BACKGROUND: An 18-year-old woman presented with thyrotoxic symptoms - right sided lid retraction and exophthalmus. She complained of diplopia on lateral gaze. Laboratory investigations confirmed Grave's disease with hyperthyroidism and TSH receptor antibodies. PATIENTS AND METHODS: Her clinical symptoms improved after thyrostatic and steroid therapy. However, diplopia recurred 2 weeks after withdrawal of steroid therapy and a ptosis of the left lid appeared for the first time. RESULTS: A positive Tensilon test and electromyographic findings confirmed the diagnosis of myasthenia gravis with a predominantly ocular manifestation. Diplopia and ptosis improved with oral pyridostigmine. CONCLUSIONS: The coexistence of myasthenia gravis should be taken into consideration in the management of patients with Graves' ophthalmopathy.
