Fatigue, Polyuria, and Hidden Uveitis: A Case of Tubulointerstitial Nephritis and Uveitis Syndrome Diagnosed in Primary Care.

Tubulointerstitial nephritis and uveitis (TINU) syndrome is a rare autoimmune condition primarily affecting adolescents. Diagnosis is frequently delayed due to the nonspecific and temporally dissociated presentation of renal and ocular symptoms. We report the case of a 15-year-old girl who presented to her general practitioner with fatigue, polyuria, and recent weight loss. Laboratory workup revealed acute kidney injury with elevated serum creatinine and a tubular pattern of proteinuria, prompting timely referral to a pediatric hospital. Renal biopsy confirmed acute, non-granulomatous tubulointerstitial nephritis. Despite lacking ocular complaints, ophthalmologic examination revealed bilateral anterior uveitis, confirming the diagnosis of TINU syndrome. Notably, symptom onset followed the initiation of sertraline, suggesting a potential drug-induced trigger. The patient responded rapidly to high-dose oral corticosteroids, with full recovery of renal function and general well-being. Mild neuropsychiatric side effects occurred during treatment but resolved without intervention. Follow-up was coordinated through pediatric nephrology and ophthalmology. This case highlights the role of primary care in the early recognition of rare systemic diseases. Tubular protein markers proved valuable in characterizing the renal injury pattern. In adolescents with unexplained renal dysfunction and constitutional symptoms, TINU should be part of the differential, even in the absence of visual complaints. Recent medication changes should raise suspicion for drug-induced immune-mediated nephritis.