Odontohypophosphatasia

A particular form of hypophosphatasia (HPP) characterized by reduced activity of unfractionated serum alkaline phosphatase, premature exfoliation of primary and/or permanent teeth and/or severe dental caries, in the absence of skeletal system abnormalities.

Epidemiology

The prevalence of odonto-HPP is not known. It is thought that odonto-HPP is the most frequent form of HPP because 74% of the cases are heterozygotes.

Clinical description

The main feature of odontohypophosphatasia is premature exfoliation of fully rooted primary teeth and/or severe dental caries. The anterior deciduous teeth are most commonly affected along with the incisors. X-rays reveal reduced alveolar bone, reduced thickness of dentin, and enlarged pulp chambers and root canals. Patients with other forms of HPP often have dental manifestations but these are always associated with skeletal abnormalities and other manifestations.

Etiology

Mutations in the ALPL gene (1p36.12) are known to cause hypophosphatasia. Specific mutations are thought to underlie this phenotype and its variable severity.

Diagnostic methods

Diagnosis is based on clinical presentation, dental panorex and laboratory findings, and can be confirmed by genetic testing.

Differential diagnosis

Other causes for premature exfoliation should be excluded. The presence of bone symptoms (osteomalacia, fractures) distinguish adult HPP from odontohypophosphatasia.

Genetic counseling

Autosomal recessive and autosomal dominant patterns of inheritance are reported in odonto-HPP.

Management and treatment

Management is with observation and supportive measures such as implementation of an oral health program, protection of the existing teeth, and aesthetic and functional restoration of the mouth (with braces or other dental devices).

Prognosis

Loss of teeth may have functional and aesthetic consequences. Overall prognosis is generally good.