Congenital adrenal hyperplasia (21-hydroxylase deficiency)
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A newborn female has ambiguous genitalia with clitoromegaly and labial fusion. She develops a salt-wasting crisis at 2 weeks of age with hyponatremia and hyperkalemia.
AR; CYP21A2 (21-hydroxylase)
- Most common cause of CAH (~95%)
Forms:
- Classic salt-wasting: Severe enzyme deficiency, cortisol + aldosterone deficiency
- Classic simple virilizing: Cortisol deficiency, aldosterone usually adequate
- Non-classic: Mild, late-onset (hirsutism, irregular menses)
- Females: Virilization, ambiguous genitalia at birth
- Males: May appear normal at birth, precocious puberty later
- Salt-wasting: Hyponatremia, hyperkalemia, hypotension, shock
- Elevated 17-hydroxyprogesterone
Newborn Screening: On RUSP (elevated 17-OHP)
- Elevated 17-hydroxyprogesterone (17-OHP) is the key biochemical marker; included on newborn screening
- ACTH (cosyntropin) stimulation test confirms borderline or non-classic cases (exaggerated 17-OHP rise)
- CYP21A2 molecular testing confirms the diagnosis and guides carrier and prenatal counseling
- Salt-wasting form: hyponatremia, hyperkalemia, low aldosterone, elevated plasma renin
- Glucocorticoid and mineralocorticoid replacement