Azathioprine hypersensitivity reactions: Caution upon rechallenge

✍ Scribed by Sandra Knowles; Neil H. Shear

• Book ID: 101249402
• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 14 KB
• Volume: 20
• Category: Article
• ISSN: 0148-639X
• DOI: 10.1002/(sici)1097-4598(199711)20:11<1467::aid-mus19>3.0.co;2-z

✦ Synopsis

We read with interest and trepidation the letter to the editors entitled ''Fever as sole and delayed manifestation of azathioprine hypersensitivity.'' 1 The authors report a patient who developed fever of unknown origin and elevated creatine kinase and erythrocyte sedimentation rate (ESR). He had been receiving azathioprine and prednisone therapy for 16 months. Workup for infectious causes was negative; after discontinuation of azathioprine, the fever resolved. The fever reappeared when azathioprine was reintroduced on two separate occasions.

Although the patient developed no serious consequences upon azathioprine rechallenge, there are over 30 cases in the literature describing severe reactions following rechallenge with azathioprine. 2,3 In these patients, a fever with or without gastrointestinal symptoms most commonly develops within hours or weeks after initiation of the azathioprine. Because the initial reaction is often misdiagnosed as an infection, a rechallenge is mistakenly carried out. Upon azathioprine rechallenge, the reaction is generally more severe and on many occasions life-threatening. As well, the ''rechallenge'' reaction usually manifests itself more rapidly than the initial episode. Hypotension or shock is reported in approximately one third of the cases. Dermatologic eruptions, hepatotoxicity, and nephritis have also been reported.

Because of the potential severity of the reaction upon rechallenge, we advise extreme caution in rechallenging any patient who experiences fever, hypotension, arthalgias, severe nausea, vomiting, and/or leukocytosis while on azathioprine.