Fabry disease-often seen, rarely diagnosed

Identification of a novel nonsense mutation in α-galactosidase A that causes Fabry disease in a Chinese family

Fabry disease, a lysosomal storage disease, is an uncommon X-linked recessive genetic disorder stemming from abnormalities in the alpha-galactosidase gene (GLA) that codes human alpha-Galactosidase A (α-Gal A). To date, over 800 GLA mutations have been found to cause Fabry disease (FD). Continued enhancement of the GLA mutation spectrum will contribute to a deeper recognition and underlying mechanisms of FD. In this study, a 27-year-old male proband exhibited a typical phenotype of Fabry disease. Subsequently, family screening for Fabry disease was conducted, and high-throughput sequencing was employed to identify the mutated gene. The three-level structure of the mutated protein was analyzed, and its subcellular localization and enzymatic activity were determined. Apoptosis was assessed in GLA mutant cell lines to confirm the functional effects. As a result, a new mutation, c.777_778del (p. Gly261Leufs*3), in the GLA gene was identified. The mutation caused a frameshift during translation and the premature appearance of a termination codon, which led to a partial deletion of the domain in C-terminal region and altered the protein's tertiary structure. In vitro experiments revealed a significant reduction of the enzymatic activity in mutant cells. The expression was noticeably decreased at the mRNA and protein levels in mutant cell lines. Additionally, the subcellular localization of α-Gal A changed from a homogeneous distribution to punctate aggregation in the cytoplasm. GLA mutant cells exhibited significantly higher levels of apoptosis compared to wild-type cells.

Fabry disease Schwann cells release p11 to induce sensory neuron hyperactivity

Patients with Fabry disease suffer from chronic debilitating pain and peripheral sensory neuropathy with minimal treatment options, but the cellular drivers of this pain are unknown. Here, we propose a mechanism we believe to be novel in which altered signaling between Schwann cells and sensory neurons underlies the peripheral sensory nerve dysfunction we observed in a genetic rat model of Fabry disease. Using in vivo and in vitro electrophysiological recordings, we demonstrated that Fabry rat sensory neurons exhibited pronounced hyperexcitability. Schwann cells probably contributed to this finding because application of mediators released from cultured Fabry Schwann cells induced spontaneous activity and hyperexcitability in naive sensory neurons. We examined putative algogenic mediators using proteomic analysis and found that Fabry Schwann cells released elevated levels of the protein p11 (S100A10), which induced sensory neuron hyperexcitability. Removal of p11 from Fabry Schwann cell media caused hyperpolarization of neuronal resting membrane potentials, indicating that p11 may contribute to the excessive neuronal excitability caused by Fabry Schwann cells. These findings demonstrate that sensory neurons from rats with Fabry disease exhibit hyperactivity caused in part by Schwann cell release of the protein p11.

Investigation of ocular involvement in patients with Fabry disease

PURPOSE

To investigate ocular abnormalities in Fabry disease (FD).

METHODS

Forty-five patients with FD diagnosed by genetic analysis were enrolled in a single medical centre. The following ocular examinations were performed: slit-lamp examination, ophthalmic fundus imaging, in vivo confocal microscopy (IVCM) and optical coherence tomography (OCT). The prevalences of typical abnormalities in the cornea, conjunctiva and retina were recorded; their differences between hemizygote and heterozygote were compared.

RESULTS

In this study, the prevalence of corneal verticillata was 97.8% (44/45). Corneal examination with IVCM demonstrated hyper-reflective intracellular inclusions located within basal epithelial cells. Conjunctival vessel malformations were observed in 64.4% (29/45) of patients, and retinal vessel tortuosity was observed in 62.2% (28/45) of patients. OCT revealed many strong hyper-reflective foci (HRF) in the inner retinal layer (in 66.7% [30/45] of patients); these foci may represent retinal vascular plexi. The prevalences of conjunctival vessel malformation, retinal vessel tortuosity and HRF were higher in hemizygote than in heterozygote.

