Its paralog, NRG1, in addition to ErbB4 also binds to ErbB2 and ErbB3. Meanwhile, a 35 kb ErbB4 deletion (HSCR-CNVR32.1, chr2:212,872,711–212,889,560) was also observed uniquely in a syndromic HSCR patient. Here, NRG1 is linked to Hirschsprung disease.