The diagnostic value of serum autoantibodies in endocrine orbitopathy and idiopathic ocular myositis.

Sera of patients with Graves' orbitopathy (GOP) often contain antibodies against retroorbital tissue components. The presence of such autoantibodies has been considered to indicate an autoimmune pathogenesis of the disease. However, their specificity has not been conclusively tested, because studies demonstrating autoantibodies used controls with no lesion in the extraocular eye muscles. Although ocular myositis (OM) is clinically distinct from GOP, damage to the retroorbital muscles is a common histopathological finding in both conditions. Using an immunoblot technique, reactions of sera from patients suffering from either disease were compared. Sera from both groups contained antibodies against a variety of antigenic determinants recognized by both sera. These autoantibodies may have been induced secondary to tissue damage and should be considered to be nonspecific. Because the role of tissue damage was not accounted for in previous studies, evidence concerning antigens supposedly specific for GOP should be reevaluated. The reaction patterns of OM and GOP sera were slightly different. These differences were specific enough to suggest that sera from patients with GOP contain antibodies against eye muscle components that are not present in the sera of patients with idiopathic OM. These findings support the assumption that GOP is an autoimmune disease. However, the major autoimmune targets remain to be identified and their pathogenic relevance is still unclear.