PREVALENCE OF PHEOCHROMOCYTOMA AND HYPERPARATHYROIDISM IN MULTIPLE ENDOCRINE NEOPLASIA TYPE-2A - RESULTS OF LONG-TERM FOLLOW-UP

Background. Multiple endocrine neoplasia type 2A (MEN 2A) is an autoso mal dominant condition in which virtually all affected kindred members have medullary thyroid carcinoma (MTC). However, the penetrance of ph eochromocytoma and hyperparathyroidism in affected kindred members is variable, and the true prevalence of these neoplasms is unclear from p revious studies. Methods. Members of MEN 2A kindreds with more than 10 years of follow-up screening for MTC, pheochromocytoma, or hyperparat hyrodism were studied. The diagnosis of pheochromocytoma was based on histologic examination and hyperparathyroidism on both parathyroid hyp erplasia plus preoperative elevation of serum calcium levels. Results. Eighty-six patients operated on for MTC from 12 different MEN 2A kind reds were studied, with a mean follow-up of 12.9 years of screening fo r pheochromocytoma (79 patients) and 15.0 years for hyperparathyroidis m (78 patients). Pheochromocytomas developed in 42% of patients with M TC, with a range of 6% to 100% in different kindreds. The prevalence o f hyperparathyroidism was 35%, ranging from 0% to 53% between kindreds . The average age at diagnosis of MTC, pheochromocytoma, and hyperpara thyroidism was 29, 37, and 36 years, respectively. Conclusions. We con clude that the penetrance of pheochromocytoma and hyperparathyroidism is variable in different kindreds with MEN 2A but that the overall pre valence of pheochromocytoma approximates 40% and that of hyperparathyr oidism 35%.