Hypophosphatasia

Hypophosphatasia is caused by changes in the ALPL gene that lower the activity of an enzyme called alkaline phosphatase.
These gene changes can be inherited from one or both parents, or can happen for the first time.
Some risks are written in our DNA, passed down through families.
Family history raises the chance of early symptoms of hypophosphatasia, and the gene change and age can shape how severe it is.
Lifestyle does not cause hypophosphatasia, but heavy bone stress and medicines such as bisphosphonates can make symptoms worse.

Genetic risk factors

In hypophosphatasia, changes in the ALPL gene reduce the activity of an enzyme that helps bones and teeth harden. Different variants and inheritance patterns can shape how severe the condition is and when it starts; they can even influence the early symptoms of hypophosphatasia. Some people inherit two changes (one from each parent), while others have a single change that acts strongly enough to cause features. Carrying a genetic change doesn’t guarantee the condition will appear.

• ALPL gene changes: Pathogenic variants in the ALPL gene are the known genetic cause of hypophosphatasia. They lower alkaline phosphatase activity, which disrupts normal bone and tooth mineralization.

• Autosomal recessive forms: When two non-working variants are inherited (one from each parent), severe or early-onset disease is more likely. Parents are often healthy or only mildly affected carriers.

• Autosomal dominant forms: A single disease-causing variant can be enough to cause hypophosphatasia in some families. This pattern often leads to milder childhood or adult-onset presentations, but severity can vary.

• Variant type matters: Variants that largely stop enzyme function usually cause more severe disease. Changes that partly reduce function tend to present later or more mildly.

• Dominant-negative effects: Some variants make abnormal enzyme units that block the normal ones from working well. This can cause disease even when only one gene copy has a variant.

• Variable expressivity: People with the same ALPL variant can have very different degrees of bone, dental, or pain issues. The age at first signs can range from infancy to late adulthood.

• Incomplete penetrance: Not everyone who inherits a disease-causing ALPL variant develops noticeable features. Some relatives may show only low alkaline phosphatase levels or early tooth loss, while others have more classic bone findings.

• Family history risks: Having an affected parent with a dominant variant gives each child a 50% chance of inheriting it. If both parents carry a recessive variant, each pregnancy has a 25% chance of an affected child.

• De novo variants: In some people, the ALPL change arises for the first time and is not inherited from either parent. Their future children can still inherit the variant.

• Founder variants: In certain regions or extended families, a shared ancestral variant can raise the local frequency of hypophosphatasia. Genetic counseling can help determine whether this applies in your family.

• Compound heterozygosity: Some people inherit two different ALPL variants, one from each parent. The specific combination can influence severity and the age when features begin.

• Genetic testing: DNA testing of ALPL can confirm the causal variant and clarify inheritance risks within a family. Finding the exact variant also helps relatives understand their personal risk.

Transmission

Hypophosphatasia is a genetic condition and is not contagious—you can’t catch it from someone, and it doesn’t spread through everyday contact, kissing, sex, or shared items.

Most cases happen because of a change in a gene called ALPL, and the genetic transmission of Hypophosphatasia can follow two patterns. In autosomal recessive inheritance, when both parents carry a nonworking change in the gene, each pregnancy has a 25% chance of a child with Hypophosphatasia, often the more severe early-onset forms. In autosomal dominant inheritance, a parent living with Hypophosphatasia has a 50% chance of passing it to each child, often with later-onset or milder features. Sometimes a new gene change arises for the first time in a child, so a family history may be absent; a genetic counselor can help clarify how Hypophosphatasia is inherited in your family.

When to test your genes

Choose genetic testing if you or close relatives had unexplained fractures, early tooth loss, low alkaline phosphatase, or suspected hypophosphatasia at any age. Test before major decisions like pregnancy, osteoporosis therapy, or surgery to guide safe treatment. Consider testing sooner if symptoms are progressing or started in childhood.

