A case of tubulointerstitial nephritis and uveitis syndrome with severe immunologic dysregulation

Idiopathic tubulointerstitial nephritis and uveitis (TINU) syndrome is an uncommon condition, characterized by acute tubulointerstitial nephritis (TIN) with a favorable course and uveitis with a chronic relapsing course. The pathogenesis remains unclear, but a lymphocyte-mediated immune mechanism has been suggested. A 9-year-old boy was evaluated for fatigue and 2 kg of weight loss. Renal glucosuria, elevated urine β₂-microglobulin (MG), progressive renal dysfunction, polyclonal hypergammaglobulinemia, various autoantibodies and abnormal lymphocyte phenotypes were found. A renal biopsy revealed acute TIN. After 2 months of treatment with prednisolone, renal function and polyclonal hypergammaglobulinemia were normalized. While tapering prednisolone, anterior uveitis developed, which was improved with topical steroid. But abnormal lymphocyte phenotypes and autoantibodies persisted on low-dose prednisolone. Uveitis became aggravated, and urine β₂-MG increased again. The second renal biopsy (7 months later) was normal except for minimal focal interstitial fibrosis. Uveitis was not responsive to systemic steroids, but improved with additional cyclosporin. Abnormal lymphocyte phenotypes improved, and most autoantibodies disappeared. We report a rare case of idiopathic TINU syndrome with severe immunologic dysregulation, which correlated with the clinicopathological and biochemical parameters. The information about lymphocyte phenotypes and autoantibodies may provide more insight into the pathophysiology and the clinical course of uveitis in this rare disorder.