Without enzyme replacement therapy, the hearts of babies with infantile onset Pompe disease progressively thicken and enlarge. These babies die before the age of one year from either cardiorespiratory failure or respiratory infection. For individuals with late onset Pompe disease, the prognosis is dependent upon the age of onset. In general, the later the age of onset, the slower the progression of the disease. Ultimately, the prognosis is dependent upon the extent of respiratory muscle involvement.