BALTIMORE (CNS) -- Nineteen-month-old Mason Shaffer has no qualms about somersaulting off a couch in his family's Pennsylvania home. He's equally fearless when exploring new surroundings or playing a spirited round of peek-a-boo with his mother. It's a far cry from a year ago when Mason couldn't even sit up or roll over. Afflicted with malignant infantile osteopetrosis, a rare bone disease, Mason was severely underdeveloped and in significant pain. His life was saved through a transplant of adult stem cells obtained from umbilical-cord blood donated to a public collecting bank. "He's cured," said Sarah Shaffer, Mason's mother. "He's completely...