A primary orbital hydatid cyst.

Echinococcosis, caused by the tapeworm Echinococcus granulosus, is an endemic zoonosis in which humans act as accidental intermediate hosts. Orbital hydatid cysts comprise 1% to 2% of all hydatid lesions. We describe a 10-year-old boy with an orbital hydatid cyst. The orbital cyst was removed totally by frontal craniotomy and orbitotomy. It should be noted that unilateral painless proptosis in patients from countries endemic for echinococcosis could be caused by an orbital hydatid cyst.