Nonclassic congenital adrenal hyperplasia due to 21-hydroxylase deficiency (NCAH) is a common milder form of congenital adrenal hyperplasia (CAH; see this term) characterized by a later onset of androgen excess symptoms seen in females and precocious pseudopuberty in both sexes.
The prevalence ranges from 1/1,000-1/500 in the general Caucasian population, but up to 1-2% among inbred populations, such as Eastern European (Ashkenazi) Jews. It is not a rare disease.
Disease onset occurs in adolescence with variable degrees of postnatal androgen excess (precocious pubarche, hirsutism, acne, alopecia, anovulation and menstrual irregularies) and in the post-pubertal period it can mimic polycystic ovary syndrome (PCOS; see this term). It is also sometimes asymptomatic.
The disease is caused by a mutation in the CYP21A2 gene located on chromosome 6p21.3. In NCAH cortisol and aldosterone levels are normal but there is an increased amount of androgens.
The disease follows an autosomal recessive pattern of inheritance.
Last update: October 2012