By this methodology, germline mutations of the MEN1 (multiple endocrine neoplasia type 1), RET (rearranged during transfection), and CDC73 (cell division cycle protein 73) (originally entitled hyperparathyroidism type 2, HRPT2) genes as events underlying the development of multiple endocrine neoplasia type 1 (MEN1), multiple endocrine neoplasia type 2A (MEN2A), and hyperparathyroidism-jaw tumor (HPT-JT) syndromes, respectively (Table 1) [28–36]. The gene discussed is MEN1; the disease is multiple endocrine neoplasia type 2A.