CONCLUSIONS

Corneal verticillata, HRF on OCT, conjunctival vessel malformation and retinal vessel tortuosity exhibit high prevalence in patients with FD. These ocular manifestations are characteristic and easily accessible; thus, they should be considered diagnostic criteria for FD.

Fabry disease and sleep disorders: a systematic review

Background

Fabry disease (FD) is an X-chromosome-linked disorder characterized by a reduced or complete absence of the enzyme α-galactosidase, resulting in the accumulation of lysosomal globotriaosylceramide. Despite the presence of these deposits in multiple organs, the problem of sleep disorders within this population has very rarely been documented.

Objective

This study aimed to investigate the types and prevalence of sleep disorders among patients with FD.

Methods

Screening of the following medical databases using key terms was performed on 10 February 2023: PubMed, Scopus, and Embase. A total of 136 records were identified. The quality assessment of the studies was conducted by using tools from the National Institutes of Health (NIH) and critical appraisal tools from the Joanna Briggs Institute (JBI).

Results

The study included nine studies on sleep disorders in patients with FD. The overall quality of the majority of these studies was assessed as either poor or fair. Among 330 patients, there was a slightly higher representation of female patients (56%). Sleep problems manifested 4-5 years after the onset of FD and sometimes even after 10-11 years. Genotypes of disease associated with sleep problems were rarely described. Within the FD population, the most commonly reported conditions were excessive daytime sleepiness (EDS) as well as obstructive and central sleep apnea (OSA, CSA). However, EDS occurred more frequently in FD patients, while the prevalence of OSA and CSA was within the ranges observed in the general population. The studies included indicated a lack of association between organ impairment by primary disease and EDS and OSA. The effectiveness of enzyme replacement therapy (ERT) in treating sleep disorders was not demonstrated.

Conclusion

The findings of this report revealed the presence of many sleep-related disorders within the FD population. However, very few studies on this subject are available, and their limited results make it difficult to truly assess the real extent of the prevalence of sleep disturbances among these individuals. There is a need to conduct further studies on this topic, involving a larger group of patients. It is important to note that there are no guidelines available for the treatment of sleep disorders in patients with FD.

Rapidly progressive aortic stenosis treated with transcatheter aortic valve implantation in a patient with Fabry disease: a case report

Background

Fabry disease (FD) is a rare lysosomal storage disease, caused by mutations in the gene encoding the enzyme α-galactosidase A (α-Gal A). Cardiac involvement is one of the main causes of death and it is characterized by progressive concentric left ventricular hypertrophy (LVH), which in most cases is symmetric. Mild thickening of the left-sided valves is seen in as many as a quarter of patients. Severe aortic stenosis is an extremely rare disorder in FD.

Case summary

In this report, we describe the case of a 57-year-old male, who was diagnosed with a cardiac variant of FD 10 years ago. Since the patient had severe LVH, he was started on enzyme replacement therapy when he was 47 years old with an intravenous infusion of 0.2 mg/kg of agalsidase alpha every 14 days. The patient remained stable and asymptomatic for 9 years, until he presented with dyspnoea in New York Heart Association functional class II-III and severe aortic stenosis (aortic valve area: 0.97 cm²) together with severe systolic dysfunction [ejection fraction (EF): 29%]. Because of the patient's comorbidities and high surgical risk, he underwent successful transfemoral transcatheter aortic valve implantation (TAVI). At 2 months following TAVI, the patient was asymptomatic and, in spite of his Fabry cardiomyopathy, the EF had increased to 45%.

Discussion

To our knowledge, this is the first case in the literature to demonstrate a rapid progression of aortic stenosis with severe impairment of left ventricular function and worsening in functional class in a patient with FD, who following TAVI improved his EF, with disappearance of symptoms and ventricular arrhythmias.

