054 A case of azathioprine-induced fever

Abstract

Background: Fever is a common presenting complaint and in patients with existing rheumatological diagnosis, can represent a flare of the underlying disease, an infection secondary to immunosuppression or an occult malignancy. Drug induced fevers represent less than 1% of all fevers but is an important differential diagnosis to consider. Methods: A 36-year-old Gujarati male was diagnosed in October of 2016 with Behçet's disease associated with pulmonary vasculitis based on a constellation of symptoms, a negative autoimmune screen and a positive PET-CT. Initial treatment with high dose steroids and infliximab failed to induce remission and following recurrent admissions, the decision was made to switch from infliximab to intravenous cyclophosphamide. Following six cycles of treatment, his disease was in remission and azathioprine (AZA) was introduced as a maintenance agent with an on-going steroid taper. Within 24 hours of starting AZA, he was admitted via A&E with fevers, severe headaches and arthralgia. Due to a concern of a meningoencephalitis, a full septic screen was performed, AZA withheld and IV ceftriaxone and acyclovir was commenced immediately. Initial observations revealed he was febrile (Temperature 39.7) and tachycardiac (heart rate 110) with a blood pressure of 126/76. Clinical examination revealed long-standing crackles at the right base, a mild degree of neck stiffness and generalised arthralgia with no synovitis. Bloods showed a WC of 14 (neutrophilia) and a CRP of 125. Chest x-ray, CT head and MRI head were reportedly normal. Three sets of blood cultures and urine cultures were negative for infection. Within 24 hours, the fevers abated and at 72 hours he was clinically well and the CRP was down to 25. He was discharged home on a course of oral co-amoxiclav. AZA was restarted on discharge. Two days later, he re-presented with a similar constellation of symptoms. On the second admission, in addition to all of the other tests, a CT Chest abdomen and pelvis performed revealed no occult infections. A review of the second admission revealed a very similar clinical pattern of recovery and an almost identical trend in the resolution of CRP (again over 72hours) with no antibiotic therapy. Results: The onset and cessation of fevers on each admission were closely related to the initiation and withdrawal of AZA, clinching the diagnosis of a drug-induced fever. AZA was discontinued indefinitely with no recurrence of fevers. His Bechet's remains in remission on MMF and a weaning regime of steroid. Conclusion: In rheumatology, azathioprine, allopurinol and bisphosphonates are common causes of a drug induced fevers. Although rare, we urge physicians to consider drug induced fever when presented with patients with new onset fever. As in this case, considering the diagnosis may have saved re-admission and so many unnecessary tests.