In 1992, a 33-year-old Lebanese woman had just immigrated to Canada and went to see a doctor. She was hunched over, and had limited mobility in her lower back, neck, shoulders and hips. Her doctor, Raymond Lewkonia at the University of Calgary, diagnosed her with ankylosing spondylitis, a medical condition that causes vertebrae in her spine to fuse, and thought that was it.

Then, about eight years later, the woman had a series of fractures in her ribs, feet, left arm and right hip. Her doctor had her take vitamin D supplements, but they had no effect: Lab tests revealed that she didn’t have any vitamin D circulating around in her blood.

That seemed impossible. Some vitamin D, after all, is thought to be essential for maintaining bone health, and taking supplements after a bone injury or fracture is commonly used to expedite the healing process. Why was none of this vital substance in the woman’s system?

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A medical geneticist who looked at this case, Dr. Patrick Ferreira, suspected that a binding protein that partners with vitamin D to get in and around the body — or a lack of it — might have something to do with this medical mystery. But losing the ability to transport vitamin D would be lethal to humans, according to what doctors conventionally know.