Pneumocystis carinii pneumonia during maintenance anti-tumor necrosis factor-α therapy with infliximab for Crohn's disease

Background: Clinical trials using infliximab have not reported cases of Pneumocystis carinii pneumonia (PCP), and PCP infection during standard medical treatment of inflammatory bowel disease is uncommon. Postmarketing Surveillance through June of 2001 has identified 10 cases of PCP occurring during treatment with infliximab; 3 patients died. Case History: A 19-year-old man with Crohn's colitis developed thrush, leukopenia, fever, shortness of breath, and dry cough 21 months after initiating maintenance therapy with azathioprine and infliximab. Azathioprine had been at a stable dose of 75 mg per day (1 mg/kg) and the patient had received his 14th infusion of infliximab 4 weeks prior to presentation. Evaluation revealed the presence of Pneumocystis carinii on induced sputum. Azathioprine was discontinued, and the patient improved after initiating treatment with steroids and trimethoprim-sulfamethoxazole. Follow-up 2 weeks later confirmed clinical response to therapy. Conclusions: This case report describes the uncommon occurrence of Pneumocystis pneumonia in the setting of maintenance therapy for Crohn's disease using infliximab and azathioprine. Mechanisms by which azathioprine and infliximab may impair the natural defense mechanisms against Pneumocystis are discussed.