Granulomatous Interstitial Nephritis With Perivascular Involvement in Carbamazepine-Induced DRESS Syndrome: A Case Report.

Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a severe hypersensitivity reaction caused by certain medications, including allopurinol, antibiotics, and antiepileptic drugs. It is characterized by a widespread rash, fever, lymphadenopathy, eosinophilia, and multiorgan dysfunction, including hepatic and renal impairment. DRESS syndrome differs from typical drug eruptions in that clinical symptoms may continue or worsen even after the causative medication has been discontinued. We report the case of a 75-year-old Japanese woman who developed DRESS syndrome after taking carbamazepine. She subsequently experienced severe acute kidney injury. Despite drug discontinuation, renal function progressively deteriorated over 2 months. Renal biopsy revealed granulomatous interstitial nephritis characterized by granulomatous lesions confined to the perivascular areas of the arcuate and interlobular arteries. Additionally, lymphangiogenesis was observed. Administration of prednisolone 0.8 mg/kg/d resulted in partial improvement in renal function; however, chronic kidney disease persisted. This patient showed perivascular granulomatous interstitial nephritis, a rare histological finding in DRESS syndrome. This finding shows that granuloma formation may involve crosstalk between persistent interstitial inflammation and lymphangiogenesis. Therefore, delayed treatment initiation may negatively affect renal outcomes, underscoring the essence of the prompt recognition and treatment of DRESS syndrome.