Fabry disease 'The New Great Imposter': results of the French Observatoire in Internal Medicine Departments (FIMeD)

Fabry disease (FD) is an X-linked lysosomal storage disorder due to α-galactosidase A deficiency. It is associated with a broad range of clinical symptoms, resulting in frequent misdiagnosis and diagnostic delay, which may impact on patient outcomes. This retrospective observational study of 58 FD patients referred to 10 internal medicine departments in France aimed to review differential diagnoses received prior to diagnosis and examines diagnostic delay. The average age at the time of diagnosis was 27.6 years (range: 10-60) and 42.2 years (range: 9-77) among the 23 males and 35 females analyzed, respectively. Most common symptoms that led to FD diagnosis were family history of FD (12 males and 27 females), followed by pain in extremities (10 males and 5 females), and angiokeratoma (8 males and 4 females). Eighteen patients had received alternative diagnoses prior to FD diagnosis, including a female patient with four previous diagnoses. Four case reports are presented, which illustrate the diagnostic 'odyssey' and delayed diagnosis often experienced by patients. Clinicians should consider a diagnosis of FD when presented with a wide range of symptoms, thus helping to shorten the diagnostic delay and facilitating early therapy with enzyme replacement therapy to improve patient outcomes.     

Fabry disease in children and response to enzyme replacement therapy: results from the Fabry Outcome Survey

The Fabry Outcome Survey (FOS) was established to extend the knowledge of the natural history of Fabry disease and to assess the effects of enzyme replacement therapy (ERT) with agalsidase alfa. As of March 2009, 64 boys and 34 girls with Fabry disease had enrolled in the FOS and been treated with agalsidase alfa for at least 6 months. The prevalence of symptoms tended to be reduced after 12 and 24 months of ERT in patients who experienced symptoms at baseline. In the entire population, non-significant decreases in the prevalence of gastrointestinal problems in boys and pain crises in girls were observed after 12-24 months. Kidney function and left ventricular mass indexed to height remained stable. Fifty-eight treatment-related adverse events were reported in 23 patients (21 boys and 2 girls), including 55 infusion reactions. Anti-agalsidase alfa IgG antibodies were found in two boys. No IgE antibodies were reported. This study represents the largest observational study of paediatric Fabry disease patients treated with ERT and indicates continued safety of long-term ERT in children. Continued long-term follow-up is recommended to determine early initiation of ERT, which could potentially slow or prevent the progression of serious morbidities of Fabry disease.     

Fabry disease: characterization of alpha-galactosidase A double mutations and the D313Y plasma enzyme pseudodeficiency allele

Fabry disease, an X-linked inborn error of glycosphingolipid catabolism, results from mutations in the gene encoding the lysosomal exoglycohydrolase, alpha-galactosidase A (alpha-Gal A; GLA). In two unrelated classically affected males, two alpha-Gal A missense mutations were identified: R112C + D313Y (c.334C>T + c.937G>T) and C172G + D313Y (c.514T>G + c.937G>T). The D313Y lesion was previously identified in classically affected males as the single mutation [Eng et al., 1993] or in cis with another missense mutation, D313Y + G411D (c.937G>T + c.1232G>A) [Guffon et al., 1998]. To determine whether the D313Y mutation was a deleterious mutation or a coding region sequence variant, the frequency of D313Y in normal X-chromosomes, as well as its enzymatic activity and subcellular localization in COS-7 cells was determined. D313Y occurred in 0.45% of 883 normal X-chromosomes, while the R112C, C172G, and G411D missense mutations were not detected in over 500 normal X-chromosomes. Expression of D313Y in COS-7 cells resulted in approximately 60% of wild-type enzymatic activity and showed lysosomal localization, while R112C, C172G, G411D, and the double-mutated constructs had markedly reduced or no detectable activity and were all retained in the endoplasmic reticulum. The expressed D313Y enzyme was stable at lysosomal pH (pH 4.6), while at neutral pH (pH 7.4), it had decreased activity. A molecular homology model of human alpha-Gal A, based on the X-ray crystal structure of chicken alpha-galactosidase B (alpha-Gal B; alpha-N-acetylgalactosaminidase) was generated [Garman et al., 2002], which provided evidence that D313Y did not markedly disrupt the alpha-Gal A enzyme structure. Thus, D313Y is a rare exonic variant with about 60% of wild-type activity in vitro and reduced activity at neutral pH, resulting in low plasma alpha-Gal A activity.     

