Hypophosphatasia

Hypophosphatasia (HPP) is a genetic condition that causes abnormal development of the bones and teeth. The severity of HPP can vary widely, from fetal death to fractures that don’t begin until adulthood. Signs and symptoms may include poor feeding and respiratory problems in infancy; short stature; weak and soft bones; short limbs; other skeletal abnormalities; and hypercalcemia. Complications can be serious. The mildest form of the condition, called odontoHypophosphatasia, only affects the teeth. HPP is caused by genetic changes in the ALPL gene. Perinatal (onset before birth) and infantile HPP are inherited in an autosomal recessive manner. The milder forms, especially adult forms and odontoHypophosphatasia, may be inherited in an autosomal recessive or autosomal dominant manner.

Genetic Mutations: Hypophosphatasia is caused by genetic mutations, also known as pathogenic variants. Genetic mutations can be hereditary, when parents pass them down to their children, or they may occur randomly when cells are dividing. Genetic mutations may also result from contracted viruses, environmental factors, such as UV radiation from sunlight exposure, or a combination of any of these.

If you suspect you may have this disease, you may want to start collecting your family health history. Information such as other family members who have had similar symptoms, when their/your symptoms first appeared, or exposures to any potential disease-causing environmental factors should be discussed with your medical team.

Yes. It is possible for a biological parent to pass down genetic mutations that cause or increase the chances of getting this disease to their child. This is known as inheritance. Knowing whether other family members have previously had this disease, also known as family health history, can be very important information for your medical team.

There are multiple ways, or patterns, a disease can be inherited depending on the gene(s) involved. Based on GARD’s current data, this disease can be inherited in the following pattern(s):

Autosomal Dominant: Autosomal means the gene involved is located on one of the numbered chromosomes. Dominant means that a child only needs to inherit one copy of the mutated gene, from either biological parent, to be affected by the disease.

People affected by an autosomal dominant disease have a 50% chance of passing on the mutated gene to their biological child.

Autosomal Recessive: Autosomal means the gene involved is located on one of the numbered chromosomes. Recessive means that a child must inherit two copies of the mutated gene, one from each biological parent, to be affected by the disease. A carrier is a person who only has one copy of the genetic mutation. A carrier usually doesn’t show any symptoms of the disease.

If both biological parents are carriers, there is a 25% chance their child inherits both copies of the mutated gene and is affected by the disease. Additionally, there is a 50% chance their child inherits only one copy of the mutated gene and is a carrier.