Tuberculosis in blood and marrow transplant recipients

Although one third of the world's population is infected with tuberculosis (TB), TB in blood and marrow transplant (BMT) recipients is relatively less well studied, as the incidence of TB is relatively low in developed countries with BMT units. Since the report of the first two cases in 1983, 52 cases of TB complicating BMT have been reported in the English literature from BMT centers in ten different countries. Not unexpectedly, the two largest series were reported from areas with a high incidence of TB in the general population, with about 45 cases per 10(5) inhabitants per year in Spain and about 100 cases per 10(5) inhabitants per year in Hong Kong respectively. The overall frequency of occurrence of TB in BMT recipients was 0.4% (52 cases among 13 881 BMT recipients), with a male:female ratio of 11:9 and median age of 33 (range 7-57). The incidence of TB in the general population is a major predictor of a higher frequency of occurrence in BMT recipients. Moreover, allogeneic transplantation, graft-versus-host disease, and total body irradiation were found to be risk factors associated with TB. Among the 48 cases in whom the time of manifestation were reported, only one case manifested during the neutropenic period (day 11). On the other hand, 11 cases (23%) manifest after engraftment but before day 100, and 36 (75%) manifest after day 100. The most important aspect towards making the diagnosis is a high index of suspicion, as TB occurred in relatively low frequencies especially in developed countries, and the clinical patterns usually mimic other more common infectious and non-infectious complications after BMT. As the incidence of drug resistant TB is increasing, we prefer to treat our patients for at least one year (as compared with six months in immunocompetent hosts) with four drugs in the first six months and two or three drugs for another six months. In those patients who could not tolerate oral medication, we used an intravenous regimen of rifampicin, ciprofloxacin, and amikacin until oral therapy could be instituted. The absence of relapse after termination of treatment in our patients suggested that secondary prophylaxis would not be necessary as long as immune function has been restored. With the rising incidence of TB in countries that previously enjoyed a very low prevalence of TB, attributed to the growing population of HIV-infected subjects with TB, and the changing patterns of population migration, it is important to bear a high index of suspicion of Mycobacterium tuberculosis as a pathogen in BMT recipients.