Photo/Illutration A Kobayashi Pharmaceutical Co. plant in Osaka’s Yodogawa Ward (Tomohiko Kaneko)

Most patients with kidney problems linked with Kobayashi Pharmaceutical Co. supplements are likely to have suffered from Fanconi syndrome, a kidney disorder, according to an ongoing investigation.

An expert on the investigation suggests the supplements may have contained potent ingredients that triggered the widespread health problems, including the condition that causes a decline in the function of the renal tubules. 

While Fanconi syndrome is commonly linked to side effects of anticancer drugs, antiviral drugs, painkillers and other medications, supplements can cause it too, according to Yoshitaka Isaka, professor of medicine at Osaka University and vice president of the Japanese Society of Nephrology, which is conducting the study.

The interim report released on April 1 also noted that some patients reported experiencing symptoms relatively soon after starting the supplements between December and February.

“Data suggests that it is more reasonable to conclude that the conditions developed relatively quickly rather than after long-term use,” Isaka said. “Given the large number of patients, it is likely that the supplement contained potent substances."

Fanconi syndrome is caused by damage to the renal tubules, which are responsible for reabsorbing essential substances such as glucose, amino acids and minerals from urine and returning them to the bloodstream.

Damage to the renal tubules can impair the kidneys' ability to reabsorb essential substances, leading to abnormally low blood levels of electrolytes such as potassium and phosphorus, along with uric acid.

These conditions can trigger various symptoms, including fatigue, swelling, dehydration, loss of appetite and abdominal pain.

Since last month, five deaths and more than 200 hospitalizations have been reported from people consuming the company's supplements containing the malted rice ingredient benikoji.

Puberulic acid, a highly toxic substance made from blue mold, was detected from the raw materials of the supplements and is suspected to be linked to the health problems.

“It has not yet been identified as the cause,” Isaka said. “We can't be certain until animal studies replicate the symptoms observed in patients.”

The society's investigation found that about a quarter of the patients required treatment with steroids or other medications, while the symptoms of the others improved simply by stopping taking the supplement.

(This article was written by Shuichi Doi and Shigeko Segawa.)

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