CYP21A2 and congenital adrenal hyperplasia: The most common form of CAH, accounting for over 95% of cases, is caused by 21-hydroxylase deficiency, which results from a mutation in the CYP21A2 gene.1 Genital ambiguity in female newborns with CAH allows for early diagnosis, while males are usually asymptomatic at birth and are generally diagnosed after life threatening adrenal crisis or they die unsuspected.2