Immunoresititution disease in relation to infection with Mycobacterium avium complex and to leprosy.

Cheng et al. [1] have reviewed the Eng-lish-language literature on immunores-titution (or immune reconstitution) disease (IRD), which describes a total of 107 patients, some of whom were HIV-negative and some HIV-positive. There were 2 reports that described 10 cases of IRD due to atypical mycobacterial infection ; all but 1 of these cases were infections with Mycobacterium avium complex. Not included were 10 other reports [2–11] that described 32 additional cases of mycobacterial IRD, which were due variously to M. avium complex (29 cases), Mycobacterium genavense (1 case), and unknown species (2 cases, for which smear results were positive but culture results were negative). Cheng et al. [1] state that the diagnosis of IRD is one of exclusion. This is true for patients who are diagnosed with IRD due to an opportunistic infection for which treatment is initiated but whose signs and symptoms subsequently show " paradoxical worsening " at the time of immune reconstitution (e.g., tuberculosis). All 17 reported episodes of HIV-related IRD due to M. tuberculosis infection were recognized and partially treated prior to the onset of IRD, which underlines that it is important to search carefully for various possible causes for the apparent failure of antituberculous therapy. However, for 32 (84%) of the 38 reported cases of IRD due to infection with M. avium complex, the mycobac-terial infection was unrecognized and usually subclinical prior to immune re-constitution. The " unmasking " of sub-clinical disease is a phenomenon associated with M. avium complex infection, but not with tuberculosis. This may be because M. avium complex infection is associated with a lower pathogenicity and, probably, a longer duration of sub-clinical disease than is tuberculosis [12]. In addition, a number of unusual features deserve mention that help distinguish infection with M. avium complex that is associated with IRD from the more usual disseminated disease in HIV-infected patients. These features include the following: disease that is frequently localized to lymph nodes coupled with blood culture results that are negative for mycobacteria; caseous necrosis of involved nodes and the development of draining sinuses (6 [75%] of 8 cases due to M. avium complex in one series [2]); the absence of wasting in most cases; a temporal association with an excellent viro-logic and immunologic response to antiretroviral therapy, reflected by a decreasing HIV plasma virus load and, usually , an increasing CD4 count; and much improved, long-term survival [13]. Given these observations, the …