Hereditary aromatase deficiency is a rare disorder resulting in estrogen deficiency and androgen excess. A mother with a fetus affected by aromatase deficiency may become virilized during the pregnancy.


Inheritance of hereditary aromatase deficiency: autosomal recessive

Affected gene: CYP19A1

Affected enzyme: aromatase cytochrome P450 (P450arom)


The mutation results in a defect in the final step in the conversion of C19 steroids to estrogens, resulting in low estrogen and high androgen levels. According to Fisher et al, placental syncytiotrophoblasts show impaired conversion of androgens to estrogens, resulting in elevated testosterone.


The fetus is homozygous for aromatase deficiency while the mother is a carrier.


The mother develops signs of virilization during pregnancy with:

(1) acne

(2) hirsutism

(3) deepening of the voice

(4) male pattern hair loss


Laboratory testing may show high normal or elevated serum testosterone.


Once the pregnancy is over then the woman should revert to normal. This differs from other causes of virilization which continue after delivery.


The patient may give a history of virilization during a previous pregnancy.


The mother may have a history of previously affected children. Female neonates may show signs of virilization. Recognition in affected male offspring may be delayed until puberty.


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