The Young Woman Was a Healthy and Avid Runner. Now She Could Barely Walk. Why?
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Version 0 of 1. The two bridesmaids — sisters of the bride — walked arm in arm past the seated guests. The older, 35, held tight to the arm of the younger, using that single support to replace the crutches on which she had come to depend. Proud but exhausted by her efforts, the older sister spent much of the rest of the celebration in a wheelchair. Until two years before this wedding, the older sister was an avid runner, competing in long-distance races. Now she could only hobble around with crutches or on good days with just a cane, barely able to get out of a chair. ↓ Permanent Pain It started with a stabbing pain in her left foot just at the point in her stride where she pushed off from the ground. She lived in rural Vermont and was training for a half-marathon, her third, when she first noticed it. She used ice and ibuprofen and got through the race, but the pain had been with her ever since. The foot wasn’t red; it was maybe a little swollen, and it hurt, initially just when she walked, then all the time. An X-ray was normal, but a CT scan revealed a stress fracture in the bone just below her big toe. She wore a surgical boot for months and was in and out of physical therapy, but the foot only seemed to get worse. Before this injury, she coached a dance team, kept up with her two school-age children and worked a full-time job. Now she did all that while hobbling around on a foot that should have healed but didn’t. And it wasn’t just the foot. Her knees, hips and back also hurt. She figured it was because of her altered gait. And she felt weak. Not being active seemed to sap her strength. A follow-up CT scan showed that the fracture had healed but somehow the pain remained. Her orthopedic surgeon thought she may have developed something known as Complex Regional Pain Syndrome (C.R.P.S.), an unusual neurological response to trauma, where after healing, patients develop a deep and burning pain at the site of the injury that is often accompanied by swelling and changes in skin color or temperature. Although rare, it is most commonly seen after fractures, sprains or surgery. The pain is severe and limits the use of the affected limb. There may be associated bone changes visible on X-ray or CT scan. Pain control and physical therapy are the mainstays of treatment. The woman went to several pain specialists. Nothing helped, and everything had side effects. She was found to have low vitamin D levels; this vitamin is essential for bone formation, and deficiencies are known to cause pain, so she was started on replacement doses. There were no side effects, but the vitamin didn’t seem to help. Her primary-care physician heard about a clinical trial on a new treatment for C.R.P.S. The testing required for entry into the study provided a new but puzzling clue: Her phosphate level turned out to be dangerously low. ↓ Too Little Phosphate Bone is made, primarily, of calcium and phosphate, absorbed from the foods we eat. Both are plentiful in most diets, so deficiencies are rare. Still, her vitamin D was also quite low, and that plays an essential role in controlling how much calcium and phosphate we absorb. Her physician put her on high doses of phosphate and vitamin D. When, after months of treatment, she was still deficient, he referred her to David Gorson, an endocrinologist and a specialist in bone metabolism. Just days before her sister’s wedding, the patient went to see Gorson. As she told him her story, he was struck by how uncomfortable she looked. She shifted from side to side in the chair as if seeking just the right spot. She walked stiffly, as if her whole body ached. And when she got to the exam table, she was too sore and too weak to climb up. She was missing a molar, he noted. She told him it fell out a couple of years earlier. The only other abnormality he found was that she was quite weak. When she held out her arms, he could easily push them down. Her legs were also weak. ↓ A New Hormone Gorson wasn’t surprised. Even before seeing her, he had a theory about what was going on. The patient’s primary-care doctor had called him to get his thoughts about her unrelenting foot pain and her baffling lab abnormalities — persistently low levels of phosphate and vitamin D. Hearing about her, Gorson recalled a recently discovered hormone called FGF23 that controls phosphate levels in the body. If a person has too much of this hormone, her body will eliminate it through the urine. Even if the person is taking in phosphate in her diet, she will, like this woman, become phosphate-deficient. Gorson had asked the doctor to check the woman’s FGF23 level. By the time she came to see him, he had the answer: Her FGF23 level was abnormally high. Bone is constantly being broken down and rebuilt — that’s how bones stay strong. This woman didn’t have enough phosphate to rebuild her bones once they’d been broken down, hence the pain in her bones and the missing tooth. Teeth, and the bone they sit in, need phosphate to stay strong. Losing her tooth was probably the first hint that she had an excess of FGF23. A lack of phosphate also made her weak; phosphate is a key component in the process that gives muscle cells the energy to function. No phosphate, no function. ↓ Searching for an Explanation Gorson felt certain that the high level of FGF23 was the cause of her bone pain and weakness. What wasn’t clear to Gorson was why her FGF23 level was so high. In most cases, abnormalities of FGF23 come from one of several rare, inherited conditions with lifelong effects. This woman had no history of that. Once she had a diagnosis, Gorson suggested that the patient contact Dr. Karl Insogna, a bone specialist at Yale School of Medicine in New Haven. It would be worth the hourslong trip to see someone with experience with this hormone and the troubles it could cause. Insogna greeted the patient, who was accompanied by her mother. He questioned them closely about the patient’s early years. She hadn’t had any bone problems as a child, and her teeth had been fine. She had been quite healthy until recently. Insogna, examining the patient, found only what had been noted by Gorson — that the young woman was weak, tender and unsteady on her feet — classic findings for osteomalacia, a bone disorder linked to an overproduction of FGF23. Insogna, who had spent decades trying to better understand diseases of the bone, had seen a handful of patients who developed osteomalacia from FGF23 excess in adulthood. Those patients had benign tumors that secreted FGF23. He suspected that this woman did, too, although it was extremely rare. ↓ A Tumor Lurking The doctor ordered a bone scan and, sure enough, a golfball-size mass was found in the patient’s left thigh. Removing this mass would stop the bone destruction that had been crippling her for so long, Insogna explained when he called her with the results. In addition, the scan identified areas all over her body that had been broken down and not rebuilt. These were all the places — her knees, hips and back — that were painful and made it difficult to walk. It would take time, he said, but she would recover. She had the tumor removed in February. It was benign, and within weeks she started to feel less weak. Just having the right amount of phosphate in her system restored much of her strength. But the bone pain got worse. Insogna had warned her that this was expected while her bones sucked up the phosphate they had been deprived of for so long and began rebuilding. After a couple of months, the pain began to ease, and she started the long process of getting stronger. This spring the patient’s sister, with whom she’d walked arm in arm at that fall wedding, married. The patient was thrilled to able to move down the aisle unassisted. She hopes to run another half marathon sometime next year. |