquartile range), 0.0 (0.0–1.0)) than treated males (TM; 15.0 (7.5–26.5)), and was similar in untreated and treated females. The percentage of untreated females with at least one criterion for treatment initiation was 76.7% versus 100.0% of treated females (p = 0.0340) and 97.1% (p = 0.0210) of TM. In discordance with Spanish consensus recommendations, a substantial number of females with evidence of FD who might benefit from ERT have not yet initiated treatment. These results suggest unequal gender perceptions with respect to ERT initiation in Spain.

Screening Fabry's disease in chronic kidney disease patients not on dialysis: a multicenter study

OBJECTIVES

Fabry's disease is an X-linked inherited, rare, progressive, lysosomal storage disorder, affecting multiple organs due to the deficient activity of α-galactosidase A (α-Gal A) enzyme. The prevalence has been reported to be 0.15-1% in hemodialysis patients; however, the information on the prevalence in chronic kidney disease not on dialysis is lacking. This study aimed to determine the prevalence of Fabry's disease in chronic kidney disease.

METHODS

The patients older than 18 years, enclosing KDIGO 2012 chronic kidney disease definitions, not on dialysis, were enrolled. Dried blood spots on Guthrie papers were used to analyze α-Gal A enzyme and genetic analysis was performed in individuals with enzyme activity ≤1.2 μmol/L/h.

RESULTS

A total of 1453 chronic kidney disease patients not on dialysis from seven clinics in Turkey were screened. The mean age of the study population was 59.3 ± 15.9 years. 45.6% of patients were female. The creatinine clearance of 77.3% of patients was below 60 mL/min/1.73 m², 8.4% had proteinuria, and 2.5% had isolated microscopic hematuria. The mean value of patients' α-Gal A enzyme was detected as 2.93 ± 1.92 μmol/L/h. 152 patients had low levels of α-Gal A enzyme activity (≤1.2 μmol/L/h). In mutation analysis, A143T and D313Y variants were disclosed in three male patients. The prevalence of Fabry's disease in chronic kidney disease not on dialysis was found to be 0.2% (0.4% in male, 0.0% in female).

CONCLUSION

Fabry's disease should be considered in the differential diagnosis of chronic kidney disease with unknown etiology even in the absence of symptoms and signs suggestive of Fabry's disease.

Double-target Antisense U1snRNAs Correct Mis-splicing Due to c.639+861C>T and c.639+919G>A GLA Deep Intronic Mutations

Fabry disease is a rare X-linked lysosomal storage disorder caused by deficiency of the α-galactosidase A (α-Gal A) enzyme, which is encoded by the GLA gene. GLA transcription in humans produces a major mRNA encoding α-Gal A and a minor mRNA of unknown function, which retains a 57-nucleotide-long cryptic exon between exons 4 and 5, bearing a premature termination codon. NM_000169.2:c.639+861C>T and NM_000169.2:c.639+919G>A GLA deep intronic mutations have been described to cause Fabry disease by inducing overexpression of the alternatively spliced mRNA, along with a dramatic decrease in the major one. Here, we built a wild-type GLA minigene and two minigenes that carry mutations c.639+861C>T and c.639+919G>A. Once transfected into cells, the minigenes recapitulate the molecular patterns observed in patients, at the mRNA, protein, and enzymatic level. We constructed a set of specific double-target U1asRNAs to correct c.639+861C>T and c.639+919G>A GLA mutations. Efficacy of U1asRNAs in inducing the skipping of the cryptic exon was evaluated upon their transient co-transfection with the minigenes in COS-1 cells, by real-time polymerase chain reaction (PCR), western blot analysis, and α-Gal A enzyme assay. We identified a set of U1asRNAs that efficiently restored α-Gal A enzyme activity and the correct splicing pathways in reporter minigenes. We also identified a unique U1asRNA correcting both mutations as efficently as the mutation-specific U1asRNAs. Our study proves that an exon skipping-based approach recovering α-Gal A activity in the c.639+861C>T and c.639+919G>A GLA mutations is active.

FAbry STabilization indEX (FASTEX): an innovative tool for the assessment of clinical stabilization in Fabry disease

Two disease severity scoring systems, the Mainz Severity Score Index (MSSI) and Fabry Disease Severity Scoring System (DS3), have been validated for quantifying the disease burden of Fabry disease. We aimed to develop a dynamic mathematical model [the FASTEX (FAbry STabilization indEX)] to assess the clinical stability. A multidisciplinary panel of experts in Fabry disease first defined a novel score of severity [raw score (RS)] based on three domains with a small number items in each domain (nervous system domain: pain, cerebrovascular events; renal domain: proteinuria, glomerular filtration rate; cardiac domain: echocardiography parameters, electrocardiograph parameters and New York Heart Association class) and evaluated the clinical stability over time. The RS was tested in 28 patients (15 males, 13 females) with the classic form of Fabry disease. There was good statistical correlation between the newly established RS and a weighted score (WS), with DS3 and MSSI (R² = 0.914, 0.949, 0.910 and 0.938, respectively). In order to refine the RS further, a WS, which was expressed as a percentage value, was calculated. This was based on the relative clinical significance of each item within the domain with the panel agreeing on the attribution of a different weight of clinical damage to a specific organ system. To test the variation of the clinical burden over time, the RS was repeated after 1 year. The panel agreed on a cut-off of a 20% change from baseline as the clinical WS to define clinical stability. The FASTEX model showed good correlation with the clinical assessment and with clinical variation over time in all patients.

