Fabry Disease in Women: Genetic Basis, Available Biomarkers, and Clinical Manifestations

Fabry Disease (FD) is a rare lysosomal storage disorder caused by mutations in the GLA gene on the X chromosome, leading to a deficiency in α-galactosidase A (AGAL) enzyme activity. This leads to the accumulation of glycosphingolipids, primarily globotriaosylceramide (Gb3), in vital organs such as the kidneys, heart, and nervous system. While FD was initially considered predominantly affecting males, recent studies have uncovered that heterozygous Fabry women, carrying a single mutated GLA gene, can manifest a wide array of clinical symptoms, challenging the notion of asymptomatic carriers. The mechanisms underlying the diverse clinical manifestations in females remain not fully understood due to X-chromosome inactivation (XCI). XCI also known as "lyonization", involves the random inactivation of one of the two X chromosomes. This process is considered a potential factor influencing phenotypic variation. This review delves into the complex landscape of FD in women, discussing its genetic basis, the available biomarkers, clinical manifestations, and the potential impact of XCI on disease severity. Additionally, it highlights the challenges faced by heterozygous Fabry women, both in terms of their disease burden and interactions with healthcare professionals. Current treatment options, including enzyme replacement therapy, are discussed, along with the need for healthcare providers to be well-informed about FD in women, ultimately contributing to improved patient care and quality of life.

Clinical features and enzyme replacement therapy in 10 children with Fabry disease

OBJECTIVE

To summarize the clinical features, diagnosis and enzyme replacement therapy(ERT) of Fabry disease (FD) in children.

METHODS

The clinical data, laboratory tests, genetic variations and treatment of 10 FD children diagnosed in Shandong Provincial Hospital from September 2020 to June 2022 were retrospectively analyzed.

RESULTS

Among the 10 cases from 6 families, 7 patients were boys of 4 to 13 years of age, and 3 were girls of 12 to 15 years of age. There were 7 symptomatic patients, including 6 boys and 1 girl. All 7 patients presented with acral neuralgia. Five patients had little or no sweating. Five patients presented with cutaneous angiokeratoma. Two patients had abdominal pain. One patient developed joint symptoms. Four patients had corneal opacity. One patient had hearing loss; one patient had short stature. One patient had mild proteinuria and 1 patient had dysplasia of the right kidney with decreased eGFR (55.28 ml/min.1.73 m²). The left ventricular mass index was slightly elevated in 1 patient. Three patients had mild obstructive ventilatory dysfunction; a small amount of effusion in the intestinal space of the lower abdomen or mild fatty liver was found in 2 patients. Partial empty sella turcica in 1 patient. A total of 6 GLA gene variants were detected in 10 children, among which C.1059_1061delGAT (p.met353del) was a newly discovered mutation. Five children received ERT, of which 4 were treated with agalsidase beta and 1 was treated with agalsidase alpha. Only 1 patient had anaphylaxis. Lyso-GL-3 levels decreased significantly in the first 3 months of ERT initiation and remained relatively stable thereafter in 3 patients. The Lyso-GL-3 level was decreased, but renal impairment continued to progress in 1 patient treated with agalsidase alpha.

CONCLUSION

The clinical manifestations of FD in childhood are diverse, and it is necessary to make a definite diagnosis by combining family history, enzyme activity, biomarkers, gene testing and other indicators. Pedigree screening and high-risk population screening are helpful for early identification, early diagnosis and early treatment. No serious adverse reactions were found during the short-term treatment with agalsidase alpha and beta.

Functional characterization of novel variants found in patients with suspected Fabry disease

The deficiency or absence of the lysosomal hydrolase α-Galactosidase A results in Fabry disease (FD), a rare and underdiagnosed X-linked disorder. The symptoms caused by FD have a direct relation with the variant present in the gene coding α-Galactosidase A (GLA) and enzyme residual activity, and it can vary drastically between men and women of the same family. Here, we present four novel variants found in patients with suspicion of FD. The patients were screened for FD by enzymatic activity and/or DNA sequencing, which showed four novel GLA missense variants. To confirm the potential pathogenicity of these variants, we employed site-directed mutagenesis. GLA wild-type and mutant plasmids were transfected into mammalian cells; RNA and proteins were extracted for expression and enzymatic activity analysis. The patients presented the variants p.Ile133Asn, p.Lys140Thr, p.Lys168Gln and p.Pro323Thr in the GLA. In vitro analysis showed pathogenic potential of three variants and one tolerated variant. The variants p.Ile133Asn and p.Lys168Gln showed no residual activity and, therefore, leading to classical phenotype, and the variant p.Lys140Thr, which presented 22% of residual activity, was considered a mild variant leading to non-classical phenotype. The variant p.Pro323Thr presented 66.7% of residual activity and alone, it is not enough to cause FD.

