ACTG2 and megacystis-microcolon-intestinal hypoperistalsis syndrome 1: In our review, we identified three cases of familial ACTG2-related MMIHS; one case was associated with somatic mosaicism in an asymptomatic parent [11] and in two other cases, a parent was not initially known to be affected but was diagnosed after the index pregnancy, and found to have a milder phenotype [8,10].