Acute Kidney Injury Associated With Red Yeast Rice (Beni-kōji) Supplement: A Report of Two Cases

Abstract

Numerous health concerns, primarily kidney injury, have been reported with the use of Beni-kōji CholesteHelp, a functional food containing red yeast rice. Here, we describe 2 cases of kidney injury caused by beni-kōji. The first case had normal kidney function before consuming the product. After several months of use, she developed hypertension. After 6 months of supplement consumption, her estimated glomerular filtration rate (eGFR) dropped to 22.5 mL/min/1.73 m². A spot urine sample showed a urinary protein-to-creatinine ratio of 2.03 g/g, leading to the diagnosis of Fanconi syndrome. Kidney biopsy showed tubular degeneration. Thirty-five days after discontinuing the supplement, proteinuria resolved and the eGFR returned to baseline level. The second case, who had diabetes and normal kidney function, experienced severe kidney injury (eGFR, 3.5 mL/min/1.73 m²) after 4 months of Beni-kōji CholesteHelp use. He required hemodialysis for >2 weeks but recovered kidney function after the product was discontinued. Kidney biopsy showed tubular injury similar to the first case and glomeruli changes consistent with diabetic nephropathy. These cases indicate that beni-kōji use is associated with tubular toxicity. Further studies are required to identify the precise etiology and mechanism of kidney injury.

Keywords: Fanconi syndrome; Red yeast rice; foods with functional claims; kidney injury; tubular injury.

Fig 1

(A) Clinical course and (B-C) micrographs of kidney biopsy specimen of case 1. (A) Clinical course. (B) Light microscopy of periodic acid–Schiff-stained sections of the biopsy specimen demonstrating prominent tubular degeneration and some tubular atrophy. Swelling, flattening, and bleb formation of tubular epithelial cells can be observed. Tubulitis is not prominent, and interstitial inflammatory cell infiltration is insignificant. The inflammatory cells are predominantly lymphocytes and plasma cells, with some eosinophils. (C) Light microscopy of periodic acid–Schiff-stained sections of the biopsy specimen demonstrating normal glomeruli. Abbreviations: eGFR, estimated glomerular filtration rate.

Fig 2

(A) Clinical course and (B-C) micrographs of kidney biopsy specimen of case 2. (A) Clinical course. Serum creatinine levels were obtained during the CHDF session and just before the session when he was on intermittent hemodialysis. (B) Light microscopy of periodic acid–Schiff-stained sections of the biopsy specimen showing marked tubular degeneration. Tubular epithelial cells are swollen and flattened, and cellular debris can be observed in some tubular lumens. Inflammatory cell infiltration of the tubulointerstitium is insignificant. The inflammatory cells are mainly lymphocytes, plasma cells, and neutrocytes. (C) Light microscopy of a periodic acid-methenamine silver-stained biopsy specimen showing nodular glomerulosclerosis, a typical finding of diabetic nephropathy. Abbreviations: CHDF, continuous hemodiafiltration; eGFR, estimated glomerular filtration rate.