INTRODUCTION: Fibrous dysplasia is a primary orbital bone tumor, described as a benign disorder in which proliferation of fibrous tissue and osteoid replaces and distorts the bone from which it derives. Unilateral keratoconus is a rare entity. Herein, we report a case of an extensive ethmoidal fibrous dysplasia associated with ipsilateral keratoconus, and review the literature on the subject.MATERIALS AND METHODS: A 22-year-old man presented with left painless proptosis evolving over 10 years. There was associated ipsilateral epiphora and gradual visual loss. On examination his visual acuity was 20/20 OD and CF OS. His left globe was displaced lateraly 12 mm, with 9 mm of proptosis. The extraocular movements were normal. Left nasolacrimal duct obstruction was noted. Clinical signs of keratoconus were present only in the left cornea. High resolution corneal topography confirmed unilateral keratoconus and a CT scan showed an ovoid mass with a well defined sclerotic margin arising from the left ethmoid sinus and invading the orbit.RESULTS: The patient underwent resection of the lesion via a modified Lynch incision. Complete regression of proptosis was observed immediately after surgery. Histopathological examination revealed irregular trabeculae of woven bone in different levels of maturation in a moderately cellular fibrous matrix without nuclear atypia. Trabeculae were without osteoblastic rimming or osteoclastic resorption. There has been no recurrence over a 2-year follow-up period.CONCLUSION: To our knowledge, the coexistence of unilateral isolated craniofacial fibrous dysplasia with ipsilateral keratoconus has not been reported so far.