• Immunodeficiency
• Atypical Mycobacterial Infection

A previously healthy 64-year-old woman presented with a 2-month history of anterior chest pain. Physical examination disclosed a 3.5×6.0 cm tender mass protruding from her mid-sternum and crusted herpes zoster lesions on her left arm. CT revealed a 3.8×4.2×6.2 cm sternal mass with osteolytic destruction, mild bronchiectasis in the lingula of the left upper lobe and multiple osteolytic lesions over vertebrae and ribs (figure 1A–C). Bone scintigraphy revealed increased tracer uptake at skull, sternum, ribs, vertebrae and pelvic bones (figure 2A). Pathological findings of the sternal tumour biopsy were necrotising granuloma and the presence of acid-fast bacilli (figure 1D–E). The specimen and sputum were culture-positive for Mycobacterium avium complex. The patient was tested negative for HIV but positive for high-titre neutralising anti-interferon-γ (IFN-γ) autoantibodies, suggesting IFN-γ autoantibody-related disseminated non-tuberculous mycobacterial (NTM) infection.