Dictionary of Human Evolution and Biology

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Congenital Adrenal Hyperplasia

Any one of half a dozen enzyme deficiencies that causes male sex hormones to accumulate abnormally in tissues. In 90% of cases, the deficient enzyme is 21-hydrolase, an autosomal recessive gene; the result is a highly polymorphic system with multiple alleles and four genotypic combinations.
(1) In the salt-wasting form, shock and death occur within a few weeks of birth.
(2) Early-onset 46,XX congenital virilizing adrenal hyperplasia (CVAH) is a simple masculinizing form in which females have normal internal reproductive organs but enlarged clitorises, and males have enlarged penises and experience precocious puberty.
(3) In the more common late onset form, profound masculinization of females occurs at puberty.
(4) In the cryptic form, there are no phenotypic symptoms but enzyme and hormone concentrations are elevated. Enlarged adrenal glands are a feature in all cases. Certain HLA haplotypes predispose individuals to this condition: B47 increases the relative risk by 15

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