[Ultrastructure study on extraocular muscle of infiltrative exophthalmos]

Abstract

Objective: To investigate histopathologic and ultrastructural changes of extraocular muscles (EOMs) in infiltrative exophthalmos in order to collect some evidences of pathogenesis.

Methods: Ten EOM samples in infiltrative exophthalmos were obtained after operation. Each of them was cut into two pieces. One of them was stained with HE and observed by light microscope. Another one was sectioned with ultrathin method and observed by transmission electron microscope.

Results: Under the light microscope, the extraocular muscular cells had no significant abnormality at the early stage, while at the middle and late stage, sarcoplasm coagulation, granular degeneration, vacuolization and necrosis were found in the cells. Under the electron microscope, there were disturbance and disappearance of the Z line in part of muscular fibers in early cases; at the middle and late stage, various degrees of sarcoplasmic reticulum dilatation, myofilament lysis and destruction with formation of vacuoles, secondary lysosome and remnant bodies were seen. In severe cases, the muscular cells could be completely destroyed and phagocytosed by macrophages, fibrosis occurred and myofibroblasts were found in some cases.

Conclusions: The EOMs in infiltrative exophthalmos are destroyed in various degrees, and the muscular cells may be the target cells in Graves' ophthalmopathy.