The affected brothers also had impaired pupillary constriction to light, a notable feature given that the M3 acetylcholine receptor is expressed in pupillary sphincter muscle, mediating its contractions.15, 16 Furthermore, male mice that carry homozygous targeted loss of function mutations of Chrm3 have a similar syndrome affecting the bladder and the eye.17 In this report, we present a second family carrying a homozygous variant in CHRM3 associated with familial urinary bladder disease. Here, CHRM3 is linked to urinary bladder disorder.