Hypophosphatasia
Hypophosphatasia (HPP) is a rare genetic disease affecting the development of bones and teeth affecting children and adults of all ages including infants, displaying different signs and symptoms depending on when the condition is diagnosed.
For those affected by HPP, the bones and teeth do not absorb enough calcium and phosphorus – nutrients needed for strong and healthy bones and teeth. This means that when there is insufficient mineralization of calcium and phosphorus this can result in early tooth loss, frequent bone injuries and fractures and muscle weakness. Experiencing pain is also another example.
What causes HPP?
Hypophosphatasia is caused by mutations in the ALPL gene, which may cause missing or not enough alkaline phosphatase (ALP) enzyme. This means that people with HPP have ALP levels lower than the healthy normal for their age and sex. When this is the case, the body has trouble making healthy bones. Low ALP levels can make bones soft, weak, and deformed, and cause other symptoms of HPP. HPP can affect many different parts of the body. Early tooth loss, frequent bone injuries, and muscle weakness and pain are some examples of impact.
All people have the ALPL gene, which makes an enzyme called ALP. The body needs ALP to form healthy bones.
The signs and symptoms of HPP look different for every person as can the seriousness of the effects of the disease. In many cases, when symptoms occur in infants and children, they are accompanied by severe health problems unlike when there are mild symptoms those individuals can have symptoms improve as they grow into adulthood.
HPP can vary in the level of severity of signs and symptoms, even within the same family with new symptoms appearing at any age. Symptoms can continue during the live cycle and can increase in seriousness and worsen over time.
Diagnosis
HPP has shared symptoms with other more common diseases including gum disease, rickets, osteoarthritis, rheumatoid arthritis, leukemia or bone cancer, and osteoporosis, often resulting in a misdiagnosis.
The combination of one or more symptoms with persistently low ALP levels that have no other explanation can lead to a diagnosis of HPP.
Treatment For Hypophosphatasia
Whether or not a child needs treatment for HPP, and what type of treatment is needed, will depend on how severe the disease is.
Enzyme replacement therapy with asfotase alfa (Strensiq®) has been the primary treatment for severe forms of hypophosphatasia in children since 2015, when it was approved for this use by the Food and Drug Administration (FDA). Given by injection, usually once a week, asfotase alfa replaces missing or ineffective TNSALP and enables healthy mineralization of the bones and teeth.
Other treatments can address specific symptoms and complications. These treatments may include:
- Non-steroidal anti-inflammatory drugs (NSAIDs) for relief of bone and joint pain
- Vitamin B6 to help to control seizures in severely affected infants
- Breathing and feeding support for severely affected infants
- Physical and occupational therapy
- Dental care to preserve teeth or replace lost teeth with dentures, bridges or dental implants
- Surgery to separate fused skull bones or a shunt to relieve the pressure fusing may cause
- Orthopedic surgery repair fractured bones or correct misaligned joints
- Dietary changes to limit the amount of calcium and vitamin D intake
Ongoing Care and Management
Ongoing care, coordinated by a primary care physician or specialist who is knowledgeable about hypophosphatasia is essential to the long-term health and well-being of children with HPP. Because the disorder can affect different body functions, coordinated care by a team of appropriate specialists is needed.
Sources taken indirectly and directly from the following:
https://www.chop.edu/conditions-diseases/hypophosphatasia-hpp and https://strensiq.com/what-is-hpp
