Long-term clinical-pathologic results of enzyme replacement therapy in pre-hypertrophic fabry disease cardiomyopathy

Abstract Background Limited ability of ERT in removing Gb-3 from cardiomyocytes is recognized for advanced FDCM. Pre-hypertrophic FDCM is believed to be cured or stabilized by ERT. However, no pathologic confirmation is available. We report here in the long-term clinical-pathologic impact of ERT on pre-hypertrophic FDCM. Purpose Long-term clinical-pathologic impact of ERT on pre-hypertrophic FDCM. Methods Fifteen Fabry patients with LVMWT ≤ 10.5 mm at CMR required EMB because of angina and/or ventricular arrhythmias. EMB showed coronary small vessel disease in angina cohort and vacuoles in smooth muscle cells and cardiomyocytes around 20% of cell surface containing myelin bodies at electron microscopy. Patients received α-agalsidase in 8 and β-agalsidase in 7 cases. Both groups referred symptoms improvement except 2 patients treated with α- and β-agalsidase respectively. After ERT administration ranging from 4 and 20 years all patients had control CMR and LVEMB because of persistence of symptoms or patients enquiry on disease resolution. Results In 13 asymptomatic FDCM patients, LVMWT and LV-mass, cardiomyocyte diameter, vacuole surface/cell surface ratio and vessels remained unchanged or minimally increased (LV-mass augmented by < 2%) even after 20 years observation and storage material was still present at electron microscopy. In 2 symptomatic patients, FDCM progressed with larger and more engulfed by Gb-3 myocytes being associated to myocardial virus-negative lymphocytic inflammation. Conclusions ERT stabilizes storage deposits and myocyte dimensions in 87% of patients with pre-hypertrophic FDCM. Gb-3 is never completely removed even after long-term treatment. Immune-mediated myocardial inflammation can overlap limiting ERT activity. Figure Legend Patient 11 (24-year-old man) with genetic and biopsy-proven diagnosis of FDCM before and after 20 years ERT. CineMR (A,B) and LGE (C,D) images, performed at baseline (A,C) and 20 years after ERT (B,D) show normal LV wall thickness (8mm and 10 mm) and absence of fibrotic areas. Panel E and F represent semithin section of Epon-embedded EMB samples, stained with basic fuchsin, showing mildly hypertrophied cardiomyocytes containing storage material that result unmodified after long-term ERT administration. Panel G and H are ultrastructural evidence of storage material to consist of myelin bodies (panel G) that remain unchanged after ERT (Panel H).