Osteochondromas are caused by genetic abnormalities in EXT1 or EXT2: homozygous deletion of EXT1 characterizes sporadic osteochondromas (non-familial/solitary), and germline mutations in EXT1 or EXT2 combined with loss of heterozygosity define hereditary multiple osteochondromas.
Pathogenetic analysis showed that HMOs are caused by mutations in either of two genes: exostosis (multiple)-1 (EXT1), which is located on chromosome 8q24.11-q24.13 or exostosis (multiple)-2 (EXT2), which is located on chromosome 11p11-12.
We illustrate this point through the characterization of a novel ∼230 kb EXT1 duplication CNV causing autosomal dominant hereditary multiple osteochondromas.
We studied 114 HMO families (158 affected individuals) with causative EXT1 or EXT2 variants identified by Sanger sequencing, or multiplex ligation-dependent probe amplification and qPCR.