Risk factors for severe clinical events in male and female patients with Fabry disease treated with agalsidase beta enzyme replacement therapy: Data from the Fabry Registry

BACKGROUND

Fabry disease, an X-linked lysosomal storage disorder, causes intracellular accumulation of glycosphingolipids leading to progressive renal, cardiovascular, and cerebrovascular disease, and premature death.

METHODS

This longitudinal Fabry Registry study analyzed data from patients with Fabry disease to determine the incidence and type of severe clinical events following initiation of enzyme replacement therapy (ERT) with agalsidase beta, as well as risk factors associated with occurrence of these events. Severe events assessed included chronic dialysis, renal transplantation, cardiac events, stroke, and death.

RESULTS

The analyses included 969 male and 442 female Fabry patients. The mean age at first agalsidase beta infusion was 35 and 44, and median treatment follow-up 4.3years and 3.2years, respectively. Among males, cardiac events were the most common on-ERT events, followed by renal, stroke, and non-cardiac death. Among females, cardiac events were also most common followed by stroke and renal events. Patients with on-ERT events had significantly more advanced cardiac and renal disease at baseline as compared with patients without on-ERT events. Severe events were also associated with older age at ERT initiation (males and females), a history of pre-ERT events (females; approaching statistical significance in males), and a higher urinary protein/creatinine ratio (females). Approximately 65% of patients with pre-ERT events did not experience subsequent on-ERT events. Of patients without pre-ERT events, most (84% of males, 92% of females) remained event-free.

CONCLUSIONS

Patients with on-ERT severe events had more advanced Fabry organ involvement at baseline than those without such events and patients who initiated ERT at a younger age had less residual risk of on-ERT events. The observed patterns of residual risk may aid clinicians in multidisciplinary monitoring of male and female patients with Fabry disease receiving ERT, and in determining the need for administration of adjunctive therapies.

Fabry's disease: an example of cardiorenal syndrome type 5

Cardiorenal syndrome type 5 (CRS-5) includes conditions where there is a simultaneous involvement of the heart and kidney from a systemic disorder. This is a bilateral organ cross talk. Fabry's disease (FD) is a devastating progressive inborn error of metabolism with lysosomal glycosphingolipid deposition in variety of cell types, capillary endothelial cells, renal, cardiac and nerve cells. Basic effect is absent or deficient activity of lysosomal exoglycohydrolase a-galactosidase A. Renal involvement consists of proteinuria, isosthenuria, altered tubular function, presenting in second or third decade leading to azotemia and end-stage renal disease in third to fifth decade mainly due to irreversible changes to glomerular, tubular and vascular structures, especially highlighted by podocytes foot process effacement. Cardiac involvement consists of left ventricular hypertrophy, right ventricular hypertrophy, arrhythmias (sinus node and conduction system impairment), diastolic dysfunction, myocardial ischemia, infarction, transmural replacement fibrosis, congestive heart failure and cardiac death. Management of FD is based on enzymatic replacement therapy and control of renal (with anti-proteinuric agents such as angiotensin-converting enzyme inhibitors-and/or angiotensin II receptor blockers), brain (coated aspirin, clopidogrel and statin to prevent strokes) and heart complications (calcium channel blockers for ischemic cardiomyopathy, warfarin and amiodarone or cardioverter device for arrhythmias).

Multicenter Female Fabry Study (MFFS) - clinical survey on current treatment of females with Fabry disease

BACKGROUND

The aim of the present study was to assess manifestations of and applied treatment concepts for females with Fabry disease (FD) according to the current European Fabry Guidelines.

METHODS

Between 10/2008 and 12/2014, data from the most recent visit of 261 adult female FD patients from six German Fabry centers were retrospectively analyzed. Clinical presentation and laboratory data, including plasma lyso-Gb3 levels were assessed.

RESULTS

Fifty-five percent of females were on enzyme replacement therapy (ERT), according to recent European FD guidelines. Thirty-three percent of females were untreated although criteria for ERT initiation were fulfilled. In general, the presence of left ventricular hypertrophy (LVH) seemed to impact more on ERT initiation than impaired renal function. In ERT-naïve females RAAS blockers were more often prescribed if LVH was present rather than albuminuria. Affected females with missense mutations showed a similar disease burden compared to females with nonsense mutations. Elevated plasma lyso-Gb3 levels in ERT-naïve females seem to be a marker of disease burden, since patients showed comparable incidences of organ manifestations even if they were ~8 years younger than females with normal lyso-Gb3 levels.

CONCLUSION

The treatment of the majority of females with FD in Germany is in line with the current European FD guidelines. However, a relevant number of females remain untreated despite organ involvement, necessitating a careful reevaluation of these females.

