<prompt> Which of the following statement about congenital adrenal hyperplasia is not true21 -alpha hydroxylase deficiency is the most common causeMales present with precocious pubeyFemales present with ambiguous genitiliaHypokalemic alkalosis is seen  <response>: Congenital adrenal hyperplasia are any of several autosomal recessive diseases resulting from mutations of genes for enzymes mediating the biochemical steps of production of mineralocoicoids, glucocoicoids or sex steroids from cholesterol by the adrenal glands steroidogenesis.Most of these conditions involve excessive or deficient production of sex steroids and can alter development of primary or secondary sex characteristics in some affected infants, children or adults hypokalemia alkalosis is not seen Each form of CAH is associated with a specific defective gene. The most common type 90-95 of cases involves the gene for 21-hydroxylase, which is found on 6p21.3 as pa of the HLA complex. 21-Hydroxylase deficiency results from a unique mutation with two highly homologous near-copies in series consisting of an active gene CYP21A2 and an inactive pseudogene CYP21A1PMutant alleles result from recombination between the active and pseudogenes gene conversion. About 5 of cases of CAH are due to defects in the gene encoding 11b-hydroxylase and consequent 11b-hydroxylase deficiency. Other, more rare forms of CAH are caused by mutations in genes including HSD3B2 3b-hydroxysteroid dehydrogenase 2, CYP17A1 17a-hydroxylase17,20-lyase, CYP11A1 P450scc; cholesterol side-chain cleavage enzyme, STAR steroidogenic acute regulatory protein; StAR, CYB5A cytochrome b5, and CYPOR cytochrome P450 oxidoreductase; POR. Ref Robbins 9e pg 155 