Complex Alleles of CYP21A2 Are the Most Frequent Causes of Congenital Adrenal Hyperplasia in Iranian Population

The purpose of this study was to investigate CYP21A2 mutations in Iranian congenital adrenal hyperplasia (CAH) patients.

In 25 patients, the first PCR was done to distinguish the gene from the pseudogene (identification of chimeras). Then, second PCR was performed in the patients who had not chimeras, followed by complete exons and introns of CYP21A2 sequencing to distinguish the mutations.

Complex alleles comprising three compound heterozygote mutations were identified; p.I173N/exon 6 cluster (15.7%), p.I173N/exon 6 cluster/p.V282L (47.3%) and IVS2-13A>C, G/exon 6 cluster/p.V282L (5.2%). In order to confirm the accuracy of mutations, the parents of the patients were also analyzed. In each family, one of the parents had a heterozygote variant (p.I173N/p.V282L) and the other had exon 6 cluster heterozygote variant without any symptoms of the disease. Two different mutations in the heterozygous state, exon 6 cluster (10.5%) and exon 6 cluster/p.V282L (5.2%) and p.G110Efs the 8 nucleotide deletion in exon 3 (5.2%), I173N in the heterozygote state (10.5%). A high frequency of variants was found in CYP21A2, including: rs6477 (56%), rs6468 (8%), rs6474 (12%), rs6472 (16%), rs6473 (16%), rs6446 (16%), rs61338903 (32%) and rs193922546, rs530758070, rs11970671, rs61732108, rs778403992, rs1058152 and rs562025438 (each 4%).

The present study showed that the compound heterozygosity and complex alleles are the most frequent cause of congenital adrenal hyperplasia in Iranian population. Patients’ clinical manifestations were correlated with mutated alleles and the residual activity of 21-hydroxylase enzyme. Based on diversity of mutations in CAH patients of this study, whole CYP21A2 gene sequencing would be preferential approach in analyzing CAH patients in our population.