Chromosome Y microdeletion syndrome

Chromosome Y microdeletion syndrome, also known as Y chromosome microdeletion or AZF (azoospermia factor) microdeletion, is a genetic condition caused by the loss of small segments of DNA on the Y chromosome. These microdeletions primarily affect the long arm of the Y chromosome (Yq11) in regions known as AZFa, AZFb, and AZFc, which contain genes critical for normal sperm production (spermatogenesis). The condition is one of the most common known genetic causes of male infertility. The primary body system affected is the male reproductive system. Men with Y chromosome microdeletions typically present with severely impaired sperm production, ranging from oligozoospermia (very low sperm count) to complete azoospermia (absence of sperm in the ejaculate). The severity of the condition depends on which AZF region is deleted: AZFa deletions generally result in Sertoli cell-only syndrome with complete absence of germ cells; AZFb deletions typically cause maturation arrest of spermatogenesis; and AZFc deletions, which are the most common, are associated with a variable phenotype ranging from oligozoospermia to azoospermia. Physical examination is often normal, and the condition is usually discovered during evaluation for infertility. Testicular size may be reduced in some cases. There is no curative treatment for Y chromosome microdeletion syndrome. However, assisted reproductive technologies (ART), particularly intracytoplasmic sperm injection (ICSI), can help affected men achieve biological fatherhood when residual sperm can be retrieved from the ejaculate or through testicular sperm extraction (TESE). Men with AZFc deletions have the best prognosis for successful sperm retrieval, while those with complete AZFa or AZFb deletions rarely have retrievable sperm. Genetic counseling is essential, as male offspring conceived through ART will inherit the Y chromosome microdeletion and will likely also experience fertility problems.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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