MEN2B (OMIM#162300) is characterized by the association
between MTC, pheochromocytoma, the absence of
hyperparathyroidism, and visible physical stigmata such asraised
bumps on the lips and tongue (caused by cutaneous
neuromas), ganglioneuromas of the intestine, and asthenic
marfanoid body habitus with skeletal deformations and
joint laxity. Pheochromcytomas occur in 50% of individuals
with MEN2B, approximately half of these are multiple and
often bilateral; the development of mucosal neuromas on
the tongue and lips (bumpy lips) (resulting in a distinctive
facial appearance), together with a marfanoid body habitus,
allows for diagnosis at a first glance. Early diagnosis by
clinical means is difficult because of the gradual development
of the typical clinical appearance during childhood.
Diffuse ganglioneuromatosis of the gastrointestinal tract is
responsible for the megacolon, constipation and diarrhea
that often present. Because of their similar clinical presentations,
the clinician should carefully differentiate the
diagnosis of Hirschsprung disease as a result of aganglioneuromatosis
from MEN2B. Brauckhoff et al. reported that
86% of patients with MEN2B demonstrate an inability to cry
tears (6). It is the rarest form of MEN2 and accounts for 5–
10% of MEN2 cases. Patients with MEN2B typically present
with MTC during the first year of life and have a more
aggressive form of MTC with higher morbidity and
mortality rates than patients with MEN2A (4). Patients with
MEN2B often do not have a family history of the disease; in
more than 50% of cases the syndrome is due to a de novo
germline RET mutation.