Transient Hyperphosphatasemia of Infancy and Early Childhood (THI) is a benign, unexplained elevation in serum alkaline phosphatase activity. If it is recognized then the patient can be spared an exhaustive workup and the parents unnecessary anxiety.
Features of THI:
(1) The patient is an infant or young child less than 5 years of age.
(2) There is a marked elevation of the serum alkaline phosphatase activity.
(3) The alkaline phosphatase activity is due to increased liver and/or bone isoenzymes.
(4) The elevation in alkaline phosphatase activity cannot be explained by bone or liver disease.
(5) The serum alkaline phosphatase activity returns to normal within 4 months.
Presentations may include:
(1) An otherwise healthy child with an isolated elevation in enzyme activity.
(2) A sick child with an increase in enzyme activity that may be related to other problems.
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