Myasthenia gravis is an autoimmune neuromuscular disorder characterised by muscle weakness and fatiguability including ocular symptoms such as ptosis and diplopia. Conversely, pituitary macroadenomas are benign tumours that may present with visual deficits due to compression of the optic chiasm, most notably bitemporal hemianopia. While both conditions can independently cause visual symptoms, their concurrent presentation is rare. We present the unique case of a patient with both myasthenia gravis and a gonadotroph macroadenoma, requiring separate simultaneous treatment modalities.
A 55-year-old male from a regional city presented with sudden onset diplopia. Past medical history included psoriatic arthritis (methotrexate). CT imaging showed a pituitary macroadenoma 14 x 20 x 20 mm with effacement of the optic chiasm, in adjunct to an incidental finding of a thymoma; 71 x 40 x 46 mm. Referral followed to a tertiary hospital for further work-up. Clinical examination revealed bilateral ptosis and fatiguable eye movements. Visual field testing confirmed bitemporal hemianopia. Laboratory tests showed FSH 16.9 IU/L (Ref: 1-12), LH 3.9 IU/L (Ref: 0.6-12.1), prolactin 1970 mIU/L (Ref: 73-410), TSH 2.79 mIU/L (Ref: 0.40-4.00) and T4 8.3 pmol/L (Ref: 9.0-19.0). Nerve conduction studies and positive acetylcholine receptor antibodies confirmed the concurrent diagnosis of myasthenia gravis. The patient underwent transsphenoidal resection of the macroadenoma. Histological examination confirmed a gonadotroph adenoma, positive for FSH, SF-1, GATA3 and ER on immunohistochemistry. Thyroxine replacement was initiated as well as prednisone for the treatment of myasthenia gravis. He was referred for consideration of a thymectomy.
This is one of few case reports describing a concurrent gonadotroph secreting macroadenoma and thymoma-associated seropositive myasthenia gravis. While thymomas are known to be associated with autoimmune disorders, a definitive association with pituitary adenomas remains undetermined. This case highlights the importance of collaborative multidisciplinary care and conducting a thorough diagnostic work-up for patients presenting with diplopia.