[Genetic bases of Hirschsprung's disease].

Hirschsprung's disease constitutes a neural crest stem cell disorder (neurocristopathy) which is caused by absent or malfunctional intestinal intramural ganglion cells. The rostral extension of the aganglionic segment is variable. Hirschsprung's disease can be classified into type 1 (short segment) and type 2 (long segment) forms. It is limited to the gastrointestinal tract, but may occur in the syndromal context of manifold genetic diseases in 12% of patients. The prevalence is 1:5,000 with a distinct male predominance of 4-5:1. Numerous genes and non-coding polymorphous DNA sequence variants are involved in the pathogenesis of Hirschsprung's disease. The most important gene is RET. Susceptibility loci on 3p21, 9q31 and 19q12 interact with this gene. Downstream of RET, two new genes, GALNACT-2 and RASGEF1A, have also been identified. A recently described, frequent, non-coding RET variant, RET+3, is significantly associated with susceptibility to Hirschsprung's disease and carries a 20-fold increased risk of contracting the disease compared to rarer alleles.