Cari Wheeler, center, and her dad Gary Boyer, seated, did not know they carried the fragile X trait until Max, center, was born with fragile X syndrome.
They called him "the singing baby." As a newborn, Maxwell Wheeler would lie in his crib, whistling shrilly as he breathed in and out. For Cari and Andrew Wheeler of Madera Ranchos, Calif., it was one of the first signs that all was not right with their second child--an infant who didn't like to be touched, refused to nurse and struggled to keep down formula. At 10 months, when Max was still spitting up more than sitting up, the Wheelers consulted an occupational therapist, who noticed an extra fold above his eyelids, prominent ears and other features she called "dysmorphic."
"I...
