Allergic Interstitial Nephritis

Allergic interstitial nephritis (AIN) is the most common form of acute interstitial nephritis. It is most often caused by exposure to a drug. AIN is often associated with an acute decline in renal function and may be associated with permanent renal insufficiency. The hallmark pathologic finding of AIN is a marked inflammatory infiltrate of the renal interstitium. The classic clinical picture of AIN (i.e., fever, rash, eosinophilia) was well-described with the use of methicillin, which caused AIN in approximately 17% of cases. Identification and discontinuation of the offending medication have been the mainstays of treatment, with conflicting evidence regarding the benefit of steroid treatment.