[Familial hyperphosphatasemia of intestinal origin]

To clarify the diagnostic laboratory procedures before a case of unknown origin hyperphosphatasemia, we have studied the electrophoretic separation of serum alkaline phosphatase activity on agarose gel with and without neuraminidase. Sera were collected from a family, four of whom showed hyperphosphatasemia. Alkaline phosphatase isoenzyme patterns on agarose gel electrophoresis demonstrated that two persons out of the six members tested had unusual isozymes, the hydrophilic and the hydrophobic intestinal isozyme representing more than 50% of total alkaline phosphatase. The advantages of this method are its simplicity and low cost. The early recognition of this benign abnormality should help to avoid unnecessary diagnostic tests (i.e. image or radioisotopic examination).