ABSTRACT
BACKGROUND: Congenital adrenal hyperplasia (CAH) results from an inherited defect in enzymatic steps required to synthesize cortisol from cholesterol. 21-hydroxylase deficiency accounts for 95% cases of CAH. It appears that the frequency and the type of the responsible mutations differ according to the ethnic background and the type of mutation can predict the clinical outcomes such as salt losing type (SL), simple virilizing type (SV) and non-classic type (NC). METHODS: We have analyzed CYP21 genes in 55 Korean cases (110 chromosomes) of CAH by Southern blotting, PCR-dot hybridization and PCR amplification-created restriction site method. The patients include 43 cases of SL and 12 of SV. None of the NC was found. RESULTS: We found the mutations in 94% (103/110) of the examined chromosomes. A total of 10 types of mutations were discovered. The mutations include aberrant splicing of intron 2 (i2, 35%), CYP21 gene deletion (32%) and I172N (11%) in order. When the relationship between the clinical types and genotypes were correlated, most of the SL patients have either i2 (42%) or CYP21 gene deletion (41%), while SV patients have I172N (33%) or P30L (21%). The parents' mutation was investigated in 20 cases. In 4 families, one of the parents was not the obligatory heterozygote carrier i.e. did not have a mutation. The results suggest the high incidence of de novo mutation. CONCLUSION: We have identified the frequency of mutations of the CYP21 in Korean AGS patients. Our results shows that the clinical type of AGS can be predicted from the genotypes of CYP21. Also the high incidence of de novo mutation of CYP21 confirmed the genetic instability of major histocompatibility III region where the CYP21 is located.