MYL9 and Mydriasis: Of note individuals with biallelic pathogenic variants in MYL9 have mydriasis as part of megacystis microcolon intestinal hypoperistalsis phenotype.11 The similarity in the bladder‐eye phenotype in the two families would indicate that the missense variant results in a loss of function comparable to that predicted by the frameshift variant identified by Weber et al.1 It will be important through murine and cellular studies to undertake functional studies to determine the mechanism of action of the reported disease‐associated variants.