XLH resources for you and your family

Connect with a community
of support for X-linked
hypophosphatemia (XLH)

CRYSVITA Educational Events for Patients and Caregivers

The CRYSVITA Educational Events program offers events that are presented by an XLH specialist. These events provide opportunities to learn more about CRYSVITA and XLH and connect with local members in the XLH community.

Ultragenyx sponsored

XLH Network

The XLH Network is a global patient support organization for people with XLH, parents, and caregivers. The website contains educational resources about XLH for patients and medical professionals.

XLHNetwork.org is an organization that supports people with XLH
NIH Genetic and Rare Diseases Information Center (GARD)

GARD maintains a list of rare diseases and related terms to help people find reliable information about their disease.

GARD is resource that maintains a list of rare diseases and related terms to help people find information about their disease
National Organization for Rare Disorders (NORD)

NORD is a patient advocacy organization dedicated to individuals with rare diseases and the organizations that serve them.

NORD is a patient advocacy organization committed to helping patients with rare diseases
Global Genes

Global Genes is a rare disease patient advocacy organization that works to build awareness, educate the global community, and provide connection and resources.

Patient Stories

Tim’s Story

“I’m proud of taking the next step forward in my life with XLH.

—Tim, age 28

Karen’s Story

“Just the fact that I’m able to participate in life more has been a gift.

—Karen, age 40



A protein that is made by the immune system or a protein that is modified in a lab to recognize and block a target that threatens the body’s normal function.


The beginning of a study, before patients are given any treatment.

bone abnormalities of the lower limbs

Distortion or misshaping of the legs (e.g., bowing).

conventional therapy

A therapeutic approach for XLH that consists of oral phosphate and a type of vitamin D called active vitamin D. Active forms of vitamin D include calcitriol, paricalcitol, doxercalciferol, and calcifediol.

fibroblast growth factor 23 (FGF23)

A protein that plays a role balancing the amount of phosphorus in the body. In XLH, the activity of FGF23 is abnormally increased, throwing off the balance of phosphorus.


Broken bones.


Low levels of phosphorus in the blood.

least squares (LS) mean change

A statistic that estimates the mean after adjusting for the effect of other variables in a study.


An average; a number that represents the central value of a set of numbers.


A process where minerals like phosphorus are deposited in the bone, causing the bone to harden.


A starting component for building bone where minerals have not yet been deposited; an unmineralized component of bone.

osteoid volume to bone volume (OV/BV)

A ratio of unmineralized bone to mineralized bone. In XLH, this ratio is large, pointing to a greater presence of unmineralized bone.


A softening and weakening of the bones in children and adults caused by deficiencies in vitamin D, calcium, or phosphate, independent of the growth plate, which allows the bones to bend easily.


A mineral that is important for proper bone development and repair.


A pill, medicine, or procedure that has no therapeutic effect. In Study 4 of adults with XLH, placebo refers to a saline injection.


A kind of fracture where the bone thickens at the site of an injury but is not completely broken.

Radiographic Global Impression of Change (RGI-C)

A way to measure the extent of healing of rickets. This score uses a 7-point scale to rank the healing of rickets and can range from -3=severe worsening to 0=no change to +3=near/complete healing. An RGI-C global score of +2.0 means a substantial healing of rickets was achieved after treatment.


A softening and weakening of the bones in children caused by deficiencies in vitamin D, calcium, or phosphate before the growth plate closes.

serum phosphorus

Amount of phosphorus in the blood.

Thacher Rickets Severity Score (RSS)

A way to measure changes in the severity of rickets. This score uses a 10-point scale to rank the severity of rickets from 0 (normal) to 10 points (severe). A lower score means reduced severity of rickets. This score is complementary to RGI-C.

Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)

A set of questions used to evaluate pain, stiffness, and physical functioning of the joints.