Is Hypophosphatasia hereditary?

Hypophosphatasia (HPP) is a genetic condition caused by mutations in the ALPL gene, which encodes the tissue-nonspecific alkaline phosphatase (TNSALP) enzyme. It is strictly hereditary, though the inheritance pattern varies depending on the specific mutation, and it is not a multifactorial or environmental disease.

Is Hypophosphatasia hereditary or genetic?

Hypophosphatasia is both a genetic and a hereditary condition. "Genetic" means it is caused by a change in DNA, while "hereditary" means these changes can be passed from parents to children. In Hypophosphatasia, the disease results from pathogenic variants in the ALPL gene. Because this gene is located on chromosome 1, the inheritance pattern depends on whether the mutation is recessive or dominant. Most severe forms of Hypophosphatasia (such as perinatal or infantile) are inherited in an autosomal recessive pattern, while milder forms often follow an autosomal dominant pattern with variable expressivity.

What are the inheritance patterns of Hypophosphatasia?

The inheritance of Hypophosphatasia is categorized by how the ALPL gene mutation is passed through generations:

• Autosomal Recessive: Both parents must be carriers (each has one mutated copy of the gene). There is a 25% chance for each child to be affected, a 50% chance to be an asymptomatic carrier, and a 25% chance to inherit two normal copies of the gene.


• Autosomal Dominant: Only one parent needs to carry the mutation for a child to be at risk. There is a 50% chance for each child to inherit the mutation.


• De Novo Mutations: While Hypophosphatasia is typically inherited, spontaneous (de novo) mutations can occur, meaning the mutation appears for the first time in an individual without a family history of the disease.

How is genetic testing and counseling utilized?

Genetic testing is the gold standard for confirming a diagnosis of Hypophosphatasia. It involves sequencing the ALPL gene to identify pathogenic variants. Genetic counseling is highly recommended for any family affected by or at risk for Hypophosphatasia. A genetic counselor can help interpret test results, calculate recurrence risks, and explain the implications for extended family members. For those planning a pregnancy, prenatal diagnosis (via amniocentesis or chorionic villus sampling) or preimplantation genetic testing (PGT) may be discussed if the specific familial mutation has been identified.

What should families know about carrier status?

Because the clinical presentation of Hypophosphatasia can vary widely—ranging from early tooth loss in adults to severe skeletal mineralization issues in infants—family members who appear healthy may still carry a mutation. Understanding the specific mutation in your family is vital because it helps clarify the risk to future children and helps identify family members who may have mild, undiagnosed symptoms. Our community at DiseaseMaps.org currently includes 9 people living with Hypophosphatasia, many of whom have navigated these complex genetic questions and shared their experiences with diagnosis and family planning.

Next steps

• Consult with a clinical geneticist to confirm your diagnosis via ALPL gene sequencing.


• Request a referral to a genetic counselor to discuss family planning and recurrence risks.


• Encourage at-risk family members to speak with their primary care physician about screening for low alkaline phosphatase (ALP) levels.


• Connect with the DiseaseMaps.org community to learn how others have managed the genetic aspects of their care.

Medical disclaimer: This information is for educational purposes only and does not constitute medical advice; always consult with a qualified healthcare professional regarding your specific genetic health.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Hypophosphatasia Overview


• Orphanet: Rare Disease Database: Hypophosphatasia


• OMIM (Online Mendelian Inheritance in Man): ALPL Gene Entry #146300


• The Hypophosphatasia Foundation: Patient Education and Support Resources