THYROID-ASSOCIATED OPHTHALMOPATHY IN BLACK SOUTH-AFRICAN PATIENTS WITH GRAVES-DISEASE - RELATIONSHIP TO ANTIFLAVOPROTEIN ANTIBODIES

Thyroid-associated ophthalmopathy (TAO) is a progressive eye disorder associated with Graves' hyperthyroidism, which is generally considered to have an autoimmune etiology. Eye muscle membrane proteins of 64 kd are good markers of ophthalmopathy in patients with thyroid autoimmun ity, The 64-kd protein is now shown from a partial sequence to be the flavoprotein subunit (Fp) of mitochondrial succinate dehydrogenase. Hy perthyroidism due to Graves' disease is increasing in incidence among urban black female Africans, possibly because of exposure to environme ntal risk factors such as increased dietary iodine ingestion and stres s. Ophthalmopathy is frequently observed in this clinical context, but its association with serum autoantibodies reactive with Fp has not be en examined. We studied 19 black South African patients with Graves' d isease during the course of prolonged antithyroid drug administration, of whom 10 had congestive ophthalmopathy, but no clinical evidence fo r eye muscle damage at the onset. Anti-Fp antibodies were detected in 2 of these patients, as well as in 2 of the 9 patients who did not hav e overt eye disease. Additionally, the antibodies became positive in 3 patients with ophthalmopathy in whom tests were negative initially, r emained positive in 1 patient throughout the study period and became n egative in 1 patient with positive tests initially. Ophthalmopathy did not develop in any of the 9 patients who lacked this complication on presentation. The reasons why we failed to demonstrate a close relatio nship between anti-Fp antibodies and the eye muscle component of ophth almopathy are unclear although one possibility is that ocular myopathy is an uncommon manifestation in African thyrotoxic patients compared with those of Caucasian origin. The relationship between anti-Fp antib odies and eye muscle inflammation in patients with thyroid autoimmunit y of different ethnic origins and environmental settings, needs to be addressed in a large prospective study.