Fanconi syndrome and renal tubular necrosis in patients following ingestion of potentially contaminated red yeast rice supplement: Two case reports.

We present two cases of middle-aged men who developed Fanconi syndrome and renal dysfunction after consuming "foods with functional claims (FFC)" containing red yeast rice. In the first case, the patient had consumed an FFC for 1 year and another FFC suspected to have contained nephrotoxin for 3 weeks; kidney biopsy performed during the acute phase of renal injury showed severe acute tubular necrosis and tubular cell regeneration. He achieved near-complete recovery 40 days after the FFC was discontinued. In the second case, the patient had consumed FFC for 4 years and stopped 70 days prior to presentation; kidney biopsy revealed significant tubular recovery, persistent tubular injuries, and interstitial fibrosis. Although the manifestations of Fanconi syndrome subsided, mild renal dysfunction persisted. These cases suggest that FFC with nephrotoxins may induce Fanconi syndrome owing to acute tubular necrosis. Recovery is possible after discontinuing the FFC; while short-term ingestion of FFC allows for tubular regeneration, its long-term ingestion may cause irreversible damage and lead to chronic kidney disease. Long-term follow-up is crucial for preventing further renal deterioration.