From Heart Murmur to Bone Involvement: Tricuspid Valve Endocarditis With First-Rib Osteomyelitis in a Patient With Methicillin-Resistant Staphylococcus aureus (MRSA) Bacteremia.

Tricuspid valve infective endocarditis (TVIE) is most commonly associated with intravenous drug use and Staphylococcus aureus bacteremia. While right-sided endocarditis may present with septic pulmonary emboli, hematogenous spread to the bone is a rare but serious complication. Among osseous sites, first-rib osteomyelitis is particularly uncommon and may be underrecognized in patients presenting with localized chest pain or swelling. We present the case of a 37-year-old woman with intravenous substance use who presented to the emergency department with left-sided upper chest pain, swelling, and erythema for two weeks. The patient was tachycardic on arrival. Laboratory evaluation revealed anemia, eosinophilia, and elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels. Computed tomography (CT) of the chest revealed findings consistent with first-rib osteomyelitis with phlegmon formation. The patient received initial antibiotic therapy in the emergency department, followed by admission for intravenous (IV) antibiotic administration and Infectious Disease consultation. This case highlights the importance of prompt recognition of osteomyelitis involving uncommon osseous structures to prevent further systemic complications and facilitate timely antimicrobial and surgical management.