FLT4 and lymphedema: Mice with a similar point mutation in Flt4, known as Chy mice, are a mouse model of congenital lymphedema.29 Thus, the Flt4iLECKO mice reported here that lack VEGFR3 protein likely mimic the dominant-negative mutations in the Milroy patients or Chy mice that have very low residual VEGFR3 signaling.