Tubulointerstitial nephritis: diagnosis, treatment, and monitoring.

Tubulointerstitial nephritis (TIN) is a frequent cause of acute kidney injury (AKI) that can lead to chronic kidney disease (CKD). TIN is associated with an immune-mediated infiltration of the kidney interstitium by inflammatory cells, which may progress to fibrosis. Patients often present with nonspecific symptoms, which can lead to delayed diagnosis and treatment of the disease. Etiology can be drug-induced, infectious, idiopathic, genetic, or related to a systemic inflammatory condition such as tubulointerstitial nephritis and uveitis (TINU) syndrome, inflammatory bowel disease, or immunoglobulin G4 (IgG4)-associated immune complex multiorgan autoimmune disease (MAD). It is imperative to have a high clinical suspicion for TIN in order to remove potential offending agents and treat any associated systemic diseases. Treatment is ultimately dependent on underlying etiology. While there are no randomized controlled clinical trials to assess treatment choice and efficacy in TIN, corticosteroids have been a mainstay of therapy, and recent studies have suggested a possible role for mycophenolate mofetil. Urinary biomarkers such as alpha1- and beta2-microglobulin may help diagnose and monitor disease activity in TIN. Screening for TIN should be implemented in children with inflammatory bowel disease, uveitis, or IgG4-associated MAD.