MTC is the major cause of premature mortality in MEN2A patients, and frequently presents at an advanced disease stage in index cases (median age of diagnosis 20-25 years for codon 634 mutations).45 PHPT occurs in ≤30% of patients with MEN2A, most commonly with codon 634 mutations, and typically presents in the 3rd to 4th decade, although PHPT has been reported as early as 2-years of age. The gene discussed is RET; the disease is medullary thyroid gland carcinoma.