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CRYSVITA® (burosumab-twza) injection 10, 20, 30 mg/mL

CRYSVITA treats

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A helpful guide to common terms in XLH

Some of the words used to talk about XLH and its treatment may be unfamiliar or seem complicated. This glossary helps explain key terms you may come across as you explore information about XLH.

A

Active vitamin D

(pronounced: AK-tiv VY-tuh-min dee)

A type of vitamin D that is already in a form your body can use right away. It helps control calcium and phosphorus levels in the blood to support healthy bones. Active vitamin D can be made by the body or given as a medicine. Active vitamin D can also be called calcitriol, 1,25(OH)2D, or 1,25 dihydroxyvitamin D.

B

Bloodstream

(pronounced: BLUD-streem)

The blood flowing through your body that delivers oxygen and nutrients to help keep the body healthy.

Bowed legs

(pronounced: boad legz)

A condition where the legs curve outward, often seen in children with XLH as a result of soft or weakened bones.

F

Fibroblast growth factor 23 (FGF23)

(pronounced: FY-broh-blast grohth fak-tor twenty-three)

A protein that helps control the amount of phosphorus in the blood. In people with XLH, too much FGF23 causes the body to lose phosphorus.

Fractures

(pronounced: FRAK-churz)

Breaks or cracks in bones that happen when they are weak or under too much pressure.

G

Gene mutation (or variant)

(pronounced: JEEN myoo-TAY-shun)

A change in a gene’s DNA, which carries the instructions inside your cells that tell your body how to work. Some changes are harmless, but others can cause health conditions.

H

Hormone

(pronounced: HOR-moan)

A chemical in your body that sends signals to help different parts of your body work properly.

Hypophosphatemia

(pronounced: hy-po-FOS-fuh-TEE-mee-uh)

A condition where there is not enough phosphorus in the blood, which can weaken bones.

O

Oral phosphate

(pronounced: OR-uhl FOS-fate)

A medicine taken by mouth that adds phosphorus to your body to help keep bones strong.

Osteoid volume to bone volume ratio

(pronunciation: OSS-tee-oyd VOL-yoom too bohn VOL-yoom RAY-shee-oh)

A measurement that shows how much new, soft bone (osteoid) there is compared to the total amount of bone. This helps doctors understand how well bones are forming and hardening.

Osteomalacia

(pronounced: ah-stee-oh-muh-LAY-shuh)

A condition in which bones become soft and weak.

P

PHEX gene

(pronounced: fex jeen)

A gene that is changed (mutated) in people with XLH, leading to too much FGF23 in the body.

Phosphorus

(pronounced: FOS-fuh-ruhs)

A mineral your body needs to keep bones strong and healthy.

Phosphate wasting

(pronounced: FOS-fayt WAY-sting)

A condition where the kidneys lose too much phosphorus through the urine.

Pseudofractures

(pronunciation: soo-doh-FRAK-churz)

Spots where the bone is weakened but not fully broken.

R

Radiographic Global Impression of Change (RGI-C)

(pronounced: ray-dee-oh-GRAF-ik gloh-buhl im-PRESH-un of change)

A scoring system doctors use to determine if rickets is improving by looking at X-rays.

Rickets

(pronounced: RIK-ets)

A bone condition in children where the growing parts of bones become soft and weak, caused by low phosphorus, calcium, or vitamin D. This can lead to bones that bend or curve (such as bowed legs).

S

Spontaneous XLH

(pronounced: spon-TAY-nee-us ex-el-aych)

A form of XLH caused by a new variant in the PHEX gene, occurring without a family history of the condition.

Subcutaneous injection

(pronounced: sub-kew-TAY-nee-uhs in-JEK-shun)

A method of delivering medicine just beneath the skin through a shot.

Supplements

(pronounced: suh-pluh-muhnts)

Medicines you take by mouth that help replace or add nutrients your body needs. For XLH, these can include phosphate and active vitamin D to help support bone health.

T

Thacher Rickets Severity Score (RSS)

(pronounced: THAK-er RIK-its sih-VER-ih-tee skor)

A tool that doctors use to measure how severe rickets is in children.

W

WOMAC patient questionnaire

(pronunciation: WOH-mak PAY-shent kwes-chuh-nair)

A set of questions patients answer about pain, stiffness, and how well they can move. Doctors use it to understand how joint problems affect daily life.

