Another "suspect": homeopathic agent associated with acute interstitial nephritis

History and clinical findings: A 70-year-old woman was admitted to hospital with fatigue, pallor and shortness of breath on mild exertion. In her past medical history only borderline hypertension and allergy to penicillin were to note. Investigations: Actual laboratory findings revealed renal failure with metabolic acidosis and hyperkalaemia. A normochrome normocytic anemia and secondary hyperparathyreoidism were suggestive of a subacute course. The renal biopsy showed histological features of a subacute tubulo-interstitial nephritis. Diagnosis, treatment and course: The chronic renal failure caused by an interstitial nephritis was treated with corticosteroids and hemodialysis treatment was started. The trigger for AIN could not be found, there was no infectious or systemically disease nor a nephrotoxic medication identified. For nearly six months the patient had taken a homeopathic agent which is a dilution of penicillium chrysogenum. In case of a determined allergy to penicillin, an extract of the fungus producing penicillin could possibly cause an interstitial nephritis. The patient was dialysis-independent with a GFR about 8-10 ml/min at the time of discharge. Conclusion: With interstitial nephritis all agents should be considered a potential suspect, even homeopathic agents.