PHOX2B and Hirschsprung disease: The molecular basis of CCHS was identified in 2009 and attributed to mutations in the paired-like homeobox 2B gene, PHOX2B. Two types of mutations have been described: polyalanine repeat mutations (PARMs), which are frequent, have a variable clinical presentation, and disease severity correlates with allele size; and nonpolyalanine repeat mutations (NPARMS) that are usually associated with a more severe presentation including Hirschsprung disease (HSCR) and an increased tumor risk [1,3].