Question: What is (are) 21-hydroxylase deficiency ?
Answer: 21-hydroxylase-deficiency is a genetic disorder of cortisol biosynthesis. It is caused by mutations in the human 21-hydroxylase gene (CYP21A2). Symptoms of 21-hydroxylase deficiency vary, but can involve salt-wasting crises in infants; ambiguous genitalia in female infants; excessive hair, deep voice, abnormal periods, no periods, and fertility problems in older girls and women; early development of masculine features in boys; and shorter than average adult height, acne, and blood pressure problems.
Source: GARD

Question: Is 21-hydroxylase deficiency inherited ?
Answer: 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.
Source: GARD