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Dr. Kaur, et al reply To the Editor: Drs. Fitch and Cron describe a case of abscess formation in a child with juvenile idiopathic arthritis who was being treated with prednisone, methotrexate (MTX), and etanercept. Our patient had rheumatoid arthritis with overlap features and developed septic arthritis and abscess formation with Actinobacillus ureae while on treatment with MTX and etanercept. We agree with their conclusion to pay close attention to safety profiles of all biologic agents. However, Fitch and Cron raise the possibility that all TNF-a inhibitors do not share the same risks for infections, based on a study of a primate model by Song, et al1. The study showed that administration of anti-TNF-a monoclonal antibody to S. aureus-challenged monkeys results in both a delay in the onset and a reduction in the incidence and severity of abscess formation, compared with saline administration1. They also administered etanercept using the same regimen, which resulted in a modest increase in the incidence of abscess formation and no improvement in the severity of abscess formation, compared with saline administration1. It is hard to predict how these findings will translate to clinical significance in humans, since abscess formation has been reported in patients being treated with all TNF-a inhibitors2-5. Septic arthritis6,7 and osteomyelitis8 have been reported in patients treated with infliximab. Therefore physicians should be vigilant to discern the earliest signs of infections in all patients treated with any of the biologic agents. PRIMAL P. KAUR, MD, Assistant Professor of Medicine, Division of Rheumatology, Temple University School of Medicine, 3401 N. Broad Street, Philadelphia, Pennsylvania 19140, USA. E-mail: primal.kaur@tuhs.temple.edu; CHRIS T. DERK, MD, Assistant Professor of Medicine, Division of Rheumatology, Thomas Jefferson University, Philadelphia, PA; MELANIE CHATTERJI, MD, The Arthritis Group, Philadelphia, PA; RAPHAEL J. DEHORATIUS, MD, Professor of Medicine, Division of Rheumatology, Thomas Jefferson University, Philadelphia, PA. REFERENCES 1. Song XY, Fox F, Gallo MA, et al. Effects of 2 different anti-tumor necrosis factor-a agents in a primate model of subcutaneous abscess formation. J Infect Dis 2002;185:204-13. 2. Giles JT, Gelber AC, Nanda S, Bartlett SJ, Bathon JM. TNF inhibitor therapy increases the risk of post-operative orthopedic infection in patients with rheumatoid arthritis [abstract]. Arthritis Rheum 2004;50 Suppl:S660. 3. Ricart E, Panaccione R, Loftus EV, Tremaine WJ, Sandborn WJ. Infliximab for Crohn's disease in clinical practice at the Mayo Clinic: the first 100 patients. Am J Gastroenterol 2001;96:722-9. 4. Baeten D, Kruithof E, van den Bosch F, et al. Systematic safety follow up in a cohort of 107 patients with spondyloarthropathy treated with infliximab: a new perspective on the role of host defence in the pathogenesis of the disease? Ann Rheum Dis 2003;62:829-34. 5. Kress S. Clinical review: adalimumab for use in treatment of rheumatoid arthritis. Center for Biologics Evaluation and Research, Office of Therapeutics Research and Review, Division of Clinical Trial Design and Analysis, Immunology and Infectious Diseases Branch, HFM-582. Bethesda, MD: National Institutes of Health; 2002:1-25. Available from: www.fda.gov/cder/biologics/review/adalabb123102r1p1.pdf. Accessed February 1, 2006. 6. Katsarolis I, Tsiodras S, Panagopoulos P, et al. Septic arthritis due to Salmonella enteritidis associated with infliximab use. Scand J Infect Dis 2005;37:304-5. 7. Strusberg I, Bertoli AM, de Pizzolato RC, Fierro G, Strusberg AM. Use of infliximab in patients of a rheumatologic center. Medicina Buenos Aires 2005;65:24-30. 8. Maksymowych WP, Jhangri GS, Lambert RG, et al. Infliximab in ankylosing spondylitis: a prospective observational inception cohort analysis of efficacy and safety. J Rheumatol 2002;29:959-65. |