Case report: is low α-Gal enzyme activity sufficient to establish the diagnosis of Fabry disease? / Relato de caso: a diminuição da enzimaα-Gal l é suficiente para estabelecer o diagnóstico?

Abstract Fabry disease is an X-linked lysosomal storage disease due to alpha-galactosidase A (α-Gal A) deficient activity which leads to the accumulation of glucoesphingolipids, such as globotriaosilceramide. There are over 700 known mutations of the enzyme gene, and most of them cause Fabry Disease. This case report describes a hemodialysis patient with a rare and controversial GLA gene mutation, the D313Y. The medecial investigation confirmed that D313Y is an alpha-galactosidase A sequence variant that causes pseudo deficient enzyme activity in plasma but not Fabry disease. Thus, clinical symptoms that prompted Fabry disease investigation could not be attributable to Fabry disease and therefore enzyme replacement therapy was not indicated.

Resumo Doença de Fabry (DF) é uma doença de depósito lisossômico ligada ao cromossomo X, causada pela deficiência da enzima alfa-galactosidase A (α-Gal A) que leva ao acúmulo de glicoesfingolipídeos, principalmente globotriaosilceramide. Existem mais de 700 mutações conhecidas do gene da enzima, a maioria delas são causadoras de DF. Este relato de caso descreve sobre um paciente em hemodiálise com uma mutação do gene GLA rara e controversa, a D313Y. A investigação médica confirmou que D313Y é uma variante que leva à pseudodeficiência plasmática da enzima, mas não ocasiona DF. Assim, os sintomas clínicos que induziram a investigação da doença não devem ser atribuídos à DF e, portanto, não foi indicada a terapia de reposição enzimática.

Screening for Fabry Disease in Left Ventricular Hypertrophy: Documentation of a Novel Mutation / Rastreio de Doença de Fabry na Hipertrofia Ventricular Esquerda: Documentação de uma Nova Mutação

AbstractBackground:Fabry disease is a lysosomal storage disease caused by enzyme α-galactosidase A deficiency as a result of mutations in the GLA gene. Cardiac involvement is characterized by progressive left ventricular hypertrophy.Objective:To estimate the prevalence of Fabry disease in a population with left ventricular hypertrophy.Methods:The patients were assessed for the presence of left ventricular hypertrophy defined as a left ventricular mass index ≥ 96 g/m2 for women or ≥ 116 g/m2 for men. Severe aortic stenosis and arterial hypertension with mild left ventricular hypertrophy were exclusion criteria. All patients included were assessed for enzyme α-galactosidase A activity using dry spot testing. Genetic study was performed whenever the enzyme activity was decreased.Results:A total of 47 patients with a mean left ventricular mass index of 141.1 g/m2 (± 28.5; 99.2 to 228.5 g/m2] were included. Most of the patients were females (51.1%). Nine (19.1%) showed decreased α-galactosidase A activity, but only one positive genetic test − [GLA] c.785G>T; p.W262L (exon 5), a mutation not previously described in the literature. This clinical investigation was able to establish the association between the mutation and the clinical presentation.Conclusion:In a population of patients with left ventricular hypertrophy, we documented a Fabry disease prevalence of 2.1%. This novel case was defined in the sequence of a mutation of unknown meaning in the GLA gene with further pathogenicity study. Thus, this study permitted the definition of a novel causal mutation for Fabry disease - [GLA] c.785G>T; p.W262L (exon 5).

ResumoFundamento:A doença de Fabry é uma doença lisossomal de sobrecarga provocada pela deficiência da enzima α-galactosidase A como resultado de mutações no gene GLA. O envolvimento cardíaco carateriza-se por hipertrofia ventricular esquerda progressiva.Objetivo:Estimar a prevalência da doença de Fabry numa população com hipertrofia ventricular esquerda.Métodos:Os doentes foram avaliados para a presença de hipertrofia ventricular esquerda definida por massa do ventrículo esquerdo indexada como ≥ 96 g/m2 para mulheres ou ≥ 116 g/m2 para homens. Estenose aórtica severa e hipertensão arterial, com hipertrofia ventricular esquerda discreta, foram critério de exclusão. Todos os doentes incluídos foram avaliados para a atividade da enzima α-galactosidase A com testes de gota seca. No caso de atividade enzimática diminuída, realizava-se estudo genético.Resultados:Foram incluídos 47 doentes com uma média de massa indexada de 141,1 g/m2 (± 28,5; 99,2 a 228,5 g/m2]. A maioria (51,1%) dos doentes era do sexo feminino. Nove deles (19,1%) tinham diminuição da atividade da α-galactosidase A, mas apenas um teste genético foi positivo − [GLA] c.785G>T; p.W262L (éxon 5), uma mutação não descrita na literatura. O trabalho de investigação clínica permitiu estabelecer uma associação entre a mutação e a apresentação clínica.Conclusão:Em uma população de doentes com hipertrofia ventricular esquerda, documentamos uma prevalência de doença de Fabry de 2,1%. O novo caso foi definido na sequência de uma mutação de significado indeterminado no gene GLA com posterior estudo de patogenicidade. Este estudo permitiu, assim, definir uma nova mutação causal para doença de Fabry - [GLA] c.785G>T; p.W262L (éxon 5).

