Transient hyperphosphatasemia of infancy.

Very high serum levels of alkaline phosphatase were found in four children aged 13 to 24 months. No other abnormalities nor explanation for the raised enzyme levels were found. The origins of the elevated enzyme levels were shown by isoenzyme studies to be the liver in one case, the bone in two cases, and undetermined in one case. Serum alkaline phosphatase levels returned to normal after periods of 5 to 20 weeks. Awareness of these benign forms of hyperphosphatasemia will aid the physician in the differential diagnosis of elevated alkaline phosphatase levels.