<qa>  What is the incidence of type II glycogen-storage disease?The incidence of type II glycogen-storage disease Pompe disease varies depending on ethnicity and geographic region. As of 2010, nine studies have been published documenting the incidence of Pompe disease. It is most common within the African American population, with an incidence of 1 in 14,000. In the U.S. more broadly speaking, the combined incidence of all three variants of the disease is 1 in 40,000. These estimates relied on the frequencies of three mutations in the gene acid alpha-glucosidase GAA, leading to variants of the disease. Criteria for inclusion in the studies were often non-selective; in many cases, molecular genetic screening was done at birth. With such a high prevalence of Pompe disease reported, it is expected that large university medical centers specializing in neuromuscular diseases would see a higher incidence of Pompe disease among their patients. From a comparable Italian multicenter study, it appears that Pompe disease accounts for 3 of all patients presenting with proximal weakness with or without CK elevation. 