Hypophosphatasia: the importance of alkaline phosphatase in bone mineralization.

The authors describe a neonate who was diagnosed with "perinatal hypophosphatasia". The clinical manifestations in this patient were small head size, soft calvarium (caput membranaceum), and short bowing forearms and legs. Laboratory investigations revealed hypercalcemia at 12.7 mg/dl, hyperphosphatemia 8.6 mg/dl, and extremely low alkaline phosphatase 0 unit/L. Roentgenographic studies of the skull showed calcification only at frontal bone and base of the skull. Spines were small and flattened. Long bones were hypomineralized and deformed. The functions of alkaline phosphatase to bone development and mineralization were reviewed. Because perinatal hypophosphatasia is a fatal condition and inherited as an autosomal recessive pattern, prenatal diagnosis is necessary. The most reliable and suitable method in our facility is serial ultrasonography from which the diagnosis can be made by the second trimester.