ABSTRACT
Answer: (d) The most common cause of ambi guous genitalia is CAH. The most common enzyme deficiency associated with CAH is 21-hydoxylase deficiency. The second most common deficiency is 11-hydroxylase. Lastly, 3beta-hydroxysteroid dehydrogenase can also cause CAH but is extremely rare. CAH, if unrecognized and untreated, is life threatening in the salt-waster secondary to poor feeding, dehydration, and hyperkalemia leading to arrhythmias and shock. When the cause is 21-hydroxylase, blood tests for 17-hydroxyprogesterone and progesterone will be elevated. These tests should be ordered after day 2 of life because they may be falsely elevated early in life from the stress of delivery. 45XX CAH patients will still have Müllerian ducal structures, such as a uterus, visible on pelvic ultrasound.
