Brown Atrophy (Xanthosis, Lipofuscinosis)

In dairy cattle with brown atrophy, the skeletal muscles and myocardium are yellow-brown to bronze. The masseter muscles and the diaphragm are affected most frequently. No clinical disease results. Microscopically, brown lipofuscin pigment granules accumulate under the sarcolemma or centrally in the muscle fibers. A genetic cause is presumed because certain breeds (eg, Ayrshire) are more predisposed than others.