MEN2A, which accounts for 95% of MEN2 cases, can be divided into four variants: classical MEN2A (represented by the uniform presence of MTC and the less frequent occurrence of pheochromocytoma or hyperparathyroidism, or both), MEN2A with cutaneous lichen amyloidosis, MEN2A with Hirschsprung’s disease, and familial MTC (families or individuals with RET germline mutations who have MTC but not pheochromocytoma or hyperparathyroidism). The gene discussed is RET; the disease is familial medullary thyroid carcinoma.