Molecular identification of combined homozygous and compound heterozygous mutations in the CYP21 gene in simple virilizing congenital adrenal hyperplasia in Taiwan.

Abstract

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder mainly caused by defects in the steroid 21-hydroxylase (CYP21) gene. We have experience of molecular analysis of in the CYP21 gene in 85 unrelated CAH families, in Taiwan for ten years. All ten exons of were analyzed by differential polymerase chain reactions (PCR) followed by single-strand conformation polymorphism (SSCP) analysis and the amplification-created restriction site (ACRS) method. More than 90% of the mutations were due to conversion of DNA sequences into its neighboring homologous pseudogene CYP21P. The most frequent mutation found in CAH patients in Taiwan was intron 2 mutation; the others were exons 8, 4 and 3, respectively, decreasing by frequency. Those were single homozygous mutations. In this report, we present two kinds of special mutations in our molecular research. Four families had their babies coming from combined homozygous mutation of both parents, that is due to both intron 2 (nt656) and 8-bp mutation. Eleven families had their babies coming from paternal codon 172 and maternal intron 2 (nt656) compound heterozygous mutations, that is codon 172 pat/int 2 (nt656) mat mutation. These two mutations had clinical manifestation of virilization, that is, enlarged clitoris only, but neither clinical nor laboratory finding of salt-losing. From our study, we found that autosomal recessive disorders such as simple virilizing CAH in our series could result from either combined homozygous mutations or compound heterozygous mutations. Further molecular study will focus on the salt-losing type in order to correlate the genotype/phenotype with this study.