Prophylactic thyroidectomy for asymptomatic 3-year-old boy with positive multiple endocrine neoplasia type 2A mutation (codon 634).

Introduction: The multiple endocrine neoplasia type 2A (MEN 2A) syndrome, comprising medullary thyroid carcinoma (MTC), pheochromocytoma and primary hyperparathyroidism (PHPT) is most frequently caused by codon 634 activating mutations of the RET (rearranged during transfection) proto-oncogene on chromosome 10. For this codon-mutation carriers, earlier thyroidectomy (before the age of 5 years) would be advantageous in limiting the potential for the development of MTC as well as parathyroid adenomas.

Case Outline: This is a case report of 3-year-old boy from the MEN 2A family (the boy's father and grandmother and paternal aunt) in which cysteine substitutes for phenylalanine at codon 634 in exon 11 of the RET proto-oncogene, who underwent thyroidectomy solely on the basis of genetic information. A boy had no thyromegaly, thyroidal irregularities or lymphadenopathy and no abnormality on the neck ultrasound examination. The pathology finding of thyroid gland was negative for MTC. Two years after total thyroidectomy, 5-year-old boy is healthy with permanent thyroxine replacement. His serum calcitonin level is < 2 pg/ml (normal < 13 pg/ml), has normal serum calcium and parathyroid hormone levels and negative urinary catecholamines. Long-term follow-up of this patient is required to determine whether very early thyroidectomy improves the long-term outcome of PHPT.

Conclusion: Children with familial antecedents of MEN 2A should be genetically studied for the purpose of determining the risk of MTC and assessing the possibilities of making prophylactic thyroidectomy before the age of 5 years.