Cardiac Imaging in Anderson-Fabry Disease: Past, Present and Future

Anderson-Fabrydisease is an X-linked lysosomal storage disorder caused by a deficiency in the lysosomal enzyme α-galactosidase A. This results in pathological accumulation of glycosphingolipids in several tissues and multi-organ progressive dysfunction. The typical clinical phenotype of Anderson-Fabry cardiomyopathy is progressive hypertrophic cardiomyopathy associated with rhythm and conduction disturbances. Cardiac imaging plays a key role in the evaluation and management of Anderson-Fabry disease patients. The present review highlights the value and perspectives of standard and advanced cardiovascular imaging in Anderson-Fabry disease.

Deficiency in the Screening Process of Fabry Disease: Analysis of Chronic Kidney Patients Not on Dialysis

Fabry Disease (FD), a rare and progressive, X-linked lysosomal storage disorder, is caused by mutations in the α-galactosidase A (GLA) gene which leads to enzymatic deficiency of GLA. Misdiagnosed and undiagnosed FD cases are common for the variable FD phenotype, ranging from asymptomatic and/or impairment of single organs, which is typically seen in females and in patients with late-onset mutation, to multiple organ disease, which is frequently found in males with classic GLA mutation. Consequently, for an early diagnosis and an efficient treatment of FD, three different strategies of screening, new-born screening, high-risk screening and familiar screening, have been conducted. However, most of FD screening in the CKD population has been carried out in hemodialysis patients and kidney transplant recipients, for whom the renal damage is already irreversible, so the effectiveness of enzymatic replacement therapy is limited and delayed therapeutic intervention results in worse long-term outcomes. This review investigates the actual strategies of screening initiatives for the identification of FD, examining in detail those performed in CKD patients not on dialysis.

Fabry Disease With Concomitant Lewy Body Disease

Although Gaucher disease can be accompanied by Lewy pathology (LP) and extrapyramidal symptoms, it is unknown if LP exists in Fabry disease (FD), another progressive multisystem lysosomal storage disorder. We aimed to elucidate the distribution patterns of FD-related inclusions and LP in the brain of a 58-year-old cognitively unimpaired male FD patient suffering from predominant hypokinesia. Immunohistochemistry (CD77, α-synuclein, collagen IV) and neuropathological staging were performed on 100-µm sections. Tissue from the enteric or peripheral nervous system was unavailable. As controls, a second cognitively unimpaired 50-year-old male FD patient without LP or motor symptoms and 3 age-matched individuals were examined. Inclusion body pathology was semiquantitatively evaluated. Although Lewy neurites/bodies were not present in the 50-year-old individual or in controls, severe neuronal loss in the substantia nigra pars compacta and LP corresponding to neuropathological stage 4 of Parkinson disease was seen in the 58-year-old FD patient. Major cerebrovascular lesions and/or additional pathologies were absent in this individual. We conclude that Lewy body disease with parkinsonism can occur within the context of FD. Further studies determining the frequencies of both inclusion pathologies in large autopsy-controlled FD cohorts could help clarify the implications of both lesions for disease pathogenesis, potential spreading mechanisms, and therapeutic interventions.

Stratification of patients with unclassified pain in the FabryScan database

Purpose

Fabry disease belongs to lysosomal storage disorders and can be successfully treated today. On the contrary, the correct diagnostic classification of its symptoms can be challenging and most patients suffer from pain for years, until they are diagnosed correctly. The aim of this project was to characterize patients with unclassified extremity pain and to present a simple algorithm for a retrospective stratification approach.

Patients and methods

The FabryScan includes a bedside-test and a questionnaire, consisting of 10 symptom-orientated and anamnestic questions. For the stratification of patients according to the likelihood for Fabry disease two different approaches were conducted. First, a prospective subgrouping based on the previously invented FabryScan evaluation system was conducted. The second retrospective approach consisted of a factor analysis and a subsequent two-way cluster analysis. Further on, 4 patients diagnosed with Fabry disease were stratified according to both approaches.

