# Two Cases of Chronic Tubular Necrosis Presenting as Fanconi Syndrome Induced by Red Yeast Rice Choleste-Help

## TL;DR

Two patients developed Fanconi syndrome from red yeast rice supplements, showing kidney damage and partial recovery after stopping the supplement.

## Contribution

Identifies red yeast rice as a novel cause of Fanconi syndrome with new histopathological and clinical insights.

## Key findings

- Fanconi syndrome resolved after discontinuing red yeast rice supplements, but renal dysfunction persisted.
- Renal biopsy showed tubulointerstitial nephritis and reduced expression of key tubular transporters.
- Uromodulin recovery was complete in one case and partial in the other after treatment.

## Abstract

Background and Clinical Significance: Although dietary supplements have often been deemed safe, some have been linked to drug-induced nephropathy due to their diverse ingredients. The aim of this report is to enhance clinical awareness of a novel and emerging cause of Fanconi syndrome due to red yeast rice supplements and to contribute new histopathological and clinical data. Case Presentation: We report two cases of renal dysfunction and Fanconi syndrome associated with the use of red yeast rice supplements. Both patients presented with renal impairment accompanied by elevated markers of tubular injury, hypouricemia, hypokalemia, and glucosuria, consistent with Fanconi syndrome. Following the discontinuation of the red yeast rice supplement and initiation of steroid therapy, Fanconi syndrome resolved, however, moderate renal dysfunction persisted. Urinary NGAL levels improved after treatment in both cases. KIM-1 normalized in one case but remained elevated in the other. Uromodulin recovery was complete in one case and partial in the other. Renal biopsy revealed mild tubulointerstitial nephritis, with notable shedding of proximal tubular epithelial cells. Immunohistochemical analysis demonstrated reduced expression of URAT-1, Na-K ATPase, and Na-Pi IIa in some tubules. Conclusions: These findings suggest that renal injury induced by red yeast rice supplements is mediated by direct proximal tubular necrosis caused by a harmful substance in the supplement, resulting in persistence of tubular dysfunction.