In 1994, an athletic man we’ll call John was involved in a car crash. He was uninjured, and X-rays of his spine showed no fractures. They did, however, reveal unusually dense bones. John’s radiologist referred him to Karl Insogna, the director of the Yale Bone Center. "His bone density was eight times higher than average for a man his age," Insogna recalls. This fact may not have surprised John, who used to sink like a stone when he tried to swim.

Six years later, Insogna heard a fellow physician mention he’d seen a family with very high bone mass. Together they traced the family tree, linking John to an extended kin group sprinkled up and down the Eastern seaboard. The affected kin all had very dense bones and unusually square jaws, but otherwise normal skeletons. One of the affected family members is a physician in Alabama. "He’s had several failed hip replacements because they can’t screw the prosthesis into his bone," Insogna says. "It’s too hard." Studying the family, Insogna’s team zeroed in on a region of chromosome 11 likely linked to the unusual trait. But at the time, he says, the region was just too long to sequence.

From The Scientist via Neatorama.

image: Torus palatinus, a bony, lobulated outgrowth typically found in the hard palate of people with a particular LRP5 mutation.

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