Carotid-cavernous fistula mimicking Graves' eye disease

We encountered two patients referred for treatment of Graves' eye disease who had atypical features and were found to have carotid-cavernous fistulae. The relevant clinical findings and investigations used to make this important distinction are described, and the factors involved in the initial diagnostic confusion are analyzed. A correct diagnosis leading to proper treatment was made once atypical features were taken note of and alternative diagnoses considered, despite the context of presumed Graves' eye disease. We conclude that these two entities are quite different but have enough similarities to overlap in certain clinical contexts.