Immune reconstitution inflammatory syndrome (IRIS) is a condition seen in some cases of HIV/AIDS or immunosuppression, in which the immune system begins to recover, but then responds to a previously acquired opportunistic infection with an overwhelming inflammatory response that paradoxically makes the symptoms of infection worse.

While this inflammatory reaction is usually self-limited, there is risk of long-term symptoms and death, particularly when the central nervous system is involved.

[5] The suppression of CD4 T cells by HIV (or by immunosuppressive drugs) causes a decrease in the body's normal response to certain infections.

Persons living with AIDS are more at risk for IRIS if they are starting HAARTTooltip HAART for the first time, or if they have recently been treated for an opportunistic infection (OI).

[9][10][11] The general mechanism behind IRIS is increased inflammation as the recovering immune system recognizes the antigens of the fungus as immunosuppression is reversed.

Steroids given to persons with anti-fungal treatment failure / cryptococcal relapse (in whom CSF cultures are not sterile) can be a fatal iatrogenic error.

Common features that may be present include clinical worsening after starting ART and localized tissue inflammation.

[19][20] IRIS was discovered in the 1980s when physicians noted paradoxical symptomatic worsening of patients being treated for pulmonary tuberculosis and leprosy.

[3] Bats recovering from white-nose syndrome (WNS) may be the first known natural occurrence of IRIS, in a report released by the USGS.

[21] WNS is typified by a cutaneous infection of the fungus Pseudogymnoascus destructans during hibernation, when the immune system is naturally suppressed to conserve energy through the winter.

This study suggests that bats undergoing an intense inflammation at the site of infection after a return to euthermia is a form of IRIS.