MUTATIONS IN THE EXT1 AND EXT2 GENES IN SPANISH PATIENTS WITH MULTIPLE OSTEOCHONDROMAS

Abstract

Multiple osteochondromas is an autosomal dominant skeletal disorder characterized by the  formation of multiple cartilage-capped tumours. Two causal genes have been identified, EXT1 and EXT2, which account for 65% and 30% of cases, respectively. We have undertaken a mutation analysis of the EXT1 and EXT2 genes in 39 unrelated Spanish patients, most of them with moderate phenotype, and looked for genotype-phenotype correlations.Wefound the mutant allele in 37 patients, 29 inEXT1 and 8 inEXT2. Five of the EXT1 mutations were deletions identified by MLPA. Two cases of mosaicism were documented. We detected a lower number of exostoses in patients with missense mutation versus other kinds of mutations. In conclusion, we found a mutation in EXT1 or in EXT2 in 95% of the Spanish patients. Eighteen of the mutations were novel.