- The patient must have a diagnosis of infantile-onset Pompe disease as defined by: a) The patient has/had onset of symptoms compatible with Pompe disease by 12 months of age adjusted for gestation, if necessary. Age at onset of symptoms must be documented in the patient's medical record(s). AND b) The patient has documented GAA deficiency, i.e., below the laboratory-defined cut-off value as determined by the laboratory performing the GAA enzyme activity assay. Tissues used for determination of GAA deficiency may include blood, muscle or skin fibroblasts.