MacCallum's patch - rheumatic heart disease
This patient has rheumatic heart disease.
Acute rheumatic endocarditis commonly involves the mitral and aortic valves, manifested as mitral insufficiency and/or aortic stenosis, which may require valvular replacement, as in this case. Left untreated, mitral stenosis develops later.
Sequelae of mitral insufficiency include left atrial enlargement, and in longstanding and severe disease, the regurgitant jet of blood is traumatic to the posterior left atrial endocardium and may subsequently result in subendocardial fibrosis and calcifications. These changes are referred to as MacCallum's triangle or patch.
It has also been proposed that rheumatic endocarditis also plays a role in the pathogenesis of MacCallum's patch.