Looking ahead can feel daunting, but many people with hypophosphatasia live into adulthood and adapt daily routines to protect bones, teeth, and energy. The outlook is not the same for everyone, but factors like the age symptoms first appear, bone strength on scans, and whether breathing or feeding was affected early in life shape the path forward. Babies with the most severe form can have life‑threatening breathing problems due to soft chest bones; without treatment, infant mortality used to be high. With modern supportive care and enzyme replacement therapy in eligible cases, survival has improved and hospital stays are often shorter.

In childhood and adult hypophosphatasia, the long‑term outlook usually centers on fracture risk, dental health, and pain management rather than life expectancy. Some people experience frequent stress fractures and early tooth loss, while others notice milder issues like foot pain after long walks or slow‑to‑heal injuries. Prognosis refers to how a condition tends to change or stabilize over time. Over time, most people with hypophosphatasia can maintain mobility and independence when pain is treated, footwear is supportive, and high‑impact activities are swapped for lower‑impact options like swimming or cycling.

Even though it can feel overwhelming, targeted treatment is changing the picture, especially for children with more active disease. Early symptoms of hypophosphatasia—such as delayed walking, repeated fractures, or premature loss of baby teeth—tend to predict who benefits most from specialized therapies and close follow‑up. In medical terms, the long‑term outlook is often shaped by both genetics and lifestyle. Talk with your doctor about what your personal outlook might look like, including whether enzyme therapy, physical therapy, dental care, vitamin B6 management, and fracture prevention strategies are right for you.

Treatment for hypophosphatasia focuses on easing symptoms, protecting bones and teeth, and, when appropriate, replacing the missing enzyme. For infants, children, and some adults with significant bone or breathing problems, enzyme replacement therapy (asfotase alfa) can improve bone strength and growth, reduce pain, and lower fracture risk. Many living with hypophosphatasia also benefit from supportive care such as tailored physical therapy, careful dental care, vitamin B6 for certain seizures in babies, and pain management that avoids medicines which can weaken bones. Doctors sometimes recommend a combination of lifestyle changes and drugs, including calcium and vitamin D only if levels are low, because too much can build up in the blood. Ask your doctor about the best starting point for you, including whether enzyme therapy is appropriate and how to monitor for side effects and treatment response.

In many families, hypophosphatasia traces back to changes in a single gene that affects how bones and teeth harden. The gene, called ALPL, helps your body make an enzyme (alkaline phosphatase) that’s important for mineralizing bone; when the gene doesn’t work well, that enzyme level is low and mineralization suffers. Family history is one of the strongest clues to a genetic influence. Hypophosphatasia can be inherited in two ways: some families show a dominant pattern, where one changed copy can be enough to cause features, while the most severe forms that start before or soon after birth are usually recessive and happen when both copies have changes. Even within the same family, symptoms and severity can vary, and some people with a dominant gene change may have very mild signs or none at all. Sometimes a gene change begins for the first time in a child, so a lack of family history doesn’t rule it out. Genetic testing of ALPL can confirm the cause, clarify how hypophosphatasia is inherited in your family, and help estimate risk for relatives and future pregnancies.

When hypophosphatasia occurs alongside other bone or joint problems, day-to-day pain and mobility limits can add up, and flare-ups may feel more frequent. A condition may “exacerbate” (make worse) symptoms of another, for example when vitamin D deficiency or thyroid/parathyroid disorders are also present, which can intensify bone pain and raise fracture risk in people with hypophosphatasia. Many adults with hypophosphatasia are first labeled with osteoporosis, and if true osteoporosis is also present, treatment must be chosen carefully because common antiresorptive drugs like bisphosphonates can worsen HPP-related bone fragility. Hypophosphatasia is linked with calcium pyrophosphate crystal buildup in joints, so pseudogout in hypophosphatasia (also called CPPD) may present as sudden joint swelling and stiffness, especially in knees or wrists. Kidney conditions can interact as well; chronic kidney disease or a history of kidney stones may change calcium and phosphate handling and raise the chance of soft-tissue calcifications, so monitoring is important. Talk with your doctor about how your conditions may influence each other, especially if more than one specialist is involved, so your plan supports bone strength, joint health, and safe medication choices.

How genes can cause diseases

Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.

Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.