Y chromosome infertility

Alternate names

Male sterility due to Y-chromosome deletions; DAZ; Deleted in azoospermia; Y chromosome microdeletions

Definition

Y chromosome infertility is a condition that affects the production of sperm, making it difficult or impossible for affected men to father children. An affected man's body may produce no sperm cells (azoospermia), a smaller than usual number of sperm cells (oligospermia), or sperm cells that are abnormally shaped or that do not move properly.

Summary

This condition accounts for between 5 percent and 10 percent of cases of azoospermia or severe oligospermia. As its name suggests, this form of infertility is caused by changes in the Y chromosome, one of the sex chromosomes.

Cause and inheritance

• Y chromosome infertility is usually caused by deletions of genetic material in regions of the Y chromosome called azoospermia factor (AZF) A, B, or C.
• Genes in these regions are believed to provide instructions for making proteins involved in sperm cell development, although the specific functions of these proteins are not well understood.
• In rare cases, changes to a single gene called USP9Y, which is located in the AZFA region of the Y chromosome, can cause Y chromosome infertility.
• Some men with Y chromosome infertility who have mild to moderate oligospermia may eventually father a child naturally.
• Assisted reproductive technologies may help other affected men. Because Y chromosome infertility impedes the ability to father children, this condition is usually caused by new deletions on the Y chromosome and occurs in men with no history of the disorder in their family.
• When men with Y chromosome infertility do father children, either naturally or with the aid of assisted reproductive technologies, they pass on the genetic changes on the Y chromosome to all their sons.
• As a result, the sons will also have Y chromosome infertility.

Signs and symptoms

• Y chromosome infertility is characterized by azoospermia (absence of sperm), severe oligozoospermia (<1 x 106 sperm/mL semen), moderate oligozoospermia (1-5 x 106 sperm/mL semen), or mild oligozoospermia (5-20 x 106 sperm/mL semen).
• Males with Y chromosome infertility usually have no obvious symptoms, although physical examination may reveal small testes.

Diagnosis

Clinical features

• A history of infertility
• Normal physical examination in ~30%
• Small testes in ~70% (males with Sertoli cell-only syndrome)

Laboratory features

• Semen analysis

Ejaculate is examined to determine the number, motility, and morphology of sperm. Semen analysis should follow the WHO guidelines.

• Testicular biopsy
• Testicular biopsy may reveal either one or a combination of the following:
• Sertoli cell-only (SCO) syndrome, in which azoospermia is associated with the absence of or only occasional germ cells in tubules that for the most part have only Sertoli cells lining them with no or rare spermatogenesis
• Maturation arrest with spermatocytes but no spermatids or mature sperm.

• Molecular genetic testing approaches can include a combination of Tier 1 testing (targeted deletion/duplication analysis or chromosomal microarray analysis) and Tier 2 testing (cytogenetic analysis and single-gene testing).

Management.

Pregnancies may be achieved by in vitro fertilization using intracytoplasmic sperm injection (ICSI), an in vitro fertilization procedure in which spermatozoa retrieved from ejaculate (in males with oligozoospermia) or extracted from testicular biopsies (in males with azoospermia) are injected into an egg harvested from the reproductive partner.

NIH genetic and rare disease info

• NIH info on Y chromosome infertility

Y chromosome infertility is a rare disease.

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