Bone and mineral metabolism in transient hyperphosphatasaemia.

Transient hyperphosphatasaemia (TH) is a benign disorder characterized by transient elevation of S-ALP activity not exceeding duration of 4 months in children under 5 years of age, with elevated activity of bone isoenzymes of ALP with no signs of bone or liver disease and variable unrelated symptoms. We observed 19 children with TH and in 3 patients with markedly elevated S-ALP activity we found increased excretion of urinary hydroxyproline, suggesting increased bone resorption followed by bone formation. In 3 children with history of TH, bone mineral density (BMD) was measured and found to be normal. Transient increased bone resorption followed by bone formation during the course of TH can not be ruled out, but this has no negative impact on BMD.