772 SCREENING FOR ANDERSON-FABRY DISEASE IN RELATIVELY YOUNG PATIENTS WITH UNEXPLAINED CONDUCTION DISORDERS REQUIRING PACEMAKER IMPLANTATION
Authors: Allegra Marta , Crea Pasquale , Poleggi Cristina , Mancinelli Anna , Parisi Francesca , Dattilo Giuseppe , Licordari Roberto , Demurtas Elisabetta , Giuffrida Giulia , Carerj Scipione , Micari Antonio , Bella Gianluca Di 
Published: December 2022

Abstract

Background
Anderson-Fabry Disease (AFD, OMIM 301500) is a rare X-linked lysosomal storage disorder caused by GLA gene mutation resulting in a deficit or absent activity of the α-galactosidase A enzyme (α-Gal A). This deficiency involves the impossibility of cleavage of glycophospholipids, resulting in an intralisosomal accumulation of them in different tissues. Due to an incidence of 1 in 80000, AFD is considered the second most common glycosphingolipid storage disorder after Gaucher disease. Cardiac manifestations include left ventricular hypertrophy (LVH) and arrhythmias. The rate of pacemaker implantation (PMI) in AFD has been described to be 25 times higher than in the general population, and the requirement of PMI has been reported to be as high as 8% in some AFD series. In this context, the presence of conduction abnormalities in young patients may suggest an undiagnosed AFD.1 Therefore, early diagnosis is important in AFD because appropriate therapies seem to be more effective when initiated promptly.

Purpose
Our aim is to detect AFD among relatively patients with unexplained conduction disturbances requiring PMI, not submitted to newborn screening.

Methods
Among 650 patients afferent to our ambulatory for routinary pacemaker follow-up, we considered a selected population with diagnosis of sinus node dysfunction or atrioventricular block (confirmed by atrial pacing rate ≥ 60% or ventricular pacing percentage ≥ 80%) and an age, at the time of PMI, ranging between ≥40 and ≤70 years old. The exclusion criteria were: patients with previous myocardial infarction; patient whit known cardiac disease (such as hypertrophic cardiomyopathy); patients who underwent cardiac surgery and patients with extracardiac disease with cardiac involvement such as autoimmune disorders. For this cohort of 26 adult patients (13 males; 13 females; mean age 63 ± 7 years) a prospective screening study for AFD was performed. After clinical evaluation, transthoracic echocardiography (analyzing signs of left ventricular hypertrophy) and pacemaker check, a dried blood spot sampled in filter paper was analyzed. This filter paper assay was performed in male patients in order to evaluate the α-Galactosidase A enzyme activity through the detection of Fabry disease biomarkers; only in the case of abnormal values, genetic investigation was performed. In female patients, the analysis was exclusively genetic.

Results
The analyses revealed 58% (15/26) of patients affected by mild LVH (IVS diameter ranging from 11 to 15 mm). No patient had severe LVH (IVS diameter ≥15 mm) or moderate-severe renal dysfunction (more than stage 3B, GFR below than 30-44 mL/min). In the restrict cohort considered, we found one 69 yo female patient with heterozygosis GLA pathogenic mutation, NM_000169.2:c.638A&gt;C p.(Lys213Thr). She had normal value of liso-Gb3 1,1 ng/ml (n.v. ≤ 1,8 ng/ml). She had mild LVH (IVS diameter 12 mm) and no renal dysfunction. Familiar screening was programmed.

Conclusion
In a highly selected sample of relatively young patients with conduction disturbances requiring pacemaker implantation, a female patient with genetic mutation causing AFD has been identified. Therefore, it seems that screening efforts should be increased in this patient population.
1 Hemelsoet D, De Keyser J, Van Heuverswyn F et al. Screening for Fabry Disease in Male Patients With Arrhythmia Requiring a Pacemaker or an Implantable Cardioverter-Defibrillator. Circulation. 2021 Feb 23;143(8):872-874. doi: 10.1161/CIRCULATIONAHA.120.051400.