Angiokeratoma corporis diffusum without systemic features in a young Kashmiri female: a rare occurrence

Angiokeratoma corporis diffusum [ACD] is a variety of angiokeratoma, characterized by diffuse cutaneous hyperkeratotic vascular lesions. ACD is usually associated with many lysosomal enzyme deficiencies, though it is not a rule. It is associated with systemic features along with skin lesions. It may also present as isolated cutaneous form. X-linked recessive form usually manifests in males and females act as carriers. We report a case of ACD without systemic features in a young Kashmiri female.

Effects of a chemical chaperone on genetic mutations in alpha-galactosidase A in Korean patients with Fabry disease

Fabry disease is an X-linked inborn error of glycosphingolipid catabolism that results from mutations in the gene encoding the alpha-galactosidase A (GLA) enzyme. We have identified 15 distinct mutations in the GLA gene in 13 unrelated patients with classic Fabry disease and 2 unrelated patients with atypical Fabry disease. Two of the identified mutations were novel (i.e., the D231G missense mutation and the L268delfsX1 deletion mutation). This study evaluated the effects of the chemical chaperones 1-deoxygalactonojirimycin (DGJ) on the function of GLA in vitro, in cells containing missense mutations in the GLA gene. Nine missense and a nonsense mutations, including one novel mutation were cloned into mammalian expression vectors. After transient expression in COS-7 cells, GLA enzyme activity and protein expression were analyzed using fluorescence spectrophotometry and Western blot analysis, respectively. DGJ enhanced GLA enzyme activity in the M42V, I91T, R112C and F113L mutants. Interestingly, the I91T and F113L mutations are associated with the atypical form of Fabry disease. However, DGJ treatment did not have any significant effect on the GLA enzyme activity and protein expression of other mutants, including C142W, D231G, D266N, and S297F. Of note, GLA enzyme activity was not detected in the novel mutant (i.e., D231G), although protein expression was similar to the wild type. In the absence of DGJ, the E66Q mutant had wild-type levels of GLA protein expression and approximately 40% GLA activity, indicating that E66Q is either a mild mutation or a functional single nucleotide polymorphism (SNP). Thus, the results of this study suggest that the chemical chaperone DGJ enhances GLA enzyme activity and protein expression in milder mutations associated with the atypical form of Fabry disease.

Genomic analysis of Brazilian patients with Fabry disease

Fabry disease is an X-linked lysosomal disorder due to a-galactosidase A deficiency that causes storage of globotriaosylceramide. The gene coding for this lysosomal enzyme is located on the long arm of the X chromosome, in region Xq21.33-Xq22. Disease progression leads to vascular disease secondary to involvement of kidney, heart and the central nervous system. Detection of female carriers based solely on enzyme assays is often inconclusive. Therefore, mutation analysis is a valuable tool for diagnosis and genetic counseling. Many mutations of the a-galactosidase A gene have been reported with high genetic heterogeneity, being most mutations private found in only one family. The disease is panethnic, and estimates of incidence range from about 1 in 40,000 to 60,000 males. Our objective was to describe the analysis of 6 male and 7 female individuals belonging to 4 different Fabry disease families by automated sequencing of the seven exons of the a-galactosidase gene. Sequencing was performed using PCR fragments for each exon amplified from DNA extracted from peripheral blood. Three known mutations and one previously described in another Brazilian family were detected. Of 7 female relatives studied, 4 were carriers. Although the present study confirms the heterogeneity of mutations in Fabry disease, the finding of the same mutation previously detected in another Fabry family from our region raises the possibility of some founder effect, or genetic drift. Finally, the present study highlights the importance of molecular analysis for carrier detection and genetic counseling.

Córnea verticilata - marcador clínico da doença de Fabry: relato de caso / Cornea verticillata - a clinical marker of Fabry disease: case report

A doença de Fabry é erro inato do metabolismo dos glicoesfingolipídeos (GL), resultante da atividade deficiente da enzima alfa-galactosidase A (a-Gal), com herança ligada ao cromossomo X. O acúmulo progressivo de GL nos tecidos resulta nas manifestações clínicas da doença, mais evidentes em homens hemizigotos, e incluem angioqueratomas, acroparestesias, córnea verticilata, hipo-hidrose, envolvimento cardíaco, renal e manifestações cerebrovasculares. Foi realizada avaliação em família acometida pela doença, sendo dois pacientes do sexo feminino e três do sexo masculino. Todos os pacientes foram submetidos a anamnese, exame oftalmológico completo e dosagem da atividade da enzima a-Gal. O único achado clínico presente em todos foi a córnea verticilata. Isto demonstra o importante papel que o exame oftalmológico apresenta no diagnóstico da doença, já que as alterações oculares são tão características.

Fabry's disease is a rare X-linked lisosomal storage disorder of glycosphingolipid (GL) metabolism, caused by a deficiency of alpha-galactosidase A activity. The progressive accumulation of GL in tissues results in the clinical manifestations of the disease, that are more evident in hemizygous males, and include angiokeratomas, acroparesthesia, cornea verticillata, cardiac and kidney involvement, cerebrovascular manifestations. A family with Fabry's disease including 2 female patients and 3 male patients is reported. The patients were submitted to complete medical history, ophthalmological examination and alpha-galactosidase activity test. Cornea verticillata was a constant finding in all patients. This demonstrates the important role of the ophtalmological examination for the diagnosis of Fabry's disease since the eye findings are so characteristic of the disease.