OBJECTIVEHereditary 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.

METHODSLinkage 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.

RESULTSA 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.

CONCLUSIONA new EXT2 nonsense mutation was found in a Chinese family with hereditary multipe exostoses. The information was used for a case of prenatal diagnosis.