Q: What is hypophosphatasia?
A: Pronounced hypo-fahs-fuh-TAY-shuh, hypophosphatasia (or HPP) is a condition that affects healthy development of bones and teeth, making bones softer and more likely to fracture. Healthy bones contain minerals, like calcium and phosphorus, and the body adds them to bones in a process called mineralization. Mineralization makes bones strong and rigid. People who have HPP have trouble making an enzyme called alkaline phosphatase, or ALP. Without this important ALP enzyme, certain chemicals build-up and prevent calcium and phosphorus from binding together and depositing in the bones. As a result, bones can become soft, curved and fragile, and teeth may become loose or fall out prematurely.
Q: What are the symptoms of HPP?
A: The symptoms of HPP can vary widely. The most severe forms of HPP usually are diagnosed before birth and/or in early infancy. Some symptoms of the condition may include:
· Weak, soft bones
· Skeletal abnormalities, particularly of the legs (bowed legs)
· Short limbs
· Enlarged wrist or ankle joints
· Abnormally shaped chest
· Soft skull bones, causing abnormal skull shape
· Early loss of “baby teeth”
Adults with HPP can have frequent fractures in the foot and thigh, which can lead to chronic pain. Adults with HPP may also lose their teeth prematurely and may be at increased risk for joint inflammation and pain.
It is important to remember that not everyone has all symptoms of HPP. If you suspect that you or your child have the condition, please visit your doctor for screening tests.
Q: Are there treatments for HPP?
A: Unfortunately, there are no FDA-approved treatments for HPP at this time. The good news is that several treatment options and approaches are currently being studied for the treatment of HPP, including enzyme replacement therapy and bone marrow transplantation therapy.
The compound ENB-0040, a human recombinant tissue non-specific alkaline phosphatase being studied in human clinical trials by Alexion Pharmaceuticals, is a bone-targeted enzyme replacement therapy in Phase 2 clinical development. In a recent study presented at the 92nd Annual Meeting of the Endocrine Society, after 12 weeks of treatment with ENB-0040, children with HPP showed improvements in bone mineralization and function, including increases in strength, endurance and mobility and reduction in pain.
Even though there are no approved treatments for HPP as an entire condition, there are ways to treat or manage many of the symptoms, so talk to your doctor about pain or symptoms you may be experiencing.
Q: Is HPP an inherited condition?
A: Yes, mutations in the ALPL gene cause HPP. The ALPL gene is responsible for making sure the body produces the alkaline phosphatase, or ALP, enzyme. Without this important ALP enzyme, certain chemicals build-up and prevent calcium and phosphorus from binding together and depositing in the bones. As a result, bones can become soft, curved and fragile, and teeth may become loose or fall out prematurely.
Q: Is there a cure for HPP?
A: Currently there is no cure for HPP; however, researchers have identified the gene that carries the HPP mutation, so there is hope that a cure for the condition will be discovered in the future. The Soft Bones Foundation continues to contribute funds to research in an effort to speed up efforts to find a cure.
Q: How rare is HPP?
A: Severe HPP is estimated to affect 1 in 100,000 babies born. It is estimated that milder cases are diagnosed more frequently, although the epidemiology is relatively unknown.
Q: Should someone with HPP take calcium supplements to aid in mineralization?
A: No. Though it sounds counter-intuitive, many infants and children with HPP have too much calcium circulating in the blood, or a condition called hypercalcemia. Physicians recommend that children follow the National Institute of Health’s (NIH) recommended daily allowances of calcium intake. For age appropriate calcium intake levels, go to http://ods.od.nih.gov/factsheets/calcium.asp. Also, it is important to talk to your doctor before taking any medications to control symptoms of HPP.