Crysvita (burosumab-twza) treats a rare disease called x-linked hypophosphatemia (XLH) with excess fibroblast growth factor 23 (FGF23). XLH is an genetic disorder of the PHEX gene on the X chromosome, where the kidneys dispose of too much phosphorus, causing levels to be too low in the bloodstream. FGF23 suppresses phosphate reabsorption so even if phosphorus is present, the body can’t utilize it.
Phosphorus is crucial for bodily functions, particularly the growth of bones. When phosphorous is wasted by the kidneys and disposed of in the urine without being reabsorbed, levels become very low, causing soft, weak bones. This leads to conditions like osteomalacia, osteoarthritis, and phosphopenic rickets.
Patients that are suffering from XLH can develop permanent disabilities and sustain injuries from their illness including bowed legs, severe bone, or dental pain, and shortened bone growth, hearing loss, bone fractures, and loss of mobility.
Crysvita is an antibody that blocks FGF23, so that the body can absorb and utilize phosphorus. It is given as a subcutaneous injection and has been shown to improve joint stiffness in these patients.
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Before your injection, it is important to drink plenty of water and come to your appointment hydrated. Additionally, you must alert us as soon as possible to any changes in your insurance to ensure that we are still an in-network provider for your infusion therapy.