Gastrointestinal manifestations of Fabry disease: clinical response to enzyme replacement therapy

Gastrointestinal symptoms are often an early and prominent manifestation of Fabry disease, an X-linked inborn error of metabolism caused by the deficient activity of the lysosomal enzyme, alpha-galactosidase A. This enzyme deficiency results in the progressive accumulation of globotriaosylceramide and other glycosphingolipids in tissue lysosomes throughout the body. In classically affected patients, glycosphingolipid accumulation in the vascular endothelium eventually culminates in life-threatening renal, cardiac, and cerebrovascular disease. In addition, over 50% of patients experience post-prandial abdominal pain and diarrhea that interferes with the ability to work and quality of life. Here, we describe four males aged 17-40 years with classic Fabry disease and severe gastrointestinal symptoms who participated in clinical trials of enzyme replacement therapy with agalsidase beta (Fabrazyme, 1 mg/kg every 2 weeks). Before therapy, the three adult patients experienced post-prandial abdominal pain, bloating, and severe diarrhea with 7-10 bowel movements per day every day and the 17-year-old had weekly episodes of diarrhea with six bowel movements per day. Other symptoms included vomiting, food intolerance, and poor weight gain. All patients took medications for these symptoms (diphenoxylate-atropine [Lomotil], ranitidine hydrochloride [Zantac], or sulfasalazine). After 6-7 months of agalsidase beta therapy, all patients reported "no or only occasional" abdominal pain or diarrhea, had discontinued their gastrointestinal medications, and had gained 3-8 kg. These marked improvements in gastrointestinal symptoms have persisted for over 3 years of treatment. In such patients, enzyme replacement at 1 mg/kg effects an early and significant clinical improvement in the gastrointestinal manifestations of Fabry disease.     

Long-term effectiveness of enzyme replacement therapy in Fabry disease with the p.Arg227Ter variant: Fabry disease in Ostrobothnia (FAST) study

Fabry disease (FD) is an X chromosome-linked, life-threatening lysosomal disease caused by one of more than 1000 currently known variants in the α-galactosidase A (GLA) gene. The follow-up part of the Fabry Disease in Ostrobothnia (FAST) study reports the long-term effect of enzyme replacement therapy (ERT) on a prospectively collected cohort of 12 patients, 4 males and 8 females, mean age 46 years (SD 16), with the classical variant c.679C > T p.Arg227Ter, which is one of the most common FD variants worldwide. In the natural history period of the FAST study, half of the patients in both sexes had at least one major event, of which 80% were of cardiac origin. During 5 years of ERT, four patients had a total of six major clinical events consisting of one silent ischemic stroke, three ventricular tachycardias and two increased left ventricular mass indexes. In addition, four patients developed minor cardiac events, four patients minor renal events, and one patient a minor neurological event. ERTs may delay but not prevent the progression of the disease in most patients with the variant Arg227Ter. This variant might be suitable for investigating the efficacy of second-generation ERTs compared to the currently used ERTs regardless of sex.     

Newborn screening for Fabry disease in Oregon: Approaching the iceberg of A143T and variants of uncertain significance

Fabry disease newborn screening (NBS) has been ongoing in Oregon for over 41 months by first-tier enzyme quantitation and second-tier DNA testing. During that period the majority of abnormal referrals received (34/60) were for the presence of the controversial c.427G > A (p.Ala143Thr) aka A143T and the majority of non-A143T referrals were for other variants of uncertain significance (17/60) resulting in at least 32 infants with an inconclusive case outcome even after clinical evaluation and/or diagnostic testing. To date there has been no significant family history or onset of symptoms in individuals with an inconclusive outcome. Based on our experience, we have developed a framework for approaching A143T and other variants of uncertain clinical significance in an attempt to balance sensitivity with the unnecessary medicalization of healthy infants.     

