Acute Interstitial Nephritis Associated with Linezolid TOTHE EDITOR: Acute interstitial nephritis(AIN) associatedwith linezolid is rare but has been previously reported. 1 ,2 We reporta case of AIN in a young man receivinglinezolid for osteomyelitis. Case Report. A 21-year-old man with a history of intravenousdrug abuse presented to the emergency department complaining of severe pain and swellingin the left thighand feverof I week's durationafter recent dynamic hip and screw surgerywith hardwareplacement. Initial diagnostictests included bloodurea nitrogen (BUN) 10 mg/dL,serumcreatinine (SCr) I mg/dL, and white blood cell (WBC) count 20.1 x 1()3/mm J with 1.1%eosinophils. These values remained stable and the WBC count normalized by the time of discharge. Vancomycin was initiated after a bone scan showed likely osteomyelitis of the femur. Blood and hip joint cultures were negative. Due to the patient's improvement on vancomycin, orallinezolid 600 mg every 12 hours for a total of 8 weekswas prescribed. Tendays afterdischarge, the patientreturnedto the hospitalwith a diffuse pruritic maculopapularrash and a fever. Vital signs were temperature 37.9 •C, blood pressure 146170 mm Hg, and heart rate 122 beatsl min. Significant laboratory test results included a WBC count of 8.9 x 1()3/mm J with 24.7% eosinophils, BUN 41 mg/dl., and SCr 3.8 mg/dL. Urine studiesshowedeosinophiluria and microscopic hematuria; a renal ultrasoundwas normal. The patient reported taking Iinezolidfor 7 days before losing the prescription bottle 4 days prior to this admission. He reported thatthepruritusand rashdeveloped shortly afterstarting linezolid. The patient received antihistaminesto control symptoms. There was no evidence of skin desquamation or mucosal involvement. SCr re-.. mainedelevatedat 3.6 mg/dLfor the first severaldays of hospitalization. Shortly after admission, the rash began to improve, but the patient remained febrile, with continued eosinophilia. A clinician from the Nephrology service diagnosed the patient with AIN due to eosinophiluria and linezolid exposure.The patientrespondedto corticosteroids and SCr began to decline on hospital day 8. Blood and urine cultures were negativeand intravenous vancomycin was the plannedtherapy.However, thepatientleft the hospitalagainstmedical advice and did not return. Discussion. There have been 2 publishedcase reports of AIN related to linezolid.P Our patient had clinical manifestations similar to those in these cases, including maculopapular rash, facial edema, eosinophilia, and elevations in SCr,all of which developed within I week of linezolid exposure and responded with supportivecare, corticosteroids,and linezoliddiscontinuation. According to the Naranjoprobability scale, the likelihood of linezolid having caused this reaction is probable.' The majorityof AIN cases are inducedby drug therapy," Withthe exception of vancomycin, our patient was not receivingany other classesof drugs that would be suspectedof inducing AIN.However,he receivedvancomycin withoutcomplications during both hos...
