Clinical study of thyroid eye disease combined with myasthenia gravis.

Purpose: To investigate the clinical features and prognostic factors of patients with thyroid eye disease (TED) combined with myasthenia gravis (MG) at a tertiary comprehensive hospital in China during a 10-year period.

Study design: retrospective study.

Methods: A case series of patients diagnosed with TED combined with MG was conducted at a tertiary general hospital over 10 years. Medical records of general conditions, clinical presentation, imaging and laboratory tests, treatment modalities, and prognostic outcomes were reviewed.

Results: Twenty-three patients with TED combined with MG were found throughout the study period. The mean age was 42.57 ± 14.89 years with 10 men and 13 women. Ocular motility disorders (82.61%), diplopia (73.91%), and ptosis (73.91%) were the primary clinical manifestations, and ocular motility disorders with limited movement in all directions were common (17 eyes) (50.00%). Active (69.57%) and moderate-to-severe (82.61%) TED was common, and hyperthyroidism was the most common complication of thyroid disease (57.17%). Ocular MG was the predominant subtype of MG (86.96%). Chest CT or pathologic examination identified thymic hyperplasia in 4 patients (17.39%) and thymoma in 1 patient (4.35%). A statistically significant association was observed between smoking and an unfavorable prognosis of TED combined with MG (P<0.05).

Conclusions: MG should be taken into account in patients with TED who exhibit the following: unilateral or bilateral ptosis, ptosis in one eye and upper eyelid retraction in the other, obvious eye movement disorders without or with mild involvement of the extraocular muscles on imaging, and symptoms of morning and evening fluctuations. Ophthalmologists should refer these patients to the Department of Neurology to avoid misdiagnosis or underdiagnosis. The co-occurrence of TED and MG is rare clinically, mostly affecting young and middle-aged women, with ocular MG and hyperthyroidism as the main clinical subtype, and thymic hyperplasia or thymoma in a small percentage. Smoking is an independent risk factor for poor prognosis of TED combined with MG.