Since 21-hydroxylase deficiency is a much more prevalent disorder, differential diagnosis often includes testing both CYP21A2 and HSD3B2 genes, although in 46,XY patients, genital ambiguity is more suggestive of HSD3B2 deficiency. This evidence concerns the gene HSD3B2 and classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency.