The clinical association between multiple endocrine neoplasia type 2 (MEN2) and 
Hirschsprung disease (HSCR) is infrequent. Germline mutations of the ret 
protooncogene are the underlying cause of the MEN2 syndromes and a proportion of 
cases of HSCR. In this report, we describe a new kindred in which the MEN2 and 
HSCR phenotypes are associated with a single C620S point mutation at one of the 
cysteine codons of the extracellular domain of the ret protooncogene. We also 
speculate about the role of a silent mutation in exon 2 of this same gene 
(A45A), present in a homozygous state in the patient with both MEN2A and HSCR. 
To investigate the contribution of GDNF to the phenotype observed in this 
kindred, we scanned the coding region of GDNF in the patient with MEN2/HSCR, but 
no mutation was found.