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Genetic and Rare Diseases Information Center (GARD)

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21-hydroxylase deficiency

Other Names for this Disease
  • 21 hydroxylase deficiency
  • Congenital adrenal hyperplasia due to 21-hydroxylase deficiency
  • CYP21 deficiency
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How is 21-hydroxylase-deficient congenital adrenal hyperplasia passed through families?

21-hydroxylase-deficient congenital adrenal hyperplasia has an autosomal recessive pattern of inheritance. In autosomal recessive conditions, both parents carry one copy of a mutated gene for the disorder. They have a 25 percent chance with each pregnancy of having a child affected by the disorder. The chance with each pregnancy of having an unaffected child who is a carrier of the disorder is 50 percent, and the chance that a child will not have the disorder and will not be a carrier is 25 percent. See the illustration below.[1]

                                            In this example, two unaffected parents each carry one copy of a gene mutation for an autosomal recessive disorder.  They have one affected child and three unaffected children, two of which carry one copy of the gene mutation.
Last updated: 7/25/2013

  1. If a genetic disorder runs in my family, what are the chances that my children will have the condition?. Genetics Home Reference. Accessed 4/4/2008.