SERUM ANTIBODIES REACTIVE WITH EYE MUSCLE MEMBRANE-ANTIGENS ARE DETECTED IN PATIENTS WITH NONSPECIFIC ORBITAL INFLAMMATION

Purpose: Nonspecific orbital inflammation, also called ''orbital pseud otumor'' has many of the features of thyroid-associated ophthalmopathy , especially when localized to the eye muscle. The purpose of this stu dy is to test for circulating autoantibodies against eye muscle antige ns and features of possible thyroid autoimmunity in patients with nons pecific orbital inflammation. Methods: The authors studied eight patie nts with diffuse or localized nonspecific orbital inflammation. The pr esence of autoantibodies reactive with pig eye muscle membrane antigen s and D-1, a recombinant 64 kilodaltons (kd) thyroid and eye muscle pr otein, were tested in sodium dodecyl sulfate-polyacrylamide gel electr ophoresis and Western blotting. Results: The most frequently detected antibodies were those reactive with eye muscle membrane proteins of 55 and 64 kd, which were demonstrated in 62.5% and 62.5%, respectively, of patients with nonspecific orbital inflammation; antibodies against 95- and 45-kd proteins were each detected in 50% of patients. In healt hy subjects, antibodies reactive with the 55- and 64-kd proteins were detected in 16% and 20% of patients, respectively; those reactive with the 95-kd protein were detected in 24% of patients and with the 45-kd protein in 20% of patients. On the other hand, antibodies to D-1 were demonstrated in only one patient with nonspecific orbital inflammatio n and not at all in healthy subjects. The prevalence of positive tests were significantly greater in patients with nonspecific orbital infla mmation than healthy patients only for antibodies reactive with a 55-k d protein. Of the four antigens, only the 55-kd protein was expressed in other (systemic) skeletal muscle. No patient had overt thyroid dise ase or detectable serum antibodies reactive with the thyroid-stimulati ng hormone receptor, and only one had antibodies reactive with the thy roid microsomal antigen. Conclusion: Serum autoantibodies reactive wit h eye muscle membrane proteins are demonstrated in the majority of pat ients with nonspecific orbital inflammation. Although the pathogenesis of this condition is unknown, autoimmunity against eye muscle antigen s is a likely mechanism. While antibodies reactive with the thyroid mi crosomal antigen were detected in only one patient and anti-thyroid-st imulating hormone receptor antibodies in none of the patients, a possi ble association of nonspecific orbital inflammation with thyroid autoi mmunity has not been excluded.