Transformation of Thyroid Eye Disease Phenotype Following Teprotumumab Treatment

We report a case of a phenotypic shift of thyroid eye disease following treatment with teprotumumab. A 35-year-old female nonsmoker with Graves disease developed mild type I thyroid eye disease featuring unilateral lid retraction and was treated with teprotumumab. Following completion of treatment, a reactivation was associated with progression to severe type II phenotype, with marked extraocular muscle enlargement, bilateral proptosis, and nonsteroid-responsive compressive optic neuropathy requiring orbital decompression. This case raises important questions regarding the potential influence of Insulin-like growth factor 1 (IGF-1) suppression on the phenotype of thyroid eye disease.