Case Report: Fatal prosthetic valve endocarditis due to Staphylococcus lugdunensis—a wolf in coagulase-negative clothing

<i>Staphylococcus lugdunensis</i> is a rare but highly virulent coagulase-negative <i>Staphylococcus</i> (CoNS) capable of causing aggressive native and prosthetic valve endocarditis. Unlike other CoNS, it resembles <i>S. aureus</i> in its ability to rapidly destroy cardiac structures and cause systemic complications. We present a woman in her 70s with a prosthetic mitral valve who initially presented with altered mental status and was diagnosed with <i>S. lugdunensis</i> prosthetic valve endocarditis. Despite targeted intravenous antibiotics, her condition deteriorated rapidly, and she unfortunately died within 5 days of admission. This case highlights the need to distinguish <i>S. lugdunensis</i> from other CoNS and to recognize its aggressive course and limited response to antibiotics alone.