Blood Cyst of the Mitral Valve: Cause of Fever of Unknown Origin

To the Editor: A 5-y-old boy was admitted with remitting fever for the last 2 wk. Physical examination, ECG and CXR were normal. WBC count was 6800/μL and ESR was 30 mm/h. The level of CRP was 1.25 mg/dl. Blood IgA-G-M were all normal. Subsequent sets of blood cultures were negative. Echocardiogram revealed a thick immobile hyperechogenic 8 × 9 mm mass with suspicion of vegetation in the mitral anterior chordae. Heart was otherwise structurally normal with normal systolic ventricular functions and trivial mitral valve insufficiency. Cardiac MRI showed an 8 × 9 mm T2A isointense mobile nodular lesion in the anterior leaflet of the mitral valve without significant contrast uptake. Considering the ongoing fever without other infectious loci, surgical excision of the cardiac mass was decided. Cystic lesion was completely resected with preserving the mitral valve apparatus. Histopathology confirmed the diagnosis of blood cyst (BC) with a fibrotic cyst wall lined by a single layer of epithelium, and small number of chronic inflammatory cells in the fibrous and edematous stroma. There was no microbiological growth in the tissue culture. Patient stayed afebrile after the procedure. …