Concurrent acute interstitial nephritis with acute pyelonephritis in DRESS syndrome: a rare case report.

Introduction: Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome is a severe, life-threatening hypersensitivity reaction characterized by fever, rash, eosinophilia, and multi-organ involvement. Renal manifestations, particularly acute interstitial nephritis (AIN), are common, but the concurrent presentation of acute pyelonephritis (APN) with AIN in DRESS syndrome is rare and not previously documented. Case presentation: A 19-year-old female presented with fever, vomiting, erythematous rash, and facial swelling. She had a history of prolonged use of Sulfasalazine and Cotrimoxazole. Laboratory tests revealed eosinophilia, nephrotic syndrome, and elevated liver enzymes. Renal biopsy showed features of APN, while clinical findings suggested AIN. Based on clinical, histopathological, and serological findings, DRESS syndrome was diagnosed. Discussion: DRESS syndrome, often triggered by medications like Sulfasalazine and Cotrimoxazole, can involve multiple organs, with renal manifestations being common. While AIN is typical, this case highlights the rare occurrence of concurrent APN. The absence of bacteriuria and pyuria suggests a non-bacterial cause for the APN, possibly related to viral reactivation. Conclusion: This case underscores the need for careful diagnosis and management of DRESS syndrome with atypical renal involvement. It highlights the importance of early identification and discontinuation of the offending drugs, as well as the necessity for further research to understand the complex renal manifestations in DRESS syndrome.