Culture-negative Prosthetic Valve Endocarditis Presenting As a Cystic Mass

A 58-year-old immunocompetent patient with previous prosthetic valve presented with chest pain, constitutional symptoms and septic shock. Blood cultures and transthoracic echocardiogram were negative, but the patient was initiated on broad spectrum antibiotics due to high clinical suspicions of infective endocarditis. The patient received a transoesophageal echocardiogram revealing a cystic bioprosthetic valve lesion. Culture-negative endocarditis workup identified active disseminated histoplasmosis with likely Histoplasma endocarditis. A multidisciplinary discussion was held, and the patient was deemed high-risk for a third re-do open heart surgery. He was treated medically with anti-fungal treatment with good clinical recovery.