[Clinical analysis of 4 children with tubulointerstitial nephritis and uveitis syndrome]

Objective: To investigate the clinical and pathological characteristics, treatment, and prognosis of tubulointerstitial nephritis and uveitis (TINU) syndrome in children. Methods: This case series study analyzed the clinical characteristics, laboratory examinations, renal biopsy findings, treatment courses, and outcomes of 4 children diagnosed with TINU syndrome, who were hospitalized in the Department of Nephrology, Capital Center for Children's Health affiliated to Capital Medical University between November 2017 and April 2024. Results: Four children with TINU syndrome included 2 males and 2 females. Their ages at diagnosis were 13 years and 11 months, 13 years and 6 months, 13 years and 7 months, and 11 years and 8 months respectively. Three patients had a history of infection or drug exposure before disease onset. Ocular symptoms preceded renal involvement by 1 month in 1 case, whereas uveitis developed 8.0, 0.5 and 14.0 months after renal involvement in the other 3 cases. All patients had acute kidney injury (AKI), including stage 2 AKI in 3 patients and stage 3 AKI in 1 patient. Glycosuria and elevated urinary β2-microglobulin levels occurred, and varying degrees of proteinuria and leukocyturia occurred in 3 patients. Serum creatinine levels at disease onset were markedly elevated at 130.0, 103.4, 188.4 and 105.7 μmol/L, and estimated glomerular filtration rates were reduced to 50.5, 56.4, 28.9 and 53.8 ml/(min·1.73 m²). Renal biopsies showed acute interstitial nephritis, and the predominant ocular manifestation was bilateral anterior uveitis. All patients received systemic glucocorticoid therapy and topical corticosteroid eye drops, and 1 patient was additionally treated with mycophenolate mofetil. During follow-up periods of 57, 82, 14 and 66 months, respectively, 1 patient progressed to stage 2 chronic kidney disease. Proteinuria resolved and ocular symptoms recurred only in 1 patient. Conclusions: Renal involvement generally has a favorable prognosis in children with TINU syndrome. However renal function may not fully recover in some patients, and uveitis may persist or recur, underscoring the need for renal and ophthalmic combined screening and long-term multidisciplinary follow-up.