XLH often runs in the family
X-linked hypophosphatemia (XLH) is a genetic condition, meaning it can be passed down in families.
The “X-linked” in XLH means it is passed through the X chromosome.
Chromosomes are structures in your cells that carry your genes. Women have two X chromosomes (XX), while men have one X and one Y (XY).
Chromosome with XLH
If a father has XLH and the mother does not:
All daughters will have XLH. No sons will have XLH. This is because daughters inherit an X chromosome from their father. No sons will have XLH because sons get the X chromosome from their mother.
Chromosome with XLH
If a mother has XLH and the father does not:
Both sons and daughters have a 50% chance of having XLH. This is because all children inherit an X chromosome from their mother.
XLH doesn’t always run in families—it can also happen randomly. This is called a spontaneous case. About 3 out of 10 people can develop a spontaneous case of XLH.
People with a spontaneous case of XLH can still pass the condition on to their children.
Get the facts on family & XLH
In this video series, Conversations in XLH: An Expert’s Perspective, Dr. Nancy Dunbar shares insights to help people living with XLH and their families better understand life with XLH.
XLH is a family condition—even when it doesn’t look the same
Learn how XLH can vary within families, and why sharing diagnoses and discussing family history can help family members take a proactive role in their health.
HEAR the facts
My grandmother had XLH. She passed it on to my father, who passed it on to me.
Shannon, living with XLH
Could my family members have XLH?
Because XLH is genetic, other people in your family might have it too.
The XLH Family Tree tool can help you map who has XLH or symptoms of it, and see which relatives, like siblings, aunts, or uncles, might be affected. Knowing this can help you support your family members in getting the care they may need.
Build your family tree
Alice and her father, Jason
Both living with XLH
COMM-US-RDS-1001 August 2026