Expert opinion on the recognition, diagnosis and management of children and adults with Fabry disease: a multidisciplinary Turkey perspective

This consensus statement by a panel of Fabry experts aimed to identify areas of consensus on conceptual, clinical and therapeutic aspects of Fabry disease (FD) and to provide guidance to healthcare providers on best practice in the management of pediatric and adult patients with FD. This consensus statement indicated the clinical heterogeneity of FD as well as a large number of pathogenic variants in the GLA gene, emphasizing a need for an individualized approach to patient care. The experts reached consensus on the critical role of a high index of suspicion in symptomatic patients and screening of certain at-risk groups to reveal timely and accurate diagnosis of FD along with an increased awareness of the treating physician about the different kinds of pathogenic variants and their clinical implications. The experts emphasized the crucial role of timely recognition of FD with minimal delay from symptom onset to definite diagnosis in better management of FD patients, given the likelihood of changing the disease's natural history, improving the patients' quality of life and the prognosis after enzyme replacement therapy (ERT) administered through a coordinated, multidisciplinary care approach. In this regard, this consensus document is expected to increase awareness among physicians about unique characteristics of FD to assist clinicians in recognizing FD with a well-established clinical suspicion consistent with pathogenic variants and gender-based heterogeneous clinical manifestations of FD and in translating this information into their clinical practice for best practice in the management of patients with FD.

Brazilian consensus recommendations for the diagnosis, screening, and treatment of individuals with fabry disease: Committee for Rare Diseases - Brazilian Society of Nephrology/2021

Fabry disease (FD) is an X-linked inherited disorder caused by mutations in the GLA gene encoding enzyme alpha-galactosidase A (α-Gal A). The purpose of this study was to produce a consensus statement to standardize the recommendations concerning kidney involvement in FD and provide advice on the diagnosis, screening, and treatment of adult and pediatric patients. This consensus document was organized from an initiative led by the Committee for Rare Diseases (Comdora) of the Brazilian Society of Nephrology (SBN). The review considered randomized clinical trials, real-world data studies, and the expertise of its authors. The purpose of this consensus statement is to help manage patient and physician expectations concerning the outcomes of treatment. Our recommendations must be interpreted within the context of available evidence. The decisions pertaining to each individual case must be made with the involvement of patients and their families and take into account not only the potential cost of treatment, but also concurrent conditions and personal preferences. The Comdora intends to update these recommendations regularly so as to reflect recent literature evidence, real-world data, and appreciate the professional experience of those involved. This consensus document establishes clear criteria for the diagnosis of FD and for when to start or stop specific therapies or adjuvant measures, to thus advise the medical community and standardize clinical practice.

A new approach to identifying patients with elevated risk for Fabry disease using a machine learning algorithm

Background

Fabry disease (FD) is a rare genetic disorder characterized by glycosphingolipid accumulation and progressive damage across multiple organ systems. Due to its heterogeneous presentation, the condition is likely significantly underdiagnosed. Several approaches, including provider education efforts and newborn screening, have attempted to address underdiagnosis of FD across the age spectrum, with limited success. Artificial intelligence (AI) methods present another option for improving diagnosis. These methods isolate common health history patterns among patients using longitudinal real-world data, and can be particularly useful when patients experience nonspecific, heterogeneous symptoms over time. In this study, the performance of an AI tool in identifying patients with FD was analyzed. The tool was calibrated using de-identified health record data from a large cohort of nearly 5000 FD patients, and extracted phenotypic patterns from these records. The tool then used this FD pattern information to make individual-level estimates of FD in a testing dataset. Patterns were reviewed and confirmed with medical experts.

Results

The AI tool demonstrated strong analytic performance in identifying FD patients. In out-of-sample testing, it achieved an area under the receiver operating characteristic curve (AUROC) of 0.82. Strong performance was maintained when testing on male-only and female-only cohorts, with AUROCs of 0.83 and 0.82 respectively. The tool identified small segments of the population with greatly increased prevalence of FD: in the 1% of the population identified by the tool as at highest risk, FD was 23.9 times more prevalent than in the population overall. The AI algorithm used hundreds of phenotypic signals to make predictions and included both familiar symptoms associated with FD (e.g. renal manifestations) as well as less well-studied characteristics.

Conclusions

The AI tool analyzed in this study performed very well in identifying Fabry disease patients using structured medical history data. Performance was maintained in all-male and all-female cohorts, and the phenotypic manifestations of FD highlighted by the tool were reviewed and confirmed by clinical experts in the condition. The platform’s analytic performance, transparency, and ability to generate predictions based on existing real-world health data may allow it to contribute to reducing persistent underdiagnosis of Fabry disease.

