A breastfed infant develops rickets despite adequate sunlight exposure. His mother has been exclusively taking cholestyramine for years. The most likely mechanism is:
- A Cholestyramine sequesters bile acids, impairing absorption of fat-soluble vitamins including vitamin D from breast milk ✓
- B Cholestyramine directly inhibits vitamin D hydroxylation in the kidney
- C Cholestyramine accelerates vitamin D catabolism in the liver
- D Cholestyramine blocks intestinal calcium absorption independent of vitamin D
Correct answer: A. Cholestyramine sequesters bile acids, impairing absorption of fat-soluble vitamins including vitamin D from breast milk
Explanation
Cholestyramine is a bile acid sequestrant resin that binds bile acids in the intestinal lumen. Since bile acids are essential for formation of mixed micelles required for absorption of all fat-soluble vitamins (A, D, E, K), long-term cholestyramine use causes fat-soluble vitamin deficiency. The mother's vitamin D stores are depleted, reducing the vitamin D content of breast milk and causing rickets in the exclusively breastfed infant despite adequate UV light exposure.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.