Hirschsprung’s disease (OMIM 142623) is a complex congenital disorder characterised by the absence of ganglion cells of the plexus myentericus and plexus submucosus in the variable lengths of the digestive tract.^1,2 Aganglionosis is attributed to a defect of the enteric nervous system, in which ganglion cells fail to innervate the lower gastrointestinal tract during embryonic development, resulting in failure to pass meconium, chronic severe constipation and colonic distention in the neonatal period.³ The receptor tyrosine kinase gene RET, which is expressed in neural crest cells during enteric neurogenesis and is required for normal development of the enteric nervous system, is the major susceptibility gene for Hirschsprung’s disease.⁴ There is growing evidence indicating that functional single nucleotide polymorphisms (SNPs) of RET could act as low susceptibility factors for Hirschsprung’s disease.^5,6 In addition, PHOX2B encodes a transcription …