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

Abstract

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.

“Not much room for mushrooms” in the heart: knowns and unknowns of fungal infective endocarditis

“…As a result, many complications may be underreported and there might be a publication bias concerning the uniqueness of a case or an unexpected outcome. This could be the reason for the surprisingly low mortality rate of the current case series, particularly those with prosthetic valve endocarditis (PVE) [1,53,58,80,89,103,107] . However, in line with prior observations, Candida species, with a reported 40%-60% rate [44,52,57,60,69,62,94,96,123,126] , is the most frequently reported infectious agent in the current case series.…”

“…For Histoplasma, serologic examination can be performed [106] , which is useful in areas where this organism is endemic [104,106,107] . Another difficulty arises when bacteria and fungi are identified simultaneously [73,77,78,103] or cultures are positive for bacteria without demonstration of fungi, while the latter can be found in the excised valve, indicating a mixed infection. The presence of bacteriemia should not reduce the suspicion of fungal IE, if other indicators such as large vegetation and emboli are present [74] .…”

“…If TTE is inconclusive and a degree of suspicion remains, TEE is indicated. Transesophageal echocardiography is more sensitive and specific compared to TTE, but serial examination is often required [41] , especially with a graft of the ascending aorta [96] , in cases with ICD [103] or valve prosthesis [110] . Repetition of these imaging modalities after 5 to 7 days has been [1] recommended.…”

Ischemic brain infarcts and vasculitis in histoplasmosis of the central nervous system: A case report and review of the literature

“…The pathophysiology of cerebrovascular disease in CNS histoplasmosis is not fully understood. Evidence to date suggests that brain infarctions can occur in two different settings: [1] granulomatous small vessel vasculitis with lacunar infarcts predominantly in the brainstem and deep white matter [15] , [16] and [2] mycotic emboli and microemboli to arteries of various calibers secondary to Histoplasma endocarditis [19] , [20] . These syndromes may coexist in severe disseminated disease [20] .…”

“…These findings appear to be one phase of a continuum spectrum of disease, that may lead to cerebritis with rim-enhancing lesions on neuroimaging and CNS histoplasmoma [14] On the other hand, Histoplasma endocarditis is rare and it is estimated to represent 1% of all endocarditis cases. The characteristic clinical presentation is a syndrome of culture-negative endocarditis, mostly affecting individuals with prosthetic valves in the contemporary era [19] , [22] , [23] . A multicenter case series describing 14 cases from 2003 to 2012 reported 4/14 (28.5%) incidence of embolisms to different organs including the CNS [22] .…”