Hypothyroidism and myasthenia gravis: A rare association

The prevalence of endocrinopathies during myasthenia is relatively common. The association of myasthenia with dysthyroidism can make the diagnosis of these two conditions difficult, because of the similaritý of some clinical signs. Several disorders of specifically thyroid immunologic origin have beeń reported in myasthenic patients. This relationship remains poorly elucidated, but an immunologic cross-reaction between the neuromuscular junction and thyroid components has been found in myasthenia and Graves' disease. It is generally accepted that the association between hyperthyroidism and myasthenia is much more frequent than that between myasthenia and hypothyroidism. However, no clear explanation has been proposed for this difference. We report the case of a 28-year-old patient who was initially followed for myasthenia under anticholinesterase therapy and whose evolution was marked by the discovery of hypothyroidism during follow-up. The patient responded well to replacement therapy with a good evolution.