Mutations in the EXT1 and EXT2 genes in Spanish patients with multiple osteochondromas

Area of Science:

• Genetics
• Skeletal Dysplasias
• Molecular Biology

Background:

• Multiple osteochondromas is an autosomal dominant skeletal disorder.
• Characterized by the development of multiple cartilage-capped tumors.
• Causal genes EXT1 and EXT2 identified, explaining most cases.

Purpose of the Study:

• Analyze mutations in EXT1 and EXT2 genes in Spanish patients.
• Investigate genotype-phenotype correlations.
• Determine the mutation detection rate in this cohort.

Main Methods:

• Mutation analysis of EXT1 and EXT2 genes.
• Utilized MLPA (Multiplex Ligation-dependent Probe Amplification) for deletion detection.
• Evaluated genotype-phenotype correlations, specifically exostosis count.

Main Results:

• Mutations found in 37 out of 39 (95%) unrelated Spanish patients.
• 29 mutations in EXT1 and 8 in EXT2 identified.
• Five EXT1 mutations were deletions; two cases of mosaicism documented.
• Patients with missense mutations showed a lower number of exostoses compared to other mutation types.
• Eighteen novel mutations were discovered.

Conclusions:

• High mutation detection rate (95%) for EXT1 or EXT2 in Spanish patients with multiple osteochondromas.
• Identified novel mutations, expanding the known mutation spectrum.
• Demonstrated a genotype-phenotype correlation, with missense mutations linked to a milder phenotype (fewer exostoses).