Tuberculosis and transplantation: battling the opportunist.

Tuberculosis (TB) reactivation after solid-organ transplant carries significant morbidity and confers high mortality (up to 30%) [1]. Incidences among transplant recipients vary—the variation depends primarily on geographic location, and incidences range from !1% in Europe and North America to 2%–15% in Africa, the Middle East, and Asia—but are generally greater than those in the general population. Rates also vary depending on the type of organ transplant performed as well as on local screening practices and immu-nosuppression protocols. In this issue of Clinical Infectious Diseases, Torre-Cisneros et al. [2] review a large Spanish database of information on organ transplant recipients (the RESITRA [Spanish Network of Infection in Transplantation] cohort) and describe an incidence of posttransplant TB of 512 cases per 10 5 patients per year in their cohort. This was significantly greater than the incidence for the general population of the country, among whom the incidence was 18.9 cases per 10 5 inhabitants per year, resulting in 26.6-fold greater relative risk. Perhaps the most comprehensive analysis conducted to date of the epidemiology of TB after transplant was published in 1998 by Singh and Paterson [1], who reviewed the published literature on TB and transplantation. Their analysis found that approximately two-thirds of TB cases occurred during the first year after transplant. Risk factors for early posttransplant TB included nonrenal transplant, allograft rejection occurring !6 months before the onset of TB, and primary immunosup-pression with muromonab-CD3 or other T cell–depleting agents. The majority of reactivation cases were pulmonary, although at least one-third of cases were disseminated. It is clear from published series that the diagnosis of active TB is often delayed because of atypical presentations and should be suspected in transplant recipients presenting with fever of unknown origin, pulmonary mass le-sions, or meningoencephalitis. A broad range of opportunistic infections are included in the differential diagnosis of such presentations. In the RESITRA cohort, the greatest incidence of posttransplant TB was observed among lung transplant recipients. Lung transplant recipients are at greater risk for pulmonary infection in general, because they are more immunosuppressed and the allograft is in direct contact with the environment. It is difficult to discern from Torre-Cisneros et al.'s study whether the TB in the lung transplant recipients represented reactivation of latent TB, new infection after transplant, or donor-derived infection. Donor-derived TB is thought to represent ∼4% of TB cases described in the literature [1]. A determination of donor transmission can be …