What is Hypophosphatasia

Hypophosphatasia is one of several disorders that resembles osteogenesis imperfecta. It is an inherited metabolic (chemical) bone disease that results from low levels of an enzyme called alkaline phosphatase (ALP).

Statistics on Hypophosphatasia

It has been estimated that the severe forms of hypophosphatasia occur in approximately one per 100,000 live births. The more mild childhood and adult forms are probably somewhat more common. About one out of every 300 individuals in the United States is thought to be a carrier for hypophosphatasia.

Risk Factors for Hypophosphatasia

The severe perinatal and infantile forms of hypophosphatasia are inherited as autosomalrecessive conditions. The patient receives one defective gene from each parent. Some of the more mild childhood and adult cases are also inherited this way. More mild adult cases are inherited in an autosomal dominant pattern where the patient gets just one defective gene from one parent.

Individuals with hypophosphatasia and parents of children with this disorder are encouraged to seek genetic counseling to understand the likelihood and severity of hypophosphatasia recurring in their family.

Prognosis of Hypophosphatasia

The outcome following a diagnosis of hypophosphatasia is variable. Cases detected in the womb or with severe deformities at birth almost invariably result in death within days or weeks.

When the diagnosis is made before six months of age, some infants have a downhill course while others survive and even do well. When diagnosed during childhood, underlying rickets may or may not result in the presence of skeletal deformities.

Premature loss of teeth when the child is under the age of five is the most usual manifestation. Adults may be troubled by recurring fractures in their feet and painful, partial fractures in their thigh bones.

How is Hypophosphatasia Treated?

There is no established medical therapy for hypophosphatasia. Disorders associated with the disease may be treated.

Hypophosphatasia References

[2] Girschick HJ, Schneider P, Kruse K, Huppertz HI: Bone metabolism and bone mineral density in childhood hypophosphatasia. Bone 1999 Sep; 25(3): 361-7
[3] MEDLINE Plus
[4] Whyte MP: Hypophosphatasia. In: Scriver CR, Beaudet AL, Sly WL, eds. The Metabolic and Molecular Basis of Inherited Disease. 7th ed. New York: McGraw-Hill; 1995: 4095-4111.