X

X-linked hypophosphatemia (XLH)

(pronounced: eks-linked hy-po-FOS-fuh-TEE-mee-uh)

A rare genetic condition that causes low levels of phosphorus in the blood, leading to weak bones.

Indication
What is CRYSVITA?

CRYSVITA is a prescription medicine used to treat adults and children 6 months of age and older with X-linked hypophosphatemia (XLH).

read more
What is CRYSVITA?

CRYSVITA is a prescription medicine used to treat adults and children 6 months of age and older with X-linked hypophosphatemia (XLH).

Important Safety Information

You should not take CRYSVITA if:

  • You take an oral phosphate supplement and/or a specific form of vitamin D supplement (such as calcitriol, paricalcitol, doxercalciferol, calcifediol).
  • Your phosphorus levels from a blood sample are within or above the normal range for age.
  • You have kidney problems.

What is the most important information you should know about CRYSVITA?

  • Some patients developed allergic reactions (e.g., rash and hives) while taking CRYSVITA. Your doctor will monitor you for symptoms of an allergic reaction while you are taking CRYSVITA. Your treatment may need to be discontinued for serious allergic reactions.
  • High levels of phosphorus in the blood have been reported in some patients taking CRYSVITA. This may be related to a risk of high calcium levels in the kidneys. Your doctor will collect blood samples to monitor your levels. If you are already taking CRYSVITA, dose interruption and/or dose reduction may be required based on your serum phosphorus levels.
  • High levels of calcium in the blood have been reported in patients taking CRYSVITA. The risk is greater in patients with pre-existing hyperparathyroidism (overactive parathyroid glands), for those who are unable to move for extended periods of time, become dehydrated, have high vitamin D levels, or have kidney issues. If you are at greater risk, your doctor will monitor your blood calcium and parathyroid hormone levels before you start and while taking CRYSVITA. If you develop high levels of blood calcium, your doctor may need to stop your treatment until it is adequately managed.
  • Administration of CRYSVITA may result in reactions at the injection site, such as hives, reddening of the skin, rash, swelling, bruising, pain, severe itching of the skin, and collection of blood outside of a blood vessel (i.e., hematoma). Call your doctor if you develop an injection site reaction. CRYSVITA may be discontinued if severe injection site reactions occur.

What are the possible side effects of CRYSVITA?

  • Adverse reactions that were seen in children with XLH are:
  • Fever
  • Injection site reaction
  • Cough
  • Vomiting
  • Pain in arms and legs
  • Headache
  • Tooth abscess
  • Dental cavities
  • Diarrhea
  • Decreased vitamin D levels
  • Toothache
  • Constipation
  • Muscle pain
  • Rash
  • Dizziness
  • Nausea
  • Adverse reactions that were seen in adults with XLH are:
  • Back pain
  • Headache
  • Tooth infection
  • Restless legs syndrome
  • Decreased vitamin D levels
  • Dizziness
  • Constipation
  • Muscle spasms
  • Phosphorus levels increased in the blood
  • Narrowing of the spaces within the spine is common in adults with XLH, and pressure on the spinal cord has been reported in adults taking CRYSVITA. It is not known if taking CRYSVITA worsens the narrowing of the spaces within the spine or the pressure on the spinal cord.

Before taking CRYSVITA, tell your doctor about all of your medications (including supplements) and medical conditions, including if you:

  • Are taking oral phosphate and/or active vitamin D (such as calcitriol, paricalcitol, doxercalciferol, calcifediol).
  • Are pregnant, think you may be pregnant, or plan to become pregnant. There is not enough experience to know if CRYSVITA may harm your unborn baby. Report pregnancies to the Kyowa Kirin, Inc. Adverse Event reporting line at 1-844-768-3544.
  • Are breastfeeding or plan to breastfeed. There is not enough experience to know if CRYSVITA passes into your breast milk. Talk with your doctor about the best way to feed your baby while you receive CRYSVITA.

While taking CRYSVITA, tell your doctor if you experience:

  • An allergic reaction such as rash or hives
  • A rash, swelling, bruising, or other reaction at the injection site
  • New or worsening restless legs syndrome

These are not all the possible side effects of CRYSVITA. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at (800) FDA-1088 or www.fda.gov/medwatch. You may also report side effects to Kyowa Kirin, Inc. at 1-844-768-3544.

