Thyroid associated orbitopathy, although seen most commonly with thyrotoxicosis, is also known to occur in primary hypothyroidism. Myasthenia gravis is an autoimmune condition with an established association with autoimmune thyroid disease. We report the case of a patient who presented with recent onset unilateral ptosis that was fatigable with a history of proptosis since a year. On examination, she had a goiter, bilateral proptosis, restriction of upward gaze and adduction both eyes and normal pupils. Investigations revealed primary hypothyroidism with anti-thyroid peroxidase positive and anti-acetylcholine receptor antibody positive. Computerized tomography orbit showed thickening of medial and inferior rectus characteristic of thyroid orbitopathy. A diagnosis of primary hypothyroidism with thyroid orbitopathy with ocular myasthenia gravis was made. Patient is on Levothyroxine and anticholinesterase medications and is on follow-up. We present this case to highlight that the presence of ptosis in a patient with thyroid orbitopathy should alert the clinician to the possible coexistence of myasthenia gravis.
Keywords: Grave's ophthalmopathy; hypothyroidism; myasthenia.