<p><b>BACKGROUND</b>
Multiple osteochondromas (MO), an inherited autosomal dominant disorder, is characterized by the presence of
multiple exostoses on the long
bones. MO is caused by
mutations in the EXT1 or EXT2
genes which encode
glycosyltransferases implicated in
heparin sulfate biosynthesis.</p><p><b>
METHODS</b>In this study, efforts were made to identify the underlying
disease-causing
mutations in
patients from two MO
families in
China.</p><p><b>RESULTS</b>Two novel EXT1
gene mutations were identified and no
mutation was found in EXT2
gene. The
mutation c.497T > A in
exon 1 of the EXT1
gene was cosegregated with the
disease phenotype in
family 1 and formed a
stop codon at
amino acid site 166. The
fetus of the proband was diagnosed negative. In
family 2, the
mutation c.1430-1431delCC in
exon 6 of the EXT1
gene would cause frameshift and introduce a
premature stop codon after the
reading frame being open for 42
amino acids. The
fetus of this
family inherited this
mutation from the
father.</p><p><b>CONCLUSIONS</b>
Mutation analysis of two MO
families in this study demonstrates its further application in MO
genetic counseling and
prenatal diagnosis.</p>