The Genetics of Hereditary Multiple Exostosis (HME)

Introduction Hereditary multiple exostosis (HME) is a skeletal disorder characterized by the presence of numerous bony outgrowths (osteochondromas or exostoses) that develop next to the growth plates of all the long bones (Solomon 1963). The most striking clinical feature of HME is the numerous cartilage-capped exostoses, which are associated with the entire skeleton. Skeletal surveys suggest that a solitary exostosis can be found in 1-2% of the general population (Mirra 1989). A diagnosis of HME is made in individuals where the presence of multiple exostoses has been noted on clinical and/or radiologic examination. The average age at identification of a first exostosis is three to four years with 96% of individuals with HME developing exostoses by the age of 12 (Schmale et al. 1994; Wicklund et al. 1995).