Screening of family members of chronic kidney disease patients with Fabry disease mutations: a very important and underrated task

Diagnosing Fabry nephropathy: the challenge of multiple kidney disease

Fabry disease (FD) is an X-linked inherited lysosomal disorder due to a deficiency of the enzyme alpha-galactosidase A (α-gla) due to mutations in the GLA gene. These mutations result in plasma and lysosome accumulation of glycosphingolipids, leading to progressive organ damage and reduced life expectancy. Due to the availability of specific disease-modifying treatments, proper and timely diagnosis and therapy are essential to prevent irreversible complications. However, diagnosis of FD is often delayed because of the wide clinical heterogeneity of the disease and multiple organ involvement developing in variable temporal sequences. This observation is also valid for renal involvement, which may manifest with non-specific signs, such as proteinuria and chronic kidney disease, which are also common in many other nephropathies. Moreover, an additional confounding factor is the possibility of the coexistence of FD with other kidney disorders. Thus, suspecting and diagnosing FD nephropathy in patients with signs of kidney disease may be challenging for the clinical nephrologist. Herein, also through the presentation of a unique case of co-occurrence of autosomal dominant polycystic kidney disease and FD, we review the available literature on cases of coexistence of FD and other renal diseases and discuss the implications of these conditions. Moreover, we highlight the clinical, laboratory, and histological elements that may suggest clinical suspicion and address a proper diagnosis of Fabry nephropathy.

Genetic and phenotypic profile of Fabry disease in the population of Vale do Paraiba and Eastern São Paulo

INTRODUCTION

Fabry disease (FD) is an inborn error of metabolism characterized by α-galactosidase A deficiency. The primary objective was to evaluate the genetic and phenotypic profile of Fabry disease in hemodialysis.

METHODS

Observational cohort study to determine the incidence of genetic variations and phenotypic changes for FD in hemodialysis patients in the Paraiba Valley and Eastern São Paulo. Genetic testing for the GLA gene was performed for men and women over 12 years of age at the hemodialysis clinics between January 2016 and December 2019 as a screening protocol.

RESULTS

The cases came from screening exams of the index case among patients with chronic kidney disease, resulting in 17 families and totaling 82 patients under study. The classification of the most prevalent variant was that of uncertain significance (54%), followed by the pathogenic variant (46%). Five patients in two families were described with two types of variants not previously described in the literature, with pathogenic behavior. Comparing the types of variants, the presence of a pathogenic variant was associated with higher levels of lysoGB3, lower values for alpha-GAL activity and higher frequency of symptoms related to FD.

CONCLUSION

We characterized an extensive population of patients with FD variants with rich genetic, clinical and biomarker details. We believe that this study can help to better characterize the Brazilian population with FD and the most frequent types of variants.

Perfil genético e fenotípico da doença de Fabry na população do Vale do Paraíba e Zona Leste de São Paulo

RESUMO Introdução: A doença de Fabry (DF) é um erro inato do metabolismo caracterizado pela deficiência da enzima α-galactosidase A. O objetivo primário foi avaliar o perfil genético e fenotípico da doença de Fabry em hemodiálise. Métodos: Estudo de coorte observacional para determinar a incidência de variações genéticas e alterações fenotípicas para DF em pacientes em hemodiálise no Vale do Paraíba e Zona Leste de São Paulo. O teste genético para o gene GLA foi realizado para homens e mulheres em todos os pacientes das clínicas de hemodiálise maiores de 12 anos entre janeiro de 2016 a dezembro de 2019 como protocolo de rastreio. Resultados: Os casos foram provenientes de exames de triagem do caso índice entre pacientes portadores de doença renal crônica, resultando em 17 famílias e totalizando 82 pacientes em estudo. A classificação da variante mais prevalente foi a de significado incerto (54%), seguida da variante patogênica (46%). Foram descritos 5 pacientes em duas famílias com dois tipos de variantes ainda não previamente descritos na literatura com comportamento patogênico. Na comparação entre os tipos de variantes, a presença de variante patogênica foi associada a maiores níveis de lysoGB3, menores valores da atividade da alfa-GAL e maior frequência de sintomas relativos à DF. Conclusão: Caracterizamos uma extensa população de pacientes com variantes para DF com riqueza de detalhes de genética, clínica e de biomarcadores. Acreditamos que este estudo possa auxiliar na melhor caracterização da população brasileira com DF e nos tipos mais frequentes de variantes.

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.