Prosthetic mitral valve thrombosis associated with new-onset hyperthyroidism due to Graves' disease: a case report.

Background: Graves' disease is linked to a range of cardiovascular diseases. However, the association of new-onset hyperthyroidism with bioprosthetic valve thrombosis has not been reported yet. Case summary: We present the case of a 59-year-old Caucasian male who developed new-onset overt hyperthyroidism 6 years after undergoing bioprosthetic mitral valve replacement. Echocardiography revealed valve failure with high transmitral gradients caused by valve thrombosis. Following appropriate thyreostatic treatment and anticoagulation, his symptoms resolved, and subsequent evaluations showed resolution of the thrombus and normal valve function. Conclusion: In this case, the association of new-onset hyperthyroidism with bioprosthetic valve thrombosis is highly likely. Hyperthyroidism, characterized by a hypercoagulable state and hypofibrinolytic disorder, is known to be associated with thrombosis and thromboembolic events. As acute hyperthyroidism shows clinical features similar to endocarditis, an interdisciplinary approach, immediate appropriate diagnostic steps and management are crucial for a favourable outcome. This case suggests that hyperthyroidism should be considered in the differential diagnosis when evaluating new-onset valvular thrombosis.