A Case of Myxoma-Like Degeneration in a Patient With Marfan Syndrome Mimicking Vegetation of Infective Endocarditis

Abstract

Infective endocarditis (IE) is often considered first in the differential diagnosis when fever, a heart murmur, and valvular vegetation are present. IE caused by Mycoplasma pneumoniae has rarely been reported. We report a case in which IE was initially suspected based on the presence of fever, a heart murmur, and an IE vegetation-like structure on the anterior leaflet of the mitral valve identified by echocardiography following admission for pneumonia caused by M. pneumoniae. However, IE was ultimately excluded, and the vegetation-like structure was determined to represent myxoma-like degeneration associated with Marfan syndrome. A seven-year-old girl with no notable family history and no characteristic physical findings presented with fever and pneumonia, and polymerase chain reaction testing was positive for M. pneumoniae. Echocardiography revealed an IE vegetation-like structure on the anterior mitral leaflet with leaflet prolapse, moderate mitral regurgitation, and enlargement of the aortic sinus of Valsalva. IE, due to M. pneumoniae, was suspected, and antimicrobial therapy was initiated. The patient's fever and pneumonia improved; however, the vegetation-like structure on the mitral valve remained unchanged. Multiple blood cultures were negative. Given suspicion for an underlying connective tissue disorder, genetic testing was performed and identified a missense mutation in FBN1, confirming Marfan syndrome. Because it is difficult to distinguish IE vegetation from myxoma-like degeneration associated with Marfan syndrome using echocardiography alone, recognition of this entity in patients with Marfan syndrome may improve diagnostic accuracy and prevent misdiagnosis.