Ibuprofen-induced tubulointerstitial nephritis with Fanconi syndrome in a patient with Behçet’s disease mimicking TINU syndrome: a diagnostic challenge clarified by a structured clinical approach

Abstract Background The coexistence of tubulointerstitial nephritis (TIN) and uveitis commonly raises suspicion for tubulointerstitial nephritis and uveitis (TINU) syndrome. However, these manifestations may arise from distinct etiologies, making diagnosis challenging. Case presentation: a 30-year-old woman presented with bilateral anterior uveitis and renal impairment. Although TINU was initially suspected, detailed history taking revealed heterochronous mucocutaneous findings compatible with Behçet’s disease, as well as daily ibuprofen use for 4 years. A laboratory evaluation demonstrated Fanconi-type proximal tubular dysfunction. The renal biopsy showed acute TIN with granulomatous inflammation. Given the rarity of TIN due to Behçet’s disease and the absence of systemic activity, ibuprofen-induced TIN was strongly suspected. The renal function improved rapidly after ibuprofen cessation without corticosteroids, whereas uveitis followed a course consistent with Behçet’s disease rather than drug-induced TINU. On the basis of these observations, we constructed a diagnostic approach to differentiate drug-induced TIN, TINU, and systemic inflammatory disease in patients presenting with TIN and uveitis. Conclusions This case demonstrates that TIN and uveitis may originate from separate disease processes. A structured diagnostic approach can help clinicians avoid premature diagnosis of TINU syndrome and correctly identify dual pathology.