Key summary points
1. Tubulointerstitial nephritis is often diagnosed late, so clinical suspicion is necessary for early identification and possible intervention (or removal of the offending agent).
2. Presenting signs and symptoms of TIN can include nonspecific systemic symptoms (fatigue, weight loss, headache, flank pain), fever, rash, eosinophilia/eosinophiluria, and evidence of elevated creatinine and Fanconi’s syndrome (glucosuria, aminoaciduria, acidosis).
3. Etiology of TIN can be drug-induced, infectious, idiopathic, genetic, or related to a systemic inflammatory condition such as tubulointerstitial nephritis and uveitis (TINU) syndrome or inflammatory bowel disease (IBD)
4. Treatment is based on etiology; aside from removal of offending agents, the mainstay of therapy is corticosteroids and, less often, mycophenolate mofetil.
5. Urinary biomarkers such as alpha1-microglobulin (A1M) and beta2-microglobulin (B2M) may help diagnose and monitor disease activity in TIN.