Endocrine Abstracts

Introduction: Myasthenia gravis is an autoimmune neuromuscular disease characterized by the presence of anti-acetylcholine receptor antibodies. It can be isolated or associated with other auto-immune conditions. Graves’ disease is an autoimmune disorder typically characterized by the presence of circulating autoantibodies that tie to and stimulate the thyroid hormone receptor. Coexisting myasthenia gravis and Graves’ disease is a rare but well recognized condition. The physiopathology of this association has not been clearly established. We report the case of a woman with known generalized myasthenia gravis who developed Graves’ disease 15 years after.

Observation: A 43-year-old woman was referred to our department for thyrotoxicosis. Her past medical history was remarkable for generalized myasthenia gravis. In fact, at the age of 28 years, the patient presented with a fluctuating muscle weakness, difficulty swallowing, double vision and fluctuating ptosis. The diagnosis of myasthenia gravis was established. Then, the patient had a total thymectomy and treated with pyridostigmine. On physical examination, she had homogenous goiter and bilateral exophthalmos. Thyroid laboratory investigation revealed overt hyperthyroidism. The diagnosis of Graves’ disease was established and the patient was initially treated with antithyroid drugs. Then, she was referred to the department of Nuclear Medicine for a radioactive iodine therapy.

Conclusion: The occurrence of Graves’ disease and myasthenia gravis in the same patient indicates a genetic predisposition to autoimmune diseases. Muscle weakness may be the first symptom of thyrotoxicosis as well as myasthenia gravis, so a distinction between the two autoimmune diseases can be difficult in some situations. The myasthenic syndrome may precede hyperthyroidism as was the case of our patient or may appear sometimes during the treatment of hyperthyroidism. Propranolol treatment is contraindicated and radical treatment of hyperthyroidism is required.