To report a case of multiple endocrine neoplasia type 2B (MEN 2B) diagnosed early based on conjunctival neuroma.

A 15-year-old female presented with red eye and conjunctival mass in both eyes. A 5 × 5 mm-sized yellowish conjunctival mass adjacent to the limbus was observed in her right eye and a 3 × 3 mm-sized mass in her left eye. Excisional biopsy was performed and the patient was diagnosed with conjunctival neuroma. Other abnormalities were not found on the ophthalmic examination, but she had characteristic appearances such as thickened upper eyelid, mild telecanthus and nodular edematous upper lip. She was transferred to the Endocrinology Department for systemic evaluation in consideration of multiple endocrine neoplasia. Abdominal pelvic computed tomography and a 24-hr urine collection analysis showed asymptomatic pheochromocytoma. Thyroid ultrasonography and fine-needle biopsy revealed medullary thyroid carcinoma. Finally, MEN type 2B was confirmed by using a RET mutation gene test.

Thyroid carcinoma can occur in MEN 2B in combination with pheochromocytoma and mucosal neuroma. Thickened corneal nerve fiber and perilimbal conjunctival mass have been regarded as ophthalmologic characteristics of MEN 2B and may be accompanied by telecanthus, thickened upper eyelid and marfanoid habitus. A biopsy of the mass is required for pathological diagnosis. Medullary thyroid carcinoma is the most significant clinical component of MEN 2B syndrome and thyroidectomy is indicated. MEN 2B may be a rare syndrome, but its consequences are serious and the ophthalmologist may play a lifesaving role in its diagnosis.