Developments in diagnosing the tubulointerstitial nephritis and uveitis (TINU) syndrome

Abstract Purpose Tubulointerstitial nephritis and uveitis (TINU) syndrome is a rare form of uveitis but there is reason to believe that this syndrome is underdiagnosed and renal manifestation may not be treated. Gold standard for diagnosisng TINU is invasive renal biopsy. Here, we show that performing beta‐2 microglobulin analysis in urine and HLA typing is helpful to find otherwise undiagnosed TINU cases with subclinical forms of nephritis. Methods Beginning January 2006 we prospectively obtained Ub2MG levels in all children with AU attending our pediatric uveitis clinic for the first time. Mandeville criteria were used to grade certainty of diagnosis. We compared with a healthy control group of children. HLA typing on patients with AU but no nephritis (n =28) by a Luminex‐based PCR‐SSO typing method was performed in another study. We compared frequencies to normal published controls and a published TINU cohort (n=20). Results The simple screening method of determining urinary Beta‐2‐Mikroglobulin showed in up to 2/3 of children with new‐onset AU subclinical renal manifestation. HLA Typing showed the TINU associated HLA DRB1*0102 in 12.5% of patients with AU with normal renal function opposed to 0.6% in healthy controls (p <0.0001; RR 14.3 (8.3‐32.0)). The allele was even more frequent in patients < 20 years with AU with 40%. Conclusion Determining the right uveitis subset is essential for therapy and prognosis, therefore TINU has to be kept in mind when considering differential diagnosis of AU. Urinary Beta‐2 micorglobulin and HLA Typing can give helpful information to direct this process.