Is HPP in Your Family Tree?

Hypophosphatasia (HPP) is a hereditary condition that may be passed down from parent to child. Learn more about two ways HPP can be inherited.

Our bodies contain genes. Genes are a set of instructions for the growth and development of every cell in the body. Genes also contain instructions for making proteins. Some of these proteins, called enzymes, help facilitate body processes, such as building bones. One gene makes an enzyme called alkaline phosphate (ALP). In people with hypophosphatasia (HPP), this gene is abnormal (or mutated), resulting in low levels of ALP enzymes.

Each gene is made up of a pair of DNA strands. Every child gets genes from their parents, one half of each pair of DNA strands from their mother and one half from their father. This means that there are two copies of every gene in each cell. Genes are copied frequently and most of the time the copying process is perfect. But sometimes it’s not, resulting in copying errors, or mutations.

In some cases, mutations are serious, causing genetic conditions such as hypophosphatasia (HPP). The following illustration can help you see two ways mutations can be passed down from parents to their child.

Autosomal recessive—Improperly working genes from both parents.

In most cases the parents of a child with the autosomal recessive form of HPP are carriers of one ALPL gene mutation.

If both parents are carriers:
There’s a 1 in 4 chance of having a child who is affected by the condition.

autosomal_recessive2

Adapted from NIH US National Library of Medicine poster

Autosomal dominant—An improperly working gene from only 1 parent is needed.

So far, all reported individuals diagnosed with the autosomal dominant form of HPP have inherited an ALPL genetic mutation from a parent (who may or may not have symptoms).

If 1 parent has an improperly working gene and the other parent has a normal gene:
There’s a 1 in 2 chance of having a child who is affected by the condition.

autosomal_dominant2

Adapted from NIH US National Library of Medicine poster

People may have many different reasons for seeking genetic testing for HPP. Some people may think it’s important to know genetic test results to help them make life decisions about insurance coverage or family planning. Others may be curious about how their symptoms relate to family history.

In addition to genetic testing, collecting a family history (family health portrait) can show a pattern that can help healthcare providers and genetic counselors locate a gene and determine how future generations in your family may be impacted.

Genetic counselors meet with people to discuss genetic risks associated with a condition. You may consider seeking genetic counseling if you have a personal or family history of HPP, need psychological support, or would like to use additional information to make a life decision, for example, family planning.

Our informative articles and patient stories are frequently being updated, so visit Stand with HPP first when you have questions about HPP or are seeking support from the HPP community. We are here to help you find what you’re looking for and help you stay connected.

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