Clinically, there are three main subtypes of MEN 2; 1) MEN2A is characterised by medullary thyroid cancer in 95% of patients, phaeochromocytoma in 40-50% and primary hyperparathyroidism in 20%-30%; 2) MEN2B accounts for approximately 5% of MEN syndromes and has medullary thyroid cancer in 100%, phaeochromocytoma in 50% of cases, a Marfanoid body habitus, and multiple mucosal ganglioneuromas; however, it is not associated with hyperparathyroidism. This evidence concerns the gene RET and primary hyperparathyroidism.