Glycosaminoglycan storage in neuroanatomical regions of mucopolysaccharidosis I dogs following intrathecal recombinant human iduronidase

Intrathecal (IT) recombinant human α-l-iduronidase (rhIDU) has been shown to reduce mean brain glycosaminoglycans (GAGs) to normal levels in mucopolysaccharidosis I (MPS I) dogs. In this study, we examined storage in neuroanatomical regions of the MPS I dog brain, including frontal lobe, cerebellum, basal ganglia, thalamus, hippocampal formation, and brainstem, to determine the response of these functional regions to treatment with IT rhIDU. GAG storage in untreated MPS I dogs was significantly different from normal dogs in all examined sections. GAG levels in normal dogs varied by region: frontal lobe (mean: 2.36 ± 0.54 μg/mg protein), cerebellum (2.67 ± 0.33), basal ganglia and thalamus (3.51 ± 0.60), hippocampus (3.30 ± 0.40), and brainstem (3.73 ± 1.10). Following IT treatment, there was a reduction in GAG storage in each region in all treatment groups, except for the brainstem. Percent reduction in GAG levels from untreated to treated MPS I dogs in the deeper regions of the brain was 30% for basal ganglia and thalamus and 30% for hippocampus, and storage reduction was greater in superficial regions, with 61% reduction in the frontal lobe and 54% in the cerebellum compared with untreated MPS I dogs. Secondary lipid storage in neurons was also reduced in frontal lobe, but not in the other brain regions examined. Response to therapy appeared to be greater in more superficial regions of the brain, particularly in the frontal lobe cortex.     

A successful approach for the detection of Fabry patients in Argentina

Fabry disease is an X-linked lysosomal disorder caused by the deficiency of the lysosomal enzyme alpha-galactosidase A (alpha-Gal A). In males, the laboratory diagnosis is based on the demonstration of decreased levels of alpha-Gal A activity, while in females, the disease is diagnosed by the identification of a mutation in alpha-Gal A gene. Fabry disease in Argentina is underdiagnosed. To date, no comprehensive screening study of Fabry disease in our country has been reported. The present study aimed at developing a targeted screening for the detection of Fabry patients from Argentina based on the set of typical signs and symptoms. We received 121 blood samples from probable Fabry patients for enzymatic and genetic assay. We diagnosed six Fabry patients from six unrelated families, representing a yield of detection of 4.96%. The mutations detected in five of the families analysed were missense mutations: p.Leu243Trp, p.Asp155His, p.Leu415Pro, p.Cys94Tyr and p.Leu191Pro. After the detection of a Fabry patient, his/her relatives were also screened. In the course of these family studies, other 64 Fabry patients, 29 males and 35 females, were detected. To our knowledge, this is the first comprehensive screening of Fabry disease in Argentina. We detected 70 patients in a period of 2.5 years. The development of targeted protocols and the constitution of interdisciplinary groups for the identification of patients with Fabry disease are recommended to obtain a higher yield in the process.     

X‐chromosome inactivation in female patients with Fabry disease

Fabry disease (FD) is an X‐linked genetic disorder caused by the deficient activity of lysosomal α‐galactosidase (α‐Gal). While males are usually severely affected, clinical presentation in female patients may be more variable ranging from asymptomatic to, occasionally, as severely affected as male patients. The aim of this study was to evaluate the existence of skewed X‐chromosome inactivation (XCI) in females with FD, its concordance between tissues, and its contribution to the phenotype. Fifty‐six females with FD were enrolled. Clinical and biological work‐up included two global scores [Mainz Severity Score Index (MSSI) and DS3], cardiac magnetic resonance imaging, measured glomerular filtration rate, and measurement of α‐Gal activity. XCI was analyzed in four tissues using DNA methylation studies. Skewed XCI was found in 29% of the study population. A correlation was found in XCI patterns between blood and the other analyzed tissues although some punctual variability was detected. Significant differences in residual α‐Gal levels, severity scores, progression of cardiomyopathy and deterioration of kidney function, depending on the direction and degree of skewing of XCI were evidenced. XCI significantly impacts the phenotype and natural history of FD in females.     

