Background: Sternal osteomyelitis following median sternotomy is an extremely uncommon type of deep sternal wound infection. It is considered a life-threatening complication that may develop after cardiothoracic surgery (2). Its occurrence is relatively low, ranging from 0.2% to 8%, with an associated mortality rate ranging from 8% to 45% (2). Due to this reason, a high index of suspicion is required in the Emergency Department setting to reach ultimate diagnosis. Case presentation: We detail a case of a middle-aged man with a history of aortic dissection repair 2 years ago who visited the emergency department with a 4-day history of chest pain and low-grade fever. Clinical evaluation revealed a tender sternal mass and diagnostic testing revealed elevated inflammatory markers and cardiac enzymes. CT angiogram displayed a destructive sternal lesions. He was admitted with a preliminary diagnosis of sternal osteomyelitis and received a multidisciplinary treatment approach, involving cardiac surgery and infectious disease specialists. Subsequent MRI confirmed the diagnosis, and aspirated subcutaneous collection culture grew Cutibacterium Acnes. This organism is a novel causal agent of sternal osteomyelitis, which has rarely been documented in literature. Subsequently, the patient was treated with a 6-week course of antibiotics. Conclusion: Sternal osteomyelitis is a difficult diagnosis to establish in the emergency department. A high index of suspicion and thorough history is necessary for appropriate disposition and ultimate management.

Keywords: case report; sternal osteomyelitis; sternotomy, Cultibacterium Acnes