Background There is a vast number of screening studies described in the literature from the beginning of the twenty-first century to the present day. Many of these studies are related to the estimation of Fabry disease (FD) morbidity among patients from high-risk groups, including adult patients with hypertrophic cardiomyopathy (HCM) and left ventricular hypertrophy (LVH). These studies show diverse detection frequencies (0–12%) depending on the methodology. Our study is the only example of large-scale selective FD screening based on the implementation of next-generation sequencing technology (NGS) as a first-level test to estimate FD morbidity in the Russian population over 18 years of age burdened with HCM. Methods The study included 1009 patients (578 males and 431 females), with a median age of 50 years, who were diagnosed with HCM according to current clinical guidelines. In the first stage of screening, all patients underwent molecular genetic testing (NGS method) of target regions. These regions included the coding sequences of 17 genes and mutations that can lead to the development of HCM. Lysosomal globotriaosylsphingosine (lyso-Gb3) concentrations and α-galactosidase A (α-gal A) enzyme activity were measured in the second stage of screening to reveal pathogenic or likely pathogenic variants in the GLA gene. Results We revealed 8 (0.8%) patients (3 (37.5%) males and 5 (62.5%) females) with an average age of 59 ± 13.3 years who had pathogenic, likely pathogenic variants and variants of uncertain significance (VUS) in the GLA gene (NM_000169.2) as a result of selective screening of 1009 Russian patients with HCM. FD was confirmed via biochemical tests in a male with the pathogenic variant c.902G > A, p.R301Q as well as in two females with likely pathogenic variants c.897C > A, p.D299E and c.1287_1288dup, p.*430Fext*?. These tests showed reduced enzymatic activity and increased substrate concentration. However, a female with the pathogenic variant c.416A > G, p.N139S and with normal enzymatic activity only had increased substrate concentrations. The revealed nucleotide variants and high values of biochemical indicators (lyso-Gb3) in these 4 patients allowed us to estimate the FD diagnosis among 1009 Russian patients with HCM. Mild extracardiac manifestations were observed in these four patients; however, both biochemical values within the reference range in females with the c.971T > G, p.L324W (VUS) variant. α-gal A activity and lyso-Gb3 concentrations were also within the normal range in two males with hemizygous variants, c.546T > C, p.D182D and c.640-794_640-791del (we regarded them as VUS), and in one female with the c.427G > A, p.A143T variant (with conflicting interpretations of pathogenicity). Conclusion The prevalence rate of FD among 1,009 adult Russian patients with HCM was 0.4%. We recommend FD screening among adult patients of both sexes with HCM and an undefined genetic cause via NGS method with subsequent analysis of α-gal A activity and lyso-Gb3 concentration in patients with pathogenic, likely pathogenic variants, and VUS. This strategy identifies patients with an atypical form of FD that is characterized by high residual activity of α-gal A, low concentrations of lyso-Gb3, and minor extracardiac manifestations.

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Болезнь Фабри (БФ), MIM 301500 - Х-сцепленное заболевание, обусловленное мутациями в гене GLA, который кодирует фермент α-галактозидазу А (α-гал А). В 2017 году в лаборатории молекулярной генетики и медицинской геномики «НМИЦ здоровья детей» Министерства Здравоохранения России был разработан и внедрен метод определения концентрации лизо-Гб3 для диагностики БФ. К настоящему времени нами исследовано 9830 образцов сухих пятен крови из различных регионов России, полученных от 8832 пациентов мужского пола и 998 женского пола, в возрасте от 12 до 70 лет. В результате проведенного исследования у 33 мужчин было выявлено снижение активности фермента, а у 31 из них - повышение концентрации лизо-Гб3, у этих мужчин были обнаружены патогенные варианты гена GLA, тогда как у двух оставшихся мужчин были найдены полиморфные варианты гена GLA, описанные ранее как аллели, обладающие псевдодефицитной активностью. Кроме того, были выявлены 2 женщины с повышенной концентрацией лизо-Гб3, у которых также были обнаружены патогенные варианты гена GLA, тогда как у 5 женщин с псевдодефицитными аллелями гена GLA концентрация лизо-Гб3 была в норме. Наше исследование продемонстрировало преимущество измерения концентрации биомаркера лизо-Гб3 по сравнению с определением активности фермента α-гал А для первичной диагностики мужчин с подозрением на БФ, a также возможность использования этого биомаркера для первичной диагностики женщин с подозрением на БФ. Fabry Disease (BF), MIM 301500 - X-linked disease caused by mutations in the GLA gene, which encodes the enzyme α-galactosidase A (α-gal A). In 2017, a method for determining the concentration of lyso-Gb3 for the diagnosis of FD was developed and introduced in the laboratory of molecular genetics and medical genomics of the “National Medical Research of Children’s Health Federal State Autonomous Institution of the Ministry of Health of the Russian Federation. To date, we have studied 9830 samples of dry blood spots from various regions of Russia, obtained from 8832 male and 998 female patients, aged 12 to 70 years. As a result of the study, a decrease in enzyme activity was detected in 33 men, and in 31 of them an increase in the concentration of lyso-Gb3, pathogenic variants of the GLA gene were found in these men, while the two remaining men found polymorphic variants of the GLA gene, previously described as alleles with pseudodeficiency activity. In addition, 2 women with an increased concentration of lyso-Gb3 were identified, in whom pathogenic variants of the GLA gene were also detected, while in 5 women with pseudo-deficient alleles of the GLA gene, the concentration of lyso-Gb3 was normal. Our study demonstrated the advantage of measuring the concentration of the lyso-Gb3 biomarker compared to determining the activity of the α-gal A enzyme for the initial diagnosis of men with suspected FD, as well as the possibility of using this biomarker for the initial diagnosis of women with suspected DF.

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