Prominent corneal nerves in patients with multiple endocrine neoplasia type 2A: diagnostic implications.

We examined corneal nerves of 22 patients from 10 families with multiple endocrine neoplasia type 2A (MEN-2A). According to the findings in slit-lamp biomicroscopic examination and photographic documentation, the increased visibility of corneal nerves were classified into 5 grades (Grade 0 = invisible to Grade 4 = as thick as in MEN-2B). All eyes of normal subjects, 19 of 20 eyes of patients with anterior keratoconus, and 11 of 12 eyes of patients with non-hereditary medullary thyroid carcinoma (MTC) were either grade 0 or 1, and the remaining 2 eyes were evaluated as grade 2. Of the 44 eyes of MEN-2A patients, 5 (11.4%) eyes were grade 0, 11 (25%) eyes were grade 1, 19 (43.2%) eyes were grade 2, 8 (18.2%) eyes were grade 3, and 1 (2.3%) eye was grade 4. Thus, more than 60% of eyes of MEN-2A patients showed pathologically thickened corneal nerves of varying degree (grade 2 or higher). There was no definite relationship between the grade of corneal nerve thickening and the patient's age or presence of pheochromocytoma. Differences in the grade of corneal nerve thickening were observed among affected members belonging to the same MEN-2A family, but unaffected members of the family never showed prominent corneal nerves of grade 2 or higher. Our findings suggest that MTC patients with thickened corneal nerves might actually be MEN-2A patients and should be carefully followed for other components of this syndrome.