EXT1 and EXT2 mutations have been detected in approximately 70% to 95% of patients with HME, with EXT1 accounting for 56% to 78% and EXT2 accounting for 21% to 44% of cases.[13] To date (May 5, 2018), in the Multiple Osteochondroma Mutation Database (http://medgen.ua.ac.be/LOVDv.2.0/home.php), the numbers of variations in EXT1 and EXT2 are 436 and 223, respectively. Here, EXT2 is linked to Multiple osteochondromas.