A 36-year-old woman with a rare genetic bone disease called X-linked hypophosphatemia (XLH) was treated with a new medicine called burosumab that helped her broken bones heal and reduced her pain. However, when her insurance stopped covering the medicine after 11 months, she had to stop taking it. Within three months, her bones started breaking again in new places, and her body’s chemical levels that control bone health shot up dramatically. This case shows that stopping this medicine too quickly might cause serious problems, and doctors need to understand better what happens when patients have to stop treatment.

The Quick Take

  • What they studied: What happens to a patient’s bones and body chemistry when they stop taking burosumab, a new medicine for a rare genetic bone disease.
  • Who participated: One 36-year-old woman with X-linked hypophosphatemia (XLH), a genetic condition that makes bones weak and causes repeated fractures.
  • Key finding: After stopping burosumab treatment, the patient’s bone-controlling chemical (FGF23) jumped from normal levels to extremely high levels (9,330 compared to a normal range of 10-50), and new bone fractures appeared within three months despite previous healing.
  • What it means for you: If you or someone you know takes burosumab for XLH, stopping the medicine suddenly may cause bones to break again quickly. Talk to your doctor before stopping this treatment, and don’t stop it without medical guidance, even if insurance coverage changes.

The Research Details

This is a case report, which means doctors documented what happened to one specific patient over time. The patient had X-linked hypophosphatemia (XLH), a rare inherited condition where the body can’t keep enough phosphate in the blood, which is essential for strong bones. She received burosumab injections, a newer type of medicine that works by blocking a chemical called FGF23 that causes phosphate loss. The doctors tracked her bone healing with X-rays and blood tests that measured FGF23 levels before, during, and after treatment.

The patient received three initial doses of burosumab and continued treatment for 11 months total. During this time, her broken thigh bones healed significantly, and she was able to stop taking pain medication. However, her insurance company stopped covering the medicine, forcing her to discontinue treatment. The doctors then monitored what happened to her bones and blood chemistry over the following three months using imaging scans and blood tests.

Case reports are valuable because they document unusual or important clinical situations that might not show up in larger studies. This case is important because it shows what can happen when a relatively new, expensive medicine is stopped suddenly. Understanding these consequences helps doctors make better decisions about when and how to use this medicine, and it highlights the need for more research on what happens when treatment ends.

This is a single case report, which means it describes one patient’s experience rather than comparing many patients. While case reports are less powerful than large studies, they are useful for documenting unexpected outcomes and raising important questions. The doctors provided detailed medical records, blood test results, and imaging scans, which makes this case well-documented. However, because it’s only one patient, we cannot assume the same thing will happen to everyone who stops burosumab treatment.

What the Results Show

The patient’s bones showed dramatic improvement while taking burosumab. After just three doses, the fracture lines in her thigh bones were no longer visible on X-rays, and she stopped needing pain medication. This improvement continued throughout the 11 months of treatment.

However, three months after stopping the medicine, the patient experienced severe thigh pain again. Bone imaging showed that while her previous fractures had healed, a completely new fracture had developed in her right thigh bone. At the same time, blood tests revealed that FGF23 (the chemical that causes bone problems in XLH) had skyrocketed to 9,330 pg/ml—nearly 200 times higher than the normal range of 10-50.

This rapid return of symptoms and extremely high chemical levels suggests that stopping burosumab caused the patient’s body to quickly revert to its untreated state. The medicine appears to have been almost completely eliminated from her body within 95 days (based on its half-life of 19 days), but her FGF23 levels rebounded extremely quickly, leading to new bone damage.

The case also revealed that the patient’s previous bilateral femoral shaft fractures (breaks in both thigh bones) had actually healed while on burosumab, which is a positive sign. However, the rapid development of a new fracture in the same area after stopping treatment suggests that the underlying disease process returned aggressively. The patient’s ability to discontinue pain medication while on treatment, then need it again after stopping, indicates that symptom relief was directly tied to the medicine’s effects.

Previous clinical trials of burosumab showed that patients on the medicine had 16.8 times more fracture healing compared to patients receiving placebo. This case report supports those findings during treatment but raises new concerns about what happens after treatment stops. While the trials showed burosumab’s benefits during use, they did not adequately study what happens when patients must discontinue the medicine, making this case report particularly valuable for understanding the full picture of treatment.

This is a single case report involving only one patient, so we cannot know if the same rapid relapse happens to all patients who stop burosumab. Different patients might respond differently based on their age, disease severity, genetics, and other factors. The patient had to stop treatment due to insurance issues rather than for medical reasons, so this may not reflect what happens with planned, medically-supervised discontinuation. Additionally, the doctors did not have detailed information about what the patient’s FGF23 levels were immediately before starting burosumab, so we cannot compare the rebound levels to her baseline. More research with multiple patients is needed to understand how common this problem is.

The Bottom Line

Based on this case, patients taking burosumab for XLH should: (1) Not stop treatment suddenly without talking to their doctor, even if insurance coverage changes; (2) Work with their healthcare team to plan any treatment changes carefully; (3) If treatment must be stopped, have close follow-up appointments with bone imaging and blood tests to monitor for relapse; (4) Be aware that symptoms may return quickly after stopping the medicine. These recommendations are based on one patient’s experience, so discuss your individual situation with your doctor.

This case is most relevant to: patients with XLH who are taking or considering burosumab, their families and caregivers, doctors who treat XLH, and insurance companies making coverage decisions. People with other bone diseases should not assume the same thing will happen with their treatments. Pregnant women or those planning pregnancy should be especially aware, since burosumab safety in pregnancy is not yet established and some patients may need to stop treatment.

In this patient’s case, new bone problems appeared within three months of stopping treatment. However, this may vary from person to person. The extremely high FGF23 levels appeared within three months, suggesting the body’s chemistry reverted quickly. If you need to stop burosumab, expect that symptoms could return within weeks to months, not years.

Want to Apply This Research?

  • If you take burosumab, track bone pain levels daily (0-10 scale) and note any new aches or limitations in movement. Also track medication doses and dates to correlate with any symptom changes. This helps you and your doctor spot problems early if treatment changes.
  • Set reminders for all scheduled burosumab injections and appointments. If you face insurance or access issues, contact your doctor immediately rather than stopping on your own. Use the app to document conversations with your insurance company and doctor about treatment plans, so you have a record of decisions made together.
  • Long-term, maintain a log of: (1) injection dates and any side effects; (2) bone pain or fracture symptoms; (3) ability to do daily activities; (4) any insurance or access changes. Share this data with your doctor at each visit. If treatment must be interrupted, increase monitoring frequency to weekly check-ins with your healthcare team for at least three months.

This case report describes one patient’s experience and should not be interpreted as medical advice for all patients with XLH or those taking burosumab. Treatment decisions must be made in consultation with your healthcare provider based on your individual medical situation. If you are taking burosumab, do not stop or change your treatment without discussing it with your doctor first. If you experience new bone pain, fractures, or other concerning symptoms, contact your healthcare provider immediately. This information is for educational purposes and does not replace professional medical evaluation or treatment.