Submucosal Supernumerary Smooth Muscle Coat: A Common Histologic Finding in Mowat-Wilson Syndrome With or Without Hirschsprung Disease.

Background: Mowat-Wilson syndrome (MWS) is a multiorgan system disorder caused by (zinc finger E-box-binding homeobox 2) mutations or deletions. One common manifestation is constipation, and approximately half of the patients have Hirschsprung disease (HSCR). In addition to classic histologic features of HSCR, an unusual supernumerary intestinal muscle coat was recently reported in a patient of MWS with HSCR.