QUIZ
Answer: Histoplasma capsulatum prosthetic valve endocarditis with arterial embolism Both the arterial embolus and the aortic valve tissue grew Histoplasma capsulatum. Histoplasma urine antigen tests performed on a specimen collected the same week as the valve replacement were negative, as were results for complement fixation antibodies. Postoperatively, the patient received approximately 2 weeks of treatment with intravenous lipid complex amphotericin B, followed by 9 months of treatment with oral itraconazole solution (200 mg twice a day for 4 months and 5 additional months of 200 mg once daily). Seven years later, the patient was physically active and without evidence of valvular dysfunction.
Fungi are the causative agents in approximately 5 to 7% of all prosthetic valve endocarditis episodes (1). H. capsulatum is rare; in a review of 270 cases of fungal endocarditis, only 6% were attributed to H. capsulatum (2). The diagnosis of H. capsulatum endocarditis can be difficult to establish, as routine blood cultures are usually negative for fungi and there are no pathognomonic signs or symptoms except for the remarkable chronicity of illness and reported frequent major arterial emboli. Most patients with chronic disease will have positive serum serologies, suggesting the diagnosis. Although H. capsulatum is a dimorphic fungus that typically grows in the yeast form in the human host, in cases of endocarditis the fungi can present in a variety of large and small yeast forms as well as with septate and branching hyphae, as was seen with the present patient (3).
Optimal treatment is unknown. Lipid complex amphotericin is considered first-line therapy. Because of his advanced age, the patient was rapidly transitioned from amphotericin to liquid itraconazole following bioprosthetic valve replacement.
(See page 771 in this issue [doi:10.1128/JCM.02078-10] for photo quiz case presentation)
Contributor Information
Jennifer Franceschelli, Division of Medicine, Geisinger Medical Center, Danville, Pennsylvania 17822.
Paul Bourbeau, Division of Laboratory Medicine, Geisinger Medical Center, Danville, Pennsylvania 17822.
REFERENCES
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