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46,XX Males

Definition

46,XX male sydrome is a chromosomal disorder in men with a male phenotype and a 46,XX karyotype (Ergun-Longmire et al., 2005). It is sometimes called de la Chappelle-syndrome (first description in 1964).

Epidemiology

The incidence of the 46,XX male syndrome is 1:20.000.

Etiology

In 80%, the 46,XX male syndrome is caused by a translocation of a Y-chromosome fragment on the paternal X chromosome. As a necessary gene for testicular development, the SRY gene was identified. In 20% of the 46,XX male syndrome· the SRY gene translocation is not detectable. In these cases, changes of the SRY-dependent genes are most likely responsible, such as activating mutations.

Signs and Symptoms of 46,XX Males

46,XX males are phenotypically and psychosexually male. They have a normal physique and normal external genitalia. Small testes, symptoms of hypogonadism, gynecomastia or hypospadia (10%) may be present. 46,XX male syndrome causes azoospermia.

Diagnostic Work-Up

Laboratory Tests:

Hypergonadotropic hypogonadism. Semen analysis reveals azoospermia.

Karyotyping:

46,XX

Testicular Biopsy:

In infertile med with proven 46,XX karyotype, testicular biopsy is not indicated. Histology will show tubular hyalinization and lack of spermatogenesis.

Treatment of 46,XX Male Syndrome

Testosterone replacement therapy for proven hypogonadism. Treatment of gynecomastia.

References

  Deutsche Version: 46,XX Männer