Endocrine Abstracts

Introduction: The coexistence of Grave disease [GD] and Myasthenia gravis [MG] may present a diagnostic dilemma especially concerning ocular manifestations. 3–10% of myasthenic patients exhibit GD, while MG is reported in only <1% of patients with thyroid disorder.

Observation:

Case 1: A 32-year-old woman, with a medical history of vitiligo, was diagnosed with GD. Immunology revealed positive anti-thyroid peroxidase antibodies [TPOAb] and TSH receptor antibodies [TRAb]. Treatment with Anti-thyroid drugs was soon withdrawn because of severe eruption and the patient received radical treatment (I-131). Two months later, she reconsulted for muscle use increasing throughout the day. The diagnosis of MG was confirmed by a Prostigmine test, and positive Acetylcholine receptors [AChR] antibodies. The treatment with Pyridostigmine was immediately initiated. But, the amplification of myastenic symptoms later led to successive immuneglobulin cures.

Case 2: A 43-year-old man consulted for exophthalmia, diplopia, asymmetric ptosis and blurring of vision. Physical examination demonstrated a goiter, a resting tremor and proximal muscle weakness. Thyroid function test showed high levels of thyroid hormones, TSH < 0.05. Both GD with severe ophthalmopathy and MG were suspected. Immunology confirmed the diagnoses, with positive TRAb, TPOAb and AChR antibodies. The patient was started on Thiamazol and Pyridostigmine, with a good evolution.

Case 3: A 41-year-old woman complaining of asthenia by the end of the day, diplopia and difficulty chewing. She reported a medical history of GD treated for 2 years with Benzylthiouracil, then Radioiodine at the age of 28. AChR antibodies and Anti-striated muscle Antibodies were positive confirming MG’s diagnosis, with a thymic tumor revealed on chest scan. Therefore, the patient underwent a total thymectomy that in association with cholinesterase inhibitors was fairly efficient.

Conclusion: GD is associated with a number of autoimmune diseases, including myasthenia. Two out of our three patients had ocular myasthenic symptoms. Thyroid disease was found to be more frequent in ocular MG patients (40%) than in generalized MG patients (12%). Accordingly, it is important for every endocrinologist to suspect the association of MG in each GD patient especially on the presence of ptosis, exotropia, muscle weakness increasing with exercise.