The uncommon forms of congenital adrenal hyperplasia.

PURPOSE OF REVIEW: Clinicians recognize 21-hydroxylase deficiency as the most common form of congenital adrenal hyperplasia (CAH), and many papers have been published on this condition. In contrast, much less awareness has been addressed to the other, rare forms of CAH.

RECENT FINDINGS: The second most common form of CAH varies with country and ethnic background. In Brazil, 17-hydroxylase/17,20-lyase deficiency is the second most common, whereas 11-hydroxylase deficiency is most common in the Middle East. In Japan and Korea, both congenital lipoid adrenal hyperplasia and P450-oxidoreductase deficiency are more common than in the rest of the world. Finally, 3β-hydroxysteroid dehydrogenase/isomerase deficiency is rare worldwide, but pockets of affected populations, such as the Amish in Lancaster County, Pennsylvania are found. The treatment of each form varies by both the nature of steroids produced in excess above the enzymatic block and the deficiencies of steroids other than cortisol past these blocks.

SUMMARY: This article summarizes the pathophysiology, diagnosis, and management of rare forms of CAH.