A 69-year-old man with a 10-year history of diabetes mellitus and 1-year history of steroid treatment for nonspecific interstitial pneumonia presented with a nightly fever of over 39°C after surgery for a false abdominal aortic aneurysm. Hypercalcemia was detected, despite acute renal dysfunction. There was no laboratory evidence of collagen disease or infection including tuberculosis. Polymerase chain reaction (PCR)-based amplification of DNA from a bone marrow biopsy specimen revealed Mycobacterium tuberculosis. Antituberculous chemotherapy was initiated. Early bone marrow biopsy and the use of new techniques such as PCR can avoid delay in initiating the proper treatment for compromised patients.