Measles in bone marrow transplant recipients

Machado et al1 should be congratulated on seizing the opportunity of the 1997 measles outbreak in São Paulo, Brazil, for learning about measles in marrow transplant recipients. Per the report, only 8 of 156 patients (5.1%) developed measles, and only 1 patient (0.6%) had a severe disease (measles pneumonia). But both the incidence and the severity of measles were likely underestimated. Measles was defined by seroconversion (appearance or 4-fold rise of specific antibodies). A significant fraction of transplant recipients cannot seroconvert (reviewed in Storek and Witherspoon2and in Parkman and Weinberg3). In the São Paulo study, patients with symptoms or signs of measles who did not seroconvert were considered to be patients without measles. The immunity of the patients who could not seroconvert was probably more compromised than the immunity of the patients who could seroconvert. Therefore, the incidence of measles in the patients who could not seroconvert may have been high and the course of the disease in these patients may have been severe. Thus, substantially more than 5.1% transplant recipients may develop measles during an outbreak, and substantially more than 0.6% patients may have a severe course.