[Repeat renal biopsy in tubulointerstitial nephritis and uveitis syndrome: report of a case]

A Japanese girl aged 12 years who presented with a month history of uveitis developed a significant elevation of urinary beta 2 microglobulin (beta 2MG) up to 13,933 micrograms/l. A percutaneous renal biopsy revealed a dense CD4-positive T-cell infiltration with focal tubulitis in the interstitium. The tubulointerstitial score (TI score) described by Foster et al. was 7 points. She was diagnosed as having tubulointerstitial nephritis and uveitis syndrome (TINU). Due to the severe interstitial infiltration, a 6-month course of prednisolone at the dose of 30 mg per alternate day was started. The levels of urinary beta 2MG dramatically decreased following treatment and the renal function remained normal. The second renal biopsy performed 6 months later revealed mild persistent CD4-positive T-cell infiltration associated with 19% periglomerular thickening, with the TI score of 4 points. These clinical observations suggest that the interstitial cell infiltration persists for a relatively long time in a proportion of patients with TINU. Since persistent interstitial infiltration has been known to be harmful to the kidney, we therefore speculate that prompt administration of corticosteroids might be beneficial to these patients. Although the renal outcome of TINU has been reported to be favorable to date, patients with severe interstitial infiltration should be followed under close observation. Study of similar patients is needed to clarify our understanding of effective therapy for TINU.