Results

In total, 183 completed datasets were included in the statistical analysis. The first approach prospectively classified patients into 3 subgroups (n=40 [likely], n=96 [possible], n=47 [unlikely]) according to the FabryScan evaluation system. The second approach retrospectively stratified patients into 3 subgroups (n=47 [cluster 1], n=95 [cluster 2], n=41 [cluster 3]). Finally, the Fabry patients were sorted to the subgroups, indicative for the highest possibility of Fabry disease in both stratification approaches A and B.

Conclusion

Both stratification approaches sorted patients with confirmed Fabry disease to the subgroups, indicative for the highest likelihood for Fabry. These results indicate validity of the initially selected FabryScan outcome parameters.

Characterization of vertigo and hearing loss in patients with Fabry disease

Background

Fabry Disease (FD) is an X-linked hereditary lysosomal storage disorder which leads to a multisystemic intralysosomal accumulation of globotriaosylceramid (Gb3). Besides prominent renal and cardiac organ involvement, patients commonly complain about vestibulocochlear symptoms like high-frequency hearing loss, tinnitus and vertigo. However, comprehensive data especially on vertigo remain scarce. The aim of this study was to examine the prevalence and characteristics of vertigo and hearing loss in patients with FD, depending on renal and cardiac parameters and get hints about the site and the pattern of the lesions.

Methods

Single-center study with 57 FD patients. Every patient underwent an oto-rhino-laryngological examination as well as videonystagmography and vestibular evoked myogenic potentials (VEMPs) and audiological measurements using pure tone audiometry and auditory brainstem response audiometry (ABR). Renal function was measured by eGFR, cardiac impairment was graduated by NYHA class.

Results

More than one out of three patients (35.1%) complained about hearing loss, 54.4% about vertigo and 28.1% about both symptom. In 74% a sensorineural hearing loss of at least 25 dB was found, ABR could exclude any retrocochlear lesion. Caloric testing showed abnormal values in 71.9%, VEMPs were pathological in 68%. A correlation between the side or the shape of hearing loss and pathological vestibular testing could not be revealed.

Conclusions

Hearing loss and vertigo show a high prevalence in FD. While hearing loss seems due to a cochlear lesion, peripheral vestibular as well as central nervous pathologies cause vertigo. Thus, both the site of lesion and the pathophysiological patterns seem to differ.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0882-7) contains supplementary material, which is available to authorized users.

Role of Handheld In Vivo Reflectance Confocal Microscopy for the Diagnosis of Fabry Disease: A Case Report

Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by the deficient activity of the lysosomal enzyme α-galactosidase that leads to a systemic accumulation of globotriaosylceramide. Handheld in vivo reflectance confocal microscopy (HH-RCM) is a useful modern technique in diagnosis and follow-ups of many skin diseases. This noninvasive device provides high-resolution and high-contrast real-time images to study both the skin and the ocular surface structures that can help clinicians to confirm the diagnosis of FD. HH-RCM could be helpful even for the follow-ups of these patients, enabling us to monitor the effect of enzyme replacement therapy on corneal cells and keratinocytes.

Clinical use of cardiac PET/MRI: current state-of-the-art and potential future applications

Combined PET/MRI is a novel imaging method integrating the advances of functional and morphological MR imaging with PET applications that include assessment of myocardial viability, perfusion, metabolism of inflammatory tissue and tumors, as well as amyloid deposition imaging. As such, PET/MRI is a promising tool to detect and characterize ischemic and non-ischemic cardiomyopathies. To date, the greatest benefit may be expected for diagnostic evaluation of systemic diseases and cardiac masses that remain unclear in cardiac MRI, as well as for clinical and scientific studies in the setting of ischemic cardiomyopathies. Diagnosis and therapeutic monitoring of cardiac sarcoidosis has the potential of a possible 'killer-application' for combined cardiac PET/MRI. In this article, we review the current evidence and discuss current and potential future applications of cardiac PET/MRI.

