Congenital Adrenal Hyperplasia, 21-Hydroxylase Deficiency - Sequence Analysis
Definition
The CYP21A2 gene encodes the 21-hydroxylase enzyme, which is involved in cortisol and aldosterone synthesis in the adrenal glands. Deficiency of this enzyme accounts for approximately 95% of congenital adrenal hyperplasia (CAH); precursors accumulate and the excess is redirected toward androgen synthesis. The classic form is divided into two subtypes: the salt-wasting form (which can lead to a life-threatening salt-wasting crisis in the newborn) and the simple virilizing form; the non-classic (late-onset) form has the mildest presentation.
Gene/region examined
CYP21A2 - Exon 1, CYP21A2 - Exon 2, CYP21A2 - Exon 3, CYP21A2 - Exon 4, CYP21A2 - Exon 5, CYP21A2 - Exon 6, CYP21A2 - Exon 7, CYP21A2 - Exon 8, CYP21A2 - Exon 9, CYP21A2 - Exon 10
Method
Sequence analysis
Accepted sample types
EDTA blood, AF, CVS
Inheritance
Autosomal recessive; a pathogenic variant in both copies of the gene is required for the classic forms to occur, and carrier parents are usually asymptomatic. The classic form occurs in approximately 1 in 15,000 newborns and is included in newborn screening programs.