Multiple endocrine neoplasia type 2A in two families with the familial medullary thyroid carcinoma associated G533C mutation of the RET proto-oncogene.

Introduction: Multiple endocrine neoplasia type 2A (MEN2A) is an autosomal dominant hereditary disorder, associated with a cluster of germline gain-of-function mutations of the RET proto-oncogene (RET), mainly in exons 10-15. The G533C mutation in exon 8 of the RET is rare and has been mainly related to the familial medullary thyroid carcinoma.

Patients-methods: We describe the RET G533C mutation in exon 8 of the RET in two unrelated female index patients, with MEN2A phenotype, consisting of pheochromocytoma which was the presenting feature and medullary thyroid carcinoma. In addition, 12 family members were also studied. DNA extraction, PCR, and sequencing of RET was performed in exons 7-19 and 21, following standard procedures.

Results: The mutation was found in both index patients and in 6 out of 12 family members (50%). Three of them were biochemically affected with histologically proven medullary thyroid carcinoma in two of them while there are no certain clues regarding the other three members as they declined further evaluation.

Conclusion: Patients with MEN2A should be also searched in exon 8 while positive carriers of this mutation should be screened annually for pheochromocytoma or other components of the syndrome.