Immune reconstitution inflammatory syndrome in Mycobacterium chimaera mediastinitis: When clinical judgment trumps imaging.

Mycobacterium chimaera has been described in postoperative cardiovascular procedures in patients after an outbreak of contaminated 3T heater-cooler units. Immune reconstitution inflammatory syndrome (IRIS) has been mostly reported in immunocompromised patients, especially HIV after starting therapy. Our case is a 52-year-old immunocompetent male who was diagnosed with M. chimaera mediastinitis a year after Type A dissection repair and was started on quadruple antimicrobial therapy. He clinically improved but 8 months into therapy he presented with a declining kidney function, pancytopenia, and hypercalcemia which after bone marrow and kidney biopsies were attributed to IRIS. Our patient's diagnosis spared him subsequent surgery. IRIS during the treatment of nontuberculous mycobacteria must be suspected even in immunocompetent patients as reaching the diagnosis is very helpful in preventing additional diagnostic and therapeutic measures.