Relationship of familial prominent corneal nerves and lesions of the tongue resembling neuromas to multiple endocrine neoplasia type 2B.

PURPOSE

We studied a two-generation family with an inherited syndrome of prominent corneal nerves and lesions of the tongue resembling neuromas without the characteristic neoplasms of the multiple endocrine neoplasia type 2B syndrome. Several different point mutations in the RET proto-oncogene on chromosome 10 have been associated with the multiple endocrine neoplasia type 2 syndromes. Molecular genetic studies of families with partial phenotypic expression of these syndromes may aid in further understanding the origin of the variety of clinical manifestations observed in multiple endocrine neoplasia type 2.

METHODS

A family consisting of an 8-year-old male proband, his 10-year-old sister, and 40-year-old mother was identified as having prominent corneal nerves and lesions of the tongue resembling neuromas. Pentagastrin-stimulated serum calcitonin levels were measured in the mother and sister. Molecular genetic studies were performed on all three affected members, to look for the specific point mutation seen in over 95% of patients with multiple endocrine neoplasia type 2B.

RESULTS

Serum calcitonin levels were normal, indicating no C-cell hyperplasia or medullary thyroid carcinoma. Molecular genetic studies on these individuals did not disclose the specific point mutation seen in multiple endocrine neoplasia type 2B.

CONCLUSIONS

This family demonstrates some of the phenotypic features of the multiple endocrine neoplasia type 2B syndrome without the characteristic neoplasms or the mutation in the RET proto-oncogene associated with multiple endocrine neoplasia type 2B. Their physical findings may be caused by genetic alterations within the RET proto-oncogene on chromosome 10 at yet undetermined sites.