Tuberculosis Not The Only Risk From New Immunological Drugs

As many as 50 million Americans may suffer from immunological disorders that are treated with drugs that suppress immunity. Among these drugs are agents that inhibit tumor necrosis factor-á (TNF), a cytokine receptor involved in cellular communication. It is known that anti-TNF therapies are associated with an increased risk of tuberculosis.

The new survey of infectious diseases physicians indicates that there is probably greater risk for other serious infections in these patients. Survey respondents reported 73 cases of Staphylococcus aureus, 56 cases of histoplasmosis, and 32 nontuberculosis mycobacterial infections among patients using these immune-modulating therapies, compared to 17 tuberculosis cases.

Kevin Winthrop, MD, of the Oregon Health and Sciences University, said: "While much attention has so far focused on tuberculosis cases occurring in patients using anti-TNF therapies, our findings suggest that nontuberculosus mycobacterial infections, histoplasmosis, and invasive S. aureus infections might all be occurring more frequently than TB in this setting within the United States."

Patients are usually screened for tuberculosis prior to initiating anti-TNF therapy and this should continue, say the authors. However, clinicians should be vigilant not just for TB, but also for nontuberculosis mycobacterial infections in patients who are beginning or using these drugs, particularly those patients with underlying lung disease from rheumatoid arthritis, emphysema, or other conditions. In addition, clinicians should also be vigilant for mycobacterial infections in patients using rituximab (Rituxan), as a small number of the cases reported in this series occurred in patients using this B lymphocyte depletion therapy.

 The survey published is in the June 1 issue of Clinical Infectious Diseases, currently available online.

The survey was conducted via the Emerging Infections Network of the Infectious Diseases Society of America. The network comprises about 900 infectious diseases physicians, who communicate via fax or the Internet. In this survey, 426 network members from throughout North America reported on the tuberculosis or nontuberculosis mycobacterial infections that they had seen in the previous six months. This survey and its results highlight the utility of the network as an active surveillance tool for emerging infectious complications associated with new drug therapies.