To the Editor: Pompe disease, a rare autosomal recessive disorder due to alpha?1,4?glucosidase (GAA) activity deficiency caused by its gene mutation, can cause an excessive lysosomal glycogen storage in muscular tissues. Pompe disease has two major clinical forms: infantile?onset and adult?onset forms. Without treatment, most infantile?onset patients die from respiratory and cardiac failure within the 1st year of life.[1,2] A small percentage of infantile?onset patients, known as an atypical infantile form,[1] present abnormalities in the 1st year and reveal a slower progression with less severe or an absence of cardiomyopathy. For this form, it is not easy to make a differential diagnosis with idiopathic hypertrophic cardiomyopathy. Here, we report a case of atypical infantile?onset Pompe disease from a Chinese family based on genetic and enzyme activity analyses.