Pompe disease is a genetic disorder caused by a deficiency of acid α-glucosidase (GAA). Infantile onset Pompe disease is uniformly lethal. Affected infants generally present in the first few months of life with hypotonia, generalized muscle weakness, and a hypertrophic cardiomyopathy, which is rapidly followed by death, usually by the age of one. The late-onset form is characterized less severe symptoms and prognosis. Therapy for Pompe disease is intended to directly address the underlying metabolic defect via intravenous infusions of recombinant human GAA to replace the missing enzyme. We report a case of atypical infantile-onset Pompe disease that presented symptoms in infancy but had less severe clinical manifestations and improved after GAA enzyme replacement (Myozyme®, Genzyme Co., MA, USA) therapy. It is very important that pediatricians become aware of signs and symptoms of Pompe disease, such as a nasal voice or a waddling gait at an early stage so that these patients can benefit from appropriate GAA replacement therapy as soon as possible.