Identification of a Missense Mutation in the α-galactosidase A Gene in a Chinese Family with Fabry Disease

Introduction:

Fabry Disease (FD), the second most common lysosomal storage disorder after Gaucher disease, is characterized by variable clinical manifestations, including angiokeratoma, corneal dystrophy, recurrent episodes of extremity pain, renal impairment, cardiac complications and cerebrovascular manifestations. It is caused by mutations in the α-galactosidase A gene (gene symbol GLA) on chromosome Xq22, which leads to deficiency of lysosomal α-galactosidase A (α-Gal A), and subsequent accumulation of glycosphingolipids in various tissues and organs. The aim of this study is to identify the disease-causing mutation in a five-generation Chinese family with FD. A c.782G>T transversion (p.G261V) in the GLA gene was identified in four patients and two asymptomatic carriers by direct sequencing, and it co-segregated with the disease in the family. The variant is predicted to be disease-causing mutation and result in seriously abnormal function of α-Gal A. Four patients in this family present with classic phenotype of FD, including acroparesthesias, hypohidrosis, angiokeratomas and intermittent burning pain in extremity.

Conclusion:

The disease severity is similar among male and female patients. Our study extends the genotype-phenotype relationship between mutations in the GLA gene and clinical findings of FD, which may be helpful in the genetic counseling of patients with FD.

Cardiac and renal dysfunction is associated with progressive hearing loss in patients with Fabry disease

Background

Fabry disease (FD) is an X-linked recessive hereditary lysosomal storage disorder which results in the accumulation of globotriaosylceramid (Gb3) in tissues of kidney and heart as well as central and peripheral nervous system.

Besides prominent renal and cardiac organ involvement, cochlear symptoms like high-frequency hearing loss and tinnitus are frequently found with yet no comprehensive data available in the literature.

Objective

To examine hearing loss in patients with FD depending on cardiac and renal function.

Material and methods

Single-center study with 68 FD patients enrolled between 2012 and 2016 at the Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery of the University of Würzburg. Every subject underwent an oto-rhino-laryngological examination as well as behavioral, electrophysiological and electroacoustical audiological testing. High-frequency thresholds were evaluated by using a modified PTA₆ (0.5, 1, 2, 4, 6, 8) and HF-PTA (6, 8 kHz). Renal function was measured by eGFR, cardiac impairment was graduated by NYHA class.

Results

Sensorineural hearing loss was detected in 58.8% of the cohort, which occurred typically in sudden episodes and affected especially high frequencies. Hearing loss is asymmetric, beginning unilaterally and affecting the contralateral ear later. Tinnitus was reported by 41.2%. Renal and cardiac impairment influenced the severity of hearing loss (p < 0.05).

Conclusions

High frequency hearing loss is a common problem in patients with FD. Although not life-threatening, it can seriously reduce quality of life and should be taken into account in diagnosis and therapy. Optimized extensive hearing assessment including higher frequency thresholds should be used.

Fabry disease in children: a federal screening programme in Russia

Our objective was to examine the prevalence of Fabry disease in Russian children with chronic pain in the distal limbs. This non-interventional, multi-centre study included children 2-18 years of age with chronic recurrent unilateral or bilateral pain, burning, or acroparesthesia in the hands or feet. The presence of Fabry disease was defined by abnormal alpha-galactosidase A activity in males or alpha-galactosidase gene (GLA) mutation in females. Among 214 patients (110 males), 84.1% had bilateral limb pain and 31.8% had unilateral limb pain recorded at some time point; 61 (28.5%) patients had a positive family history possibly associated with Fabry disease. Alpha-galactosidase A activity was within the normal range in all 109 of the male patients tested. One female patient had a GLA mutation (C937G > T) and alpha-galactosidase A activity within the normal range.

