Pompe disease is an autosomal recessive disorder caused by a deficiency in 1,4-a-glucosidase, characterized by progressive glycogen accumulation in cellular lysosomes. It ultimately leads to cellular damage. Infantile-onset Pompe disease (IOPD) is the most severe type of this disease and is characterized by severe hypertrophic cardiomyopathy and generalized hypotonia. To date, approximately 400 pathogenic mutations have been reported in the GAA gene. we identified a novel mutation in the acid alpha-glucosidase (GAA) gene: C.[236_246del11], The patient was a 5 months years old female with hypertrophic cardiomyopathy and a family history of sister dead at earlier age. After definite diagnosis, enzyme-replacement therapy (ERT) was started for the patient. But unfortunately, she dead 4 months after beginning of the treatment by decompensation of her heart diseases by viral bronchiolitis.