A case report of Histoplasma capsulatum prosthetic valve endocarditis: an extremely rare presentation with characteristic findings

Histoplasma capsulatum is an extremely rare cause of prosthetic valve endocarditis (PVE) and can present with non-specific symptoms leading to a delay in diagnosis with unfavourable outcomes.

A 65-year-old male patient with a history of a bioprosthetic aortic valve replacement and non-obstructive coronary artery disease was admitted for altered mentation, failure to thrive, and a 20-pound unintentional weight loss over the past 4 months. Upon examination, he was lethargic but afebrile and haemodynamically stable. A late peaking ejection murmur was heard on exam. Skin exam was significant for embolic phenomenon involving the extremities. Inflammatory markers and serum calcium were elevated. A bedside echocardiogram showed severe obstruction across the aortic valve prosthesis. Two years prior, he had an echocardiogram with a normal functioning prosthesis. Routine blood cultures were negative and serologic screening was unrevealing. Urine Histoplasma antigen screen was positive on hospital day 3 and on hospital day 10, fungal blood cultures were positive for H. capsulatum. Unfortunately, the patient died shortly afterwards as a result of multiorgan failure from embolic manifestations of the infection.

Based on our patient's findings and those of previously reported cases in the literature, H. capsulatum PVE should be strongly considered in patients from endemic areas with non-specific symptoms and negative routine blood cultures.