Phenotype: clinical description of MEN2
Three distinct clinical subtypes of MEN2 have been
characterized (Table 1). They differ with respect to incidence,
genetics, age-related penetrance, association with other
diseases, aggressiveness of MTC, and prognosis (3,4).
MEN2A syndrome (OMIM#171400) is characterized by the
presence of MTC, bilateral pheochromocytoma and/or
multiple tumors of the parathyroid glands (primary hyperparathyroidism)
within a single patient or family. It is the
most common form of MEN2 syndrome, representing 55% of
cases (5). The frequency of MTC is .90% among patients
with MEN2A, while the frequencies of pheochromocytoma
and multiple parathyroid gland hyperplasia are 40–50% and
10–20%, respectively. MTC is generally the first manifestation
of MEN2A and presents when patients are between 5 and 25
years of age. Rare variants of MEN2A exist, including
MEN2A with cutaneous lichen amyloidosis (this skin lesion
is located over the upper portion of the back) and MEN2A/
familial MTC (FMTC) with Hirschsprung’s disease (see
below).