Objective To identify a novel pathogenicity mutation of acid alpha‐glucosidase(GAA) gene in a Chinese family with two siblings affected with juvenile onset form glycogen storage disease Ⅱ(GSD Ⅱ) .Methods The clinical and family data of two siblings presenting recurrent respiratory tract infections ,respiratory failure associated with systemic muscle weakness ,were an‐alyzed and diagnosed with GSD Ⅱ by detecting alpha‐1 ,4‐glucosidase activity .DNA was extracted from peripheral blood of the proband ,younger brother and his parents .All 20 exons and the intron‐exon splice sites of GAA gene were amplified by polymerase chain reaction (PCR) .Mutations were detected by direct sequencing the PCR products .Results The younger brother was found to be compound heterozygous for two mutations in the GAA gene :c .1216G>A (p .Asp406Asn) missense mutation in the exon 8 from his father and c .1935C>A (p .Asp645Glu) missense mutation in the exon 14 from his mother .Conclusion The compound hetero‐zygous c .1216G>A and c .1935C>A mutations caused the juvenile onset form GSD Ⅱ characterized by dyspnea and cardiac hyper‐trophy .The novel c .1216G>A mutation may be related to the juvenile onset form GSD Ⅱ .