Hirschsprung disease is a congenital malformation, where absence of intramural 
ganglia in the hindgut results in a defect in the coordination of peristaltic 
movement. This leads to ileus in the newborn or, more often, constipation in 
children and adults. The disease affects one in 5000 live births. Siblings of 
affected cases are at an increased risk (4%) of developing the disease. Among 
cases. males are affected more often than females. The first major 
susceptibility gene for Hirschsprung disease is the RET proto-oncogene on 
10q11.2. Germline RET mutations in Hirschsprung disease are mainly inactivating, 
and have been reported to account for up to 20 and 50% of sporadic and familial 
cases, respectively. We have screened Swedish population-based samples from 62 
sporadic cases and seven familial cases of Hirschsprung disease with single 
strand conformation polymorphism (SSCP), and found five mutations.