Consensus recommendations for diagnosis,management and treatment of Fabry disease in paediatric patients

Fabry disease (FD), a rare X-linked disease, can be treated with bi-monthly infusion of enzyme replacement therapy (ERT) to replace deficient α-galactosidase A (AGAL-A). ERT reduces symptoms, improves quality of life (QoL), and improves clinical signs and biochemical markers. ERT initiation in childhood could slow or stop progressive organ damage. Preventative treatment of FD from childhood is thought to avoid organ damage in later life, prompting a French expert working group to collaborate and produce recommendations for treating and monitoring children with FD. Organ involvement should be assessed by age 5 for asymptomatic boys (age 12-15 for asymptomatic girls), and immediately for children diagnosed via symptoms. The renal, cardiac, nervous and gastrointestinal systems should be assessed, as well as bone, skin, eyes, hearing, and QoL. The plasma biomarker globotriaosylsphingosine is also useful. ERT should be considered for symptomatic boys and girls with neuropathic pain, pathological albuminuria (≥3 mg/mmol creatinine), severe GI involvement and abdominal pain or cardiac involvement. ERT should be considered for asymptomatic boys from the age of 7. Organ involvement should be treated as needed. Early diagnosis and management of FD represents a promising strategy to reduce organ damage, morbidity and premature mortality in adulthood.     

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.     

Gastrointestinal involvement in Fabry disease. So important,yet often neglected

Fabry disease is an X‐linked metabolic storage disorder due to the deficiency of lysosomal alpha‐galactosidase A which causes accumulation of glycosphingolipids, primarily globotriaosylceramide, throughout the body. Gastrointestinal signs and symptoms – abdominal pain, nausea, diarrhea and diverticular disease – are some of the most frequently reported complaints in patients with Fabry disease but are often neglected. Gastrointestinal symptoms are due to intestinal dysmotility as well as impaired autonomic function, vasculopathy and myopathy. Since 2001, enzyme replacement therapy has been a mainstay in treatment of gastrointestinal symptoms of Fabry disease (FD), resulting in reduced gastrointestinal symptoms. Here, we report on four patients with Fabry disease (FD) who manifested early gastrointestinal involvement.     

Treatment of Fabry disease with different dosing regimens of agalsidase: effects on antibody formation and GL-3

Two different enzyme preparations are used for the treatment of Fabry disease patients, agalsidase alfa (Replagal, Shire) and agalsidase beta (Fabrazyme, Genzyme). Therapeutic efficacy of both products has been variable probably due to differences in gender, severity, age and other patient characteristics. We studied the occurrence of α-Gal A antibodies and their effect on urinary and plasma globotriaosylceramide (GL-3), plasma chitotriosidase and clinical outcome in 52 patients after 12 months of treatment with either 0.2 mg/kg agalsidase alfa (10 males, 8 females) or beta (8 males, 5 females) or 1.0 mg/kg agalsidase beta (10 males, 11 females). Antibodies were detected in 18/28 male patients after 6 months. None of the females developed antibodies. Following 12 months of 0.2 mg/kg treatment, urinary GL-3 decreased in antibody negative (AB−) but increased in antibody positive (AB+) patients.Treatment with 1.0 mg/kg gave a reduction in urinary GL-3 in both AB− and AB+ patients. Levels of plasma GL-3 and chitotriosidase decreased in all patient groups. Twelve months of 0.2 mg/kg treatment did not change renal function or left ventricular mass. Further, no change in renal function was seen following 1.0 mg/kg treatment and left ventricular mass decreased in both AB− and AB+ patients. In summary, α-Gal A antibodies frequently develop in male Fabry disease patients and interfere with urinary GL-3 excretion. Infusion of a dose of 1.0 mg/kg results in a more robust decline in GL-3, less impact, if any of antibodies, stable renal function and reduction of LVMass.     

Inner ear involvement in Fabry disease: Clinical and audiometric evaluation of a large cohort of patients followed in a reference centre

Background

Fabry disease (FD) is a lysosomal storage disorder (LSD) that involves the cochleovestibular system. Tinnitus and progressive sensorineural hearing loss are frequent complains. A stabilization of hearing function has been reported with enzyme replacement therapy (ERT). This study aims to characterize the inner ear involvement, identify factors associated to hearing loss and evaluate the effect of ERT on the hearing function of FD patients.

