ABSTRACT
Objective To report the prenatal molecular diagnosis for two gravida in a family with spondylepiphyseal dysplasia congenita(SEDC)caused by G504S mutation of COL2A1 gene.Methods DNA of the two fetuses was extracted from amniotic fluid at the 19+3 and 18+6 weeks of gestation respectively.Direct sequencing of two samples were performed after amplifying exon 23 of COL2A1 containing the potential mutation.The femur length and biparietal diameter of the first fetus were measured by sonographic scans every two weeks from 17+3 weeks to 27+3 weeks of gestation,and for the second fetus these parameters were measured from 16+1 to 19+1 weeks of gestation.Results Sequncing analysis revealed the first fetus and his mother presented the same mutation which is specifically associated with SEDC,but the second fetus did not show the mutation of COL2A1 gene.Biparietal diameters of the both fetuses were appropriate for gestational age.Femur length of the second fetus was normal for gestational age but that of the first fetus was shortened evidently after the 23 week of gestation.The parents of the first fetus determined to terminate the pregnancy.A medical termination was carried out at 27+5 weeks of gestation and a male fetus with a relatively large head and short limbs was delivered.The radiological findings of the fetus were consistent with SEDC including generalized platy spondesand shortened long bones.Conclusions Prenatal molecular diagnosis is important for the fetus with risk of SEDC and useful for genetic counseling.Genotype of fetus with risk of SEDC can be identified before sonographic scan.Molecular genetic analysis in conjunction with sonographic monitoring was helpful in prenatal diagnosis of SEDC.
