Molecular diagnosis of patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency

Abstract

Background: Congenital adrenal hyperplasia (CAH) is an autosomal recessive group of diseases. 21-Hydroxylase deficiency (21OHD) accounts for between 95 and 99% of all CAH cases.

Objectives: To characterize the genotype of patients clinically diagnosed with 21OHD and to identify the most frequent mutations in the Cuban population.

Methods: Cross-sectional descriptive study that included all patients diagnosed with 21OHD from January 2000 to December 2018. For the molecular analysis of the CYP21A2 gene, a protocol was used that used the polymerase chain reaction in 2 stages; in the first stage genomic DNA was amplified and 5 point mutations were detected in the second stage (Intron 2, Deletion of 8 bp, G318X, I172N and P30L).

Results: The 5 point mutations were identified in 31 of the 55 (56%) studied patients, 16/21 (76%) in the salt-wasting, 12/18 (67%) in the simple virilizing and 3/16 (19%) in the nonclassical form. The Intron 2 mutation was the most frequent, followed by G318X and 8 bp deletion. Compound heterozygotes were found in 10 patients, all corresponded to classic forms of the disease.

Conclusions: The causal CYP21A2 gene mutation was detected in 56% (72% in classic CAH), which makes the method encouraging. The most frequent mutations observed were Intron 2 and G318X. The detection of mutations offers confirmation of diagnosis, prediction of phenotype and genetic counseling.

Keywords: Congenital adrenal hyperplasia; Genetics; Point mutations.

Fig. 1

Distribution of affected alleles according to point mutations found in each clinical phenotype. Panel a Patients with salt-wasting phenotype. Panel b Patients with simple virilizing phenotype. Panel c Patients with nonclassical phenotype

Fig. 2

Affected alleles according to the five explored point mutations