A case of acute tubulointerstitial nephritis with suspected Saikokaryukotsuboreito involvement responding to glucocorticoid therapy.

Drug-induced kidney injury is a major cause of acute tubulointerstitial nephritis (AIN). The standard treatment for AIN is discontinuation of the causative agent; however, if discontinuation alone is insufficient, glucocorticoid therapy may be effective. A 51-year-old woman was admitted to our hospital with acute kidney injury, presenting with an estimated glomerular filtration rate (eGFR) of 6.3 mL/min/1.73m². She was diagnosed with AIN after a renal biopsy. Drug-induced lymphocyte stimulation tests were performed on the herbal medicine she had been taking for 5 months, Saikokaryukotsuboreito (comprising Bupleurum root, Pinellia tuber, Scutellaria root, and Ginseng as key ingredients). The test results were positive for all four components. The patient discontinued the causative agent, and her renal function improved with oral glucocorticoid therapy (prednisolone 30 mg/day). After 6 months of treatment, her renal function stabilized, with only minor residual tubular acidosis. This case of AIN induced by Saikokaryukotsuboreito, which responded to glucocorticoid therapy, highlights the potential for recovery with appropriate treatment.