Epibulbar Osseous Choristoma

INTRODUCTION Epibulbar osseous choristoma is a choristomatous lesion of the conjunctiva containing bone in an otherwise normal eye. It is usually a congenital lesion arising as an abnormal development of embryonic pleuripotential mesenchyme, presenting in childhood. However, some lesions may be associated with trauma, presenting in adulthood, and possibly related to inflammation. 70% of cases are in females and 80% occur in the superotemporal quadrant. Lesions can sometimes be associated with other choristomatous lesions such as cartilage, dermoid cyst, and ectopic lacrimal tissue.

Epibulbar Osseous Choristoma (Contd.)

CLINICAL PRESENTATION This lesion most commonly presents as an isolated epibulbar lesion in the super-otemporal conjunctival quadrant, but it can be seen in other areas as well. It is typically present at birth and shows slow growth. It appears as a fatty yellowish subconjunctival mass without hair, and resembles a dermolipoma. A central hard core of bone is present surrounded by a more fibrous mass. The lesion may have a firm attachment to the underlying sclera or to the insertion of an extraocular muscle.

Epibulbar Osseous Choristoma

HISTOPATHOLOGY This choristomatous lesion of the conjunctiva is composed of mature, compact bone surrounded by fibrous connective tissue. Haversian canals are present and are surrounded by concentric lamellae of bone. Other choristomatous tissues including fibroadipose tissue, nerves, and lacrimal acini have been seen occasionally in these rare lesions of the conjunctiva.

Epibulbar Osseous Choristoma

DIFFERENTIAL DIAGNOSIS The differential diagnosis includes limbal dermoid, epithelial inclusion cyst, prolapsed orbital fat, papilloma, dermolipoma, and complex choristoma.

TREATMENT Since these are benign lesions that are usually asymptomatic, they can be safely observed without treatment. Indications for treatment include cosmetic improvement, ocular inflammation, or chronic epiphora. Surgical excision can be achieved with care taken to preserve the insertion of extraocular muscles.

REFERENCES

Dreizen NG, Schacat AP, Shields JA, Augsburger JJ. Epibulbar osseous choristoma. J Pediatr Ophthalmol Strabismus 1983; 20:247-249.

Gayre GS, Proia AD, Dutton JJ. Epibulbar osseous choristoma: case report and review of the literature. Ophthal Surg Lasers 2002; 33:410-415.

Epibulbar Osseous Choristoma (Contd.)

Gonnering RS, Fuerste FH, Lemke BN, Sonneland PR. Epibulbar osseous choristomas with scleral involvement.

Ophthal Plast Reconstr Surg 1988; 4:63-66. Melki TS, Zimmerman LE, Chavis RM, Ellsworth R, O'Neill JF. A unique epibulbar osseous choristoma. J Pediatr Ophthalmol

Strabismus 1990; 27:252-254. Oritz JM, Yanoff M. Epipalpebral conjunctival osseous choristoma. Br J Ophthalmol 1979; 63:173-176. Shields JA, Eagle RC, Sheilds CL, DePotter P, Schnall BM. Epibulbar osseous choristoma: computed tomography and clinicopathologic correlation. Ophthalmic Practice 1997; 15:110-112. Trojet S, Kamoun H, El Afrit MA, et al. Epibulbar osseous choristoma: two case reports. J Fr Ophtalmol 2003; 26:481-483.

Essentials of Human Physiology

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