The earliest enzyme replacement for infantile-onset Pompe disease in Japan.

Background: Infantile-onset Pompe disease (IOPD) is the most severe phenotype of a lysosomal storage disorder caused by acid alpha-glucosidase (GAA) deficiency. An enzymatic newborn screening (NBS) program started regionally in Japan in 2013 for early enzyme replacement therapy (ERT). We report the ERT responses of the first NBS-identified Japanese IOPD case and of another case diagnosed prior to NBS, to discuss the problems of promptly starting ERT in Japan.