Atypical bone lesion of the fifth metatarsal bone in an HIV-positive patient: A challenging radiologic-pathologic correlation of tuberculous osteomyelitis

Musculoskeletal tuberculosis (TB) represents a small fraction of extrapulmonary TB, accounting for only 1%-3% of cases. Involvement of the foot bones is exceedingly rare, particularly in adults, and often mimics neoplastic or pyogenic processes. Early diagnosis is challenging, especially in immunocompromised individuals, where radiologic findings can be atypical. We describe a 66-year-old HIV-positive male (CD4 count 17 cells/μL) who presented with progressive bilateral foot swelling. Radiography revealed a permeative osteolytic lesion with cortical thinning of the left fifth metatarsal bone. Ultrasound identified a complex fluid collection extending into deep soft tissues. MRI demonstrated marrow infiltration, cortical disruption, and an adjacent abscess with peripheral enhancement, raising suspicion for subacute osteomyelitis versus soft-tissue sarcoma. Surgical debridement and partial metatarsal resection were performed. Histopathology showed granulomatous inflammation with caseous necrosis, and cultures confirmed <i>Mycobacterium tuberculosis</i>. The patient declined antituberculous and antiretroviral therapy, opting for local management only. This case underscores the diagnostic complexity of tuberculous osteomyelitis in atypical locations and immunocompromised hosts. The multimodal imaging approach integrating conventional radiography, ultrasound, and MRI was pivotal in characterizing the lesion and guiding biopsy. Despite suggestive imaging findings, definitive diagnosis required histopathologic and microbiologic confirmation. Tuberculous osteomyelitis of the foot is a rare but important consideration in the differential diagnosis of aggressive bone lesions, particularly in HIV-positive patients. Radiologists play a critical role in early recognition, facilitating timely biopsy and appropriate management to prevent irreversible complications.