This is the first case report of acute kidney injury and Fanconi syndrome in a patient taking many health supplements, including Red Yeast Rice Cholesterol Help®.

As previously mentioned, acquired Fanconi syndrome can be caused by various diseases. Therefore, we evaluated the patient’s blood biochemistry, but were unable to identify any related diseases. The results were negative for serum and urine protein electrophoresis and normal for the ratio of free light-chain κ/λ ratio for MGRS, including LCPT. The results were negative for antinuclear antibodies and anti-SSA antibodies for Sjogren syndrome. There was no tubulointerstitial nephritis on light microscopy and no uveitis. Serum IgG4 levels were not elevated. The results were also negative for anti-mitochondrial M2 antibodies for TINU syndrome, IgG4RKD, and IgMPC-TIN. There was no history of chemical exposure and no elevation of cadmium, lead, or chromium levels.

Since the patient experienced persistent loss of appetite and weight, there might have been some pre-renal components to his condition. The values of FENa and FEUN also suggested the presence of a mild pre-renal component, although the patient’s blood pressure was not low. However, Fanconi syndrome is not associated with pre-renal damage.

Since the patient was receiving several drugs other than Red Yeast Rice Cholesterol Help®, their influence on the renal injury could not be ruled out. Regarding drug-related effects, there have been reports of kidney injury with P-CAB. However, kidney dysfunction was recognized before he started taking P-CAB, and there have been no reports of Fanconi syndrome due to P-CAB therapy. In particular, since nephropathy induced by AA in Fanconi syndrome has been reported [6], we strongly suspected its influence. However, no Chinese herbal medicine containing AA is currently available in Japan.

Recently, in Japan, many patients taking with Red Yeast Rice Cholesterol Help® oral medication in a certain period, presented with fatigue, anorexia and diagnosed with acute kidney injury and Fanconi syndrome. Japanese Society of Nephrology shows the data of questionnaires of 47 patients [11], but the mechanism due to the drug is unknown. Citrinin is a substance produced by the mold used for production of red yeast rice, which causes proximal tubular damage [8]. As mentioned previously, citrinin is not produced by the mold M. pilosus, which is used in the production of the new red yeast rice, Red Yeast Rice Cholesterol Help®. In this case, it was clear from the patient’s laboratory data and histological images that proximal tubular damage had occurred, although we could not identify other possible causes. Although the causative agent is not yet clear, we predicted that a substance might have caused the renal tubular damage. In fact, it was recently reported that Red Yeast Rice Cholesterol Help® created during a certain period contained puberulic acid. Puberulic acid is produced by the genus Blue Mold, although details about its nephrotoxic effects are not known. While it is possible that puberulic acid causes proximal tubular damage, further investigation of this is required in the future.

In this case, the patient was able to stop taking Red Yeast Rice Cholesterol Help® at an early stage, resulting in gradual recovery of his kidney function. This might suggest that early discontinuation of its administration is important in acute kidney injury and Fanconi syndrome potentially caused by Red Yeast Rice Cholesterol Help®.