Acute tubulointerstitial nephritis (ATIN) including drug-induced, tubulointerstitial nephritis and uveitis (TINU), ANCA-associated vasculitis (AAV), kidney- limited sarcoidosis, and hemolysis: a case series from Syria.

This study aimed to detail acute tubulointerstitial nephritis (ATIN) patients, from relevant clinical manifestations to outcomes. We reviewed ATIN patients between 2018 and 2022. All demographic data, labs, biopsy findings, treatment protocols, and outcomes were reported. ATIN was diagnosed in nine patients, eight by kidney biopsy and one clinically. Drug-induced ATIN (DI-ATIN) was reported in five patients, including rifampin (RIF), allopurinol, mesalamine, and two with cephalosporins. Severe ATIN resulted after the first dose of RIF aligned with liver injury, hemolysis, and thrombocytopenia. Also, mesalamine and allopurinol induced gradual kidney failure a few months after the drug initiation. A patient with Tubulointerstitial nephritis and uveitis (TINU) syndrome showed refractory uveitis presenting during glucocorticoids (GCs) tapering, which resolved quickly with azathioprine (AZA) when not responding to GCs reescalation. Among the rarest cases, ATIN induced by a kidney-limited sarcoidosis, G6PD patient with hemolysis induced ATIN, and isolated ATIN induced by ANCA-associated vasculitis (AAV) with positive C-ANCA, which the latter representing the first case in our country and the fourth case worldwide. Labs showed anemia (88.8%), ESR elevation (85.7%), microscopic hematuria (in all patients), pyuria (44.4%), and proteinuria (77.7%). Biopsies showed interstitial infiltrations mainly with lymphocytes and monocytes. Eosinophils were found in one biopsy and neutrophils showed in 4 biopsies (50%). ATIN is a disease with a diagnostic challenge, thus clinicians should maintain a high suspicion for diagnosis. The combination of AKI with positive tests (especially abnormal urine sediment, ESR elevation, and anemia) may suggest ATIN diagnosis and further support the treatment initiation, particularly when kidney biopsy is unable to be performed or when the inciting agent is predictable.