Primary Intra-Orbital Hydatid Cyst: A Case Report of a Rare Cause of Exophthalmos

<bold>Background:</bold> Hydatid disease is a tapeworm parasitic infection caused by Echinococcus granulosus that commonly affects the liver and lungs during its life cycle in the human body. Orbital involvement is a very rare occurrence and isolated orbital Echinococcosis is extremely rare.<br /> <bold>Case Presentation:</bold> A 60-year-old female Eritrean woman presented with 3-month history of painless protrusion of the left eye. Physical examination showed significantly decreased visual acuity of the left eye, left eye proptosis, and papilledema. Laboratory investigations were normal and orbital CT scan examination was suggestive of orbital hydatid cyst. After giving two weeks course of oral Albendazole, anterior orbitotomy and cyst excision was done. Post-op biopsy was conclusive of orbital hydatid cyst. She had mild lid swelling and adduction deficit on her post-operative follow-up. Subsequent longer duration of follow-up of the patient was not possible since the patient relocated back to Eritrea.<br /> <bold>Conclusion:</bold> Orbital hydatid cyst is an extremely rare presentation of human Echinococcus granulosus infection. However, it should be considered one of the differential diagnoses among patients living in an endemic area and presenting with proptosis of the eye. A preoperative course of anthelmintic followed by surgical excision of the cyst is the definitive management