There are some challenges to accurate diagnosis of ocular myasthenia gravis (MG) in thyroid-associated ophthalmopathy (TAO) patients because the clinical features of these diseases are similar. The aim of this study was to discuss the clinical features and treatment options that may help differentiate these 2 diseases.

We performed a retrospective analysis using the medical records of patients who visited our clinic and were diagnosed with ocular MG and TAO, from January 2002 to December 2012. The diagnosis of Ocular MG was made on the basis of clinical symptoms and signs with laboratory evaluation, including assays for antithyroid and antiacetylcholine receptor (AchRAb) antibodies, and the Ice, neostigmine, and electromyography tests.

Of the 9 ocular MG patients with associated ophthalmopathy, 5 were male and 4 were female. The mean age was 36 ± 16.0 years and the follow-up period was 45.6 ± 36.6 months. Graves' disease (8 patients) was predominant and all patients showed abnormal thyroid function. Atypical symptoms and/or mild clinical features were predominant in ocular MG patients with TAO. Positive test results were obtained as follows: Neostigmine test 33.3%, electromyography 44.4%, ice test 77.8% and anti-AchR titer test 77.8%. Thyroid function test results were abnormal in all patients. In 3 patients who were first diagnosed with TAO, symptoms remained persistent despite steroid therapy then improved dramatically by administration of an anti-acetylcholinesterase agent. These patients were diagnosed with ocular MG in conjunction with TAO.

Patients with thyroid disease who show atypical features, symptomatic changes with fatigue, odd appearing ptosis, and who, do not exhibit good response to treatment of TAO need to be examined for ocular MG with additional tests and treatment.