Grades of exophthalmos and thyrotropin-binding inhibitory immunoglobulin in patients with myasthenia gravis.

Exophthalmos and thyrotropin-inhibitory immunoglobulin (TBII) were examined in myasthenia gravis (MG) patients with normal thyroid function. Exophthalmos was found in 7 of 31 (22.6%) MG patients, and TBII was detected in 4 of 21 (19.0%) MG patients. The grades of exophthalmos did not decrease after extraocular muscle weakness was improved by treatment. Patients with MG whose diplopia was Tensilon unresponsive were only found among those with exophthalmos. TBII was more frequently detected in MG patients with exophthalmos than in those without. The present study revealed that exophthalmos is not rare in MG patients, even if they do not show any signs of Graves' disease other than exophthalmos and their thyroid functions are within the normal limit. The presence of TBII in MG patients may relate to the development of exophthalmos, and exophthalmos itself might enhance ocular symptoms of MG.