This disease presents sometimes with diplopia with or preceded by ptosis, which becomes worse as the day goes by. Any one extraocular muscle or group of muscles can be affected. The symptoms and signs show a transient improvement seconds after the intravenous injection of edrophonium chloride (Tensilon). Diagnosis can be confirmed by high serum titres of acetylcholine receptor antibodies. Approximately 10% of cases are associated with a thymoma, which can become malignant. A chest X-ray is, therefore, mandatory in any patient suspected of having myasthenia gravis. Treatment is with an anti-cholinesterase such as pyridostigmine.
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