Variations in plasma and urinary lipids in response to enzyme replacement therapy for Fabry disease patients by nanoflow UPLC-ESI-MS/MS

A deficiency of α-galactosidase A causes Fabry disease (FD) by disrupting lipid metabolism, especially trihexosylceramide (THC). Enzyme replacement therapy (ERT) is clinically offered to FD patients in an attempt to lower the accumulated lipids. Studies on specific types of lipids that are directly or indirectly altered by FD are very scarce, even though they are crucial in understanding the biological process linked to the pathogenesis of FD. We performed a comprehensive lipid profiling of plasma and urinary lipids from FD patients with nanoflow liquid chromatography electrospray-ionization tandem mass spectrometry (nLC-ESI-MS/MS) and identified 129 plasma and 111 urinary lipids. Among these, lipids that exhibited alternations (>twofold) in patients were selected as targets for selected reaction monitoring (SRM)-based high-speed quantitation using nanoflow ultra-performance LC-ESI-MS/MS (nUPLC-ESI-MS/MS) and 31 plasma and 26 urinary lipids showed significant elevation among FD patients. Higher percentages of sphingolipids (SLs; 48% for plasma and 42% for urine) were highly elevated in patients; whereas, a smaller percentage of phospholipids (PLs; 15% for plasma and 13% for urine) were significantly affected. Even though α-galactosidase A is reported to affect THC only, the results show that other classes of lipids (especially SLs) are changed as well, indicating that FD not only alters metabolism of THC but various classes of lipids too. Most lipids showing significant increases in relative amounts before ERT decreased after ERT, but overall, ERT influenced plasma lipids more than urinary lipids.

Histiocytic disorders of the chest: imaging findings

Histiocytic disorders of the chest comprise a broad spectrum of diseases. The lungs may be involved in isolation or as part of systemic disease. Some of these disorders are primary and have unknown etiology, and others result from a histiocytic response to a known cause. Among primary histiocytic disorders, pulmonary Langerhans cell histiocytosis (PLCH) is the most common; others include Erdheim-Chester disease and Rosai-Dorfman disease. Adult PLCH occurs almost exclusively in adults aged 20-40 years who smoke. Pediatric PLCH is extremely rare and typically occurs as part of multisystemic disease. Erdheim-Chester disease affects middle-aged and older adults; thoracic involvement usually occurs as part of systemic disease. Rosai-Dorfman disease affects children and young adults and manifests as painless cervical lymphadenopathy. Examples of secondary histiocytic disorders are storage diseases such as Gaucher disease, Niemann-Pick disease, and Fabry disease; pneumoconiosis such as silicosis and coal workers' pneumoconiosis; and infections such as Whipple disease and malakoplakia. These disorders are characterized at histopathologic examination on the basis of infiltration of alveoli or the pulmonary interstitium by histiocytes, which are a group of cells that includes macrophages and dendritic cells. Dendritic cells are a heterogeneous group of nonphagocytic antigen-presenting immune cells. Immunohistochemical markers help to distinguish among various primary histiocytic disorders. Characteristic radiologic findings in the appropriate clinical context may obviate biopsy to establish a correct diagnosis. However, in the absence of these findings, integration of clinical, pathologic, and radiologic features is required to establish a diagnosis.

Paediatric Fabry disease

Fabry disease is a rare, progressive X-linked inborn error of the glycosphingolipid metabolic pathway. Mutations of the GLA gene result in deficiency of the lysosomal enzyme, α-galactosidase A (α-Gal A) with accumulation of glycosphingolipids, particularly globotriaosylceramide (GL3) in the vascular endothelium of various tissues. Accumulation of GL3 eventually leads to life threatening renal, cardiac and cerebrovascular complications typically in the third to fifth decades of life. The first signs and symptoms of classic Fabry disease however appear in childhood but diagnosis is often delayed. The symptoms most commonly experienced in childhood include neuropathic pain, gastrointestinal dysfunction, hyperhidrosis and heat intolerance. Timely diagnosis is important as early treatment with enzyme replacement therapy reduces GL3 accumulation, can stabilize disease progression and potentially prevent irreversible organ damage. Physicians should be familiar with the signs and symptoms of Fabry disease in childhood and be particularly vigilant for unusual or non-specific but recurrent or episodic symptoms.

Gastrointestinal Symptoms of Patients with Fabry Disease

In order to characterize gastrointestinal (GI) symptoms of 50 patients with Fabry disease (FD) (22 M; age range: 4–70 y; 35 adults and 15 children), validated questionnaires of GI symptoms were used to diagnose the functional gastrointestinal disorders (FGIDs) of the patients with GI symptoms (33/50 (66%); 25/35 adults and 8/15 children) according to Rome III criteria. In 16/25 of these adults and 2/8 of these children, the symptoms mimicked FGID. The adult subgroup included patients with unspecified functional bowel disorder (n = 9), functional bloating (n = 7), and IBS (n = 5), and the child subgroup included patients with abdominal migraine (n = 1) and IBS (n = 1). Among the 25 adults, 14 reported feeling full after a regular-size meal, and 12 complained of abdominal bloating/distension. All of the children with GI symptoms complained of low abdominal pain associated with changes in the form of the stool/improvements with defecation. In conclusion, according to Rome III criteria, the most frequent diagnoses of FGID among the adults with FD were unspecified functional bowel disorder, followed by functional bloating and IBS. The most frequent GI symptom in the children in our population was IBS-like abdominal pain, while the adults exhibited a full feeling following a regular-size meal and abdominal bloating/distension.

Exploratory screening for Fabry's disease in young adults with cerebrovascular disorders in northern Sardinia

BACKGROUND

The etiologic determinants of stroke in young adults remain a diagnostic challenge in up to one-fourth of cases. Increasing evidences led to consider Fabry's disease (FD) as a possible cause to check up. We aimed at evaluating the prevalence of unrecognized FD in a cohort of patients with juvenile stroke in northern Sardinia.

