Aromatase Deficiency

A rare disorder that disrupts the synthesis of estradiol, resulting in hirsutism of mothers during gestation of an affected child; pseudohermaphroditism and virilization in women; and tall stature, osteoporosis and obesity in men.

Epidemiology

Fewer than 20 cases have been reported to date.

Clinical description

Affected female newborns present with different degrees of ambiguous genitalia, virilization and non-palpable gonads, in one case female genitalia were present. Female internal genitalia differentiation is unaffected. Ovarian cystic follicles may appear in childhood, even at birth, or adolescence when patients manifest primary amenorrhea and no pubertal growth spurt. Breasts remain hypoplastic after initial development during puberty, while pubic hairs develop in a normal fashion. Males may present with cryptorchidism, but are generally asymptomatic until after puberty when patients present with bone pain and tall stature. The pubertal growth spurt is absent, but linear growth continues due to incomplete epiphyseal closure and progressive genu valgum, eunuchoid proportion of the skeleton and osteoporosis manifest. For these reasons the diagnosis is often overlooked in men. Metabolic co-morbidities may manifest as obesity, steatohepatitis, insulin resistance with acanthosis nigricans and dyslipidemia. Fertility is partially or completely disrupted in male patients.

Etiology

Aromatase (CYP19A1, 15q21.1), or cytochrome P450, synthesizes estradiol from androgens. Several null mutations have been identified, placental expression of aromatase converts androgens to estradiol; excess androgens affect both the mother and fetal development. One reported case of a promoter region mutation exclusively inhibited placental expression.

Diagnostic methods

Females are generally diagnosed at birth. Male patients are usually diagnosed during adulthood due to continuing linear growth in height and unfused epiphyses are revealed by hand radiographs. Measurement of serum estradiol, testosterone and luteinizing hormone may be followed by genetic testing.

Differential diagnosis

In female patients, differential diagnosis includes congenital adrenal hyperplasia (see this term); in male patients, estrogen resistance syndrome 46,XY disorder of sex development due to isolated 17, 20 lyase deficiency, congenital adrenal hyperplasia due to cytochrome P450 oxidoreductase deficiency and congenital hypogonadotropic hypogonadism (see these terms).

Antenatal diagnosis

During the third trimester of gestation, mothers exhibit severe acne, deep voice and in some cases clitoral enlargement and hirsutism, symptoms resolve spontaneously post-partum. Genetic testing is recommended in these cases.

Genetic counseling

Genetic testing is recommended for families who have had one affected child, transmission is autosomal recessive.

Management and treatment

Female patients are candidates for surgical modification of genitalia depending on the degree of ambiguity and must be monitored for ovarian cysts. Upon puberty, daily treatment with estrogen must be administered (0.625 mg/twice weekly increasing to daily) and may be supplemented with progesterone-like hormone and monthly treatments of gonadotrophin-releasing hormone antagonists. Adult men should be treated immediately upon diagnosis: daily transdermal administration of up to 50 µg of estradiol (serum estradiol at 40 pg/ml) for 6-9 months to complete skeletal maturation. Upon epiphyseal closure, estradiol replacement may be reduced to 25 µg daily. Hypocaloric diet should be complemented with calcium, vitamin D and physical activity. Dyslipidemia, glucose intolerance or insulin resistance must be treated symptomatically.

Prognosis

Lifetime hormone replacement therapy is obligatory. In male patients with late diagnosis, skeletal defects remain even after successful hormonal treatment and may require surgical correction. Furthermore, adiposity and fertility defects are not alleviated by estradiol treatment.