On the basis of data collected during neonatal screening, the incidence of 21-hydroxylase deficiency is 1 in 14,500. Only affected females have ambiguous genitalia, which is caused by the ACTH-stimulated hypersecretion of adrenal androgens. Development of the ovaries and internal female reproductive organs is unaffected. This defect impairs the conversion of androstenedione to testosterone in the testis. Sixty cases have been reported from one inbred community in the Gaza Strip.
Inheritance is autosomal recessive.
Most XY cases have either ambiguous or female genitalia. In that group, at least 14 mutations in the 17beta-hydroxysteroid reductase 3 gene have been detected. In infancy and 5alpha-Reductase Deficiency. In this rare Placental Aromatase Deficiency. C19 androgens of fetal adrenal origin into estrogens.