New-Onset Thrombocytopenia after Treatment of Mitral Valve Endocarditis, Resolution Following Valve Replacement: A Case Report.

Thrombocytopenia developing after apparent resolution of infective endocarditis (IE) is uncommon. We report the case of a 61-year-old woman with severe rheumatic mitral stenosis and native mitral valve IE caused by Lactococcus garvieae. Her platelet count remained normal during antibiotic therapy but declined to 46-84×103/μL during routine outpatient follow-up after discharge. Follow-up echocardiography showed resolution of the vegetation, and inflammatory markers had normalized; however, corticosteroid treatment did not improve the platelet count. Elective surgery was performed for severe mitral stenosis with moderate tricuspid regurgitation and atrial fibrillation. After mitral valve replacement with concomitant tricuspid valve repair and a maze procedure, the platelet count normalized immediately and remained within the normal range during approximately 3 months of postoperative follow-up, without further thrombocytopenia-directed therapy. This case suggests a possible valve- and atrium-related mechanism for thrombocytopenia developing after treated IE and indicates that valve surgery may contribute to platelet recovery in selected patients.