PMC6893257_01
The right side shows more normal muscle. Towards the left half, the muscle contains a number of fibers that have bluer (basophilic) cytoplasm (arrow) and some internal degenerative vacuoles (arrowhead). The left lower corner shows some of the inflammatory cells in the sample (lightning bolt). H&E stain.
CRIM2019-6251426.001.jpg
PMC6893257_01_CRIM2019-6251426.001.jpg
fig1
These features are consistent with a diagnosis of dermatomyositis (DM), see Figures 1 and 2.
There are clustered fibers with cytoplasmic staining (arrow). Cytoplasmic activation of the membrane attack complex (MAC) is seen in necrotic myofibers due to ongoing necrosis. The background also shows small brown dots between muscle cells (arrowhead). These correspond to capillaries with abnormal expression of the MAC due to capillary damage in dermatomyositis. MAC immunohistochemistry stain.
CRIM2019-6251426.002.jpg
PMC6893257_01_CRIM2019-6251426.002.jpg
fig2
These features are consistent with a diagnosis of dermatomyositis (DM), see Figures 1 and 2.