Congenital adrenal hyperplasia (CAH)

Alternative name	Classical CAH due to 21-hydroxylase deficiency
About the condition	CAH is an adrenal endocrine disorder. It is a hereditary disease caused by a missing enzyme (21-hydroxylase) needed in the production of cortisol, which is important in the normal metabolic response to stress. The deficiency also causes an increase in androgen hormones, which results in virilisation of external genitalia. Aldosterone may be decreased, which impairs electrolyte and water balance and may cause life-threatening complications.
Inheritance	Autosomal recessive
Year screening occurred in WA	2022
Incidence in WA	1 in 15,000 births
Enzyme defect	Deficiency of 21-hydroxylase, an enzyme required for cortisol and aldosterone production.
Symptoms if untreated	Females may present with virilisation of external genitalia at birth due to excess androgens and can be identified early. Males usually appear normal at birth and present with later signs in the first few weeks of life that include poor feeding, lethargy, vomiting, weight loss and dehydration. Detection by newborn screening is therefore important for early treatment.
Metabolites on bloodspot screening	Increased 17-hydroxyprogesterone.
Diagnostic tests	Serum steroid profile CYP21A2 gene analysis
Treatment	Glucocorticoids and mineralocorticoid therapy, and other treatment as required.
Screening issues	Newborn screening for CAH is directed to the classical form, which is caused by severe 21-hydroxylase deficiency. Milder forms of CAH that occur may not be detected by screening.