GAA and cardiac hypertrophy: While the existing Gaatm1Rabn/J KO mouse model of Pompe disease was also reported to feature reduced GAA expression and enzymatic activity as well as progressive muscle weakness and glycogen accumulation in affected tissue13, cardiac hypertrophy – a key distinguishing feature of IOPD – was not fully characterized in Gaatm1Rabn/J mice and was not observed until 32 weeks of age in another knockout model of Pompe disease12.