Ginger Crowley, a flame-haired Irish-American, says something called the Celtic Curse stands between her and raising a pint of Guinness this St. Patrick's Day.

Last year, as others celebrated the feast day, Crowley learned she had triple the normal amount of iron in her blood, a likely result of hereditary hemochromatosis. The common genetic disorder, also called iron overload affects about 1 million Americans, according to the Centers for Disease Control and Prevention, most often those of Northern European, particularly Irish, descent