METHODS

For this study, we enrolled 178 patients consecutively admitted to our Neurological Ward for ischemic stroke, transient ischemic attack, intracerebral haemorrhage, neuroradiological evidence of silent infarcts, or white matter lesions possibly related to cerebral vasculopathy at brain MRI, and cerebral venous thrombosis. The qualifying events have to occur between 18 and 55 years of age.

RESULTS

We identified two patients with an α-galactosidase A gene variant, with a prevalence of 0.9 %. According to recent diagnostic criteria, one patient, included for the occurrence of multiple white matter lesions at brain MRI, had a diagnosis of definite FD, the other, included for ischemic stroke, had a diagnosis of uncertain FD.

CONCLUSIONS

Our study places in a middle position among studies that found a prevalence of FD up to 4 % and others that did not find any FD patients. Our findings confirm that FD should be considered in the differential diagnosis of patients with juvenile stroke, particularly those with a personal or familial history positive for cerebrovascular events, or evidence of combined cardiologic and/or renal impairment. All types of cerebrovascular disorders should be screened for FD, including patients with white matter lesions possibly related to cerebral vasculopathy at brain MRI.

The role of imaging in the diagnosis and management of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy, affecting approximately 1:500 people. As the yield of genetic testing is only about 35-60%, the diagnosis of HCM is still clinical and based on the demonstration of unexplained and usually asymmetric left ventricular (LV) hypertrophy by imaging modalities. In the past, echocardiography was the sole imaging modality used for the diagnosis and management of HCM. However, in recent years other imaging modalities such as cardiac magnetic resonance have played a major role in the diagnosis, management and risk stratification of HCM, particularly when the location of left ventricular hypertrophy is atypical (apex, lateral wall) and when the echocardiographic imaging is sub-optimal. However, the most unique contribution of cardiac magnetic resonance is the quantification of myocardial fibrosis. Exercise stress echocardiography is the preferred provocative test for the assessment of LV outflow tract obstruction, which is detected only on provocation in one-third of the patients.

Broad spectrum of Fabry disease manifestation in an extended Spanish family with a new deletion in the GLA gene

Background

Fabry disease (FD) is an X-linked inherited disease based on the absence or reduction of lysosomal-galactosidase (Gla) activity. The enzymatic defect results in progressive impairment of cerebrovascular, renal and cardiac function. Normally, female heterozygote mutation carriers are less strongly affected than male hemizygotes aggravating disease diagnosis.

Method

Close examination of the patients by renal biopsy, echo- and electrocardiography and MRI. Blood work and subsequent DNA analysis were carried out utilizing approved protocols for PCR and Sequencing. MLPA analysis was done to unveil deletions within the GLA gene locus. Quantitative detection of Glycolipids in patient plasma and urine were carried out using HPLC/MS-MS and ESI-MS.

Results

In the presented case, a female index patient led to the examination of three generations of a Spanish family. She presented with severe oto-cochlear symptoms and covert renal and cardiac involvement. While conventional sequencing failed to detect a causative mutation, MLPA analysis revealed a deletion within the GLA gene locus, which we were able to map to a region spanning exon 2 and adjacent intronic parts. The analysis of different biomarkers revealed elevated lyso-Gb3 levels in all affected family members.

Conclusion

Our findings highlight the broad intrafamilial spectrum of symptoms of FD and emphasise the need to use MLPA screening in symptomatic females without conclusive sequencing result. Finally, plasma lyso-Gb3 proved to be a reliable biomarker for the diagnosis of FD.

Prevalence of Raynaud phenomenon and nailfold capillaroscopic abnormalities in Fabry disease: a cross-sectional study

Fabry disease (FD) is a lysosomal disorder leading to progressive systemic involvement, including microvascular damage that leads to neurological and cardiovascular disorders. We hypothesize that the latter could be documented at an early stage by performing a microcirculation study with nailfold capillaroscopy and evaluation of Raynaud phenomenon.The objective was to measure the prevalence of Raynaud phenomenon and nailfold capillaroscopic abnormalities in FD.This cross-sectional study included a standardized questionnaire and a nailfold capillaroscopy that assessed previously reported patterns in FD (dystrophic and giant capillaries, avascular fields, irregular architecture, dilatation and density of capillaries, hemorrhage), and was conducted on 32 Fabry patients and 39 controls. Capillaroscopic photographs were reviewed by 2 independent blinded investigators.Twelve Fabry patients (38%) suffered from Raynaud phenomenon, 5 were males (ie, 50% of male Fabry patients), compared with 2 controls (13%) (P < 0.001), of whom none were males (P < 0.001). Raynaud phenomenon was concomitant or before the occurrence of pain in the extremities in 42% of Fabry patients.More ramified capillaries were significantly observed in Fabry patients (12/32, 38%) than in controls (5/39, 13%, P = 0.016).Secondary Raynaud phenomenon should lead to screening for FD, especially in men. By extension, in high-risk populations for FD, the presence of Raynaud phenomenon and ramified capillaries should be assessed.

Fabry disease and the heart

Fabry disease is induced by a mutation in the alpha-galactosidase A gene, causing a deficiency of the enzyme alpha-galactosidase A. (1) The enzyme defect leads to progressive intracellular accumulation of globotriaosylceramide in lysosomes of various tissues and organs, including heart, kidney and nerve system. Cardiac involvement is common and is presenting as concentric left ventricular hypertrophy. Myocardial replacement fibrosis is a typical feature of more advanced stages of Fabry cardiomyopathy, first limited to the mid-myocardial layers of the basal postero-lateral wall, then spreading to transmural fibrosis. Since 2001, enzyme replacement therapy is available. If therapy is started early, before myocardial fibrosis has developed, a long-term improvement of myocardial morphology, function and exercise capacity can be achieved. In end-stage cardiomyopathy enzyme replacement therapy might prevent further progression of the disease. This review provides an overview of Fabry disease, with a focus on cardiac involvement with its characteristic features, clinical presentation and possible treatment.

