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What is hypophosphatasia? 

Hypophosphatasia is a genetic condition (passed down from parents) that causes problems with bone and tooth development. Usually, bones and teeth use calcium and phosphorus to get stronger. This process is called mineralization.

In children with hypophosphatasia, the process of mineralization doesn’t work correctly. As a result, their bones and teeth may form improperly or break easily.

What causes hypophosphatasia?

Hypophosphatasia occurs because of a change (mutation) in the ALPL gene, which plays a key role in forming and growing teeth and bones. This gene change causes the body to make a different version of an enzyme called alkaline phosphatase (ALP).

Parents pass this gene change to their children. Most infants and young children diagnosed with hypophosphatasia inherit it as an autosomal recessive condition, meaning both parents need to have the gene mutation for their child to develop the condition. Because it’s a recessive condition, a child must have two copies of the mutated gene to be affected. Parents who are “carriers”, have only one copy of the gene may not even know they carry it. 

Some older children diagnosed with hypophosphatasia have an autosomal dominant version of the condition. This means that only one gene change (mutation) is needed to cause the condition. This can be inherited from one parent or can be a new change.

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