Some patients with Graves' disease will show diffuse thymic hyperplasia.

Clinical features:

(1) signs and symptoms of Graves' disease (thyrotoxicosis)

(2) presence of diffuse thymic hyperplasia

(3) variable myopathy with fluctuating limb weakness


In this setting the myopathy may represent either:

(1) thyrotoxic myopathy (pseudo-myasthenia)

(2) true myasthenia gravis


Medical therapy of the thyrotoxicosis results in regression of thymic hyperplasia and improvement in muscle symptoms. In true myasthenia the muscle weakness persist or get worse.

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