OBJECTIVETo detect the underlying genetic defect in two Chinese families with hereditary multiple exostoses and provide genetic counseling.

METHODSPotential mutations in EXT1 and EXT2 genes in the probands were detected by direct sequencing of PCR-amplified exons. Suspected mutations were verified in all available family members and 200 unrelated healthy controls.

RESULTSA heterozygous frameshift mutation c.346_356delinsTAT in exon 1 of EXT1 and a heterozygous deletion mutation c.2009-2012del(TCAA) in exon 10 of EXT1 were respectively detected in affected members from the two families. The same mutations were not detected in unaffected members and 200 unrelated healthy controls. No mutations in EXT2 were detected in the two families.

CONCLUSIONTwo novel mutations of EXT1 have been detected in association with hereditary multiple exostoses in two Chinese families. Above results have provided a basis for genetic counseling for the two families and expanded the spectrum of EXT1 mutations.