Cytogenetic and Biochemical Genetic Techniques for Personalized Drug Therapy in Europe

For many authorized drugs, accumulating scientific evidence supports testing for predictive biomarkers to apply personalized therapy and support preventive measures regarding adverse drug reactions and treatment failure. Here, we review cytogenetic and biochemical genetic testing methods that are available to guide therapy with drugs centrally approved in the European Union (EU). We identified several methods and combinations of techniques registered in the Genetic Testing Registry (GTR), which can be used to guide therapy with drugs for which pharmacogenomic-related information is provided in the European public assessment reports. Although this registry provides information on genetic tests offered worldwide, we identified limitations regarding standard techniques applied in clinical practice and the information on test validity rarely provided in the according sections.

Accuracy diagnosis improvement of Fabry disease from dried blood spots: Enzyme activity, lyso-Gb3 accumulation and GLA gene sequencing

The purpose of this study was to examine the applicability of the use of samples in dried blood spot (DBS) for the definitive diagnosis of Fabry disease (FD) in males and females and to compare the diagnostic role of α-galactosidase A activity (α-Gal A), levels of lyso-Gb3 and sequencing of the GLA gene in screening patients with suspected FD. Measurement of α-Gal A activity in suspected FD patients in DBS was made followed by lyso-Gb3 determination and GLA gene sequencing. Of the 2381 subjects analyzed, FD was confirmed in 24 patients. Thirteen different variants were considered like pathogenic, five of which had not been previously described (c.143A > G; c.455A > C; c.487G > T; c.554delA; c.1045_1046insA). None of the patients with normal enzyme activity had FD confirmation. The DBS measurement of α-Gal A was more sensitive than lyso-Gb3 levels in both men and women. Definitive diagnosis of FD from a single DBS is possible, allowing samples to be easily sent from anywhere to the reference laboratory.

Renal Manifestations of Fabry Disease: A Narrative Review

Purpose of review

In this narrative review, we describe general aspects, histological alterations, treatment, and implications of Fabry disease (FD) nephropathy. This information should be used to guide physicians and patients in a shared decision-making process.

Source of information

Original peer-reviewed articles, review articles, and opinion pieces were identified from PubMed and Google Scholar databases. Only sources in English were accessed.

Methods

We performed a focused narrative review assessing the main aspects of FD nephropathy. The literature was critically analyzed from a theoretical and contextual perspective, and thematic analysis was performed.

Key findings

FD nephropathy is related to the progressive accumulation of GL3, which occurs in all types of renal cells. It is more prominent in podocytes, which seem to play an important role in the pathogenesis of this nephropathy. A precise detection of renal disorders is of fundamental importance because the specific treatment of FD is usually delayed, making reversibility unlikely and leading to a worse prognosis.

Limitations

As no formal tool was applied to assess the quality of the included studies, selection bias may have occurred. Nonetheless, we have attempted to provide a comprehensive review on the topic using current studies from experts in FD and extensive review of the literature.

Correlation between GLA variants and alpha-Galactosidase A profile in dried blood spot: an observational study in Brazilian patients

BACKGROUND

Fabry disease is a rare X-linked inherited disorder caused by deficiency of α-Galactosidase A. Hundreds of mutations and non-coding haplotypes in the GLA gene have been described; however, many are variants of unknown significance, prompting doubts about the diagnosis and treatment. The α-Galactosidase A enzymatic activity in dried blood spot (DBS) samples are widely used for screening purposes; however, even when values below the normal are found, new tests are required to confirm the diagnosis. Here we describe an analysis of GLA variants and their correlation with DBS α-Galactosidase A enzymatic activity in a large Brazilian population with Fabry disease symptoms.

RESULTS

We analyzed GLA variants by DNA sequencing of 803 male patients with suspected Fabry disease or belonging to high-risk populations; in 179 individuals, 58 different exonic variants were detected. From these, 50 are variants described as pathogenic and eight described as variants of unknown significance. The other individuals presented complex non-coding haplotypes or had no variants. Interestingly, the enzymatic activity in DBS was different among pathogenic variants and the other genotypes, including variants of unknown significance; the first presented mean of 12% of residual activity, while the others presented levels above 70% of the activity found in healthy controls.

CONCLUSION

The activity of α-Galactosidase A in DBS was markedly reduced in males with known pathogenic variants when compared with subjects presenting variants of unknown significance, non-coding haplotypes, or without variants, indicating a possible non-pathogenic potential of these latter genotypes. These findings bring a better understanding about the biochemical results of α-Galactosidase A in DBS samples, as well as the possible non-pathogenic potential of non-coding haplotypes and variants of unknown significance in GLA gene. These results certainly will help clinicians to decide about the treatment of patients carrying variants in the gene causing this rare but life-threatening disease.