Sternal mycobacterial infections

Isolated primary cold abscess of the sternum: a case report

Background

Musculoskeletal tuberculosis forms 10–25% of extrapulmonary tuberculosis which mainly involves the spine or weight-bearing joints. Tuberculous involvement of the sternum is a rare clinical entity even in countries where tuberculosis has high prevalence. Primary tuberculous sternal osteomyelitis accounts for approximately 0.3% of all types of tubercular osteomyelitis and the probable source appears to be extension from paratracheal or hilar lymph nodes. Despite tuberculosis being a common disease in endemic countries and worldwide, a thorough literature search of the PubMed database for keywords “primary tuberculosis of sternum” and “primary tuberculous osteomyelitis of sternum” yielded 30 and 22 articles, respectively.

Case presentation

We present an unusual case of a large dumb-bell-shaped cold abscess arising due to infection of the sternum. A 23-year-old immunocompetent Asian woman presented with a gradually progressing painless swelling on anterior chest wall for the last 5 months. She had a large visible swelling on anterior chest wall which was 12.5 cm in diameter, soft, non-tender, temperature was not raised, and fluctuant. Magnetic resonance imaging showed a large dumb-bell-shaped hyperintense collection in upper anterior chest wall with marrow edema and cortical irregularity in left side of manubrium. Pus was positive for nucleic acid testing (cartridge-based nucleic acid amplification test) for Mycobacterium tuberculosis and later culture was also positive. She was started on anti-tubercular therapy and aspirated twice. Currently, she has completed 6 months of therapy and the swelling has now disappeared.

Discussion

Swelling, pain localized to sternum, or ulceration of the skin with discharging sinus along with or without constitutional symptoms are the usual presentation. A high element of suspicion is needed for early diagnosis and treatment to prevent its complications. Sternal mycobacterial infections are categorized as primary, secondary, and/or acquired postoperatively. Although radiological investigations aid in diagnosis, the diagnosis is established by positive culture or histopathological examination. Anti-tubercular therapy is the mainstay of treatment with standard four-drug regimen for 6–9 months. Surgical drainage of the abscess should be considered only if it does not resolve by aspiration and anti-tubercular therapy.

Delayed diagnosis of chronic postoperative sternal infection: a rare case of sternal tuberculosis

Sternal osteomyelitis secondary to mycobacterium tuberculosis (TB) is rare, with <1% of musculoskeletal TB cases reported. The recurrent scenario is unresolving infection and delayed diagnosis. A 75-year-old woman presented with a persistently discharging sternal wound 10 months after coronary artery bypass grafting. Multiple antibiotics, wound debridement and removal of sternal wires was attempted; however, progression to local osteomyelitis and sternoclavicular joint destruction occurred. Tissue biopsies were finally sent for mycobacterial culture testing positive for Mycobacterium tuberculosis High index of suspicion is necessary for diagnosis of sternal tuberculosis, confirmed through timely microbiological investigations. MRI may identify soft-tissue and bone oedema characteristic of TB osteomyelitis. This patient had no TB risk factors. The source of infection is unclear and warrants further investigation. Sternal TB osteomyelitis is uncommon and largely reported through case reports, thus management and indications for surgery remain undefined. If sensitive, standard TB four-drug regimen may be trialled.