Anti-Titin Antibodies in Myasthenia Gravis: Tight Association With Thymoma and Heterogeneity of Nonthymoma Patients.
Yamamoto, Ana Maria
Archives of Neurology; Jun2001, Vol. 58 Issue 6, p885, 6p
Background: Titin is the major autoantigen recognized by anti–striated muscle antibodies, which are characteristic of generalized myasthenia gravis (MG). Objective: To seek a correlation between anti-titin antibodies and other features of MG patients, including histopathology, age at diagnosis, anti–acetylcholine receptor (anti-AChR), autoantibody titers, and clinical severity. Methods: A novel, highly specific radioligand assay was performed on a large group of 398 patients with generalized MG. Results: Among thymectomized patients, anti-titin antibodies were present in most patients with thymoma (56/70 [80%]), contrasting with only a minority of patients with thymus atrophy or hyperplasia (17/165 [10%]). They were also present in 64 (41%) of 155 nonthymectomized patients who had a radiologically normal thymus. In these patients and in those who had a histologically normal thymus, anti-titin antibodies were associated with a later age at onset of disease and with intermediate titers of anti-AChR antibodies. After controlling for these 2 variables, disease severity was not significantly influenced by anti-titin antibodies. Conclusions: Anti-titin antibodies are a sensitive marker of thymoma associated with MG in patients 60 years and younger, justifying the insistent search for a thymoma in MG patients of this age group who have these antibodies. In nonthymoma patients, anti-titin antibodies represent an interesting marker complementary to the anti-AChR antibody titer, identifying a restricted subset of patients. These clinical correlations should prompt further studies to examine the mechanisms leading to the production of anti-titin antibodies. [ABSTRACT FROM AUTHOR]
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