ABSTRACT
Multiple endocrine neoplasia (MEN) Ila is an inherited disease characterized by the development of medullary thyroid carcinoma, pheochromocytoma and hyperparathyroidism. It has been shown to be associated with germ-line mutatians in the RET proto-oncogene. Presymptomatic screening of medullary thyroid carcinoma in MEN IIa families enables the early diagnosis of this tumor with its significant morbidity, We describe a 19-year-old woman fmm a MEN IIa family who was founded by DNA analysis to be a gene carrier of MEN IIa and then was diagnosed, using a pentagastrin stimulation test, as having presymptomatie medullary thyroid carcinoma She underwent thyroidectomy and histologic examination confirmed medullary thyroid carcinoma. It is cancluded that direct genetic analysis for mutations in the RET proto-oncogene should be the diagnstlc test of choice for identifying family members at risk for MEN IIa and thyroidectomy on the basis of genetic analysis is a rational course of action.