Two novel mutations in the alpha-galactosidase A gene in Chinese patients with Fabry disease

Fabry disease is an X-linked disorder caused by a deficiency of the lysosomal alpha-galactosidase A [EC 3.2.1.22]. The molecular diagnosis of Fabry disease is important for genotype/phenotype correlation, pre-natal or early diagnosis, and detection of carrier status. Although more than 200 genotypes of the alpha-galactosidase A gene have been identified, mutation data on the Chinese population is sparse. We recently identified two unrelated Chinese families with Fabry disease. Mutation analysis was performed by polymerase chain reaction (PCR) sequencing of the seven exons and adjacent introns of the alpha-galactosidase A gene. Two novel mutations were identified: in family I, a C-to-A transversion resulted in an early termination at amino acid 222 (Y222X), while in family II, an A-to-G transition resulted in a substitution of alanine for threonine at amino acid 410 (T410A). Carrier status was identified in all four females in the two families. The genotype Y222X is associated with classic Fabry disease, with unexpectedly rapid deterioration of visual acuity, while T410A is associated with a milder Fabry disease, with ventricular hypertrophy and neuropathic pain.     

Pathological findings in a patient with Fabry disease who died after 2.5 years of enzyme replacement

We describe the postmortem findings of a 47-year-old man with Fabry disease, an X-linked glycolipid storage disorder, who was on enzyme replacement therapy with recombinant α-galactosidase A for more than 2 years. The patient had widespread atherosclerotic coronary artery disease that culminated in a massive acute myocardial infarction. Atherosclerotic lesions were seen in the right and left coronary systems, aorta, and the basilar artery. Typical Fabry cardiomyopathy and glomerular nephropathy were found. With the exception of vascular endothelial cells, extensive glycolipid storage deposits were seen in all vascular and nonvascular cells and organ systems. We conclude that, at least in this patient, repeated infusions with α-galactosidase A over a prolonged period did not appreciably clear storage material in cells other than vascular endothelial cells. These findings also illustrate accelerated atherosclerosis in susceptible patients with Fabry disease.     

Replacement of alpha-galactosidase A in Fabry disease: effect on fibroblast cultures compared with biopsied tissues of treated patients

The function and intracellular delivery of enzyme therapeutics for Fabry disease were studied in cultured fibroblasts and in the biopsied tissues of two male patients to show diversity of affected cells in response to treatment. In the mutant fibroblasts cultures, the final cellular level of endocytosed recombinant alpha-galactosidases A (agalsidases, Fabrazyme, and Replagal) exceeded, by several fold, the amount in control fibroblasts and led to efficient direct intra-lysosomal hydrolysis of ((3)H)Gb3Cer. In contrast, in the samples from the heart and some other tissues biopsied after several months of enzyme replacement therapy (ERT) with Fabrazyme, only the endothelial cells were free of storage. Persistent Gb3Cer storage was found in cardiocytes (accompanied by increase of lipopigment), smooth muscle cells, fibroblasts, sweat glands, and skeletal muscle. Immunohistochemistry of cardiocytes demonstrated, for the first time, the presence of a considerable amount of the active enzyme in intimate contact with the storage compartment. Factors responsible for the limited ERT effectiveness are discussed, namely post-mitotic status of storage cells preventing their replacement by enzyme supplied precursors, modification of the lysosomal system by longstanding storage, and possible relative lack of Sap B. These observations support the strategy of early treatment for prevention of lysosomal storage.     

Novel sequence variants of the alpha-galactosidase A gene in patients with Fabry disease

We carried out molecular studies of 15 unrelated Hungarian families diagnosed with Fabry disease (FD). Genetic analysis of the α-galactosidase A gene was performed in 22 hemizygous males and 34 females. One of the female patients with severe disease phenotype showed homozygosity for the recurrent c.644A > G mutation due to parental consanguinity. The c.644A > G mutation that has previously been found mostly in patients with the cardiac variant of FD, was associated with renal but not cardiac involvement in this female and in two other family members. In nine families, eight novel sequence variants such as small deletions (c.363delT, c.477delT, c.746delAC) and single nucleotide changes (c.107T > C, c.493G > C, c.796G > T, c.866T > G, c.871G > A) were found in addition to six previously described private mutations. This report contributes to the identification of novel disease-causing mutations in FD, and increases our knowledge on demographics and molecular characteristics of this rare lysosomal storage disorder. This is the first comprehensive overview of molecular genetic features of Hungarian patients with FD.