Thus, based on the 150 chromosomes with known normal CYP21A2 and the 93 chromosomes of In2G CYP21A2 (55 patients with 21-OHD CAH and 24 carriers) in our cohort, we found that at least 13.3% (20/150) and 11.8% (11/93) of unaffected and In2G CYP21A2 alleles shared a chromosome with one or more copies of this TNXA variant allele, respectively. This evidence concerns the gene CYP21A2 and classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency.