Clinical Differences between Predominantly Fat Increase and Muscle Increase Subtypes of Thyroid Eye Disease in Chinese Patients

Objective: To compare the clinical differences between the subtypes of thyroid eye disease, involving predominant fat increase and muscle increase Design: Retrospective, observational case series Setting: Zhongshan Ophthalmic Center Subjects: Thirty-six patients with thyroid eye disease Intervention: None Main outcome measures: Main characteristics of predominant fat increase and muscle increase subtypes in thyroid eye disease Results: The patients with predominantly fat increase were younger (median: 25 vs. 51 years, P = 0.007), had larger exophthalmometry values (median: 23 vs. 21.5 mm, P = 0.049) and much longer duration of exophthalmos (median: 60 vs. 6.5 months, P < 0.001), but lower clinical activity scores (median: 0.5 vs. 2, P = 0.005), compared to those patients with predominant muscle increase. The subtype with predominant fat increase had a smaller percentage of dysthyroid optic neuropathy than the subtype with predominant muscle increase (12.5% [1/8] vs. 79% [22/28], P < 0.001). In the predominant fat increase subtype, the corrected visual acuity in the one eye with dysthyroid optic neuropathy was 0.4. In the predominant muscle increase subtype, the median corrected visual acuity in the eyes with dysthyroid optic neuropathy was 0.15. Conclusions: There are distinct differences between Chinese thyroid eye disease patients with predominant fat increase and muscle increase subtypes. In the predominant fat increase subtype, dysthyroid optic neuropathy rarely occurs, and visual loss caused by dysthyroid optic neuropathy tends to be relatively mild.