The mutation resulting in the Chy phenotype is an A-to-T mutation at position 3157 resulting in an isoleucine to phenylalanine substitution at position 1053 in the tyrosine kinase domain. This mutation is located in a highly conserved catalytic domain of the receptor, in close proximity to the VEGFR-3 mutations in human primary lymphedema. In addition, the Chy mutation was shown to be allelic to an existing targeted mutation in this gene. (J:72387)