[A new EXT2 mutation in a Chinese family with hereditary multiple exostoses].

OBJECTIVE: Hereditary multiple exostoses (HME) is an autosomal dominant disorder characterized by formation of benign cartilage-capped tumors (exostoses), typically located at the juxtaepiphyseal regions of long bones. It is genetically heterogeneous with at least three chromosomal loci: EXT1 on 8q24.1, EXT2 on 11p11, and EXT3 on 19p. EXT1 and EXT2 have been cloned and are responsible for over 80% of cases. A Chinese family with HME has been analyzed in the present study. METHODS: Linkage analysis was firstly performed to determine which of the three EXT genes could be the candidate gene, then mutation screening by PCR and direct sequencing was carried out. RESULTS: A novel nonsense mutation (c.1006C>T) in exon 6 of EXT2, which converts the codon CAA (Gln) to the stop codon (TAA) (Gln336X), was identified. Next, prenatal diagnosis was performed and the pregnancy was determined to be normal. CONCLUSION: A new EXT2 nonsense mutation was found in a Chinese family with hereditary multipe exostoses. The information was used for a case of prenatal diagnosis.