Introduction:
Infection of the sternoclavicular joint is a rare condition,
representing less than 1% of all bone infections. Most patients who
develop this condition have known risk factors, such as
immunosuppression, diabetes, intravenous drug use, or rheumatoid
arthritis1. The acquisition of MRSA-positive septic
arthritis can be attributed to various factors and sources.
Staphylococcus aureus, including methicillin-resistant strains, is a
predominant pathogen responsible for a significant proportion of septic
arthritis cases, with MRSA accounting for 6% to 22% of S. aureus
isolates2. Particularly injection drug users are at a
higher risk for MRSA infections and joint complications, including
septic arthritis, though this association is relatively rare and lacks
proper documentation3. This case report details a rare
presentation of MRSA-positive septic arthritis in a patient with a
history of multiple intravenous (IV) and intramuscular (IM) injections.
The rarity of this case is the presence of a mass in the left
sternocleidomastoid muscle extending into the left superior mediastinum
with associated lymphadenopathy, giving the impression of a mediastinal
malignancy. Radiology revealed sternoclavicular septic arthritis. The
involvement of the sternoclavicular joint in septic arthritis is
uncommon, and when coupled with atypical presentations mimicking other
conditions like mediastinal masses, the diagnosis becomes
challenging4. The combination of MRSA-positive septic
arthritis, sternoclavicular joint involvement, mediastinal mimicry, and
a history of multiple injections creates a unique and rare clinical
scenario that requires careful evaluation and
management5.