Renal and gastrointestinal complications following tosufloxacin therapy for suspected mycoplasma infection in a 10-year-old child.

Tosufloxacin, a fluoroquinolone antibiotic, is increasingly prescribed for pediatric patients, particularly for macrolide-resistant Mycoplasma pneumoniae infections in Japan. While its efficacy is well-documented, adverse effects such as renal impairment and gastrointestinal symptoms have raised growing concerns. We report a case of a 10-year-old girl who developed sequential symptoms following tosufloxacin administration. On the day after starting tosufloxacin, she experienced right-sided flank pain, followed by the onset of gastrointestinal symptoms, including abdominal pain, diarrhea, and vomiting, on the subsequent day. Contrast-enhanced computed tomography revealed increased fatty tissue opacity surrounding the kidney and duodenal wall thickening, suggestive of localized inflammation extending from the kidney to adjacent structures. Urine microscopy demonstrated needle- and sea urchin-shaped drug crystals, strongly implicating tosufloxacin in the development of renal and gastrointestinal symptoms. This case provides the first evidence suggesting that kidney inflammation may contribute to gastrointestinal symptom onset via localized inflammatory extension. The patient's symptoms resolved promptly with the discontinuation of tosufloxacin and supportive care. This report underscores the importance of monitoring pediatric patients for renal and gastrointestinal adverse effects following tosufloxacin administration.