For important risk and use information, please see the full Prescribing Information for CRYSVITA.

What is CRYSVITA?

CRYSVITA is a prescription medicine used to treat adults and children 6 months of age and older with X-linked hypophosphatemia (XLH).

Important Safety Information

You should not take CRYSVITA if:

  • You take an oral phosphate supplement and/or a specific form of vitamin D supplement (such as calcitriol, paricalcitol, doxercalciferol, calcifediol).
  • Your phosphorus levels from a blood sample are within or above the normal range for age.
  • You have kidney problems.

What is the most important information you should know about CRYSVITA?

  • Some patients developed allergic reactions (e.g., rash and hives) while taking CRYSVITA. Your doctor will monitor you for symptoms of an allergic reaction while you are taking CRYSVITA. Your treatment may need to be discontinued for serious allergic reactions.
  • High levels of phosphorus in the blood have been reported in some patients taking CRYSVITA. This may be related to a risk of high calcium levels in the kidneys. Your doctor will collect blood samples to monitor your levels. If you are already taking CRYSVITA, dose interruption and/or dose reduction may be required based on your serum phosphorus levels.
  • High levels of calcium in the blood have been reported in patients taking CRYSVITA. The risk is greater in patients with pre-existing hyperparathyroidism (overactive parathyroid glands), for those who are unable to move for extended periods of time, become dehydrated, have high vitamin D levels, or have kidney issues. If you are at greater risk, your doctor will monitor your blood calcium and parathyroid hormone levels before you start and while taking CRYSVITA. If you develop high levels of blood calcium, your doctor may need to stop your treatment until it is adequately managed.
  • Administration of CRYSVITA may result in reactions at the injection site, such as hives, reddening of the skin, rash, swelling, bruising, pain, severe itching of the skin, and collection of blood outside of a blood vessel (i.e., hematoma). Call your doctor if you develop an injection site reaction. CRYSVITA may be discontinued if severe injection site reactions occur.

What are the possible side effects of CRYSVITA?

  • Adverse reactions that were seen in children with XLH are:
  • Fever
  • Injection site reaction
  • Cough
  • Vomiting
  • Pain in arms and legs
  • Headache
  • Tooth abscess
  • Dental cavities
  • Diarrhea
  • Decreased vitamin D levels
  • Toothache
  • Constipation
  • Muscle pain
  • Rash
  • Dizziness
  • Nausea
  • Adverse reactions that were seen in adults with XLH are:
  • Back pain
  • Headache
  • Tooth infection
  • Restless legs syndrome
  • Decreased vitamin D levels
  • Dizziness
  • Constipation
  • Muscle spasms
  • Phosphorus levels increased in the blood
  • Narrowing of the spaces within the spine is common in adults with XLH, and pressure on the spinal cord has been reported in adults taking CRYSVITA. It is not known if taking CRYSVITA worsens the narrowing of the spaces within the spine or the pressure on the spinal cord.

Before taking CRYSVITA, tell your doctor about all of your medications (including supplements) and medical conditions, including if you:

  • Are taking oral phosphate and/or active vitamin D (such as calcitriol, paricalcitol, doxercalciferol, calcifediol).
  • Are pregnant, think you may be pregnant, or plan to become pregnant. There is not enough experience to know if CRYSVITA may harm your unborn baby. Report pregnancies to the Kyowa Kirin, Inc. Adverse Event reporting line at 1-844-768-3544.
  • Are breastfeeding or plan to breastfeed. There is not enough experience to know if CRYSVITA passes into your breast milk. Talk with your doctor about the best way to feed your baby while you receive CRYSVITA.

While taking CRYSVITA, tell your doctor if you experience:

  • An allergic reaction such as rash or hives
  • A rash, swelling, bruising, or other reaction at the injection site
  • New or worsening restless legs syndrome

These are not all the possible side effects of CRYSVITA. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at (800) FDA-1088 or www.fda.gov/medwatch. You may also report side effects to Kyowa Kirin, Inc. at 1-844-768-3544.

For important risk and use information, please see the full Prescribing Information for CRYSVITA.

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COMM-US-CRY-0930 June 2026