Comprehensive Genetic Testing of CYP21A2: A Retrospective Analysis in Patients with Suspected Congenital Adrenal Hyperplasia

Abstract

The most common form of congenital adrenal hyperplasia (CAH) results from a deficiency of the 21-hydroxylase enzyme (21-OHD), presenting with a broad spectrum of clinical phenotypes according to the CYP21A2 gene mutations. Of the 59 patients with suspected CAH, 62.7% presented a positive genetic result. Of them, 78.4% and 18.9% presented with non-classical and classical forms, respectively. An overall phenotype-genotype correlation of 88.9% was observed. Biochemically, 17-hydroxiprogesterone concentrations were significantly higher in genetically confirmed patients. Genetically, 36 patients presented with previously reported pathogenic variants, and one presented a new variant in homozygosis. Among the 74 alleles tested, point mutations were found in 89.2% and large rearrangements were found in the rest. The most prevalent pathogenic variant was p.(Val282Leu). The inclusion of relatives revealed one further case. Interestingly, 87.5% of relatives were carriers of a pathogenic variant, including two siblings initially classified as genetically positive. In addition, the study of male partners with gestational desire identified several carriers of mild mutations. Studying the allelic distribution of the variants also allowed for reclassifying one patient. In conclusion, a genetic approach including Sanger sequencing, multiplex ligation-dependent probe amplification (MLPA) analysis, and allelic distribution of the pathogenic variants represents a beneficial tool for better classifying patients with 21-OHD.

Neonatal Screening for Congenital Adrenal Hyperplasia in Indian Newborns with Reflex Genetic Analysis of 21-Hydroxylase Deficiency

“…Compared to other world population distribution of p.Gln319Ter, the mutation occurred at a higher frequency (21.2%) in the present Indian neonates [ 20 ]. The mutation p.Val282Leu is found in greater frequency in most other aucasian populations but is absent in the current Indian newborn screening study and other studies conducted in the Indian population [ 23 , 24 ]. Variant p.Val282Leu is usually associated with the non-classic form which is not the primary target of newborn screening for CAH…”

“…In the current study, the majority of the mutations was carried in the homozygous condition (72.22%), and this percentage is higher compared to the countries such as Serbia 13%, China 16.1%, USA 21%, Tunisia 24%, the Netherlands 28.3%, Croatia 33%, Romania 33.3%, and Brazil 39% [ 23 , 24 ]. This can be attributed to the higher frequency of consanguineous marriages, especially in southern states of India.…”