A CASE OF BENIGN FAMILIAL HYPERPHOSPHATASEMIA OF INTESTINAL ORIGIN

We recently encountered a case of hyperphosphatasemia, in which >90% o f serum alkaline phosphatase (ALP) was of intestinal origin. The patie nt, a 51-year-old man, was found to have hyperphosphatasemia (2,341 U/ L) during a routine medical checkup. All other laboratory tests and ph ysical findings were normal. The agarose gel electrophoresis pattern o f the patient's serum ALP was identical to that of common intestinal A LP from healthy adults, and only a single band of intestinal ALP was d etected by immunoaffinity electrophoresis. In addition, 89% of total A LP was defined as intestinal ALP by an immunoprecipitation method. The molecular mass of the ALP was 154 kDa, almost identical with that of adult duodenal ALP. Analysis of the sugar chain structure showed an in creased la fraction (74%) compared with adult duodenal ALP. Genealogic al study revealed that two persons in the 5 members of the proband's f amily had hyperphosphatasemia of intestinal origin, indicating possibl e autosomal dominant inheritance.