The Frequency of Eight Common Point Mutations in CYP21 Gene in Iranian Patients with Congenital Adrenal Hyperplasia

Background: Congenital Adrenal Hyperplasia (CAH, the inherited inability to synthesize cortisol) is one of the most common (1 in 10000 to 1 in 15000) autosomal recessive disorders. More than 95% of cases of CAH are caused by 21-hydroxylase deficiency (21-OHD). Females with severe, classic 21-OHD are exposed to excess androgens prenatally and are born with virilized external genitalia. Most patients cannot synthesize sufficient aldosterone to maintain sodium balance and may develop potentially fatal salt wasting crisis if not treated. Methods: We applied allele specific PCR to detect the eight common mutations in the CYP21 gene in patients. Fifty unrelated patients with symptoms of classical CAH were studied. Results and Conclusion: Seventy percent of our subjects had these mutations. The most frequent mutations were found to be I2G and del-8bp (28% and 13%, respectively). The frequencies of other alleles were as following: I172N, 9% V281L, 3% exon 6 cluster (I236N, V237E and M239K), 4% Q318X, 9% R356W, 5% and P30L, 0%. The frequency of mutations did not differ substantially from other ethnics, however, a higher rate of del-8 bp (13%) was found in our population. The aim of this study was to detect common mutations for setting up a molecular method for prenatal diagnosis.