CNP and thanatophoric dysplasia: Recent research indicated that CNP and NT-proCNP levels are significantly elevated in several skeletal dysplasias (achondroplasia, hypochondroplasia, thanatophoric dysplasia, and Maroteaux type of acromesomelic dysplasia) caused by mutations in the FGFR3 (fibroblast growth factor receptor 3) or NPR2 (natriuretic peptide receptor 2) gene [69].