Autopsy of a patient with chronic rheumatic mitral disease shows a well-demarcated area of thickened, fibrotic endocardium on the posterior wall of the left atrium above the mitral valve. What is this lesion called and what causes it?

• A McCallum plaque, caused by direct Aschoff nodule ulceration
• B Zahn infarct, caused by mural thrombus organization
• C MacCallum patch, caused by jet stream injury from mitral regurgitation ✓
• D Loeffler endocarditis, caused by hypereosinophilic infiltration

Explanation

The MacCallum patch is a focus of thickened, opacified left atrial endocardial fibrosis classically located on the posterior atrial wall above the posterior mitral leaflet. It forms where the regurgitant jet of mitral insufficiency strikes the endocardium, producing chronic friction injury and fibrous thickening. It is not itself composed of Aschoff bodies, although it occurs in the setting of rheumatic disease. Zahn refers to layered arterial thrombus and Loeffler endocarditis is eosinophil mediated.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.