The National Institutes of Health defines hypophosphatasia (HPP) as a heritable disorder that weakens bones and teeth at different life stages. It interferes with the metabolism of a substance called alkaline phosphatase, which affects the mineralization process. Mineralization is important for making your teeth and bones rigid and strong.
HPP has degrees of severity typically determined by the timing of the symptoms. Males and females are affected equally, reports the National Organization of Rare Diseases (NORD). The most severe form of HPP may be life-threatening, and the least severe classification may only cause dental abnormalities. Generally, the younger the person is at diagnosis, the more severe and problematic their condition.
Types of Hypophosphatasia
The types of HPP as well as their symptoms and prognosis include the following, as stated by NORD.
- Perinatal HPP. This condition is diagnosed when symptoms are recognized at birth or with an ultrasound before birth. It manifests as skeletal abnormalities that include deformed chest walls and long bones. On an X-ray, the bones of the body will show the tell-tale hypomineralization. This type of HPP may be fatal, with a high incidence of stillbirth or death soon after birth.
- Infantile HPP. Infantile HPP is diagnosed by the age of 6 months. Its characteristics, which include rickets and fractures, are detected by X-ray. The lack of minerals and the defective metabolic process affect the infant's ability to develop. This type of HPP may be fatal.
- Childhood HPP. Childhood hypophosphatasia is diagnosed when signs and symptoms appear after 6 months of age. It is recognized initially when the child fails to develop and reach motor skill milestones. The most common symptom is the early loss of baby teeth, including the root, usually by age 5. This differs from normal tooth loss, where the baby teeth fall out gradually after the roots resorb from around age 5 through the preteen years.
- Adult HPP. The adult classification is often present earlier in life, but remains undiagnosed until adulthood. Adult HPP presents with unspecific musculoskeletal disorders, slow healing and frequent fractures of the femur and the foot's metatarsal bones. It manifests as a softening of bones, and adults affected may lose teeth prematurely and suffer from chronic joint and muscle pain.
- Odontohypophosphatasia. The last category is odontohypophosphatasia, a condition that affects only the teeth. It is the least severe form of HPP. People diagnosed with it will have abnormal tooth development and premature loss of permanent teeth.
Therapy and Treatment for Hypophosphatasia
In the past, the only treatment for hypophosphatasia was to manage and alleviate symptoms caused by this disease. The only recommendation was to seek genetic testing and counseling to establish the likelihood of passing the disorder on to future generations.
In October 2015, the drug asfotase alfa was approved for use in the United States after clinical trials showed promising results in treating HPP presenting before the age of 18, notes a paper in the journal Drugs. It was designated by the Food and Drug Administration as a breakthrough therapy for bone-targeted medicine. This drug, the brand name of which is Strensiq, is administered through injection and results demonstrate rapidly improved bone mineralization that was maintained after three years of treatment, explains the Drugs study.
If you know that the HPP gene runs in the family or early signs of this disease arise, seek the advice of a medical professional.