Caravaca Fontán, FernandoShabaka, AmirSánchez Álamo, BeatrizLorenzo, Alberto deDíaz, MarthaBlasco Pelícano, MiquelRodríguez, EvaSierra Carpio, MilagrosMalek Marín, TamaraUrrestarazú, AndrésCorona Cases, ClaraPraga, ManuelFernández Juárez, GemaSpanish Group for the Study of Glomerular Diseases (GLOSEN)2021-04-222021-04-222020Caravaca-Fontán F, Shabaka A, Sánchez-Álamo B, de Lorenzo A, Díaz M, Blasco M, Rodríguez E, Sierra-Carpio M, Malek Marín T, Urrestarazú A, Corona Cases C, Praga M, Fernández-Juárez G; Spanish Group for the Study of Glomerular Diseases (GLOSEN). Recurrent acute interstitial nephritis: what lies beneath. Clin Kidney J. 2020;14(1):197-204. DOI: 10.1093/ckj/sfaa0182048-8505http://hdl.handle.net/10230/47186Background: Acute interstitial nephritis (AIN) is an emerging cause of acute kidney disease. While this disease usually follows an acute course, it may occasionally recur, representing a major challenge for the clinician. Methods: We performed a retrospective, observational cohort study in 13 nephrology departments belonging to the Spanish Group for the Study of Glomerular Diseases. Patients with biopsy-proven AIN between 1996 and 2018 were included. Results: The study group consisted of 205 patients with AIN, 22 of which developed recurrent AIN (RAIN) after a median of 111 days from diagnosis. RAIN was due to a surreptitious reintroduction of a previously known implicated drug or toxic in six patients (27%), sarcoidosis in two (9%), Sjögren's syndrome in three (14%), light-chain-mediated AIN in two (9%) and tubulointerstitial nephritis and uveitis syndrome in two (9%), while in the rest of cases (32%), no precise cause could be identified. Microscopic haematuria was more frequent in patients with underlying systemic diseases. The first RAIN episode was treated with a repeated course of corticosteroids in 21 patients (95%). In six cases (27%), azathioprine and mycophenolate mofetil were added as corticosteroid-sparing agents. During a median follow-up of 30 months, 50 patients (27%) with no recurrences and 12 patients (55%) with RAIN reached Stages 4 and 5 chronic kidney disease (CKD). By multivariable logistic regression analysis, RAIN was independently associated with the risk of reaching Stages 4 and 5 CKD, even after adjusting for potential covariables. Conclusions: RAIN is infrequent but is associated with poor kidney survival. RAIN should prompt clinicians to search for an underlying aetiology other than drug induced. However, in a large percentage of cases, no precise cause can be identified.application/pdfeng© The Author(s) 2020. Published by Oxford University Press on behalf of ERA-EDTA. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.cominfo:eu-repo/semantics/articlehttp://dx.doi.org/10.1093/ckj/sfaa018Acute interstitial nephritisChronic kidney diseaseRecurrent acute interstitial nephritisinfo:eu-repo/semantics/openAccess