CONCLUSION

We did not find definitive evidence of Fabry disease in these children with a history of chronic recurrent unilateral or bilateral limb pain or acroparesthesia. The presence of chronic limb pain does not appear to be highly predictive of a diagnosis of Fabry disease in Russian children and adolescents, suggesting that key early signs and symptoms of Fabry disease are not specific to the disease. What is Known: • Signs and symptoms of Fabry disease are seen in children < 10 years of age; pain in the distal limbs is a common early symptom. What is New: • Fabry disease was not diagnosed in this population of Russian children with a history of chronic limb pain. • The presence of acroparesthesia or chronic limb pain does not appear to be highly predictive of a diagnosis of Fabry disease in Russian children and adolescents, suggesting that these early symptoms of Fabry disease are not specific to the disease.

[The neurological manifestations of Fabry disease. A review]

Fabry disease (Anderson-Fabry disease) is an X-linked recessive lysosomal storage disorder resulting from deficient activity of lysosomal hydrolase, alpha-galactosidase A (alpha-Gal A), which leads to progressive accumulation of globotriaosylceramide (Gb3) in various cells, predominantly endothelial and vascular smooth muscle cells, with clinical manifestations affecting major organs including the central nervous system. Manifestations of Fabry disease include progressive renal and cardiac insufficiency, neuropathic pain, stroke and cerebral disease, skin and gastrointestinal symptoms. Clinical onset usually occurs in childhood, but many severe patients are diagnosed in adulthood. Females may be severely affected as males and both may die prematurely due to stroke, heart disease and renal failure. Early recognition of symptoms, enzyme activity levels, concentration of Gb3 levels in the blood, urine and skin biopsies, as well as genetic testing (GLA gene) enable establishment of early diagnosis and therapeutic intervention with enzyme replacement therapy. Enzyme replacement therapy can stabilize or reduce the progression of the disease. Early therapy may prevent complications of the disease.

High variability of Fabry disease manifestations in an extended Italian family

Fabry disease (FD) is an inherited metabolic disorder caused by partial or full inactivation of the lysosomal hydrolase α-galactosidase A (α-GAL). The impairment of α-GAL results in the accumulation of undegraded glycosphingolipids in lysosomes and subsequent cell and microvascular dysfunctions. This study reports the clinical, biochemical, and molecular characterization of 15 members of the same family. Eight members showed the exonic mutation M51I in the GLA gene, a disease-causing mutation associated with the atypical phenotype. The clinical history of this family highlights a wide phenotypic variability, in terms of involved organs and severity. The phenotypic variability of two male patients is not related to differences in α-GAL enzymatic activity: though both have no enzymatic activity, the youngest shows severe symptoms, while the eldest is asymptomatic. It is noticeable that for two female patients with the M51I mutation the initial clinical diagnosis was different from FD. One of them was diagnosed with Familial Mediterranean Fever, the other with Multiple Sclerosis. Overall, this study confirms that the extreme variability of the clinical manifestations of FD is not entirely attributable to different mutations in the GLA gene and emphasizes the need to consider other factors or mechanisms involved in the pathogenesis of Fabry Disease.

Vascular tortuosities of the upper eyelid: a new clinical finding in fabry patient screening

Purpose. To report a new clinical finding related to Fabry disease. Methods. Fabry subjects were enrolled in the study, matched for age and sex with healthy individuals as a control group. This is a prospective review of all upper lid pictures taken for every subject at their last visit. A 4-step grading scale is proposed to classify this new entity. Results. Group A (Fabry) comprised 16 males and 22 females, aged 40 (±14) years on average. Group B (control) comprised 7 males and 8 females, aged 37 (±12) Vessels tortuosity was identified on the external superior lid in 36 of the Fabry patients (94.7%), while none of the subjects in group B showed similar vessels tortuosity. In addition, microaneurysms (MAs) were found in 10/38 group A subjects while none in group B presented a similar finding. The differences are highly significant. Conclusion. This paper proposes that blood vessels tortuosity on the upper eyelid be recognized as a new clinical entity for inclusion among the classic ocular manifestations of Fabry's disease. Without evidence of any negative impact, it should be considered a benign sign contributing to evidence of suspected Fabry disease.