<prompt> Commonest cause of congenital adrenal hyperplasia is21 hydroxylase deficiency11 B-hydroxylase deficiency17 alpha-hydroxylase deficiency18 hydroxylase deficiency  <response>: 21 hydroxylase 489-90-G 492-Ghai 7th 21 hydroxylase 11-b hydroxylase deficiency are common varieties21 hydroxylase11-b hydroxylase deficiency May present as salt-wasting form of CAH, due to the associated aldosterone deficiency resulting in life threatening emergencies in the early postnatal life These may present with severe vomiting and vascular collapse Boys with CAH do not have anomaly of the external genitals at birth Results in accumulation of deoxycortisol DOC because enzymatic block is beyond this stage These children develop hypertension of varying severity due to excessive DOC 