Can a drug for one bone disease help another? a Rare-Disorder trial puts it to the test

NCT ID NCT03993821

First seen Jul 30, 2026 · Last updated Jul 31, 2026 · Updated 1 time

Summary

This early-phase trial is testing whether burosumab, a drug already approved for X-linked hypophosphatemia (XLH), can safely raise phosphate levels in a single patient with cutaneous skeletal hypophosphatemia syndrome (CSHS). Both conditions involve abnormally high FGF23 activity leading to low phosphate. The patient will receive burosumab injections over 52 weeks, with the main goal of measuring changes in blood phosphate levels.

What this could mean

Our plain-language read of the trial. This is informational only — not medical advice or a prediction.

Active substance
burosumab (Crysvita), an antibody that blocks FGF23 to raise phosphate levels
What this could lead to
If successful, burosumab could offer a treatment option for people with CSHS, a rare condition with no approved therapies.
What could go wrong
This is a very early, single-patient trial, so results may not apply to others. Burosumab is not yet approved for CSHS, and side effects are possible.

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Conditions

The condition(s) this trial relates to.

epidermal nevus syndrome Nevus, Sebaceous of Jadassohn

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

Contacts and locations

Locations

  • Children's National Hospital

    Washington D.C., District of Columbia, 20010, United States