Hypophosphatasia varies widely in clinical
presentation. It has been subdivided into five categories: perinatal,
infantile, childhood, adult, and odontohypophosphatasia. The earlier the
symptoms occur, the more severe the disease. Perinatal form presents with a history of
poor feeding, failure to thrive, hypotonia, and skin-covered spurs extending
from the forearms or legs; it is lethal in 50% of cases. Childhood form often presents
as delayed walking, early loss of deciduous teeth, and bone pain. Adult form has mild
symptoms (foot pain as a result of spontaneous fractures of metatarsal
bones). Odontohypophosphatasia is limited to dental problems (premature loss of adult teeth).
Severe forms are characterized by widespread failure of ossification of the
skeleton and marked shortening of long bones. Multiple rib fractures may
lead to flail chest and predispose to pneumonia. There may be failure of
ossification of the cranial vault. Hypercalcemia may lead to
nephrocalcinosis and renal failure. In milder childhood forms, the skeletal
abnormalities are less severe, but frequent fractures and bone pain are
typical. There is defective development of the teeth leading to premature
loss. There is no effective treatment, but some spontaneous improvement may
occur as the child ages.