A disproportionate contribution of papillary muscles and trabeculations to total left ventricular mass makes choice of cardiovascular magnetic resonance analysis technique critical in Fabry disease

BACKGROUND

Sphingolipid deposition in Fabry disease causes left ventricular (LV) hypertrophy, of which the accurate assessment is essential. Cardiovascular magnetic resonance (CMR) has been proposed as the gold standard. However, there is debate in the literature as to whether papillary muscles and trabeculations (P&T) should be included in LV mass (LVM).

METHODS/RESULTS

We examined the accuracy of 2 CMR methods of assessing LVM and LV volumes, including (M inc P&T) or excluding (M ex P&T) P&T, in a cohort of Fabry disease subjects (n = 20) compared to a matched control group (n = 20). Significant differences between the two measurement methods were observed for LV end-diastolic volume, LV end-systolic volume, LVM, and LV ejection fraction (LVEF) in both groups. These differences were significantly greater in the Fabry group compared to controls, except for LVEF. P&T contributed to a greater percentage of LVM in Fabry subjects than controls (20 ± 1% vs 13 ± 2%, p = 0.01). In the control group, both volume-derived methods (M inc P&T or MexP&T) provided accurate SV measurements compared with the internal reference of velocity-encoded aortic flow. In the Fabry group, inclusion of P&T (M inc P&T) resulted in good concordance with phase contrast flow imaging (difference between flow and volume techniques: 1 ± 3 ml, p = 0.7).

CONCLUSION

The volumetric contribution of P&T in Fabry disease is markedly increased relative to healthy controls. Failure to account for this results in significant underestimation of LVM and results in misclassification of a proportion of subjects.

Innate and Adaptive Immune Response in Fabry Disease

Fabry disease is an X-linked lysosomal storage disease in which mutations of the gene (GLA) cause a deficiency of the lysosomal hydrolase α-galactosidase A (α-Gal). This defect results in an accumulation of glycosphingolipids, primarily globotriaosylceramide (Gb3) which causes a multisystemic vasculopathy. Available since 2001 in Europe, enzyme replacement therapy consists in the administration of agalsidase, a recombinant form of α-galactosidase A. Enzyme replacement therapy was shown to improve the global prognosis but allowed partial success in preventing critical events such as strokes and cardiac arrests. As in most lysosomal storage diseases, frequent immune reactions have been described in naive Fabry disease patients. Humoral immune responses following enzyme replacement therapy have also been described, with unclear consequences on the progression of the disease. While cost-effectiveness of enzyme replacement therapy in Fabry disease begins to be questioned and new therapeutic strategies arise such as chaperone or gene therapy, it appears necessary to better understand the immune responses observed in the treatment of naive patients and during enzyme replacement therapy with agalsidase. We propose a comprehensive review of the available literature concerning both innate and adaptive responses observed in Fabry disease. We particularly highlight the probable role of the toll-like receptor 4 (TLR4) and CD1d pathways triggered by Gb3 accumulation in the development of local and systemic inflammation that could lead to irreversible organ damages. We propose an immunological point of view of Fabry disease pathogenesis involving immune cells notably the invariant natural killer T cells. We finally review anti-agalsidase antibodies, their development and impact on outcomes.

Enzyme enhancers for the treatment of Fabry and Pompe disease

Lysosomal storage disorders (LSD) are a group of heterogeneous diseases caused by compromised enzyme function leading to multiple organ failure. Therapeutic approaches involve enzyme replacement (ERT), which is effective for a substantial fraction of patients. However, there are still concerns about a number of issues including tissue penetrance, generation of host antibodies against the therapeutic enzyme, and financial aspects, which render this therapy suboptimal for many cases. Treatment with pharmacological chaperones (PC) was recognized as a possible alternative to ERT, because a great number of mutations do not completely abolish enzyme function, but rather trigger degradation in the endoplasmic reticulum. The theory behind PC is that they can stabilize enzymes with remaining function, avoid degradation and thereby ameliorate disease symptoms. We tested several compounds in order to identify novel small molecules that prevent premature degradation of the mutant lysosomal enzymes α-galactosidase A (for Fabry disease (FD)) and acid α-glucosidase (GAA) (for Pompe disease (PD)). We discovered that the expectorant Ambroxol when used in conjunction with known PC resulted in a significant enhancement of mutant α-galactosidase A and GAA activities. Rosiglitazone was effective on α-galactosidase A either as a monotherapy or when administered in combination with the PC 1-deoxygalactonojirimycin. We therefore propose both drugs as potential enhancers of pharmacological chaperones in FD and PD to improve current treatment strategies.

Delphi consensus on the current clinical and therapeutic knowledge on Anderson-Fabry disease

BACKGROUND

Management of Anderson-Fabry disease (AFD) is contentious, particularly regarding enzyme replacement therapy (ERT). We report results of a Delphi consensus panel on AFD management.

