CYP21A2 and congenital adrenal hyperplasia: NAHR-mediated deletion between TNXB and TNXA leads to loss of CYP21A2, the causal gene of autosomal recessive 21-hydroxylase deficiency (classical congenital adrenal hyperplasia, CAH), as well as C4B, absence of which may contribute to reduced complement 4 production.