Fanconi syndrome following administration of oral supplements containing red yeast rice: several months follow-up of three cases.

To date, the treatment strategy and long-term prognosis of acute kidney injury (AKI) after taking Benikoji CholesteHelp^®, a red yeast rice supplement, remains unclear. We present three cases wherein renal dysfunction improved within a few months of supplement discontinuation, without immunosuppressive therapy. Case 1: A 59-year-old woman with a history of hypertension, treated with telmisartan (serum creatinine [sCr]: 0.65 mg/dL; estimated glomerular filtration rate [eGFR]: 71.3 mL/min/1.73 m²) and Benikoji CholesteHelp^® for 7 months, developed Fanconi syndrome (FS) and severe renal impairment (sCr: 2.32 mg/dL; eGFR: 17.7 mL/min/1.73 m²). Renal biopsy and gallium-67 scintigraphy revealed no active drug-induced interstitial nephritis. Her condition improved significantly after supplement discontinuation. Her renal function gradually improved, with 3-month follow-up sCr and eGFR values of 0.96 mg/dL and 46.5 mL/min/1.73 m², respectively; however, these were still worse than the pre-onset values. Case 2: A 48-year-old man had mild renal dysfunction (sCr: 1.12 mg/dL; eGFR: 56.76 mL/min/1.73 m²) after taking Benikoji CholesteHelp^® for approximately 2 years; this was reversed upon supplement discontinuation. Case 3: A 47-year-old man with FS and mild renal dysfunction (sCr: 1.09 mg/dL; eGFR: 58.5 mL/min/1.73 m²) after taking Benikoji CholesteHelp^® for approximately 4 months, showed notable improvement in FS after supplement discontinuation; however, the mild renal dysfunction persisted. The primary intervention in all cases was immediate supplement discontinuation, leading to rapid improvement in renal function, without need for immunosuppressive therapy. These findings increase our understanding of renal impairment caused by red yeast rice, with improvement after withdrawal, sometimes after several months.