A 16-year-old male presents with recurrent renal colic. Stone analysis reveals hexagonal crystals. Urinalysis shows excessive cystine along with lysine, arginine, and ornithine. Which is the most appropriate long-term therapy to prevent stone recurrence?
- A Allopurinol and urine alkalinization to pH 7.5
- B Penicillamine restriction and dietary purine limitation
- C High fluid intake, urine alkalinization, and tiopronin ✓
- D Pyridoxine supplementation and methionine loading
Correct answer: C. High fluid intake, urine alkalinization, and tiopronin
Explanation
Cystinuria stems from defective dibasic amino acid transport, making cystine poorly soluble and stone forming. Management is high fluid intake, alkalinization of urine since cystine solubility rises with pH, and chelating agents such as tiopronin or D-penicillamine that form soluble disulfide complexes. Allopurinol treats uric acid stones, and methionine loading would worsen cystine formation.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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