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

BACKGROUND : 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. CASE SUMMARY : 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. DISCUSSION : 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.