Long-term outcome of biopsy-proven idiopathic tubulointersitial nephritis with or without uveitis in children-a nationwide follow-up study.

BACKGROUND: Only a few studies reporting the long-term outcome of children with idiopathic tubulointerstitial nephritis (TIN) and uveitis syndrome (TINU) are available. We studied the long-term kidney and ocular outcome in a nationwide cohort of children with TIN or TINU. METHODS: All patients followed up for a minimum of 1 year by a paediatrician and an ophthalmologist were enrolled. The data on plasma creatinine (P-Cr), estimated glomerular filtration rate (eGFR), proteinuria, hypertension and uveitis were collected retrospectively. RESULTS: Fifty-two patients were studied. Median age at time of diagnosis was 13.1 (1.8-16.9) years and median follow-up time was 5.7 (1.1-21.2) years. Forty-five (87%) patients were initially treated with glucocorticoids. The median of the maximum P-Cr was 162 µmol/l (47-1,016) and that of eGFR 47 ml/min/1.73m2 (8-124). Uveitis was diagnosed in 33 patients (63%) and 21 (40%) patients developed chronic uveitis. P-Cr normalised in a median of 2 months. Eleven (21%) patients had nephritis recurrence during or after discontinuation of glucocorticoids. At the latest follow-up, 13 (25%) patients had eGFR < 90 ml/min/1.73m2 (median 83; 61-89 ml/min/1.73m2). Six patients had tubular proteinuria; all presented with TIN without uveitis. Seven (13%) patients were hypertensive. Eleven (21%) patients had uveitis. One patient developed uraemia and was later transplanted. CONCLUSIONS: Our study questions the previously reported good long-term kidney and ocular outcome of patients with TIN/TINU. Decreased kidney function and/or ocular co-morbidities may persist for several years; thus, both kidney and ocular follow-up for at least 1 year is warranted. A higher resolution version of the Graphical abstract is available as Supplementary information.

IL-10 polymorphisms +434T/C, +504G/T, and -2849C/T may predispose to tubulointersititial nephritis and uveitis in pediatric population.

BACKGROUND: Tubulointerstitial nephritis (TIN) and uveitis syndrome (TINU) are likely to be autoimmune diseases. Based on previous studies, adults with isolated idiopathic uveitis have polymorphisms in interleukin 10 (IL-10) and tumor necrosis factor α (TNF-α) genes. We aimed to evaluate the presence of IL-10 and TNF-α polymorphisms in a nationwide cohort of pediatric TIN/TINU patients. METHODS: Single nucleotide polymorphisms in IL-10 (+434T/C, +504G/T, -1082G/A, -2849C/T) and in TNFα (-308G/A, -238G/A, -857C/T) genes were genotyped in 30 well-defined pediatric patients with idiopathic TIN/TINU syndrome. Control group frequencies for these SNPs were obtained from 393 independent Finnish subjects. RESULTS: The homozygous minor allele in IL-10 +434T (rs2222202) and IL-10+504G (rs3024490) was found in all patients with TIN or TINU syndrome while the frequency of these minor alleles in the control population was 44% and 23%, respectively (p <0.001). In IL-10 SNP -2849 (rs6703630) a significant difference was found with genotype TT in all patients (p = 0.004) and in subgroups with TINU syndrome (p = 0.017) and TINU syndrome with chronic uveitis (p = 0.01) compared to reference population. There were no statistical differences in any of the studied TNF-α genotypes between TIN/TINU patients and control population. CONCLUSIONS: A significant difference in the frequency of IL-10+434T and +504G alleles was found between TIN/TINU patients and control population. Genotype -2849TT was more frequently present in patients with TINU syndrome than in the reference subjects. Genetic variation in the inflammatory mediators may predispose to autoimmune nephritis and uveitis.

FOXP3+ T cells are present in kidney biopsy samples in children with tubulointerstitial nephritis and uveitis syndrome.

BACKGROUND: Tubulointerstitial nephritis (TIN) is an inflammatory disease of unknown pathogenesis. To evaluate a possible role of regulatory T cells (Tregs) in the pathophysiology of TIN with (TINU) and without uveitis, we investigated the presence and quantity of FOXP3+ T regulatory lymphocytes in diagnostic kidney biopsies from pediatric patients. METHODS: A total of 33 patients (14 TIN and 19 TINU) were enrolled. The quantity of CD4+, FOXP3+ and double-positive T cells in formalin-fixed kidney biopsies was determined using double label immunohistochemistry with anti-human CD4 and FOXP3 antibodies. RESULTS: FOXP3 staining was successful in all 33 patients. In patients with chronic uveitis, the density of FOXP3+ cells was significantly lower (p = 0.046) than in TIN patients without uveitis or with uveitis lasting <3 months. CD4+ staining was successful in 23 patients. The density of all lymphocytes (CD4+, CD4+FOXP3+ and FOXP3+ cells) was significantly lower (p = 0.023) in patients with chronic uveitis than in other patients. CONCLUSIONS: FOXP3+ T cells are present in kidney biopsy samples from TIN and TINU patients. In patients with chronic uveitis, the density of FOXP3+ T cells is significantly lower than in other patients, suggesting a different pathomechanism for these clinical conditions.