We recently encountered a case of hyperphosphatasemia, in which >90% of serum alkaline phosphatase (ALP) was of intestinal origin. The patient, a 51-year-old man, was found to have hyperphosphatasemia (2,341 U/L) during a routine medical check-up. All other laboratory tests and physical findings were normal.
The agarose gel electrophoresis pattern of the patient's serum ALP was identical to that of common intestinal ALP from healthy adults, and only a single band of intestinal ALP was detected by immunoaffinity electrophoresis. In addition, 89% of total ALP 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 increased la fraction (74%) compared with adult duodenal ALP.
Genealogical study revealed that two persons in the 5 members of the proband's family had hyperphosphatasemia of intestinal origin, indicating possible autosomal dominant inheritance.
mained at high levels. The isoenzyme in our cases was characterized by biochemical, immunochemical, and genealogical studies of the proband.
Case report
In September, 1987, a 51-year-old man of blood type B was found to have hyperphosphataeemia during a routine medical check-up. All other laboratory tests, physical examination, and clinical signs were normal, but his ALP activity was extremely high (2,341 U/L; our reference range: 102-330 U/L).