METHODS

A survey to gauge consensus among AFD experts was distributed online and responses were analysed. Statements on: 1) diagnosis; 2) when starting ERT; 3) management of ERT infusion and adverse reactions; and 4) follow-up/monitoring response to therapy and progression of disease were included. Responses without consensus were discussed with an enlarged panel and modified to reach consensus.

RESULTS

15 experts responded to the survey. After plenary discussion among the enlarged panel, consensus was reached on most statements. Key points were the use of a target organ biopsy to show Gb3 deposits in symptomatic women with negative molecular analysis, the need for ERT in symptomatic women and in all patients with persistent signs and symptoms ± organ damage. It was agreed to assess vital signs before ERT administration and use a 0.2 μL filter on infusion to reduce the risk of adverse reactions, that serum should be drawn prior to the first infusion for anti-agalsidase antibody analysis to have a baseline value if a subsequent adverse reaction appears, and that pre-medication is required in those with prior infusion reactions. Holter ECG monitoring, cardiac and brain MRI, renal parameters, and abdominal ultrasound were considered important for the assessment of disease progression and response at ERT.

CONCLUSIONS

This consensus supplies guidance to healthcare providers on best practice in the management of patients with AFD and indicates a need for more guidance.

Fabry disease: Evidence for a regional founder effect of the GLA gene mutation 30delG in Brazilian patients

The Fabry disease is caused by mutations in the gene (GLA) that encodes the enzyme α-galactosidase A (α-Gal A). More than 500 pathologic variants of GLA have already been described, most of them are family-specific. In southern Brazil, a frequent single-base deletion (GLA 30delG) was identified among four families that do not recognize any common ancestral. In order to investigate the history of this mutation (investigate the founder effect, estimate the mutation age and the most likely source), six gene-flanking microsatellite markers of the X chromosome on the mutation carriers and their parents, 150 individuals from the same population and 300 individuals that compose the Brazilian parental populations (Europeans, Africans and Native Americans) were genotyped. A common haplotype to the four families was identified and characterized as founder. The age was estimated with two statistics software (DMLE 2.2 and ESTIAGE) that agreed with 11 to 12 generations old. This result indicates that the mutation GLA 30delG was originated from a single event on the X chromosome of a European immigrant, during the southern Brazil colonization between 1710 and 1740.

Clinical neurogenetics: neuropathic lysosomal storage disorders

The lysosomal storage disorders are a clinically heterogeneous group of inborn errors of metabolism, associated with the accumulation of incompletely degraded macromolecules within several cellular sites. Affected individuals present with a broad range of clinical problems, including hepatosplenomegaly and skeletal dysplasia. Onset of symptoms may range from birth to adulthood. Most are associated with neurologic features. Later-onset forms are often misdiagnosed as symptoms, which might include psychiatric manifestations, are slowly progressive, and may precede other neurologic or systemic features. Symptomatic care, which remains the mainstay for most subtypes, can lead to significant improvement in quality of life.

The kidney in Fabry's disease

Fabry disease (FD) is an X-linked disease in which mutations of the GLA gene result in a deficiency of the enzyme α-galactosidase A and subsequent progressive, intralysosomal deposition of undegraded glycosphingolipid products, primarily globotriaosylceramide, in multiple organs. Progressive nephropathy is one of the main features of FD and is marked by an insidious development, with an overall rate of progression of chronic kidney disease (CKD) very similar to diabetic nephropathy. Untreated patients usually develop end stage renal disease in their 50s. The decline in renal function in FD is adversely affected by male gender, advanced CKD, hypertension and, in particular, severe proteinuria. Enzyme replacement therapy (ERT) has been shown to slow the progression of Fabry nephropathy. The current consensus is that ERT should be started in all men and women with signs of renal involvement.

Clinical course of patients with Fabry disease who were switched from agalsidase-β to agalsidase-α

BACKGROUND

Between 2009 and 2012, there was a worldwide shortage of agalsidase-β for the treatment of Fabry disease. Therefore, alternative treatments were needed, including switching to a different enzyme-replacement therapy.

PURPOSE

This is an ongoing observational study assessing the effects of switching from agalsidase-β (1.0 mg/kg every other week) to agalsidase-α (0.2 mg/kg every other week) in 11 patients with Fabry disease.

METHODS

Clinical data were collected for 5 years-2 years before switching and 3 years after switching.

RESULTS

Measures of renal function such as estimated glomerular filtration rate remained stable during the 3 years after switching to agalsidase-α. Improvements in cardiac mass were recorded in both male and female patients 12 months after switching to agalsidase-α, and the benefit was maintained during 36 months of follow-up. There was no significant difference in the severity of pain experienced by patients before and after switching enzyme-replacement therapy, and no difference in quality-of-life parameters. Agalsidase-α was generally well tolerated, and no patients experienced allergy or developed antibodies to agalsidase-α.

CONCLUSION

This observational study supports the safety of switching from agalsidase-β to agalsidase-α at the approved doses, with no loss of efficacy. It also suggests that if an infusion-related allergic reaction occurs in a patient receiving agalsidase-β, switching to agalsidase-α may be a viable option.

Globotriaosylceramide Induces Lysosomal Degradation of Endothelial K Ca 3.1 in Fabry Disease

Objective—

Globotriaosylceramide (Gb3) induces K Ca 3.1 downregulation in Fabry disease (FD). We investigated whether Gb3 induces K Ca 3.1 endocytosis and degradation.

