Rapid Regression of Myocardial Hypertrophy with First-Line Avalglucosidase Alfa in Infantile-Onset Pompe Disease: A Case Report.

A male infant born at 38 weeks of gestation was found to have myocardial hypertrophy on neonatal screening echocardiography, with a left ventricular mass index (LVMI) of 102.1 g/m2 (Z-score 3.1). No skeletal muscle weakness was noted. At 2 months, he developed feeding difficulty and progressive myocardial hypertrophy and was rehospitalized at 3 months with severe cardiomegaly (LVMI 419.5 g/m2, Z-score 12.3) and respiratory distress. Based on reduced GAA enzymatic activity and genetic testing revealing a pathogenic GAA mutation, infantile-onset Pompe disease (IOPD) was confirmed. Enzyme replacement therapy (ERT) with avalglucosidase alfa 40 mg/kg every 2 weeks was initiated. Myocardial hypertrophy and heart failure symptoms began to improve within 1 week after initiation of ERT. The LVMI had decreased to approximately one-third of the baseline value (148.0 g/m2, Z-score 5.2) at 8 weeks, and it had normalized (67.2 g/m2, Z-score 1.5) at 16 weeks of ERT. During the 36-month follow-up, the LVMI remained within the normal range and no treatment-related adverse events occurred. Avalglucosidase alfa produced rapid and substantial regression of myocardial hypertrophy in this atypical IOPD case lacking skeletal muscle involvement. These findings may support the early introduction of avalglucosidase alfa as a first-line therapy to reverse cardiac remodeling and improve clinical outcomes in IOPD.