Mitral valve prosthesis endocarditis unveiling metastatic colorectal cancer as the primary infection source: a case study

Background This case report is significant due to its illustration of how infectious endocarditis on a prosthetic mitral valve revealed an underlying metastatic colorectal cancer. Although uncommon, associations between cardiac infection and advanced malignancy, particularly with malignancy serving as the source of infection, have been documented in the literature, making this case clinically significant and complex. Case presentation A 54-year-old postmenopausal woman with insulin-dependent diabetes and poorly managed hypertension, who had previously undergone mitral valve replacement with a mechanical prosthesis and tricuspid valve repair for rheumatic mitral stenosis, was admitted for atrial fibrillation with rapid ventricular response. On admission, she presented with normochromic normocytic anaemia (7.7 g/dL), elevated inflammatory markers (CRP 250 mg/L), and leukocytosis (14,000/µL, neutrophils 10,000/µL). Transthoracic and transesophageal echocardiography identified vegetation on the mitral prosthesis with elevated gradients. Blood cultures were positive for Escherichia coli. A thoraco-abdominopelvic CT scan revealed a rectal tumor, confirmed by FDG-PET, with features consistent with metastatic colorectal cancer, considered the entry point for the infectious endocarditis. Tumor markers including ACE, CA 19 − 9, and CA 72 − 4 were elevated. The patient was treated with dual antibiotic therapy and showed initial clinical improvement but later died due to ventricular tachycardia. Conclusions This case highlights the importance of considering atypical sources, such as metastatic cancer, in unresolved cases of endocarditis. It underscores the need for comprehensive diagnostic assessment, including oncologic evaluation, in patients with prosthetic valve endocarditis caused by atypical pathogens like E. coli. It also stresses the importance of multidisciplinary collaboration between cardiology and oncology teams. This case report is significant due to its illustration of how infectious endocarditis on a prosthetic mitral valve revealed an underlying metastatic colorectal cancer (CRC).