Most common type of Congenital adrenal hyperplasia (CAH)?

Ans. a (21-hydroxylase deficiency) (Ref OP Ghai 7th/ p. 492; H-17th/p. 2267).The 21-hydroxylase deficiency is the commonest form of CAH, accounting for > 90% of all cases.Type of CAHFeatures1.21-hydroxylase deficiency# Most common cause of ambiguous genitalia at birth# Salt-losing form of CAH# Episodes of acute adrenal insufficiency with hyponatremia, hyperkalemia, dehydration, and vomiting.# These infants and children often crave salt.# Deficits in both cortisol and aldosterone secretion.2.11-hydroxylase deficiency# Ambiguous genitalia# Hypertensive form of CAH# Diagnosis is confirmed by demonstrating increased levels of 11-deoxycortisol in the blood or increased amounts of tetrahydro-11-deoxycortisol in the urine.3.3b hydroxylase deficiency# Very high levels of urine DHEA with low levels of pregnanetriol and of cortisol metabolites in urine are characteristic.# Marked salt-wasting may also occur.4.17 a-hydroxylase deficiency# Female or ambiguous.# CAH# Hypertension due to | corticosterone & 11-deoxycorticosterone, except in isolated 17,20-lyase deficiency.5.Adults with late-onset adrenal hyperplasia (partial deficiency of CYP21A2, CYP11B1, or 3-HSD2)# Characterized by normal or moderately elevated levels of urinary 17-ketosteroids and plasma DHEA sulfate.# A high basal level of a precursor of cortisol biosynthesis (such as 17-hydroxy- progesterone, 17-hydroxypregnenolone, or 11-deoxycortisol), or elevation of such a precursor after ACTH stimulation, confirms the diagnosis of a partial deficiency.# Measurement of steroid precursors 60 min after bolus administration of ACTH is usually sufficient.# Adrenal androgen output is easily suppressed by the standard low-dose (2 mg) dexamethasone test.