Approach and Results—

K Ca 3.1, especially plasma membrane–localized K Ca 3.1, was downregulated in both Gb3-treated mouse aortic endothelial cells (MAECs) and human umbilical vein endothelial cells. Gb3-induced K Ca 3.1 downregulation was prevented by lysosomal inhibitors but not by a proteosomal inhibitor. Endoplasmic reticulum stress–inducing agents did not induce K Ca 3.1 downregulation. Gb3 upregulated the protein levels of early endosome antigen 1 and lysosomal-associated membrane protein 2 in MAECs. Compared with MAECs from age-matched wild-type mice, those from aged α-galactosidase A (Gla)-knockout mice, an animal model of FD, showed downregulated K Ca 3.1 expression and upregulated early endosome antigen 1 and lysosomal-associated membrane protein 2 expression. In contrast, no significant difference was found in early endosome antigen 1 and lysosomal-associated membrane protein 2 expression between young Gla-knockout and wild-type MAECs. In aged Gla-knockout MAECs, clathrin was translocated close to the cell border and clathrin knockdown recovered K Ca 3.1 expression. Rab5, an effector of early endosome antigen 1, was upregulated, and Rab5 knockdown restored K Ca 3.1 expression, the current, and endothelium-dependent relaxation.

Conclusions

—Gb3 accelerates the endocytosis and lysosomal degradation of endothelial K Ca 3.1 via a clathrin-dependent process, leading to endothelial dysfunction in FD.

A metabolomic study to identify new globotriaosylceramide-related biomarkers in the plasma of Fabry disease patients

Fabry disease is an X-linked lysosomal storage disorder caused by a deficiency of the enzyme α-galactosidase A, which results in the progressive accumulation of glycosphingolipids. In addition to the two biomarkers, globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3), which are routinely used for detection and high-risk screening of Fabry disease patients, novel urinary Gb3-related isoforms/analogues as well as newly defined lyso-Gb3 analogues in plasma and urine from Fabry patients have recently been described by our group. The aim of this study was to extend our recent analyses to identify and evaluate new potential Gb3-related biomarkers in the plasma of untreated male Fabry disease patients using a mass spectrometry metabolomic approach. A multivariate statistical analysis revealed five Gb3-related novel biomarkers in the plasma of male Fabry patients. Three of these new biomarkers correspond to Gb3, which has an extra double bond on the sphingosine with C16:0, C18:0, and C22:1 fatty acid chains. The fourth biomarker corresponds to a mixture of two structural isomers, the first with a d16:1 sphingosine and a C16:0 fatty acid and the second with a d18:1 sphingosine and a C14:0 fatty acid. To our knowledge, it is the first time that a Gb3 analogue with a d16:1 sphingosine moiety has been reported. In addition, this Gb3 analogue was also present in its methylated form. These biomarkers are part of a metabolic profile that may provide insight into the pathophysiology of Fabry disease.

Functional characterisation of alpha-galactosidase a mutations as a basis for a new classification system in fabry disease

Fabry disease (FD) is an X-linked hereditary defect of glycosphingolipid storage caused by mutations in the gene encoding the lysosomal hydrolase α-galactosidase A (GLA, α-gal A). To date, over 400 mutations causing amino acid substitutions have been described. Most of these mutations are related to the classical Fabry phenotype. Generally in lysosomal storage disorders a reliable genotype/phenotype correlation is difficult to achieve, especially in FD with its X-linked mode of inheritance. In order to predict the metabolic consequence of a given mutation, we combined in vitro enzyme activity with in vivo biomarker data. Furthermore, we used the pharmacological chaperone (PC) 1-deoxygalactonojirimycin (DGJ) as a tool to analyse the influence of individual mutations on subcellular organelle-trafficking and stability. We analysed a significant number of mutations and correlated the obtained properties to the clinical manifestation related to the mutation in order to improve our knowledge of the identity of functional relevant amino acids. Additionally, we illustrate the consequences of different mutations on plasma lyso-globotriaosylsphingosine (lyso-Gb3) accumulation in the patients' plasma, a biomarker proven to reflect the impaired substrate clearance caused by specific mutations. The established system enables us to provide information for the clinical relevance of PC therapy for a given mutant. Finally, in order to generate reliable predictions of mutant GLA defects we compared the different data sets to reveal the most coherent system to reflect the clinical situation.

Fabry disease is caused by a single gene deficiency. It is the second most common lysosomal storage disorder and the result is a build-up of glycosphingolipids in different areas of the body (kidneys, intestine, etc). It is an important consideration for clinicians in the diagnosing of stroke, kidney and cardiovascular diseases. Many symptoms of Fabry are seen in other diseases as well (both inherited and non- inherited), which makes diagnosis difficult. We observed numerous novel mutations in patients that displayed a monosymptomatic, however life-threatening course of Fabry disease. This prompted us to study and characterise those mutations with regard to their biochemical and clinical consequences. Overall, 171 Fabry mutations were considered in an overexpression system for the prediction of the clinical course of Fabry disease. Furthermore, we highlight the usefulness of the in vitro system that we developed which will help with therapeutical decisions, by testing the responsiveness of mutant enzymes to the pharmacological chaperone DGJ. This work aims to draw the attention of clinicians and researchers to milder forms of Fabry disease which might at first appear unrelated to this clinically heterogenous disease.

