Thyrotoxic myopathy and myasthenia gravis: a case report.

Abstract

ALTHOUGH muscular weakness is characteristic of hyperthyroidism, L the simultaneous occurrence of this condition and myasthenia gravis in the same patient is relatively rare (1–4). However, 6 per cent of patients at the Mayo Clinic with myasthenia gravis either had associated hyperthyroidism or had had this disease before the onset of myasthenia gravis (5). In the Johns Hopkins series of 270 cases of ocular myasthenia gravis (220 generalized and 50 localized), 12 showed some abnormality of the thyroid gland; and of these, 8 had hyperthyroidism (6). The myasthenia of chronic thyrotoxic myopathy superficially resembles myasthenia gravis and the two conditions may be easily confused, particularly when exophthalmic ophthalmoplegia is present (4). In 1908, Rennie (7, 8) published the first report of hyperthyroidism and associated myasthenia gravis. In 1946, Cohen (4) suggested that perhaps this was an instance of exophthalmic ophthalmoplegia and not of the combined diseases. Since then, several cases of this d...