mitral annular calcification (MAC) 1--Definition Caseous calcification of the mitral annulus is a degenerative, chronic process in which the calcium deposits within the posterior mitral annulus undergo liquefaction necrosis, forming a toothpaste-like or “caseous” (cheese-like) material inside the calcified shell. 2--Pathophysiology Begins as typical MAC, usually in the posterior annulus. Over time, central areas of necrosis, fatty degeneration, and cholesterol crystals appear. The lesion becomes