Homocysteine and erythrocyte sedimentation rate correlate with cerebrovascular disease in fabry disease

BACKGROUND

Cerebrovascular disease (CVD) is a common clinical problem in Fabry disease; however, expression of this disease manifestation is not uniform and risk factors for its development are not well studied. A number of common CVD risk factors are known in the general population, and these may also play a role in the development of CVD in Fabry disease.

AIM

To evaluate the potential associations between various risk factors and CVD in patients with Fabry disease.

METHODS AND RESULTS

Thirty-two Fabry disease patients were studied, with 15 having evidence of CVD. T-tests were used to compare the positive and negative CVD groups and logistic regression was used to look for correlations with CVD history. CVD-positive patients were older (49.73 vs. 37.59 years, p<0.001) and had worse renal function (GFR 61.53 vs. 96.61 mL/min/1.73 m(2), p < 0.005), higher homocysteine (17.79 vs. 10.53 μmol/L, p < 0.05) and erythrocyte sedimentation rate (ESR) levels (23.8 vs. 7.64 mm/h, p < 0.001), and elevated Mainz Severity Score Index (MSSI) scores (23.8 vs. 11.8, p < 0.001). Correlations were found between age (odds ratio (OR) 1.11), DTPA glomerular filtration rate (OR 0.95), homocysteine concentration (OR 1.22), ESR (OR 1.16) and the MSSI (OR 1.19) scores with a positive CVD history (all p < 0.05).

CONCLUSION

Elevated homocysteine and ESR are independent risk factors for CVD in Fabry disease. This finding adds to our ability to predict those patients with Fabry disease who are at a higher risk of developing CVD, and may be an aid in deciding which patients should have primary CVD prevention therapies.

Vascular endothelial growth factor (VEGF-a) in Fabry disease: association with cutaneous and systemic manifestations with vascular involvement

INTRODUCTION

Fabry disease is an X-linked inherited metabolic disorder characterized by the deficiency of lysosomal α-galactosidase A enzyme. This leads to the accumulation, into lysosomes through the body, of glycosphingolipids, mainly Gb3. Skin involvement and progressive multi-organ failure are usually observed. Endothelium is the preferential target of the Gb3 storage that determines endothelial dysfunction and vasculopathy leading to the clinical manifestations of the disease. The serum levels of Vascular Endothelial Growth Factor-A (VEGF-A), a specific endothelial cell mitogen, were analyzed in Fabry patients to explore a possible association to the clinical manifestations with vascular involvement.

METHODS

Thirty-five patients with a biochemical and genetic diagnosis of Fabry disease, along with an age-gender-matched healthy control group, were enrolled. Serum samples were collected and analyzed by ELISA. The genetic mutations, the specific organ dysfunction, and the cardiovascular risk factors such as dyslipidaemia, diabetes, smoking habits and hypertension were evaluated in Fabry patients.

RESULTS

The mean serum level of VEGF-A in Fabry patients group was significantly higher than in the control group (P=0.006). A statistical significant association, between VEGF-A levels and the skin manifestation including angiokeratomas, sweating abnormalities and Fabry Facies was found. An association was also found between high VEGF-A and specific GLA mutations, the male gender, the renal and neurological manifestations, the presence of eye vessels tortuosity, smoking habit and hypertension.

CONCLUSIONS

We detected increased VEGF-A levels in patients with Fabry disease compared to the controls, and we hypothesized that this could be a response to the vascular damage characterising this lysosomal disorder. However, further studies are necessary to clarify the role of VEGF-A in Fabry.

Measuring patient experiences in Fabry disease: validation of the Fabry-specific Pediatric Health and Pain Questionnaire (FPHPQ)

Introduction

Common symptoms for children with Anderson-Fabry Disease (FD) such as acroparaesthesia and gastrointestinal manifestations can only be objectively assessed in patients using a valid instrument. To date, no such instrument exists.

Methods

A preliminary 40-item measure of symptoms and experience with FD, the Fabry-specific Paediatric Health and Pain Questionnaire (FPHPQ) was developed, but lacked a formal assessment of its measurement properties. The FPHPQ was used in the Fabry Outcome Survey (FOS), a registry for all patients with a confirmed diagnosis of FD who are receiving agalsidase alfa, or are treatment naïve and who are managed by physicians participating in FOS. After an item analysis to explore how items performed and combined into domains, a battery of psychometric analyses was performed to assess the measurement properties of this new instrument.

Results

Eighty-seven children (ages 4-18 years) completed the questionnaire. Twenty-three items in three subscales of the questionnaire emerged: pain associated with heat or exertion, pain associated with cold, and abdominal pain and fatigue symptoms. Internal consistency reliability for all three subscales was good (Cronbach alpha ≥ 0.84). Reliability was equally high for all age groups (4-7, 8-12, and 13-18). Test-retest reliability was high for all three subscales (intraclass correlation coefficient ≥ 0.74). Construct validity was demonstrated by moderate correlation with brief pain inventory (BPI), KINDL, and EQ-5D. Known group validity showed all subscales were able to discriminate between Fabry disease severity groups as classified by above or below median of the FOS MSSI (Mainz Severity Score Index) grade. The heat or exertion subscale was responsive to change in symptoms between responders and non-responders as defined by change in EQ-5D index scores between the first and second visit.

Conclusions

Preliminary results indicate that the measurement properties of FPHPQ are valid and reliable for assessing patient-reported symptoms of FD. The questionnaire could be a useful tool for clinicians to understand the progression of disease and monitor treatment effects. FPHPQ will be further validated and refined as the FOS registry is continuously adding more patients.