Genetic profiling of CAH Egyptian children: rapid guide to clinical interpretation of common mutations.

OBJECTIVES: The prevalence of CAH in Egypt is reported to be ten times more than that of the worldwide prevalence. The study aimed at genetic screening of children diagnosed with 21-alpha hydroxylase deficiency congenital adrenal hyperplasia (21OHD-CAH). In addition, the study offers a rapid and easy guide for clinical reporting of common mutations for endocrinologists. METHODS: A cohort of 174 unrelated Egyptian children with 21OHD-CAH were screened for 11 common CYP21A2 gene mutations using a strip hybridization assay, and then, bioinformatics analysis was done to report the pathogenicity of the common mutations for clinical classification. RESULTS: The most common mutations were I2 splice and p.Q318X. Deletions/conversions comprised 45.9% of the cohort, whereas 7.4% of the cases were negative for all mutations. The least positively detected point mutations were p.P453S, cluster E6, p.R483P, and p.L307FS, which were detected in fewer than 5% of cases. CONCLUSION: Strip hybridization assay is a rapid screening tool for the diagnosis of CAH. The authors hypothesized an easy and rapid scheme for clinical interpretation of the strip results to gain the highest value of the strip in diagnosis.

High frequency of splice site mutation in 21-hydroxylase deficiency children.

PURPOSE: Steroid 21-hydroxylase deficiency (21-OHD) is the common type of congenital adrenal hyperplasia (CAH) caused by defects in the CYP21A2 gene, as an autosomal recessive disease, genetic analysis has a prominent role in its diagnosis. Our objectives were to determine the prevalence of common mutations in a group of Egyptian patients with 21-OHD and their families using rapid methods, and also to detect the rate of deletion, duplication and conversions in CYP21A2 gene. METHODS: Rapid detection methods were used: allele-specific PCR for c.293-13A>G (g.659A>G), c.518T>A (p.I172N) variants and c.332_339del (8-bp deletion in exon 3), and real-time, quantitative PCR assay was used to detect deletion in the CYP21A2 gene. 29 Egyptian patients, 38 family members, and 20 healthy controls were all included in the study. RESULTS: The frequency of c.293-13A>G splice mutation was reported in 96.6 % cases, G allele had 2.5-folds higher risk to develop CAH than other alleles. The c.518T>A mutation was reported in 69 % cases, children carrying the mutant allele were 2.1 times more risk. The most frequent combined mutations detected were c.293-13A/C>G/c.518T>A in 58.6 % cases. CONCLUSION: The genetic analysis of the splice site mutation c.293-13A>G and c.518T>A variant can be used as good biomarkers for early detection of cases and carriers in 21-OHD CAH Egyptian children, since the methods used have rapid turnaround time.