A 43-year-old Taiwanese man was admitted because of septic arthritis presented with progressive right hip pain for 1 week. Eight years earlier, the patient had received a diagnosis of HIV infection, for which he started receiving tenofovir, lamivudine, and nevirapine with good adherence and response (Fig. 1a). He had no other chronic medical conditions, denied any use of immunosuppressants, and encountered no stressful event before disease onset.

After admission, he underwent debridement of the right hip in addition to empiric antibacterial therapy. Both blood cultures and surgical specimen cultures subsequently grew Salmonella spp. group D. His pain and mobility improved after a 6-week course of ciprofloxacin, and the C-reactive protein (CRP) level gradually decreased from 17.89 to 3.53 mg/dl. However, he reported aggravated right hip pain 1 month later, with an increased CRP level (15.30 mg/dl). MRI of the pelvis showed severe osteomyelitis of the right hip joint with multiple surrounding tiny abscesses, as well as infective spondylodiskitis of the left lumbar spine (Fig. 1b). A second surgical debridement was performed, and the histopathological examination of the excised femoral head and surrounding tissue revealed caseating granuloma with the presence of acid-fast bacilli. A QuantiFERON-TB Gold in-Tube (QFT-GIT; Qiagen, Carnegie, Australia) assay was conducted and the result was indeterminate because of low mitogen response. The culture of the surgical specimen revealed MAC ultimately.