Serum alkaline phosphatase (ALP) is elevated in a 14-year-old girl with no bone or liver disease. The family history reveals a similar finding in her father. This physiological variant of elevated ALP is most likely due to which isoenzyme source?

• A Intestinal ALP isoenzyme ✓
• B Placental ALP (Regan isoenzyme)
• C Bone ALP from rapid growth
• D Hepatic ALP from induction by fatty liver

Explanation

Familial benign hyperphosphatasemia often involves increased intestinal ALP, which is a distinct isoenzyme that can be elevated in blood group O and B secretor individuals (especially after a fatty meal). Bone ALP is elevated in growing adolescents but peaks earlier and is expected in this context; it's also elevated here but the familial-dominant pattern points specifically to intestinal isoenzyme variant. Placental (Regan) isoenzyme is a tumour marker for some carcinomas. Separating isoenzymes by heat stability or L-phenylalanine inhibition distinguishes them clinically.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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