(absence of enteric nerve cells) in the gastrointestinal tract
(Hirschsprung disease). The lack of neuroenteric plexi
impairs smooth muscle activity of the intestines (particularly
the colon), resulting in refractory constipation. Up to
50% of familial cases and up to 35% of simplex cases (i.e., a
single occurrence in a family) of Hirschsprung disease are
caused by germline loss-of-function mutations in the RET
proto-oncogene (20). There are some families and individuals
harboring germline RET mutations in exon 10 that cosegregate
with MEN2A/FMTC and Hirschsprung disease.
Because of a seemingly similar clinical presentation,
clinicians should be careful to differentiate the diagnosis
CLINICS 2012;67(S1):69-75 Genotype-phenotype correlation in MEN2
Raue F and Frank-Raue K
71
of Hirschsprung disease from the constipation/obstipation
that result from ganglioneuromatosis associated with
MEN2B.