Pure eye muscle involvement in endocrine orbitopathy.

We present a long-term follow-up examination concerning patients with isolated extra-ocular muscle involvement in thyroid-related orbitopathy. Within the previous 13 years we observed 7 patients with endocrine orbitopathy and marked myopathy of the extra-ocular muscles. Five of these patients had no detectable proptosis, 2 of them showed a minimal unilateral proptosis. Five patients showed elevated thyroid-stimulating hormone (TSH) receptor auto-antibodies and 6 patients a marked swelling of the extra-ocular eye muscles on CT or MRI scans. One patient had elevated antibodies against thyroid peroxidase and against thyroglobulin and normal TSH receptor auto-antibodies. Four of 7 patients underwent clinical and radiological follow-up examination 1-9 years later. In 3 of these 4 patients, the clinical syndrome had completely resolved. None of the patients had developed any proptosis. The swelling of the eye muscles on radiological imaging had at least partially resolved. We conclude from our results that apart from the frequent subtype of endocrine orbitopathy with predominant proptosis there is a separate subtype in which proptosis neither exists initially nor develops in the further course. Probably these subtypes have a specific immunological antibody profile although they do not differ concerning the thyroid-stimulating antibodies.