法布里病是由α-半乳糖苷酶A缺乏引起的罕见X连锁遗传性疾病。已经描述了GLA基因中的数百种突变和非编码单倍型;然而,许多是未知意义的变体,引起对诊断和治疗的怀疑。干血斑(DBS)样品中的α-半乳糖苷酶A酶活性被广泛用于筛选目的;然而,即使发现低于正常值,需要新的测试来确认诊断。在这里,我们描述了GLA变体的分析及其与DBSα-半乳糖苷酶A酶活性的相关性。
我们通过DNA测序分析了803名疑似法布里病或属于高危人群的男性患者的GLA变异;在179人中,检测到58种不同的外显子变体。从这些,50个是描述为致病性的变体,8个描述为未知意义的变体。其他个体呈现复杂的非编码单倍型或没有变体。有趣的是,DBS中的酶活性在致病变体和其他基因型之间是不同的,包括未知意义的变体;第一个呈现的12%的残余活性的平均值,而其他人的水平高于健康对照中发现的活性的70%。
与具有未知意义的变异的受试者相比,具有已知致病变异的男性DBS中α-半乳糖苷酶A的活性显着降低。非编码单倍型,或者没有变体,表明这些后一种基因型可能具有非致病性。这些发现使人们更好地了解DBS样品中α-半乳糖苷酶A的生化结果,以及GLA基因中的非编码单倍型和未知意义的变异的可能的非致病潜力。这些结果肯定会帮助临床医生决定对携带导致这种罕见但危及生命的疾病的基因变异的患者的治疗。
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.
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.
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.