Congenital Adrenal Hyperplasia (CAH) (CYP21A2)
Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder which results from a deficiency in enzymes involved in cortisol biosynthesis. Approximately 95% of cases of CAH are caused by defects in the CYP21A2 gene, which leads to a deficiency of the steroid 21-hydroxylating enzyme. Approximately 1 in 12 individuals is a carrier of CAH. Symptoms of CAH vary based on the form of CAH, the age of diagnosis, and the sex of the patient. The classic presentation of CAH includes ambiguous genitalia, precocious puberty, and excessive facial hair, and in severe cases includes inadequate adrenal aldosterone secretion that can result in fatal salt-wasting crises. The milder form, non-classic CAH, is not typically detected through newborn screening and is often not diagnosed until later in childhood or adulthood. Treatment for CAH usually includes steroids to replace the low hormones. The long-term prognosis for individuals with CAH is usually favorable, and with lifelong treatment, affected individuals typically have good health and normal lifespans.
For information about carrier frequency and residual risk, please see the residual risk table.