21-hydroxylase deficiency

21-hy·drox·y·lase de·fi·cien·cy (hi-drokґsə-lās) an autosomal recessive disorder of steroidogenesis caused by mutation in the CYP21 gene (locus: 6p21.3) , which encodes steroid 21-monooxygenase, and the adjacent pseudogene CYP21P; the resulting enzyme deficiency impairs the ability to produce all glucocorticoids. It is lethal if severe and untreated. It causes several forms of the most common type of congenital adrenal hyperplasia (type III): the more severe classic forms present at birth (salt-wasting and simple virilizing), and the less severe nonclassic forms of later onset (late-onset, or attenuated, and cryptic). The simple virilizing form is characterized clinically by female pseudohermaphroditism and postnatal virilization with advanced somatic development and biochemically by elevated androgens and decreased corticoids. The salt-wasting form is additionally characterized by aldosterone deficiency and salt wasting. Patients with nonclassic forms display variable expression of androgen excess later in life, ranging from hirsutism and infertility (late onset) to absence of clinical signs (cryptic). See also table at hyperplasia.