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46,XX Male Syndrome

Definition

46,XX male syndrome 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 prevalence 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. The SRY gene translocation is not detectable in 20%; changes in the SRY-dependent genes, such as activating mutations, are most likely responsible.

Signs and Symptoms of 46,XX Males

46,XX males are phenotypically and psychosexually male. They present with normal skeletal proportions, common findings are small testes, gynecomastia, or hypospadias. Patients without SRY gene translocation may present with genital ambiguity.

Diagnostic Workup

Laboratory Tests:

Hypergonadotropic hypogonadism (increased FSH and LH, low testosterone) is common. Semen analysis reveals azoospermia.

Karyotyping and Genetic Testing:

Karyotype 46,XX. Genetic testing may detect the SRY gene.

Testicular Biopsy:

In infertile men 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 therapy therapy corrects hypogonadism and prevents gynecomastia.

References

Ergun-Longmire, B.; Vinci, G.; Alonso, L.; Matthew, S.; Tansil, S.; Lin-Su, K.; McElreavey, K. & New, M. I. Clinical, hormonal and cytogenetic evaluation of 46,XX males and review of the literature.
J Pediatr Endocrinol Metab, 2005, 18, 739-748

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