[The clinical features of myasthenia gravis associated with thyroid abnormalities]

To analyze the clinical characteristics of myasthenia gravis (MG) associated with thyroid abnormalities.

A total of 300 MG patients admitted to the department of neurology from July 2008 to September 2009 were reviewed retrospectively. Based on the thyroid function and abnormality of thyroid related antibodies (thyroglobulin antibody and peroxidase antibody), the patients with MG were divided into two groups (260 cases without thyroid disease and 40 cases with thyroid abnormalities). The different clinical features, the relationship between the antithyroid antibodies and anti-acetylcholine receptor antibody (AChRAb) and the distribution of T cell subsets between the two groups were compared.

(1) Among the 300 MG patients, 13.3% of them was accompanied with thyroid disease and the most common abnormality was positive thyroid antibody. (2) Between the groups of MG with and without thyroid abnormalities, no significant differences on the sex percentage, age of onset, duration of disease, clinical classification and thymic abnormalities were found (P>0.05). (3) The blood levels of AChRAb in postsynaptic membrane in the thyroid antibody-positive patients were 1.15±0.11, being much higher than those in the antibody-negative patients (1.01±0.11). (4) The percentage of CD8+ T cells was significantly decreased [(21.63±5.17)% vs (24.28±5.79)%] and the ratio of CD4+/CD8+ T cells was increased (2.10±0.67 vs 1.81±0.61, P<0.05) in the group of MG with thyroid abnormality as compared with the group of MG with normal thyroid.

In MG patients the incidence positive thyroid related antibodies was much higher than that of other thyroid abnormalities. It is suggested that there are higher levels of AChRAb in MG coexisting with positive thyroid antibodies and more abnormalities of T lymphocyte subset distribution in MG patients with thyroid disease.