GAA and hereditary hemochromatosis: Examples we have found in Viking Genes include Pompe disease (MIM: 232300), caused by a deficiency of the enzyme acid alpha-glucosidase (GAA), which can lead to nerve and muscle problems; Wilson disease (MIM: 277900), caused by copper overload; and the iron-overload condition hereditary hemochromatosis (MIM: 235200) (HFE).