HLA-DR Typing by PCR-SSP in Prenatal Diagnosis of Congenital Adrenal Hyperplasia Due to the 21-hydroxylase Deficiency

The close genetic linkage between the gene for congenital adrenal hyperplasia (CAH) dice to 21-hydroxylase deficiency and HLA-A,B,DR genes allowed us to use the polymorphism of this system as a marker of the disease. Prenatal diagnosis of CAH by HLA typing is based on the fact that all affected children in a family will be HLA identical. HLA typing of fetal cells is performed on the amniotic fluid cells grown in vitro. As the expression of HLA-DR antigens on the fetal cells is weak, classical serological typing only allows the determination of fetal HLA-A,B antigens. In the latest six prenatal diagnoses rue have introduced HLA-DR typing of fetal DNA, using polymerase chain reaction-sequence specific primers (PCR-SSP) method. In all cases HLA-DR typing was performed successfully, predicting in one case affected homozygous and in five cases unaffected carrier The supplementary use of HLA-DR typing proved helpful in families with HLA-A,B homozigosity and in cases where HLA-A,B typing could not be performed.